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	<front>
		<journal-meta>
			<journal-id journal-id-type="publisher-id">av</journal-id>
			<journal-title-group>
				<journal-title>Abanico veterinario</journal-title>
				<abbrev-journal-title abbrev-type="publisher">Abanico vet</abbrev-journal-title>
			</journal-title-group>
			<issn pub-type="ppub">2007-428X</issn>
			<issn pub-type="epub">2448-6132</issn>
			<publisher>
				<publisher-name>Sergio Martínez González</publisher-name>
			</publisher>
		</journal-meta>
		<article-meta>
			<article-id pub-id-type="doi">10.21929/abavet2021.41</article-id>
			<article-id pub-id-type="other">00128</article-id>
			<article-categories>
				<subj-group subj-group-type="heading">
					<subject>Artículos originales</subject>
				</subj-group>
			</article-categories>
			<title-group>
				<article-title>Factores ambientales asociados a la prevalencia de <italic>Haemonchus</italic> spp en corderos de la zona centro de Sinaloa</article-title>
			</title-group>
			<contrib-group>
				<contrib contrib-type="author">
					<contrib-id contrib-id-type="orcid">0000-0001-6866-5912</contrib-id>
					<name>
						<surname>Solis-Carrasco</surname>
						<given-names>Jesús</given-names>
					</name>
					<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
				</contrib>
				<contrib contrib-type="author">
					<contrib-id contrib-id-type="orcid">0000-0002-5078-7636</contrib-id>
					<name>
						<surname>Gaxiola-Camacho</surname>
						<given-names>Soila</given-names>
					</name>
					<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
				</contrib>
				<contrib contrib-type="author">
					<contrib-id contrib-id-type="orcid">0000-0001-6205-6083</contrib-id>
					<name>
						<surname>Enríquez-Verdugo</surname>
						<given-names>Idalia</given-names>
					</name>
					<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
				</contrib>
				<contrib contrib-type="author">
					<contrib-id contrib-id-type="orcid">0000-0002-5990-7841</contrib-id>
					<name>
						<surname>Portillo-Loera</surname>
						<given-names>Jesús</given-names>
					</name>
					<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
				</contrib>
				<contrib contrib-type="author">
					<contrib-id contrib-id-type="orcid">0000-0002-7557-5576</contrib-id>
					<name>
						<surname>López-Valencia</surname>
						<given-names>Gilberto</given-names>
					</name>
					<xref ref-type="aff" rid="aff2"><sup>2</sup></xref>
				</contrib>
				<contrib contrib-type="author">
					<contrib-id contrib-id-type="orcid">0000-0001-5248-3719</contrib-id>
					<name>
						<surname>Castro-del-Campo</surname>
						<given-names>Nohemi</given-names>
					</name>
					<xref ref-type="corresp" rid="c1"><sup>*</sup></xref>
					<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
				</contrib>
			</contrib-group>
			<aff id="aff1">
				<label>1</label>
				<institution content-type="original">Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Sinaloa. </institution>
				<institution content-type="normalized">Universidad Autónoma de Sinaloa</institution>
				<institution content-type="orgdiv1">Facultad de Medicina Veterinaria y Zootecnia</institution>
				<institution content-type="orgname">Universidad Autónoma de Sinaloa</institution>
				<country country="MX">Mexico</country>
			</aff>
			<aff id="aff2">
				<label>2</label>
				<institution content-type="original">Instituto de Investigaciones en Ciencias Veterinarias, Universidad Autónoma de Baja California </institution>
				<institution content-type="normalized">Universidad Autónoma de Baja California</institution>
				<institution content-type="orgdiv1">Instituto de Investigaciones en Ciencias Veterinarias</institution>
				<institution content-type="orgname">Universidad Autónoma de Baja California</institution>
				<country country="MX">Mexico</country>
			</aff>
			<author-notes>
				<corresp id="c1">
					<label>*</label>Autor responsable y de correspondencia: ncastro@uas.edu.mx Blvd. San Ángel S/N, Colonia San Benito, Culiacán, Sinaloa, México. CP 80246. E-mail: <email>danielsolis84@gmail.com,</email>
					<email>soilagaxiola@uas.edu.mx</email>, <email>enver@uas.edu.mx</email>, <email>portillo6422@uas.edu.mx</email>, <email>gilbertolopez@uabc.edu.mx</email>, <email>ncastro@uas.edu.mx</email>
				</corresp>
			</author-notes>
			<pub-date date-type="pub" publication-format="electronic">
				<day>28</day>
				<month>02</month>
				<year>2022</year>
			</pub-date>
			<pub-date date-type="collection" publication-format="electronic">
				<season>Jan-Dec</season>
				<year>2021</year>
			</pub-date>
			<volume>11</volume>
			<elocation-id>e128</elocation-id>
			<history>
				<date date-type="received">
					<day>26</day>
					<month>07</month>
					<year>2021</year>
				</date>
				<date date-type="accepted">
					<day>08</day>
					<month>11</month>
					<year>2021</year>
				</date>
			</history>
			<permissions>
				<license license-type="open-access" xlink:href="https://creativecommons.org/licenses/by-nc/4.0/" xml:lang="es">
					<license-p>Este es un artículo publicado en acceso abierto bajo una licencia Creative Commons</license-p>
				</license>
			</permissions>
			<abstract>
				<title>RESUMEN</title>
				<p>Los ovinos son una especie explotada en diferentes ámbitos de la producción. Estos son propensos a diferentes patógenos, destacando parásitos como <italic>Haemonchus contortus</italic>. El clima predominante y las prácticas de manejo en la crianza se consideran los principales factores que impulsan la distribución espacial y temporal del nematodo. Su distribución es mundial, ocasiona pérdidas económicas por morbilidad y mortalidad, se han reportado estudios de prevalencia en diferentes países como en India, España, Nigeria, México; por ello, el objetivo de este trabajo fue determinar los factores edafoclimáticos de las distintas zonas del municipio de Culiacán y sistema de producción que influyen en la prevalencia de <italic>Haemonchus</italic> spp en corderos. La investigación se realizó en el municipio de Culiacán, Sinaloa, México, en un periodo de un año, fue un estudio observacional, para el cual se incluyeron 23 unidades de producción ovina distribuidas en 10 sindicaturas del municipio, se realizó un muestreo por época del año colectando un total de 1520 muestras de heces procedentes de animales menores a 3 meses de edad. Las heces se procesaron individualmente por técnica de flotación. La prevalencia general fue de 13.42 %, y la época de otoño (OR 2.38 (1.69-3.34) P&lt;0.001), zona de valle (OR 2.70 (1.21-6.02); P&lt;0.016) y sistema extensivo (OR 4.81 (3.38-6.85); P&lt;0.0001) resultaron factores de riesgo asociados a la presencia del nematodo en los corderos, por lo que deben considerarse para el establecimiento de medidas preventivas y de control de la parasitosis.</p>
			</abstract>
			<kwd-group xml:lang="es">
				<title>Palabras clave:</title>
				<kwd>Haemonchus</kwd>
				<kwd>prevalencia</kwd>
				<kwd>ovinos</kwd>
				<kwd>factor de riesgo</kwd>
				<kwd>nematodo gastrointestinal</kwd>
			</kwd-group>
			<counts>
				<fig-count count="2"/>
				<table-count count="6"/>
				<equation-count count="4"/>
				<ref-count count="36"/>
				<page-count count="1"/>
			</counts>
		</article-meta>
	</front>
	<body>
		<sec sec-type="intro">
			<title>INTRODUCCIÓN</title>
			<p>Las infecciones por nematodos gastrointestinales afectan la salud de pequeños rumiantes comprometiendo su producción y reproducción, con mayor frecuencia en animales jóvenes en desarrollo, provocando baja ganancia de peso y retraso en el crecimiento, por lo cual son una de las principales causas de pérdidas económicas (<xref ref-type="bibr" rid="B12">González <italic>et al</italic>., 2011</xref>; <xref ref-type="bibr" rid="B2">Asmare <italic>et al</italic>., 2016</xref>; <xref ref-type="bibr" rid="B17">Kuma <italic>et al</italic>., 2019</xref>), principalmente en los costos incurridos en el tratamiento y control (<xref ref-type="bibr" rid="B33">Tramboo <italic>et al</italic>., 2015</xref>). Los ovinos por lo general son más propensos a parasitismo gastrointestinal, debido a su alimentación en pastos contaminados con larva 3 (<xref ref-type="bibr" rid="B32">Tariq <italic>et al</italic>., 2008</xref>). Entre los parásitos gastrointestinales, <italic>Haemonchus</italic> es la especie con mayor importancia económica (<xref ref-type="bibr" rid="B28">Rinaldi <italic>et al</italic>., 2015</xref>). Este nematodo se localiza en el abomaso, se alimenta de la sangre de ovinos y caprinos, puede encontrarse en otros rumiantes como bovinos (<xref ref-type="bibr" rid="B11">Getachew <italic>et al</italic>., 2007</xref>), es de los más patógenos en ovejas (<xref ref-type="bibr" rid="B4">Besier <italic>et al</italic>., 2016</xref>), su extensa distribución geográfica y resistencia contra las medidas de control antihelmínticas lo convierte en una amenaza para la sostenibilidad de la ganadería de ovinos (<xref ref-type="bibr" rid="B29">Saccareau <italic>et al</italic>., 2017</xref>). La época de lluvia favorece su frecuencia, con animales en pastoreo durante las primeras horas de la mañana (<xref ref-type="bibr" rid="B21">Mederos <italic>et al</italic>., 2010</xref>), el clima predominante (temperatura, lluvia y humedad) y las prácticas de manejo en la crianza se consideran los principales factores que impulsan su distribución (<xref ref-type="bibr" rid="B28">Rinaldi <italic>et al</italic>., 2015</xref>); su distribución es heterogénea y depende de variables que difieren de un área a otra, incluso de una granja a otra, como el manejo, prevención y control (<xref ref-type="bibr" rid="B24">Musella <italic>et al</italic>., 2011</xref>). Por otro lado, estudios sobre la prevalencia en animales en pastoreo es alta en zonas de climas tropicales de ambos hemisferios (<xref ref-type="bibr" rid="B26">O´connor <italic>et al</italic>., 2006</xref>), los animales jóvenes y hembras preñadas son más susceptibles a los helmintos a diferencia de los animales adultos debido a su estado nutricional y su bajo nivel de inmunidad (<xref ref-type="bibr" rid="B34">Vieira <italic>et al</italic>., 2014</xref>). La prevalencia de <italic>Haemonchus</italic> se ha reportado a nivel mundial, en India <xref ref-type="bibr" rid="B33">Tramboo <italic>et al</italic>. (2015)</xref> de un total de 1200 de animales muestreados el 55 % fue positivo al nematodo; en México, se encontró un 32 % positivos de 219 muestreados procedentes de ovinos en pastoreo (<xref ref-type="bibr" rid="B13">Hernández <italic>et al</italic>., 2007</xref>); en la región de Sinaloa al analizar 120 ovinos de un sistema de producción extensivo se reportó una frecuencia de 17.5 % (<xref ref-type="bibr" rid="B10">Gaxiola <italic>et al</italic>., 2010</xref>). Por lo tanto, el objetivo de trabajo fue determinar los factores edafoclimáticos de las distintas zonas del municipio de Culiacán y sistema de producción que influyen en la prevalencia de <italic>Haemonchus</italic> spp en corderos de la zona centro de Sinaloa.</p>
		</sec>
		<sec sec-type="materials|methods">
			<title>MATERIAL Y MÉTODOS</title>
			<sec>
				<title>Área de estudio</title>
				<p>Se realizó en el municipio de Culiacán, Sinaloa, México (24o 46’ 13’’ LN y 107o 21’ 14’’ LO). La región se caracteriza por tener un clima BS1 (h’) w(w)(e), se define como clima semiseco, muy cálido, con lluvias en verano, según la clasificación de Köppen y modificada por García (2004); con temperatura promedio anual de 25.9 ºC, máxima promedio de 30.4 ºC en junio y julio, y mínima promedio de 20.6 ºC en enero; la humedad relativa promedio es de 68 %, con máxima de 81 % en septiembre y mínima de 51 % en abril; la precipitación anual promedio es de 688.5 mm (<xref ref-type="bibr" rid="B8">CIAPAN, 2002</xref>).</p>
			</sec>
			<sec>
				<title>Tipo de estudio y tamaño de muestra</title>
				<p>Es un estudio observacional, transversal, descriptivo. Se muestrearon 23 ranchos extensivos, semi-intensivos e intensivos. En el municipio de Culiacán se tienen registradas 125 Unidades de Producción Ovina (UPO) (<xref ref-type="bibr" rid="B30">SIAP, 2013</xref>), por lo que la muestra representó el 18.4 % de las UPO. Se consideraron 10 de las 18 sindicaturas del municipio de Culiacán, Sinaloa (<xref ref-type="fig" rid="f1">Fig. 1</xref>), la selección de las unidades de producción se realizó por conveniencia, con base a la cooperación del propietario y la facilidad para su acceso. El tamaño de muestra se determinó con la siguiente fórmula:</p>
				<p>
					<fig id="f1">
						<label>Figura 1</label>
						<caption>
							<title>Localización de las sindicaturas de las unidades de producción ovinas muestreadas en el Municipio de Culiacán, Sinaloa, México</title>
						</caption>
						<graphic xlink:href="2448-6132-av-11-e128-gf1.gif"/>
					</fig>
				</p>
				<disp-formula id="e1"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" ><mml:mi>n</mml:mi><mml:mo>=</mml:mo><mml:mfrac><mml:mrow><mml:msup><mml:mrow><mml:mi>Z</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup><mml:mi>p</mml:mi><mml:mi>q</mml:mi></mml:mrow><mml:mrow><mml:msup><mml:mrow><mml:mi>B</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:mfrac></mml:math></disp-formula>
				
				<p>Donde: n es tamaño de la muestra, Z es 1.96 para el 95 % de confianza, p es frecuencia esperada del factor a estudiar, q es 1 - p, B es precisión o error admitido (<xref ref-type="bibr" rid="B16">Jaramillo &amp; Martínez, 2010</xref>). El tamaño de muestra calculado fue de 380 muestras de heces en cada estación (verano, otoño, invierno y primavera) y debido a que al realizar la visita a la unidad de producción se desconocía el número de corderos existentes, se consideró el número de adultos (<xref ref-type="table" rid="t1">Cuadro 1</xref>), y se muestreó un número de corderos que representó al menos el 10% de los adultos en cada unidad de producción, los cuales se seleccionaron al azar para completar el tamaño de la muestra calculada. Se realizó un muestreo por época del año y se obtuvieron un total de 1520 muestras procedentes de corderos menores de noventa días (d) de edad.</p>
				<p>
					<table-wrap id="t1">
						<label>Cuadro 1</label>
						<caption>
							<title>Ubicación de unidad de producción ovina por sindicatura y población de ovinos adultos</title>
						</caption>
						<table>
							<colgroup>
								<col/>
								<col/>
								<col/>
								<col/>
							</colgroup>
							<thead>
								<tr>
									<th align="center">Sindicatura</th>
									<th align="center">*UPO</th>
									<th align="center">Ovinos adultos</th>
									<th align="center">Corderos muestreados</th>
								</tr>
							</thead>
							<tbody>
								<tr>
									<td align="justify">Villa Adolfo L.M</td>
									<td align="justify">Agrícola Limón <p>La Hacienda</p><p>La granjita</p><p>Alboradas</p></td>
									<td align="center">80<p>150</p><p>120</p><p>180</p></td>
									<td align="center">10<p>20</p><p>17</p><p>18</p></td>
								</tr>
								<tr>
									<td align="justify">El Salado</td>
									<td align="justify">El alacrán</td>
									<td align="center">70</td>
									<td align="center">11</td>
								</tr>
								<tr>
									<td align="justify">Costa Rica</td>
									<td align="justify">El trabajo<p>Agrícola Sanfer</p><p>Agrícola Tabachines</p></td>
									<td align="center">20<p>150</p><p>180</p></td>
									<td align="center">5<p>15</p><p>18</p></td>
								</tr>
								<tr>
									<td align="justify">Quilá</td>
									<td align="justify">Naranjos<p>La Loma</p></td>
									<td align="center">70<p>30</p></td>
									<td align="center">12<p>5</p></td>
								</tr>
								<tr>
									<td align="justify">Aguaruto</td>
									<td align="justify">Fetasas<p>Agrícola del Río</p><p>Los Cabritos</p></td>
									<td align="center">200<p>45</p><p>200</p></td>
									<td align="center">22<p>5</p><p>20</p></td>
								</tr>
								<tr>
									<td align="justify">Culiacancito</td>
									<td align="justify">San Sebastián<p>Agrícola Quiroz</p><p>Los Otates</p></td>
									<td align="center">250<p>250</p><p>180</p></td>
									<td align="center">25<p>25</p><p>20</p></td>
								</tr>
								<tr>
									<td align="justify">Las Tapias</td>
									<td align="justify">Santa María</td>
									<td align="center">130</td>
									<td align="center">13</td>
								</tr>
								<tr>
									<td align="justify">Sanalona</td>
									<td align="justify">Baldomero</td>
									<td align="center">20</td>
									<td align="center">5</td>
								</tr>
								<tr>
									<td align="justify">Imala</td>
									<td align="justify">Guayacanes</td>
									<td align="center">200</td>
									<td align="center">24</td>
								</tr>
								<tr>
									<td align="justify">Culiacán</td>
									<td align="justify">Guásima<p>Agrícola Mojolo</p><p>Ganadera Verdugo</p><p>Campo Morelia</p></td>
									<td align="center">230<p>300</p><p>80</p><p>180</p></td>
									<td align="center">23<p>32</p><p>15</p><p>20</p></td>
								</tr>
							</tbody>
						</table>
						<table-wrap-foot>
							<fn id="TFN1">
								<p>*UPO= Unidades de Producción Ovina</p>
							</fn>
						</table-wrap-foot>
					</table-wrap>
				</p>
			</sec>
			<sec>
				<title>Recolección de muestras y análisis de laboratorio</title>
				<p>Durante cada visita a las unidades de producción se llenó un formato de registro de información sobre los siguientes factores: época del año (verano, otoño, invierno o primavera), localización (zona de altos o valle), sistema de producción (intensivo, semiintensivo, extensivo. Los corderos se eligieron de forma aleatoria. Las heces se tomaron directamente del recto con guante de látex, se identificaron individualmente, se refrigeraron en contenedores a 4 ºC con hielo y refrigerantes para su traslado al laboratorio de Parasitología de la Facultad de Medicina Veterinaria y Zootecnia, para su proceso y análisis.</p>
				<p>El diagnóstico de Haemonchus spp se realizó por análisis coproparasitoscópico mediante la técnica cualitativa de flotación de Faust (<xref ref-type="bibr" rid="B35">Zajac &amp; Conboy, 2011</xref>), al ser un medio útil y ampliamente utilizado en estudios preliminares para determinar qué tipos de parásitos están presentes en muestras fecales (<xref ref-type="bibr" rid="B20">Medeiros et al., 2018</xref>), para la detección del parásito se utilizó microscopio óptico con los objetivos de 10x y 40x, los huevos se identificaron en base a su morfología característica, blastómeros de color marrón oscuro y tamaño descrita por <xref ref-type="bibr" rid="B18">Ljungström et al., 2018</xref>.</p>
			</sec>
			<sec>
				<title>Análisis estadístico</title>
				<p>Los corderos se consideraron positivos con al menos un huevo de Haemonchus spp; la prevalencia se estimó como el número de ovinos positivos entre el total de ovinos muestreados según la categoría.</p>
				<p>Los resultados de la observación al microscopio (positivo o negativo) se resumieron en cuadros de contingencia por factor y se analizaron para detectar la asociación entre el resultado y el factor, con la prueba de Ji cuadrada. Se consideró diferencia estadística con una P≤0.05.</p>
				<p>En los factores con más de dos categorías, los resultados se dicotomizaron. Enseguida, para determinar los factores de riesgo de resultados positivos se aplicó análisis de regresión logística multivariado. El modelo general fue:</p>
				<disp-formula id="e2"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" ><mml:mi>π</mml:mi><mml:mfenced separators="|"><mml:mrow><mml:mi>x</mml:mi></mml:mrow></mml:mfenced><mml:mo>=</mml:mo><mml:mfrac><mml:mrow><mml:mrow><mml:mrow><mml:mi mathvariant="normal">exp</mml:mi></mml:mrow><mml:mo>⁡</mml:mo><mml:mrow><mml:mo>(</mml:mo><mml:mi>α</mml:mi><mml:mo>+</mml:mo><mml:mi mathvariant="normal">Σ</mml:mi><mml:mi> </mml:mi><mml:mi>β</mml:mi><mml:mi>i</mml:mi><mml:mi>x</mml:mi><mml:mi>i</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:mrow></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mo>+</mml:mo><mml:mi mathvariant="normal">e</mml:mi><mml:mi mathvariant="normal">x</mml:mi><mml:mi mathvariant="normal">p</mml:mi><mml:mo>⁡</mml:mo><mml:mo>(</mml:mo><mml:mi>α</mml:mi><mml:mo>+</mml:mo><mml:mi mathvariant="normal">Σ</mml:mi><mml:mi>β</mml:mi><mml:mi>i</mml:mi><mml:mi>x</mml:mi><mml:mi>i</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:mfrac></mml:math></disp-formula>
				<p>Donde: π (x), el valor de π puede variar a medida que cambia el valor de x, y se quiere describir su dependencia; los valores de xi = (x1,…,xp) son las variables predictoras p, xi representa el vector de variables independientes; exp es la base de los logaritmos naturales 2.71828; α es el valor del intercepto; βi son los valores de los coeficientes de regresión. Para este análisis se utilizó el procedimiento LOGISTIC (SAS, 2001) con la opción hacia atrás, para estimar el grado de asociación [razón de probabilidades (OR)] y los intervalos de confianza. El nivel de alfa para considerar asociación entre el factor con el resultado positivo, y estimar el factor de riesgo fue P ≤ 0.05.</p>
			</sec>
		</sec>
		<sec sec-type="results|discussion">
			<title>RESULTADOS Y DISCUSIÓN</title>
			<p>De un total de 1520 muestras analizadas, 204 resultaron positivas a Haemonchus spp representando una prevalencia de 13.42 % en el período anual analizado; el método utilizado para detectar al nematodo fue la técnica de flotación, prueba principalmente usada en examen de heces en diagnóstico animal, concentra huevos, ooquistes de parásitos y separa los desechos presentes en la muestra (<xref ref-type="bibr" rid="B35">Zajac &amp; Conboy, 2011</xref>; <xref ref-type="bibr" rid="B28">Rinaldi et al. 2011</xref>; <xref ref-type="bibr" rid="B20">Medeiros et al., 2018</xref>), una de las principales ventajas de utilizar esta prueba es que tiene una alta tasa recuperación de huevos (<xref ref-type="bibr" rid="B20">Medeiros et al., 2018</xref>), causa menos daño a los quistes y huevos (<xref ref-type="bibr" rid="B35">Zajac &amp; Conboy, 2011</xref>), lo que permite una identificación morfológica adecuada facilitando la observación de la estructura característica, dimensiones del huevo a identificar (<xref ref-type="bibr" rid="B15">Indre et al., 2010</xref>; <xref ref-type="bibr" rid="B19">Mahmood et al., 2019</xref>), la técnica impide la flotación de huevos de trematodos y no es tan específica para determinar la especie de los parásitos observados (<xref ref-type="bibr" rid="B35">Zajac &amp; Conboy, 2011</xref>; <xref ref-type="bibr" rid="B18">Ljungström et al., 2018</xref>), por lo tanto los resultados mediante esta técnica reportan sólo el género de Haemonchus. Los factores estudiados se presentan en el <xref ref-type="table" rid="t2">cuadro 2</xref>, las pruebas de Ji Cuadrada indicaron que los tres factores fueron significativos (P&lt;0.05), época del año, zona de producción, sistema de producción; de igual forma para el análisis de los factores de riesgo resultaron significativos (P≤0.05) en el modelo de regresión logística multivariada (<xref ref-type="table" rid="t3">Cuadro 3</xref>). Los resultados por época del año mostraron una mayor prevalencia en otoño con 20.53 %, no se observó diferencia entre la época de invierno y primavera y la menor prevalencia se encontró la época de verano con 7.89 % (P&lt;0.0001).</p>
			<p>
				<table-wrap id="t2">
					<label>Cuadro 2</label>
					<caption>
						<title>Factores de Riesgo Asociados a la presencia de huevos de Haemonchus spp en heces de corderos en UPO ubicadas en el municipio de Culiacán, Sinaloa, México</title>
					</caption>
					<table>
						<colgroup>
							<col/>
							<col/>
							<col/>
							<col/>
							<col/>
						</colgroup>
						<thead>
							<tr>
								<th align="center">Factor de riesgo</th>
								<th align="center">N</th>
								<th align="center">Muestras Positivas</th>
								<th align="center">Porcentaje</th>
								<th align="center">P<sup>1</sup></th>
							</tr>
							<tr>
								<th align="center">Época del año</th>
								<th align="center"> </th>
								<th align="center"> </th>
								<th align="center"> </th>
								<th align="center">0.0001</th>
							</tr>
						</thead>
						<tbody>
							<tr>
								<td align="center">Verano</td>
								<td align="center">380</td>
								<td align="center">30</td>
								<td align="center">7.89<sup>c</sup></td>
								<td align="center"> </td>
							</tr>
							<tr>
								<td align="center">Otoño</td>
								<td align="center">380</td>
								<td align="center">78</td>
								<td align="center">20.53<sup>a</sup></td>
								<td align="center"> </td>
							</tr>
							<tr>
								<td align="center">Invierno</td>
								<td align="center">380</td>
								<td align="center">50</td>
								<td align="center">13.16<sup>b</sup></td>
								<td align="center"> </td>
							</tr>
							<tr>
								<td align="center">Primavera</td>
								<td align="center">380</td>
								<td align="center">46</td>
								<td align="center">12.11b<sup>c</sup></td>
								<td align="center"> </td>
							</tr>
							<tr>
								<td align="center">Zona de producción</td>
								<td align="center"> </td>
								<td align="center"> </td>
								<td align="center"> </td>
								<td align="center">0.0001</td>
							</tr>
							<tr>
								<td align="center">Altos</td>
								<td align="center">183</td>
								<td align="center">7</td>
								<td align="center">3.83<sup>b</sup></td>
								<td align="center"> </td>
							</tr>
							<tr>
								<td align="center">Valles</td>
								<td align="center">1337</td>
								<td align="center">197</td>
								<td align="center">14.73<sup>a</sup></td>
								<td align="center"> </td>
							</tr>
							<tr>
								<td align="center">Sistema de producción</td>
								<td align="center"> </td>
								<td align="center"> </td>
								<td align="center"> </td>
								<td align="center">0.0001</td>
							</tr>
							<tr>
								<td align="center">Extensivo</td>
								<td align="center">437</td>
								<td align="center">112</td>
								<td align="center">25.63<sup>a</sup></td>
								<td align="center"> </td>
							</tr>
							<tr>
								<td align="center">Semiintensivo</td>
								<td align="center">248</td>
								<td align="center">50</td>
								<td align="center">20.16<sup>a</sup></td>
								<td align="justify"> </td>
							</tr>
							<tr>
								<td align="center">Intensivo</td>
								<td align="center">835</td>
								<td align="center">42</td>
								<td align="center">5.03<sup>b</sup></td>
								<td align="center"> </td>
							</tr>
						</tbody>
					</table>
					<table-wrap-foot>
						<fn id="TFN2">
							<label><sup>1</sup></label>
							<p> Valores de probabilidad de la prueba de Ji cuadrada. <sup>abc</sup> Literales diferentes
								en los porcentajes de muestras positivas en cada factor de riesgo
								indican diferencia estadística (P ≤ 0.01).</p>
						</fn>
					</table-wrap-foot>
				</table-wrap>
			</p>
			<p>
				<table-wrap id="t3">
					<label>Cuadro 3</label>
					<caption>
						<title>Odds ratios para los Factores de Riesgo Asociados a la presencia de huevos de Haemonchus spp en heces de corderos en UPO ubicadas en el municipio de Culiacán, Sinaloa, México</title>
					</caption>
					<table>
						<colgroup>
							<col/>
							<col/>
							<col/>
							<col/>
						</colgroup>
						
							<thead>
							<tr>
								<th align="center">Factor de Riesgo</th>
								<th align="center">Odd ratio</th>
								<th align="center">IC 95 %</th>
								<th align="center">Valor de P</th>
							</tr>
							</thead>
						<tbody>
							<tr>
								<td align="center">Época del año:<p>V-I-P</p><p>Otoño</p></td>
								<td align="center"><p> </p> <p>Referencia</p><p>2.38</p></td>
								<td align="center"><p> </p> <p>1.69-3.34</p></td>
								<td align="center"><p> </p> 	0.001</td>
							</tr>
							<tr>
								<td align="center">Zona de producción: <p>Altos</p><p>Valles</p></td>
								<td align="center"><p> </p> <p>Referencia</p> <p>2.70</p></td>
								<td align="center"><p> </p> <p>1.21-6.02</p></td>
								<td align="center"><p> </p> <p>0.016</p></td>
							</tr>
							<tr>
								<td align="center">Sistema de producción: <p>Intensivo-Semi</p> <p>Extensivo</p></td>
								<td align="center"><p> </p> <p>Referencia</p> <p>4.81</p></td>
								<td align="center"><p> </p> <p>3.38-6.85</p></td>
								<td align="center"><p> </p> <p>0.0001</p></td>
							</tr>
						</tbody>
					</table>
					<table-wrap-foot>
						<fn id="TFN3">
							<p>V=Verano, I=Invierno, P=Primavera; IC = Intervalo de confianza; P = Probabilidad.</p>
						</fn>
					</table-wrap-foot>
				</table-wrap>
			</p>
			<p>Los resultados del estudio mostraron que al comparar las épocas del año existe 2.38 veces mayor riesgo de presentar Haemonchus spp en época de otoño que en el resto de las estaciones (P&lt;0.001). Los resultados de la presente investigación en relación a la época del verano con 7.89 % son cercanos a los descritos en Inglaterra con 10.5 % (<xref ref-type="bibr" rid="B5">Broughan &amp; Wall., 2007</xref>), la baja prevalencia en verano se puede atribuir a razón de las elevadas temperaturas que se presentan en este época en la zona descrita, por lo cual la larva disminuye su actividad, debido al fototropismo negativo a la luz intensa (<xref ref-type="bibr" rid="B31">Soca et al., 2005</xref>), en otro estudio relacionado a épocas del año en la India informaron la presencia del orden Strongylida con 63.2 % en verano y 58.4 % en otoño, 52.77 % en invierno y 61.3 % en primavera (<xref ref-type="bibr" rid="B33">Tramboo et al., 2015</xref>), denotando diferencia con el actual trabajo, ya que en otoño se presentó una prevalencia de 20.52 % siendo mayor que la del verano con 7.89 %, esto se puede interpretar por las temperaturas máximas que se presentan en verano en el área de estudio, además del aumento de humedad en los pastos en la época de otoño que favorecen la migración larvaria por hidrotropismo positivo (<xref ref-type="bibr" rid="B31">Soca et al., 2005</xref>), en lo referente a invierno y primavera de igual forma se encontraron diferencias entre los dos estudios, ya que en la India aumentó la prevalencia de invierno a primavera, esto lo atribuyen a las precipitaciones que favorecen la humedad de los pastos para la presencia del parásito, contrario al presente resultado, no hubo diferencia significativa de invierno a primavera con relación a la presencia del nematodo, esto se interpreta al estado de hipobiosis en el que ingresa el helminto, en periodo desfavorable nutricionalmente, por lo cual tiende a bajar tu metabolismo y actividad (<xref ref-type="bibr" rid="B31">Soca et al., 2005</xref>); en un estudio realizado en Irán (<xref ref-type="bibr" rid="B22">Moghaddar, 2008</xref>), muestrearon corderos menores de cinco meses, durante las cuatro épocas del año, se reportó la presencia de nematodos 25.9, 22.3, 50 y 53.1 % para otoño, invierno, primavera y verano, respectivamente; las diferencias que destacan entre los estudios es el informe de los nematodos en general por ende mayor porcentaje de corderos positivos, otro factor que indica diferencia entre la prevalencia entre épocas del año es la precipitación, en el caso de Irán se presenta más lluvias en marzo y abril por lo cual se presenta mayor cantidad de nematodos en primavera y verano y en la región de estudio Culiacán, las lluvias se presentan en agosto y septiembre favoreciendo las condiciones para Haemonchus en otoño, coincidiendo con una investigación realizada en la misma zona con el protozoario Cryptosporidium spp en corderos presentando 2.2 veces más riesgo de presentarse el parásito en otoño que en verano (<xref ref-type="bibr" rid="B6">Castro et al., 2017</xref>), si bien se encuentran clasificados taxonómicamente en distinto phylum las condiciones climáticas en esta época favorecen a ambos.</p>
			<p>Al analizar la zona geográfica de la región los resultados indican una mayor prevalencia para el valle con 14.73 % a diferencia de zona de altos con 3.83 % (P&lt;0.0001), y 2.70 veces mayor riesgo de presentarse el nematodo en los corderos en zona de valle (P&lt;0.016), presentando similitud a lo encontrado en Etiopia la diferencia que se reportó de forma general fueron nematodos gastrointestinales, en zona de producción de valle fue mayor que la zona de altos, con 95 % y 68.6 % respectivamente y coinciden en cuanto a más alto el riesgo de presentar Haemonchus en la zona de producción de valle (<xref ref-type="bibr" rid="B2">Asmare et al., 2016</xref>), así mismo en Suiza en zonas altas se reportó una baja presencia del parásito en comparación con zonas medias y bajas de Italia e Irlanda (<xref ref-type="bibr" rid="B28">Rinaldi et al., 2015</xref>), la fuente de agua es una de las características claves para la supervivencia y diseminación de nematodos como Haemonchus (<xref ref-type="bibr" rid="B24">Musella et al., 2011</xref>; Rinaldi et al., 2015), el cual se presentó más en zona de valle principalmente por diques, estas zonas son áreas más bajas que pueden por afluentes de agua arrastrar contaminantes, entre ellos huevos de parásitos provenientes de unidades de producción o de animales silvestres que habitan en partes altas, favoreciendo la diseminación de estos al utilizarse esta agua para riego, consumo de los animales, entre otras actividades de uso común. Los parásitos gastroentéricos y en especial Haemonchus han logrado adaptarse a distintos ecosistemas, su capacidad de adaptación y sobrevivencia diferentes ambientes permiten la infección de nuevos hospederos (<xref ref-type="bibr" rid="B23">Munguía et al., 2018</xref>).</p>
			<p>De acuerdo con el sistema de producción la presencia de Haemonchus spp se encontró un 25.63 % en sistema de producción extensivo, 20.13 % en sistema semiintensivo y 5.03% en sistema intensivo (P&lt;0.0001) y al analizar la asociación de la parasitosis ésta fue de 4.81 veces más riesgo de presentarse en corderos bajo un sistema de producción extensivo (P&lt;0.0001). Los resultados difieren de los realizados por <xref ref-type="bibr" rid="B36">Zapata et al. (2016)</xref> y <xref ref-type="bibr" rid="B14">Herrera et al. (2013)</xref> en los cuales no se encuentran diferencia estadística entre los tres sistemas de producción analizados. Las condiciones del presente estudio en animales bajo sistemas extensivos no son sistematizadas, no manejaban un calendario de desparasitación, lo que concuerda con <xref ref-type="bibr" rid="B21">Mederos et al. (2010)</xref> quienes indican que los niveles más altos de parásitos gastrointestinales se presentan en unidades de producción donde no se da un manejo de desparasitación rutinario; además del tipo alimentación basada en pastoreo facilita la ingesta de las larvas del parásito presente en la vegetación, y permite la transmisión ya que los mismos animales contaminan el área de pastoreo (<xref ref-type="bibr" rid="B3">Belina et al., 2017</xref>; <xref ref-type="bibr" rid="B1">Akyüz et al., 2019</xref>); por su parte en los sistemas semiintensivo e intensivo el manejo de desparasitación era programado y se operaba una alimentación con dietas preparadas principalmente en el sistema intensivo lo que favoreció a un menor porcentaje de la presencia del parásito en estos sistemas debido al impacto positivo que dan las dietas de mejor calidad sobre la salud; <xref ref-type="bibr" rid="B7">Cériac et al. (2019)</xref> y <xref ref-type="bibr" rid="B25">Naeem et al. (2021) </xref>señalan que una nutrición de calidad suplementada con alto contenido de proteínas, aminoácidos estimula la expresión de resistencia y resiliencia del hospedador, estimula la inmunidad, disminuye la proliferación de parásitos.</p>
		</sec>
		<sec sec-type="conclusions">
			<title>CONCLUSIÓN</title>
			<p>La época de otoño, zona del valle y sistema de producción extensivo son los factores edafoclimáticos que se asocian a la prevalencia de Haemonchus spp (13.42%) en corderos en el municipio de Culiacán, Sinaloa; por lo que estos aspectos deben tomarse en cuenta para desarrollar estrategias de prevención y control de la parasitosis. H. contortus es reconocido como uno de los principales parásitos que afectan a los ovinos lo que hace necesaria la consideración de este agente como posible causante de afecciones productivas aún en etapas tempranas de edad de los animales, así como una posible fuente de infección de los animales jóvenes al resto del rebaño.</p>
		</sec>
	</body>
	<back>
		<ack>
			<title>AGRADECIMIENTOS</title>
			<p>A la Asociación de Criadores de Ovinos y Caprinos Culiacán AC. y al Consejo Nacional de Ciencia y Tecnología (CONACyT) México, por el apoyo económico para la formación de recursos humanos en este proyecto.</p>
		</ack>
		<ref-list>
			<title>LITERATURA CITADA</title>
			<ref id="B1">
				<mixed-citation>Akyüz M, Kirman R. Yaya S, Gülbeyen H, Güven E. 2019. Endoparasites Determined by Fecal Examination in Sheep in Erzurum Province. Turkiye Parazitol Derg. 43(4): 187-193. https://doi.org/10.4274/tpd.galenos.2019.6512</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Akyüz</surname>
							<given-names>M</given-names>
						</name>
						<name>
							<surname>Kirman</surname>
							<given-names>R.</given-names>
						</name>
						<name>
							<surname>Yaya</surname>
							<given-names>S</given-names>
						</name>
						<name>
							<surname>Gülbeyen</surname>
							<given-names>H</given-names>
						</name>
						<name>
							<surname>Güven</surname>
							<given-names>E.</given-names>
						</name>
					</person-group>
					<year>2019</year>
					<article-title>Endoparasites Determined by Fecal Examination in Sheep in Erzurum Province</article-title>
					<source>Turkiye Parazitol Derg</source>
					<volume>43</volume>
					<issue>4</issue>
					<fpage>187</fpage>
					<lpage>193</lpage>
					<pub-id pub-id-type="doi">10.4274/tpd.galenos.2019.6512</pub-id>
				</element-citation>
			</ref>
			<ref id="B2">
				<mixed-citation>Asmare K, Sheferaw D, Aragaw K, Abera M, Sibhat B, Haile A, Kiara H, Szonyi B, Skjerve E, Wieland B. 2016. Gastrointestinal nematode infection in small ruminants in Ethiopia: A systematic review and meta-analysis. Acta Tropica. 160: 68-77. ISSN: 0001-706X. https://doi.org/10.1016/j.actatropica.2016.04.016</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Asmare</surname>
							<given-names>K</given-names>
						</name>
						<name>
							<surname>Sheferaw</surname>
							<given-names>D</given-names>
						</name>
						<name>
							<surname>Aragaw</surname>
							<given-names>K</given-names>
						</name>
						<name>
							<surname>Abera</surname>
							<given-names>M</given-names>
						</name>
						<name>
							<surname>Sibhat</surname>
							<given-names>B</given-names>
						</name>
						<name>
							<surname>Haile</surname>
							<given-names>A</given-names>
						</name>
						<name>
							<surname>Kiara</surname>
							<given-names>H</given-names>
						</name>
						<name>
							<surname>Szonyi</surname>
							<given-names>B</given-names>
						</name>
						<name>
							<surname>Skjerve</surname>
							<given-names>E</given-names>
						</name>
						<name>
							<surname>Wieland</surname>
							<given-names>B.</given-names>
						</name>
					</person-group>
					<year>2016</year>
					<article-title>Gastrointestinal nematode infection in small ruminants in Ethiopia: A systematic review and meta-analysis</article-title>
					<source>Acta Tropica</source>
					<volume>160</volume>
					<fpage>68</fpage>
					<lpage>77</lpage>
					<issn>0001-706X</issn>
					<pub-id pub-id-type="doi">10.1016/j.actatropica.2016.04.016</pub-id>
				</element-citation>
			</ref>
			<ref id="B3">
				<mixed-citation>Belina D, Giri A, Hailu S, Eshetu A. 2017. Gastrointestinal Nematodes in Ruminants: The Parasite Burden, Associated Risk Factors and Anthelmintic Utilization Practices in Selected Districts of East and Western Hararghe, Ethiopia. Journal of Veterinary Science and Technology. 8: 433. https://doi.org/10.4262/2157-7579.1000433</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Belina</surname>
							<given-names>D</given-names>
						</name>
						<name>
							<surname>Giri</surname>
							<given-names>A</given-names>
						</name>
						<name>
							<surname>Hailu</surname>
							<given-names>S</given-names>
						</name>
						<name>
							<surname>Eshetu</surname>
							<given-names>A.</given-names>
						</name>
					</person-group>
					<year>2017</year>
					<article-title>Gastrointestinal Nematodes in Ruminants: The Parasite Burden, Associated Risk Factors and Anthelmintic Utilization Practices in Selected Districts of East and Western Hararghe, Ethiopia</article-title>
					<source>Journal of Veterinary Science and Technology</source>
					<volume>8</volume>
					<fpage>433</fpage>
					<lpage>433</lpage>
					<pub-id pub-id-type="doi">10.4262/2157-7579.1000433</pub-id>
				</element-citation>
			</ref>
			<ref id="B4">
				<mixed-citation>Besier RB, Kahn LP, Sargison ND, Van-Wyk JA. 2016. The Pathophysiology, Ecology and Epidemiology of Haemonchus contortus Infection in Small Ruminants. Haemonchus contortus and Haemonchosis - Past, Present and Future. Trends. 93: 95-143. ISSN: 0065- 308X. https://doi.org/10.1016/bs.apar.2016.02.022</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Besier</surname>
							<given-names>RB</given-names>
						</name>
						<name>
							<surname>Kahn</surname>
							<given-names>LP</given-names>
						</name>
						<name>
							<surname>Sargison</surname>
							<given-names>ND</given-names>
						</name>
						<name>
							<surname>Van-Wyk</surname>
							<given-names>JA.</given-names>
						</name>
					</person-group>
					<year>2016</year>
					<article-title>The Pathophysiology, Ecology and Epidemiology of Haemonchus contortus Infection in Small Ruminants. Haemonchus contortus and Haemonchosis - Past, Present and Future</article-title>
					<source>Trends</source>
					<volume>93</volume>
					<fpage>95</fpage>
					<lpage>143</lpage>
					<issn>0065- 308X</issn>
					<pub-id pub-id-type="doi">10.1016/bs.apar.2016.02.022</pub-id>
				</element-citation>
			</ref>
			<ref id="B5">
				<mixed-citation>Broughan JM, Wall R. 2007. Faecal soiling and gastrointestinal helminth infection in lambs. International journal for parasitology. 37(11): 1255-68. ISSN: 0020-7519. https://doi.org/10.1016/j.ijpara.2007.03.009</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Broughan</surname>
							<given-names>JM</given-names>
						</name>
						<name>
							<surname>Wall</surname>
							<given-names>R.</given-names>
						</name>
					</person-group>
					<year>2007</year>
					<article-title>Faecal soiling and gastrointestinal helminth infection in lambs</article-title>
					<source>International journal for parasitology</source>
					<volume>37</volume>
					<issue>11</issue>
					<fpage>1255</fpage>
					<lpage>1268</lpage>
					<issn>0020-7519</issn>
					<pub-id pub-id-type="doi">10.1016/j.ijpara.2007.03.009</pub-id>
				</element-citation>
			</ref>
			<ref id="B6">
				<mixed-citation>Castro DCN, Castro DCN, Enríquez VI, Portillo LJJ, Gaxiola CSM. 2017. Prevalencia y factores de riesgo asociados a Cryptosporidium spp en corderos de pelo del municipio de Culiacán, Sinaloa, México. Revista Científica de la Facultad de Ciencias Veterinarias de la Universidad de Zulia. 27(4): 211-220. ISSN: 2477-944X. <ext-link ext-link-type="uri" xlink:href="https://www.redalyc.org/jatsRepo/959/95953011003/html/index.html">https://www.redalyc.org/jatsRepo/959/95953011003/html/index.html</ext-link>
				</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Castro</surname>
							<given-names>DCN</given-names>
						</name>
						<name>
							<surname>Castro</surname>
							<given-names>DCN</given-names>
						</name>
						<name>
							<surname>Enríquez</surname>
							<given-names>VI</given-names>
						</name>
						<name>
							<surname>Portillo</surname>
							<given-names>LJJ</given-names>
						</name>
						<name>
							<surname>Gaxiola</surname>
							<given-names>CSM.</given-names>
						</name>
					</person-group>
					<year>2017</year>
					<article-title>Prevalencia y factores de riesgo asociados a Cryptosporidium spp en corderos de pelo del municipio de Culiacán, Sinaloa, México</article-title>
					<source>Revista Científica de la Facultad de Ciencias Veterinarias de la Universidad de Zulia</source>
					<volume>27</volume>
					<issue>4</issue>
					<fpage>211</fpage>
					<lpage>220</lpage>
					<pub-id pub-id-type="doi">2477-944X</pub-id>
					<ext-link ext-link-type="uri" xlink:href="https://www.redalyc.org/jatsRepo/959/95953011003/html/index.html">https://www.redalyc.org/jatsRepo/959/95953011003/html/index.html</ext-link>
				</element-citation>
			</ref>
			<ref id="B7">
				<mixed-citation>Cériac S, Archimède H, Feuillet D, Félicité Y, Giorgi M, Bambou JC. 2019. Supplementation with rumen-protected proteins induces resistance to Haemonchus contortus in goats. Scientific Reports. 9(1): 1237. https://doi.org/10.1038/s41598-018-37800-3</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Cériac</surname>
							<given-names>S</given-names>
						</name>
						<name>
							<surname>Archimède</surname>
							<given-names>H</given-names>
						</name>
						<name>
							<surname>Feuillet</surname>
							<given-names>D</given-names>
						</name>
						<name>
							<surname>Félicité</surname>
							<given-names>Y</given-names>
						</name>
						<name>
							<surname>Giorgi</surname>
							<given-names>M</given-names>
						</name>
						<name>
							<surname>Bambou</surname>
							<given-names>JC.</given-names>
						</name>
					</person-group>
					<year>2019</year>
					<article-title>Supplementation with rumen-protected proteins induces resistance to Haemonchus contortus in goats</article-title>
					<source>Scientific Reports</source>
					<volume>9</volume>
					<issue>1</issue>
					<fpage>1237</fpage>
					<lpage>1237</lpage>
					<pub-id pub-id-type="doi">10.1038/s41598-018-37800-3</pub-id>
				</element-citation>
			</ref>
			<ref id="B8">
				<mixed-citation>CIAPAN (Centro de Investigaciones Agrícolas del Pacífico Norte). 2002. Guía para la asistencia técnica del Valle de Culiacán. Instituto Nacional de Investigaciones Agrícolas, Forestales y Pecuarias. Culiacán, Sinaloa, México. Pp. 92.</mixed-citation>
				<element-citation publication-type="book">
					<person-group person-group-type="author">
						<collab>CIAPAN (Centro de Investigaciones Agrícolas del Pacífico Norte)</collab>
					</person-group>
					<year>2002</year>
					<source>Guía para la asistencia técnica del Valle de Culiacán</source>
					<publisher-name>Instituto Nacional de Investigaciones Agrícolas, Forestales y Pecuarias</publisher-name>
					<publisher-loc>Culiacán, Sinaloa, México</publisher-loc>
				</element-citation>
			</ref>
			<ref id="B9">
				<mixed-citation>Garcia E. 2004. Modificaciones al sistema de clasificación climática de Köppen (para adaptarla a las condiciones climáticas de la República Mexicana). QuintaEdición. Instituto de Geografía. Universidad Nacional Autónoma de México. Pp. 144. ISBN 970- 32-1010-4.</mixed-citation>
				<element-citation publication-type="book">
					<person-group person-group-type="author">
						<name>
							<surname>Garcia</surname>
							<given-names>E.</given-names>
						</name>
					</person-group>
					<year>2004</year>
					<source>Modificaciones al sistema de clasificación climática de Köppen (para adaptarla a las condiciones climáticas de la República Mexicana)</source>
					<edition>Quinta</edition>
					<publisher-name>Instituto de Geografía. Universidad Nacional Autónoma de México</publisher-name>
					<fpage>144</fpage>
					<lpage>144</lpage>
					<isbn>970- 32-1010-4</isbn>
				</element-citation>
			</ref>
			<ref id="B10">
				<mixed-citation>Gaxiola CSM, Castro DCN, Borbolla IJE, Cárcamo ANM, Cota GSC, Villalba RJ E, Gaxiola MJ, Barraza TCL, Pérez CJA, Martínez T, Sosa GC, Meza TMA, Mimiaga LG, Rodríguez GMA. 2010. Frecuencia de parásitos gastrointestinales en ovinos del municipio de Culiacán, Sinaloa, México. 6° Seminario Internacional en Reproducción Animal y Producción de Leche y Carne. 2° Seminario Internacional de Avances en Producción Animal. Mazatlán, Sinaloa, México, 11 y 12 de marzo. Pp. 295.</mixed-citation>
				<element-citation publication-type="confproc">
					<person-group person-group-type="author">
						<name>
							<surname>Gaxiola</surname>
							<given-names>CSM</given-names>
						</name>
						<name>
							<surname>Castro</surname>
							<given-names>DCN</given-names>
						</name>
						<name>
							<surname>Borbolla</surname>
							<given-names>IJE</given-names>
						</name>
						<name>
							<surname>Cárcamo</surname>
							<given-names>ANM</given-names>
						</name>
						<name>
							<surname>Cota</surname>
							<given-names>GSC</given-names>
						</name>
						<name>
							<surname>Villalba RJ</surname>
							<given-names>E</given-names>
						</name>
						<name>
							<surname>Gaxiola</surname>
							<given-names>MJ</given-names>
						</name>
						<name>
							<surname>Barraza</surname>
							<given-names>TCL</given-names>
						</name>
						<name>
							<surname>Pérez</surname>
							<given-names>CJA</given-names>
						</name>
						<name>
							<surname>Martínez</surname>
							<given-names>T</given-names>
						</name>
						<name>
							<surname>Sosa</surname>
							<given-names>GC</given-names>
						</name>
						<name>
							<surname>Meza</surname>
							<given-names>TMA</given-names>
						</name>
						<name>
							<surname>Mimiaga</surname>
							<given-names>LG</given-names>
						</name>
						<name>
							<surname>Rodríguez</surname>
							<given-names>GMA.</given-names>
						</name>
					</person-group>
					<year>2010</year>
					<source>Frecuencia de parásitos gastrointestinales en ovinos del municipio de Culiacán, Sinaloa, México</source>
					<conf-name>6Seminario Internacional en Reproducción Animal y Producción de Leche y Carne. 2° Seminario Internacional de Avances en Producción Animal</conf-name>
					<conf-loc>Mazatlán, Sinaloa, México</conf-loc>
					<fpage>295</fpage>
					<lpage>295</lpage>
				</element-citation>
			</ref>
			<ref id="B11">
				<mixed-citation>Getachew T, Dorchies P, Jacquiet P. 2007. Trends and challenges in the effective and sustainable control of Haemonchus contortus infection in sheep. Review. Parasite-Journal De La Societe Francaise De Parasitologie. 14: 3-14. ISSN: 1252-607X. https://doi.org/10.1051/parasite/2007141003</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Getachew</surname>
							<given-names>T</given-names>
						</name>
						<name>
							<surname>Dorchies</surname>
							<given-names>P</given-names>
						</name>
						<name>
							<surname>Jacquiet</surname>
							<given-names>P.</given-names>
						</name>
					</person-group>
					<year>2007</year>
					<article-title>Trends and challenges in the effective and sustainable control of Haemonchus contortus infection in sheep</article-title>
					<source>Review. Parasite-Journal De La Societe Francaise De Parasitologie</source>
					<volume>14</volume>
					<fpage>3</fpage>
					<lpage>14</lpage>
					<issn>1252-607X</issn>
					<pub-id pub-id-type="doi">10.1051/parasite/2007141003</pub-id>
				</element-citation>
			</ref>
			<ref id="B12">
				<mixed-citation>González GR, Córdova PC, Torres HT, Mendoza GP, Arece GJ. 2011. Prevalencia de parásitos gastrointestinales en ovinos sacrificados en un rastro de Tabasco, México. Veterinaria México. 42: 125-135. ISSN: 0301-5092. <ext-link ext-link-type="uri" xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S0301-50922011000200003">http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S0301-50922011000200003</ext-link>
				</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>González</surname>
							<given-names>GR</given-names>
						</name>
						<name>
							<surname>Córdova</surname>
							<given-names>PC</given-names>
						</name>
						<name>
							<surname>Torres</surname>
							<given-names>HT</given-names>
						</name>
						<name>
							<surname>Mendoza</surname>
							<given-names>GP</given-names>
						</name>
						<name>
							<surname>Arece</surname>
							<given-names>GJ.</given-names>
						</name>
					</person-group>
					<year>2011</year>
					<article-title>Prevalencia de parásitos gastrointestinales en ovinos sacrificados en un rastro de Tabasco, México</article-title>
					<source>Veterinaria México</source>
					<volume>42</volume>
					<fpage>125</fpage>
					<lpage>135</lpage>
					<issn>0301-5092</issn>
					<ext-link ext-link-type="uri" xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S0301-50922011000200003">http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S0301-50922011000200003</ext-link>
				</element-citation>
			</ref>
			<ref id="B13">
				<mixed-citation>Hernández S, Segura I, Olivares PJ, Almazán MT. 2007. Prevalencia de nematodos gastrointestinales en ovinos en pastoreo en la parte alta del MPIO. de Cuetzala del Progreso, Guerrero-México. Redvet. 8(9): 1-7. ISSN: 1695-7504. <ext-link ext-link-type="uri" xlink:href="https://www.researchgate.net/publication/26475878_Prevalencia_de_nematodos_gastrointestinales_en_ovinos_en_pastoreo_en_la_parte_alta_del_MPIO_De_Cuetzala_del_Pr ogreso_Guerrero-Mexico">https://www.researchgate.net/publication/26475878_Prevalencia_de_nematodos_gastrointestinales_en_ovinos_en_pastoreo_en_la_parte_alta_del_MPIO_De_Cuetzala_del_Pr ogreso_Guerrero-Mexico</ext-link>
				</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Hernández</surname>
							<given-names>S</given-names>
						</name>
						<name>
							<surname>Segura</surname>
							<given-names>I</given-names>
						</name>
						<name>
							<surname>Olivares</surname>
							<given-names>PJ</given-names>
						</name>
						<name>
							<surname>Almazán</surname>
							<given-names>MT.</given-names>
						</name>
					</person-group>
					<year>2007</year>
					<article-title>Prevalencia de nematodos gastrointestinales en ovinos en pastoreo en la parte alta del MPIO. de Cuetzala del Progreso, Guerrero-México</article-title>
					<source>Redvet</source>
					<volume>8</volume>
					<issue>9</issue>
					<fpage>1</fpage>
					<lpage>7</lpage>
					<issn>1695-7504</issn>
					<ext-link ext-link-type="uri" xlink:href="https://www.researchgate.net/publication/26475878_Prevalencia_de_nematodos_gastrointestinales_en_ovinos_en_pastoreo_en_la_parte_alta_del_MPIO_De_Cuetzala_del_Pr ogreso_Guerrero-Mexico">https://www.researchgate.net/publication/26475878_Prevalencia_de_nematodos_gastrointestinales_en_ovinos_en_pastoreo_en_la_parte_alta_del_MPIO_De_Cuetzala_del_Pr ogreso_Guerrero-Mexico</ext-link>
				</element-citation>
			</ref>
			<ref id="B14">
				<mixed-citation>Herrera OL, Ríos OL, Zapata SR. 2013. Frecuencia de la infección por nemátodos gastrointestinales en ovinos y caprinos de cinco municipios de Antioquia. Revista MVZ Córdoba. 18(3): 3851-3860. ISSN: 0122-0268. https://doi.org/10.21897/rmvz.157</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Herrera</surname>
							<given-names>OL</given-names>
						</name>
						<name>
							<surname>Ríos</surname>
							<given-names>OL</given-names>
						</name>
						<name>
							<surname>Zapata</surname>
							<given-names>SR.</given-names>
						</name>
					</person-group>
					<year>2013</year>
					<article-title>Frecuencia de la infección por nemátodos gastrointestinales en ovinos y caprinos de cinco municipios de Antioquia</article-title>
					<source>Revista MVZ Córdoba</source>
					<volume>18</volume>
					<issue>3</issue>
					<fpage>3851</fpage>
					<lpage>3860</lpage>
					<issn>0122-0268</issn>
					<pub-id pub-id-type="doi">10.21897/rmvz.157</pub-id>
				</element-citation>
			</ref>
			<ref id="B15">
				<mixed-citation>Indre D, Dărăbuş GH, Oprescu I, Morariu S, Mederle N, Ilie MS, Imre M. 2010. Morphometrical studies on some eggs of gastrointestinal nematodes from sheep. Lucrări Ştiinłifice Medicină Veterinară. 1: 30-35. <ext-link ext-link-type="uri" xlink:href="https://www.usab-tm.ro/vol10MV/5_vol10.pdf">https://www.usab-tm.ro/vol10MV/5_vol10.pdf</ext-link>
				</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Indre</surname>
							<given-names>D</given-names>
						</name>
						<name>
							<surname>Dărăbuş</surname>
							<given-names>GH</given-names>
						</name>
						<name>
							<surname>Oprescu</surname>
							<given-names>I</given-names>
						</name>
						<name>
							<surname>Morariu</surname>
							<given-names>S</given-names>
						</name>
						<name>
							<surname>Mederle</surname>
							<given-names>N</given-names>
						</name>
						<name>
							<surname>Ilie</surname>
							<given-names>MS</given-names>
						</name>
						<name>
							<surname>Imre</surname>
							<given-names>M.</given-names>
						</name>
					</person-group>
					<year>2010</year>
					<article-title>Morphometrical studies on some eggs of gastrointestinal nematodes from sheep</article-title>
					<source>Lucrări Ştiinłifice Medicină Veterinară</source>
					<volume>1</volume>
					<fpage>30</fpage>
					<lpage>35</lpage>
					<ext-link ext-link-type="uri" xlink:href="https://www.usab-tm.ro/vol10MV/5_vol10.pdf">https://www.usab-tm.ro/vol10MV/5_vol10.pdf</ext-link>
				</element-citation>
			</ref>
			<ref id="B16">
				<mixed-citation>Jaramillo C, Martínez JJ. 2010. Epidemiologia veterinaria. España: Editorial el Manual Moderno. Pp 110-125. ISBN: 978-607-448-038-2. <ext-link ext-link-type="uri" xlink:href="https://www.manualmoderno.com/apoyos_electronicos/9786074480382/jaramillo_main_ p.php">https://www.manualmoderno.com/apoyos_electronicos/9786074480382/jaramillo_main_ p.php</ext-link>
				</mixed-citation>
				<element-citation publication-type="book">
					<person-group person-group-type="author">
						<name>
							<surname>Jaramillo</surname>
							<given-names>C</given-names>
						</name>
						<name>
							<surname>Martínez</surname>
							<given-names>JJ.</given-names>
						</name>
					</person-group>
					<year>2010</year>
					<source>Epidemiologia veterinaria</source>
					<publisher-loc>España</publisher-loc>
					<publisher-name>Editorial el Manual Moderno</publisher-name>
					<fpage>110</fpage>
					<lpage>125</lpage>
					<isbn>978-607-448-038-2</isbn>
					<ext-link ext-link-type="uri" xlink:href="https://www.manualmoderno.com/apoyos_electronicos/9786074480382/jaramillo_main_ p.php">https://www.manualmoderno.com/apoyos_electronicos/9786074480382/jaramillo_main_ p.php</ext-link>
				</element-citation>
			</ref>
			<ref id="B17">
				<mixed-citation>Kuma B, Abebe R, Mekbib B, Sheferaw D, Abera M. 2019. Prevalence and intensity of gastrointestinal nematodes infection in sheep and goats in semi-intensively managed farm, South Ethiopia. Journal of Veterinary Medicine and Animal Health. 11(1): 1-5. ISSN: 2141-2529. https://doi.org/10.5897/JVMAH2018.0705</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Kuma</surname>
							<given-names>B</given-names>
						</name>
						<name>
							<surname>Abebe</surname>
							<given-names>R</given-names>
						</name>
						<name>
							<surname>Mekbib</surname>
							<given-names>B</given-names>
						</name>
						<name>
							<surname>Sheferaw</surname>
							<given-names>D</given-names>
						</name>
						<name>
							<surname>Abera</surname>
							<given-names>M.</given-names>
						</name>
					</person-group>
					<year>2019</year>
					<article-title>Prevalence and intensity of gastrointestinal nematodes infection in sheep and goats in semi-intensively managed farm, South Ethiopia</article-title>
					<source>Journal of Veterinary Medicine and Animal Health</source>
					<volume>11</volume>
					<issue>1</issue>
					<fpage>1</fpage>
					<lpage>5</lpage>
					<issn>2141-2529</issn>
					<pub-id pub-id-type="doi">10.5897/JVMAH2018.0705</pub-id>
				</element-citation>
			</ref>
			<ref id="B18">
				<mixed-citation>Ljungström S, Melville L., Skuce PJ, Höglund J. 2018. Comparison of Four Diagnostic Methods for Detection and Relative Quantification of Haemonchus contortus Eggs in Feces Samples. Frontiers in veterinary science. 4: 239-239. ISSN: 2297-1769. https://doi.org/10.3389/fvets.2017.00239</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Ljungström</surname>
							<given-names>S</given-names>
						</name>
						<name>
							<surname>Melville</surname>
							<given-names>L.</given-names>
						</name>
						<name>
							<surname>Skuce</surname>
							<given-names>PJ</given-names>
						</name>
						<name>
							<surname>Höglund</surname>
							<given-names>J.</given-names>
						</name>
					</person-group>
					<year>2018</year>
					<article-title>Comparison of Four Diagnostic Methods for Detection and Relative Quantification of Haemonchus contortus Eggs in Feces Samples</article-title>
					<source>Frontiers in veterinary science</source>
					<volume>4</volume>
					<fpage>239</fpage>
					<lpage>239</lpage>
					<issn>2297-1769</issn>
					<pub-id pub-id-type="doi">10.3389/fvets.2017.00239</pub-id>
				</element-citation>
			</ref>
			<ref id="B19">
				<mixed-citation>Mahmood OI, Muhsin SN, Hussein M. 2019. Morphological Diagnosis for Some Eggs of Gastrointestinal Nematodes from Sheep. Tikrit Journal for Agricultural Sciences. 19(3): 6-9. ISSN: 2664-0597. <ext-link ext-link-type="uri" xlink:href="https://www.researchgate.net/publication/343738495_Morphological_Diagnosis_for_Some_Eggs_of_Gastrointestinal_Nematodes_from_Sheep">https://www.researchgate.net/publication/343738495_Morphological_Diagnosis_for_Some_Eggs_of_Gastrointestinal_Nematodes_from_Sheep</ext-link>
				</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Mahmood</surname>
							<given-names>OI</given-names>
						</name>
						<name>
							<surname>Muhsin</surname>
							<given-names>SN</given-names>
						</name>
						<name>
							<surname>Hussein</surname>
							<given-names>M.</given-names>
						</name>
					</person-group>
					<year>2019</year>
					<article-title>Morphological Diagnosis for Some Eggs of Gastrointestinal Nematodes from Sheep</article-title>
					<source>Tikrit Journal for Agricultural Sciences</source>
					<volume>19</volume>
					<issue>3</issue>
					<fpage>6</fpage>
					<lpage>9</lpage>
					<issn>2664-0597</issn>
					<ext-link ext-link-type="uri" xlink:href="https://www.researchgate.net/publication/343738495_Morphological_Diagnosis_for_Some_Eggs_of_Gastrointestinal_Nematodes_from_Sheep">https://www.researchgate.net/publication/343738495_Morphological_Diagnosis_for_Some_Eggs_of_Gastrointestinal_Nematodes_from_Sheep</ext-link>
				</element-citation>
			</ref>
			<ref id="B20">
				<mixed-citation>Medeiros KL, Lucio FA, Bowman DD. 2018. Evaluation of Parasite Egg and Cyst Recovery Using Devices Designed for Centrifugal or Stationary Flotation. J Am Anim Hosp Assoc. 54(1):36-45. https://doi.org/10.5326/JAAHA-MS-6549</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Medeiros</surname>
							<given-names>KL</given-names>
						</name>
						<name>
							<surname>Lucio</surname>
							<given-names>FA</given-names>
						</name>
						<name>
							<surname>Bowman</surname>
							<given-names>DD.</given-names>
						</name>
					</person-group>
					<year>2018</year>
					<article-title>Evaluation of Parasite Egg and Cyst Recovery Using Devices Designed for Centrifugal or Stationary Flotation</article-title>
					<source>J Am Anim Hosp Assoc</source>
					<volume>54</volume>
					<issue>1</issue>
					<fpage>36</fpage>
					<lpage>45</lpage>
					<pub-id pub-id-type="doi">10.5326/JAAHA-MS-6549</pub-id>
				</element-citation>
			</ref>
			<ref id="B21">
				<mixed-citation>Mederos A, Fernandez S, Vanleeuwen J, Peregrine AS, Kelton D, Menzies P, LeBoeuf A, Martin R. 2010. Prevalence and distribution of gastrointestinal nematodes on 32 organic and conventional commercial sheep farms in Ontario and Quebec, Canada (2006- 2008). Veterinary parasitology. 170: 244-52. ISSN: 0304-4017. https://doi.org/10.1016/j.vetpar.2010.02.018</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Mederos</surname>
							<given-names>A</given-names>
						</name>
						<name>
							<surname>Fernandez</surname>
							<given-names>S</given-names>
						</name>
						<name>
							<surname>Vanleeuwen</surname>
							<given-names>J</given-names>
						</name>
						<name>
							<surname>Peregrine</surname>
							<given-names>AS</given-names>
						</name>
						<name>
							<surname>Kelton</surname>
							<given-names>D</given-names>
						</name>
						<name>
							<surname>Menzies</surname>
							<given-names>P</given-names>
						</name>
						<name>
							<surname>LeBoeuf</surname>
							<given-names>A</given-names>
						</name>
						<name>
							<surname>Martin</surname>
							<given-names>R.</given-names>
						</name>
					</person-group>
					<year>2010</year>
					<article-title>Prevalence and distribution of gastrointestinal nematodes on 32 organic and conventional commercial sheep farms in Ontario and Quebec, Canada (2006- 2008)</article-title>
					<source>Veterinary parasitology</source>
					<volume>170</volume>
					<fpage>244</fpage>
					<lpage>252</lpage>
					<issn>0304-4017</issn>
					<pub-id pub-id-type="doi">10.1016/j.vetpar.2010.02.018</pub-id>
				</element-citation>
			</ref>
			<ref id="B22">
				<mixed-citation>Moghaddar N. 2008. Seasonal variation in the incidence of gastro-intestinal nematodes in sheep in Iran. Journal of Applied Animal Research. 34: 153-155. ISSN: 0974-1844. https://doi.org/10.1080/09712119.2008.9706961</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Moghaddar</surname>
							<given-names>N.</given-names>
						</name>
					</person-group>
					<year>2008</year>
					<article-title>Seasonal variation in the incidence of gastro-intestinal nematodes in sheep in Iran</article-title>
					<source>Journal of Applied Animal Research</source>
					<volume>34</volume>
					<fpage>153</fpage>
					<lpage>155</lpage>
					<issn>0974-1844</issn>
					<pub-id pub-id-type="doi">10.1080/09712119.2008.9706961</pub-id>
				</element-citation>
			</ref>
			<ref id="B23">
				<mixed-citation>Munguía XJ, Navarro GR, Hernández CJ, Molina BR, Cedillo CJ, Granados RJ. 2018. Parásitos gastroentéricos, población Haemonchus contortus en caprinos en clima semiárido de Bacum, Sonora, México. Abanico Veterinario. 8(3): 42-50. ISSN 2448-6132. http://dx.doi.org/10.21929/abavet2018.83.2</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Munguía</surname>
							<given-names>XJ</given-names>
						</name>
						<name>
							<surname>Navarro</surname>
							<given-names>GR</given-names>
						</name>
						<name>
							<surname>Hernández</surname>
							<given-names>CJ</given-names>
						</name>
						<name>
							<surname>Molina</surname>
							<given-names>BR</given-names>
						</name>
						<name>
							<surname>Cedillo</surname>
							<given-names>CJ</given-names>
						</name>
						<name>
							<surname>Granados</surname>
							<given-names>RJ.</given-names>
						</name>
					</person-group>
					<year>2018</year>
					<article-title>Parásitos gastroentéricos, población Haemonchus contortus en caprinos en clima semiárido de Bacum, Sonora, México</article-title>
					<source>Abanico Veterinario</source>
					<volume>8</volume>
					<issue>3</issue>
					<fpage>42</fpage>
					<lpage>50</lpage>
					<issn>2448-6132</issn>
					<pub-id pub-id-type="doi">10.21929/abavet2018.83.2</pub-id>
				</element-citation>
			</ref>
			<ref id="B24">
				<mixed-citation>Musella V, Catelan D, Rinaldi L, Lagazio C, Cringoli G, Biggeri A. 2011. Covariate selection in multivariate spatial analysis of ovine parasitic infection. Preventive veterinary medicine. 99: 69-77. ISSN: 1873-1716. https://doi.org/10.1016/j.prevetmed.2010.11.012</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Musella</surname>
							<given-names>V</given-names>
						</name>
						<name>
							<surname>Catelan</surname>
							<given-names>D</given-names>
						</name>
						<name>
							<surname>Rinaldi</surname>
							<given-names>L</given-names>
						</name>
						<name>
							<surname>Lagazio</surname>
							<given-names>C</given-names>
						</name>
						<name>
							<surname>Cringoli</surname>
							<given-names>G</given-names>
						</name>
						<name>
							<surname>Biggeri</surname>
							<given-names>A.</given-names>
						</name>
					</person-group>
					<year>2011</year>
					<article-title>Covariate selection in multivariate spatial analysis of ovine parasitic infection</article-title>
					<source>Preventive veterinary medicine</source>
					<volume>99</volume>
					<fpage>69</fpage>
					<lpage>77</lpage>
					<issn>1873-1716</issn>
					<pub-id pub-id-type="doi">10.1016/j.prevetmed.2010.11.012</pub-id>
				</element-citation>
			</ref>
			<ref id="B25">
				<mixed-citation>Naeem M, Iqbal Z., Roohi N. 2020. Ovine haemonchosis: a review. Tropical Animal Health and Production. 53(1): 19. https://doi.org/10.1007/s11250-020-02439-8</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Naeem</surname>
							<given-names>M</given-names>
						</name>
						<name>
							<surname>Iqbal</surname>
							<given-names>Z.</given-names>
						</name>
						<name>
							<surname>Roohi</surname>
							<given-names>N.</given-names>
						</name>
					</person-group>
					<year>2020</year>
					<article-title>Ovine haemonchosis: a review</article-title>
					<source>Tropical Animal Health and Production</source>
					<volume>53</volume>
					<issue>1</issue>
					<fpage>19</fpage>
					<lpage>19</lpage>
					<pub-id pub-id-type="doi">10.1007/s11250-020-02439-8</pub-id>
				</element-citation>
			</ref>
			<ref id="B26">
				<mixed-citation>O'connor LJ, Walkden BSW, Kahn LP. 2006. Ecology of the free-living stages of major trichostrongylid parasites of sheep. Veterinary Parasitology. 142: 1-15. ISSN: 0304-4017. https://doi.org/10.1016/j.vetpar.2006.08.035</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>O'connor</surname>
							<given-names>LJ</given-names>
						</name>
						<name>
							<surname>Walkden</surname>
							<given-names>BSW</given-names>
						</name>
						<name>
							<surname>Kahn</surname>
							<given-names>LP.</given-names>
						</name>
					</person-group>
					<year>2006</year>
					<article-title>Ecology of the free-living stages of major trichostrongylid parasites of sheep</article-title>
					<source>Veterinary Parasitology</source>
					<volume>142</volume>
					<fpage>1</fpage>
					<lpage>15</lpage>
					<issn>0304-4017</issn>
					<pub-id pub-id-type="doi">10.1016/j.vetpar.2006.08.035</pub-id>
				</element-citation>
			</ref>
			<ref id="B27">
				<mixed-citation>Rinaldi L, Coles GC, Maurelli MP, Musella V, Cringoli G. 2011. Calibration and diagnostic accuracy of simple flotation, McMaster and FLOTAC for parasite egg counts in sheep. Vet Parasitol. 177(3-4): 345-52. https://doi.org/10.1016/j.vetpar.2010.12.010</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Rinaldi</surname>
							<given-names>L</given-names>
						</name>
						<name>
							<surname>Coles</surname>
							<given-names>GC</given-names>
						</name>
						<name>
							<surname>Maurelli</surname>
							<given-names>MP</given-names>
						</name>
						<name>
							<surname>Musella</surname>
							<given-names>V</given-names>
						</name>
						<name>
							<surname>Cringoli</surname>
							<given-names>G.</given-names>
						</name>
					</person-group>
					<year>2011</year>
					<article-title>Calibration and diagnostic accuracy of simple flotation, McMaster and FLOTAC for parasite egg counts in sheep</article-title>
					<source>Vet Parasitol</source>
					<volume>177</volume>
					<issue>3-4</issue>
					<fpage>345</fpage>
					<lpage>352</lpage>
					<pub-id pub-id-type="doi">10.1016/j.vetpar.2010.12.010</pub-id>
				</element-citation>
			</ref>
			<ref id="B28">
				<mixed-citation>Rinaldi L, Catelan D, Musella V, Cecconi L, Hertzberg H, Torgerson PR, Mavrot F, De Waal T, Selemetas N, Coll T, Bosco A, Biggeri A, Cringoli G. 2015. Haemonchus contortus: spatial risk distribution for infection in sheep in Europe. Geospatial Health. 9(2): 325-331. ISSN: 1970-7096. https://doi.org/10.4081/gh.2015.355</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Rinaldi</surname>
							<given-names>L</given-names>
						</name>
						<name>
							<surname>Catelan</surname>
							<given-names>D</given-names>
						</name>
						<name>
							<surname>Musella</surname>
							<given-names>V</given-names>
						</name>
						<name>
							<surname>Cecconi</surname>
							<given-names>L</given-names>
						</name>
						<name>
							<surname>Hertzberg</surname>
							<given-names>H</given-names>
						</name>
						<name>
							<surname>Torgerson</surname>
							<given-names>PR</given-names>
						</name>
						<name>
							<surname>Mavrot</surname>
							<given-names>F</given-names>
						</name>
						<name>
							<surname>De Waal</surname>
							<given-names>T</given-names>
						</name>
						<name>
							<surname>Selemetas</surname>
							<given-names>N</given-names>
						</name>
						<name>
							<surname>Coll</surname>
							<given-names>T</given-names>
						</name>
						<name>
							<surname>Bosco</surname>
							<given-names>A</given-names>
						</name>
						<name>
							<surname>Biggeri</surname>
							<given-names>A</given-names>
						</name>
						<name>
							<surname>Cringoli</surname>
							<given-names>G.</given-names>
						</name>
					</person-group>
					<year>2015</year>
					<article-title>Haemonchus contortus: spatial risk distribution for infection in sheep in Europe</article-title>
					<source>Geospatial Health</source>
					<volume>9</volume>
					<issue>2</issue>
					<fpage>325</fpage>
					<lpage>331</lpage>
					<issn>1970-7096</issn>
					<pub-id pub-id-type="doi">10.4081/gh.2015.355</pub-id>
				</element-citation>
			</ref>
			<ref id="B29">
				<mixed-citation>Saccareau M, Salle G, Robert-Granie C, Duchemin T, Jacquiet P, Blanchard A, Cabaret J, Moreno CR. 2017. Meta-analysis of the parasitic phase traits of Haemonchus contortus infection in sheep. Parasites &amp; Vectors. (10): 201. ISSN: 1756-3305. https://doi.org/10.1186/S13071-017-2131-7</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Saccareau</surname>
							<given-names>M</given-names>
						</name>
						<name>
							<surname>Salle</surname>
							<given-names>G</given-names>
						</name>
						<name>
							<surname>Robert-Granie</surname>
							<given-names>C</given-names>
						</name>
						<name>
							<surname>Duchemin</surname>
							<given-names>T</given-names>
						</name>
						<name>
							<surname>Jacquiet</surname>
							<given-names>P</given-names>
						</name>
						<name>
							<surname>Blanchard</surname>
							<given-names>A</given-names>
						</name>
						<name>
							<surname>Cabaret</surname>
							<given-names>J</given-names>
						</name>
						<name>
							<surname>Moreno</surname>
							<given-names>CR.</given-names>
						</name>
					</person-group>
					<year>2017</year>
					<article-title>Meta-analysis of the parasitic phase traits of Haemonchus contortus infection in sheep</article-title>
					<source>Parasites &amp; Vectors</source>
					<issue>10</issue>
					<fpage>201</fpage>
					<lpage>201</lpage>
					<issn>1756-3305</issn>
					<pub-id pub-id-type="doi">10.1186/S13071-017-2131-7</pub-id>
				</element-citation>
			</ref>
			<ref id="B30">
				<mixed-citation>SIAP (Servicio de Información Agroalimentaria y Pesquera). 2013. Población ganadera ovina. Culiacán, Sinaloa, México. <ext-link ext-link-type="uri" xlink:href="https://nube.siap.gob.mx/cierre_pecuario/">https://nube.siap.gob.mx/cierre_pecuario/</ext-link>
				</mixed-citation>
				<element-citation publication-type="webpage">
					<person-group person-group-type="author">
						<collab>SIAP (Servicio de Información Agroalimentaria y Pesquera)</collab>
					</person-group>
					<year>2013</year>
					<source>Población ganadera ovina</source>
					<publisher-loc>Culiacán, Sinaloa, México</publisher-loc>
					<ext-link ext-link-type="uri" xlink:href="https://nube.siap.gob.mx/cierre_pecuario/">https://nube.siap.gob.mx/cierre_pecuario/</ext-link>
				</element-citation>
			</ref>
			<ref id="B31">
				<mixed-citation>Soca M, Roque E, Soca M. 2005. Epizootiología de los nematodos gastrointestinales de los bovinos jóvenes. Pastos y Forrajes. 28: 175-185. ISSN: 0864-0394. <ext-link ext-link-type="uri" xlink:href="https://www.redalyc.org/pdf/2691/269121675001.pdf">https://www.redalyc.org/pdf/2691/269121675001.pdf</ext-link>
				</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Soca</surname>
							<given-names>M</given-names>
						</name>
						<name>
							<surname>Roque</surname>
							<given-names>E</given-names>
						</name>
						<name>
							<surname>Soca</surname>
							<given-names>M.</given-names>
						</name>
					</person-group>
					<year>2005</year>
					<article-title>Epizootiología de los nematodos gastrointestinales de los bovinos jóvenes</article-title>
					<source>Pastos y Forrajes</source>
					<volume>28</volume>
					<fpage>175</fpage>
					<lpage>185</lpage>
					<issn>0864-0394</issn>
					<ext-link ext-link-type="uri" xlink:href="https://www.redalyc.org/pdf/2691/269121675001.pdf">https://www.redalyc.org/pdf/2691/269121675001.pdf</ext-link>
				</element-citation>
			</ref>
			<ref id="B32">
				<mixed-citation>Tariq KA, Chishti MZ, Ahmad F, Shawl AS. 2008. Epidemiology of gastrointestinal nematodes of sheep managed under traditional husbandry system in Kashmir valley. Veterinary parasitology. (158): 138-143. ISSN: 0304-4017. https://doi.org/10.1016/j.vetpar.2008.06.013</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Tariq</surname>
							<given-names>KA</given-names>
						</name>
						<name>
							<surname>Chishti</surname>
							<given-names>MZ</given-names>
						</name>
						<name>
							<surname>Ahmad</surname>
							<given-names>F</given-names>
						</name>
						<name>
							<surname>Shawl</surname>
							<given-names>AS.</given-names>
						</name>
					</person-group>
					<year>2008</year>
					<article-title>Epidemiology of gastrointestinal nematodes of sheep managed under traditional husbandry system in Kashmir valley</article-title>
					<source>Veterinary parasitology</source>
					<issue>158</issue>
					<fpage>138</fpage>
					<lpage>143</lpage>
					<issn>0304-4017</issn>
					<pub-id pub-id-type="doi">10.1016/j.vetpar.2008.06.013</pub-id>
				</element-citation>
			</ref>
			<ref id="B33">
				<mixed-citation>Tramboo SR, Shahardar RA, Allaie IM, Wani ZA, Bushra MS. 2015. Prevalence of gastrointestinal helminth infections in ovine population of Kashmir Valley. Veterinary world. 8(10): 1199-1204. ISSN: 0972-8988. https://doi.org/10.14202/vetworld.2015.1199-1204</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Tramboo</surname>
							<given-names>SR</given-names>
						</name>
						<name>
							<surname>Shahardar</surname>
							<given-names>RA</given-names>
						</name>
						<name>
							<surname>Allaie</surname>
							<given-names>IM</given-names>
						</name>
						<name>
							<surname>Wani</surname>
							<given-names>ZA</given-names>
						</name>
						<name>
							<surname>Bushra</surname>
							<given-names>MS.</given-names>
						</name>
					</person-group>
					<year>2015</year>
					<article-title>Prevalence of gastrointestinal helminth infections in ovine population of Kashmir Valley</article-title>
					<source>Veterinary world</source>
					<volume>8</volume>
					<issue>10</issue>
					<fpage>1199</fpage>
					<lpage>1204</lpage>
					<issn>0972-8988</issn>
					<pub-id pub-id-type="doi">10.14202/vetworld.2015.1199-1204</pub-id>
				</element-citation>
			</ref>
			<ref id="B34">
				<mixed-citation>Vieira VD, Vilela VL, Feitosa TF, Athayde AC, Azevedo SS, Souto DV, Silveira GL, Melo LR. 2014. Sheep gastrointestinal helminthiasis in the Sertão region of Paraíba State, Northeastern Brazil: prevalence and risk factors. Brazilian journal of veterinary parasitology. 23(4): 488-494. ISSN: 0103-846X. https://doi.org/10.1590/s1984-29612014089</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Vieira</surname>
							<given-names>VD</given-names>
						</name>
						<name>
							<surname>Vilela</surname>
							<given-names>VL</given-names>
						</name>
						<name>
							<surname>Feitosa</surname>
							<given-names>TF</given-names>
						</name>
						<name>
							<surname>Athayde</surname>
							<given-names>AC</given-names>
						</name>
						<name>
							<surname>Azevedo</surname>
							<given-names>SS</given-names>
						</name>
						<name>
							<surname>Souto</surname>
							<given-names>DV</given-names>
						</name>
						<name>
							<surname>Silveira</surname>
							<given-names>GL</given-names>
						</name>
						<name>
							<surname>Melo</surname>
							<given-names>LR.</given-names>
						</name>
					</person-group>
					<year>2014</year>
					<article-title>Sheep gastrointestinal helminthiasis in the Sertão region of Paraíba State, Northeastern Brazil: prevalence and risk factors</article-title>
					<source>Brazilian journal of veterinary parasitology</source>
					<volume>23</volume>
					<issue>4</issue>
					<fpage>488</fpage>
					<lpage>494</lpage>
					<issn>0103-846X</issn>
					<pub-id pub-id-type="doi">10.1590/s1984-29612014089</pub-id>
				</element-citation>
			</ref>
			<ref id="B35">
				<mixed-citation>Zajac AM, Conboy GA. 2011. Veterinary clinical parasitology. Iowa, USA: Editorial John Wiley &amp; Sons, Inc. Pp. 354. ISBN: 978-0-8138-2053-8. <ext-link ext-link-type="uri" xlink:href="https://www.wiley.com/en-ad/Veterinary+Clinical+Parasitology%2C+8th+Edition-p-9780813820538">https://www.wiley.com/en-ad/Veterinary+Clinical+Parasitology%2C+8th+Edition-p-9780813820538</ext-link>
				</mixed-citation>
				<element-citation publication-type="webpage">
					<person-group person-group-type="author">
						<name>
							<surname>Zajac</surname>
							<given-names>AM</given-names>
						</name>
						<name>
							<surname>Conboy</surname>
							<given-names>GA.</given-names>
						</name>
					</person-group>
					<year>2011</year>
					<source>Veterinary clinical parasitology</source>
					<publisher-loc>Iowa, USA</publisher-loc>
					<publisher-name>Editorial John Wiley &amp; Sons, Inc</publisher-name>
					<fpage>354</fpage>
					<lpage>354</lpage>
					<isbn>978-0-8138-2053-8</isbn>
					<ext-link ext-link-type="uri" xlink:href="https://www.wiley.com/en-ad/Veterinary+Clinical+Parasitology%2C+8th+Edition-p-9780813820538">https://www.wiley.com/en-ad/Veterinary+Clinical+Parasitology%2C+8th+Edition-p-9780813820538</ext-link>
				</element-citation>
			</ref>
			<ref id="B36">
				<mixed-citation>Zapata SR, Velásquez VR, Herrera OLV, Ríos OL, Polanco EDN. 2016. Prevalencia de nematodos gastrointestinales en sistemas de producción ovina y caprina bajo confinamiento, semiconfinamiento y pastoreo en municipios de Antioquia, Colombia. Revista de Investigaciones Veterinarias del Perú. 27(2): 344-354. ISSN: 1609-9117. https://doi.org/10.15381/rivep.v27i2.11647</mixed-citation>
				<element-citation publication-type="journal">
					<person-group person-group-type="author">
						<name>
							<surname>Zapata</surname>
							<given-names>SR</given-names>
						</name>
						<name>
							<surname>Velásquez</surname>
							<given-names>VR</given-names>
						</name>
						<name>
							<surname>Herrera</surname>
							<given-names>OLV</given-names>
						</name>
						<name>
							<surname>Ríos</surname>
							<given-names>OL</given-names>
						</name>
						<name>
							<surname>Polanco</surname>
							<given-names>EDN</given-names>
						</name>
					</person-group>
					<year>2016</year>
					<article-title>Prevalencia de nematodos gastrointestinales en sistemas de producción ovina y caprina bajo confinamiento, semiconfinamiento y pastoreo en municipios de Antioquia, Colombia</article-title>
					<source>Revista de Investigaciones Veterinarias del Perú</source>
					<volume>27</volume>
					<issue>2</issue>
					<fpage>344</fpage>
					<lpage>354</lpage>
					<issn>1609-9117</issn>
					<pub-id pub-id-type="doi">10.15381/rivep.v27i2.11647</pub-id>
				</element-citation>
			</ref>
		</ref-list>
		<fn-group>
			<fn fn-type="other" id="fn1">
				
				<p>Clave: e2021-49.</p>
			</fn>
		</fn-group>
	</back>
	<sub-article article-type="translation" id="s1" xml:lang="en">
		<front-stub>
			<article-categories>
				<subj-group subj-group-type="heading">
					<subject>Original Article</subject>
				</subj-group>
			</article-categories>
			<title-group>
				<article-title>Environmental factors associated with the prevalence of Haemonchus spp in lambs from the central zone of Sinaloa</article-title>
			</title-group>
			<abstract>
				<title>ABSTRACT</title>
				<p>Sheep are a species exploited in different areas of production. They are prone to different pathogens, highlighting parasites such as Haemonchus contortus. The prevailing climate and husbandry management practices are considered the main factors driving the spatial and temporal distribution of the nematode. Its distribution is worldwide, causing economic losses due to morbidity and mortality, and prevalence studies have been reported in different countries such as India, Spain, Nigeria, and Mexico; therefore, the aim of this study was to determine the edaphoclimatic factors of different zones from Culiacan municipality and the production system that influence the prevalence of Haemonchus spp. in lambs. The research was carried out in Culiacan municipality, Sinaloa, Mexico, over a period of one year. It was an observational study, which included 23 sheep production units distributed in 10 districts of the municipality, with a total of 1520 samples of feces from animals under 3 months of age. Feces were processed individually by flotation technique. The overall prevalence was 13.42 %, and the autumn season (OR 2.38 (1.69-3.34) P&lt;0.001), valley zone (OR 2.70 (1.21-6.02); P&lt;0.016) and extensive system (OR 4.81 (3.38-6.85); P&lt;0.0001) were risk factors associated with the presence of the nematode in lambs, so they should be considered for the establishment of preventive measures and control of parasitosis.</p>
			</abstract>
			<kwd-group xml:lang="en">
				<title>Keywords:</title>
				<kwd>Haemonchus</kwd>
				<kwd>prevalence</kwd>
				<kwd>sheep</kwd>
				<kwd>risk factor</kwd>
				<kwd>gastrointestinal nematode</kwd>
			</kwd-group>
		</front-stub>
		<body>
			<sec sec-type="intro">
				<title>INTRODUCTION</title>
				<p>Gastrointestinal nematode infections affect the health of small ruminants compromising their production and reproduction, more frequently in young developing animals, causing low weight gain and growth retardation, making them one of the main causes of economic losses (<xref ref-type="bibr" rid="B12">González et al., 2011</xref>; <xref ref-type="bibr" rid="B2">Asmare et al., 2016</xref>; <xref ref-type="bibr" rid="B17">Kuma et al., 2019</xref>), mainly in the costs incurred in treatment and control (<xref ref-type="bibr" rid="B33">Tramboo et al., 2015</xref>). Sheep are generally more prone to gastrointestinal parasitism, due to their feeding on larvae 3 contaminated pastures (<xref ref-type="bibr" rid="B32">Tariq et al., 2008</xref>). Among gastrointestinal parasites, Haemonchus is the species with the highest economic importance (<xref ref-type="bibr" rid="B28">Rinaldi et al., 2015</xref>). This nematode is located in the abomasum, feeds on the blood of sheep and goats, can be found in other ruminants such as cattle (<xref ref-type="bibr" rid="B11">Getachew et al., 2007</xref>), it is among the most pathogenic in sheep (<xref ref-type="bibr" rid="B4">Besier et al., 2016</xref>), its extensive geographical distribution and resistance against anthelmintic control measures makes it a threat to the sustainability of sheep farming (<xref ref-type="bibr" rid="B29">Saccareau et al., 2017</xref>). The rainy season favors its frequency, with animals grazing during the early morning hours (<xref ref-type="bibr" rid="B21">Mederos et al., 2010</xref>), the prevailing climate (temperature, rain and humidity) and management practices in husbandry are considered the main factors driving its distribution (<xref ref-type="bibr" rid="B28">Rinaldi et al., 2015</xref>); its distribution is heterogeneous and depends on variables that differ from one area to another, even from one farm to another, such as management, prevention and control (<xref ref-type="bibr" rid="B24">Musella et al., 2011</xref>). On the other hand, studies on the prevalence in grazing animals is high in areas with tropical climates in both hemispheres (<xref ref-type="bibr" rid="B26">O´connor et al., 2006</xref>), young animals and pregnant females are more susceptible to helminths as opposed to adult animals due to their nutritional status and low level of immunity (<xref ref-type="bibr" rid="B34">Vieira et al., 2014</xref>). The prevalence of Haemonchus has been reported worldwide, in India <xref ref-type="bibr" rid="B33">Tramboo et al. (2015)</xref> out of a total of 1200 animals sampled 55 % were positive to the nematode; in Mexico, 32 % were found positive out of 219 sampled from grazing sheep (<xref ref-type="bibr" rid="B13">Hernández et al., 2007</xref>); in the Sinaloa region when analyzing 120 sheep from an extensive production system a frequency of 17.5 % was reported (<xref ref-type="bibr" rid="B10">Gaxiola et al., 2010</xref>). Therefore, the aim of this study was to determine the edaphoclimatic factors of different zones from Culiacán municipality and the production system that influence the prevalence of Haemonchus spp. in lambs in the central zone of Sinaloa.</p>
			</sec>
			<sec sec-type="materials">
				<title>MATERIAL AND MHETHODS</title>
				<sec>
					<title>Study area</title>
					<p>The study was carried out in Culiacán municipality, Sinaloa, Mexico (24º 46' 13'' NL and 107º 21' 14'' WL). The region is characterized by a BS1 (h') w(w)(e) climate, defined as semi-dry, very warm, with rainfall in summer, according to the Köppen classification and modified by García (2004); with an average annual temperature of 25. 9 ºC, with an average maximum of 30.4 ºC in June and July, and an average minimum of 20.6 ºC in January; the average relative humidity is 68%, with a maximum of 81% in September and a minimum of 51% in April; the average annual rainfall is 688.5 mm (<xref ref-type="bibr" rid="B8">CIAPAN, 2002</xref>).</p>
				</sec>
				<sec>
					<title>Type of study and sample size</title>
					<p>This is an observational, cross-sectional, descriptive study. Twenty-three extensive, semi- intensive and intensive ranches were sampled. In the municipality of Culiacán, 125 Sheep Production Units (SPU) are registered (<xref ref-type="bibr" rid="B30">SIAP, 2013</xref>), so the sample represented 18.4% of the SPUs. Ten of the 18 districts of Culiacán municipality, Sinaloa were considered (Figure. 1), the selection of the production units was made by convenience, based on the cooperation of the owner and ease of access. The sample size was determined with the following formula:</p>
					<p>
					<fig id="f2">
						<label>Figure 1</label>
						<caption>
							<title>Location of the sheep production unit sampled in Culiacán Municipality, Sinaloa Mexico.</title>
						</caption>
						<graphic xlink:href="2448-6132-av-11-e128-gf2.gif"/>
					</fig>
					</p>
					<disp-formula id="e3"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" ><mml:mi>n</mml:mi><mml:mo>=</mml:mo><mml:mfrac><mml:mrow><mml:msup><mml:mrow><mml:mi>Z</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup><mml:mi>p</mml:mi><mml:mi>q</mml:mi></mml:mrow><mml:mrow><mml:msup><mml:mrow><mml:mi>B</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:mfrac></mml:math></disp-formula>
					
					<p>Where: n is the sample size, Z is 1.96 for 95 % confidence, p is the expected frequency of the factor to be studied, q is 1-p, B is precision or admitted error (<xref ref-type="bibr" rid="B16">Jaramillo &amp; Martínez, 2010</xref>). The calculated sample size was 380 feces samples in each season (summer, fall, winter and spring) and because the number of lambs in the production unit was unknown at the time of the visit, the number of adults was considered (<xref ref-type="table" rid="t4">Table 1</xref>), and a number of lambs representing at least 10% of the adults in each production unit was sampled, which were randomly selected to complete the calculated sample size. Sampling was conducted by time of year and a total of 1520 samples were obtained from lambs less than ninety days (d) of age.</p>
					<p>
						<table-wrap id="t4">
							<label>Table 1</label>
							<caption>
								<title>Location of sheep production unit by district and population of adult sheep</title>
							</caption>
							<table>
								<colgroup>
									<col/>
									<col/>
									<col/>
									<col/>
								</colgroup>
								<thead>
									<tr>
										<th align="center">District</th>
										<th align="center">*SPU</th>
										<th align="center">Adult sheep</th>
										<th align="center">Lambs sampled</th>
									</tr>
								</thead>
								<tbody>
									<tr>
										<td align="center">Villa Adolfo L.M</td>
										<td align="center">Agrícola Limón <p>La Hacienda</p><p>La granjita</p><p>Alboradas</p></td>
										<td align="center"><p>80</p><p>150</p><p>120</p> 180</td>
										<td align="center"><p>10</p><p>20</p><p>17</p><p>18</p></td>
									</tr>
									<tr>
										<td align="center">El Salado</td>
										<td align="center">El alacrán</td>
										<td align="center">70</td>
										<td align="center">11</td>
									</tr>
									<tr>
										<td align="center">Costa Rica</td>
										<td align="center">El trabajo <p>Agrícola Sanfer</p><p>Agrícola Tabachines</p></td>
										<td align="center"><p>20</p><p>150</p><p>180</p></td>
										<td align="center"><p>5</p><p>15</p><p>18</p></td>
									</tr>
									<tr>
										<td align="center">Quilá</td>
										<td align="center">Naranjos<p>La Loma</p></td>
										<td align="center">70 <p>30</p></td>
										<td align="center">12<p>5</p></td>
									</tr>
									<tr>
										<td align="center">Aguaruto</td>
										<td align="center">Fetasas <p>Agrícola del Río</p><p>Los Cabritos</p></td>
										<td align="center"><p>200</p> <p>45</p><p> 200</p></td>
										<td align="center"><p>22</p><p>5</p><p>20</p></td>
									</tr>
									<tr>
										<td align="center">Culiacancito</td>
										<td align="center">San Sebastián <p>Agrícola Quiroz</p><p>Los Otates</p></td>
										<td align="center">250<p>250</p><p>180</p></td>
										<td align="center">25<p>25</p><p>20</p></td>
									</tr>
									<tr>
										<td align="center">Las Tapias</td>
										<td align="center">Santa María</td>
										<td align="center">130</td>
										<td align="center">13</td>
									</tr>
									<tr>
										<td align="center">Sanalona</td>
										<td align="center">Baldomero</td>
										<td align="center">20</td>
										<td align="center">5</td>
									</tr>
									<tr>
										<td align="center">Imala</td>
										<td align="center">Guayacanes</td>
										<td align="center">200</td>
										<td align="center">24</td>
									</tr>
									<tr>
										<td align="center">Culiacán</td>
										<td align="center">Guásima <p>Agrícola Mojolo</p><p>Ganadera Verdugo</p><p>Campo Morelia</p></td>
										<td align="center">230<p>300</p><p>80</p>180</td>
										<td align="center">23<p>32</p><p>15</p>20</td>
									</tr>
								</tbody>
							</table>
							<table-wrap-foot>
								<fn id="TFN4">
									<p>*SPU= Sheep Production Units</p>
								</fn>
							</table-wrap-foot>
						</table-wrap>
					</p>
				</sec>
				<sec>
					<title>Sample collection and laboratory analysis</title>
					<p>During each visit to the production units, a form was filled out to record information on the following factors: time of year (summer, fall, winter or spring), location (highlands or valley), production system (intensive, semi-intensive, extensive). The lambs were chosen randomly. Feces were taken directly from the rectum with a latex glove, individually identified, and refrigerated in containers at 4 ºC with ice and refrigerants for transfer to the Parasitology laboratory of the Faculty of Veterinary Medicine and Animal Husbandry for processing and analysis.</p>
					<p>The diagnosis of Haemonchus spp was performed by coproparasitoscopic analysis using the qualitative Faust flotation technique (<xref ref-type="bibr" rid="B35">Zajac &amp; Conboy, 2011</xref>), being a useful and widely used means in preliminary studies to determine what types of parasites are present in fecal samples (<xref ref-type="bibr" rid="B20">Medeiros et al., 2018</xref>), for parasite detection, optical microscopy with 10x and 40x objectives was used, eggs were identified based on their characteristic morphology, dark brown blastomeres and size described by <xref ref-type="bibr" rid="B18">Ljungström et al., 2018</xref>.</p>
				</sec>
				<sec>
					<title>Statistical analysis</title>
					<p>Lambs were considered positive with at least one Haemonchus spp egg; prevalence was estimated as the number of positive sheep among the total sheep sampled according to category.</p>
					<p>The results of microscopic observation (positive or negative) were summarized in contingency tables by factor and analyzed for association between the result and the factor, using the Chi-squared test. Statistical difference was considered statistical difference with a P≤0.05.</p>
					<p>For factors with more than two categories, the results were dichotomized. Next, to determine the risk factors for positive results, multivariate logistic regression analysis was applied. The general model was:</p>
					<disp-formula id="e4"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" ><mml:mi>π</mml:mi><mml:mfenced separators="|"><mml:mrow><mml:mi>x</mml:mi></mml:mrow></mml:mfenced><mml:mo>=</mml:mo><mml:mfrac><mml:mrow><mml:mrow><mml:mrow><mml:mi mathvariant="normal">exp</mml:mi></mml:mrow><mml:mo>⁡</mml:mo><mml:mrow><mml:mo>(</mml:mo><mml:mi>α</mml:mi><mml:mo>+</mml:mo><mml:mi mathvariant="normal">Σ</mml:mi><mml:mi>β</mml:mi><mml:mi>i</mml:mi><mml:mi>x</mml:mi><mml:mi>i</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:mrow></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mo>+</mml:mo><mml:mi mathvariant="normal">e</mml:mi><mml:mi mathvariant="normal">x</mml:mi><mml:mi mathvariant="normal">p</mml:mi><mml:mo>⁡</mml:mo><mml:mo>(</mml:mo><mml:mi>α</mml:mi><mml:mo>+</mml:mo><mml:mi mathvariant="normal">Σ</mml:mi><mml:mi>β</mml:mi><mml:mi>i</mml:mi><mml:mi>x</mml:mi><mml:mi>i</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:mfrac></mml:math></disp-formula>
					<p>Where: π (x), the value of π can vary as the value of x changes, and we want to describe its dependence; the values of xi = (x1,...,xp) are the predictor variables p, xi represents the vector of independent variables; exp is the base of the natural logarithms 2.71828; α is the value of the intercept; βi are the values of the regression coefficients. For this analysis, the LOGISTIC procedure (SAS, 2001) with the backward option was used to estimate the degree of association [odds ratio (OR)] and confidence intervals. The alpha level to consider association between the factor with the positive outcome, and to estimate the risk factor was P ≤ 0.05.</p>
				</sec>
			</sec>
			<sec sec-type="results|discussion">
				<title>RESULTS AND DISCUSSION</title>
				<p>From a total of 1520 samples analyzed, 204 were positive for Haemonchus spp representing a prevalence of 13.42 % in the annual period analyzed; the method used to detect the nematode was the flotation technique, a test mainly used in stool examination in animal diagnosis, it concentrates eggs, parasite oocysts and separates the debris present in the sample (<xref ref-type="bibr" rid="B35">Zajac &amp; Conboy, 2011</xref>; <xref ref-type="bibr" rid="B27">Rinaldi et al. 2011</xref>; <xref ref-type="bibr" rid="B20">Medeiros et al., 2018</xref>), one of the main advantages of using this test is that it has a high egg recovery rate (<xref ref-type="bibr" rid="B21">Medeiros et al., 2018</xref>), causes less damage to cysts and eggs (<xref ref-type="bibr" rid="B35">Zajac &amp; Conboy, 2011</xref>), which allows proper morphological identification facilitating the characteristic structure observation, egg dimensions to be identified (<xref ref-type="bibr" rid="B15">Indre et al., 2010</xref>; <xref ref-type="bibr" rid="B19">Mahmood et al., 2019</xref>), the technique prevents flotation of trematode eggs and it is not as specific to determine the species of parasites observed (<xref ref-type="bibr" rid="B35">Zajac &amp; Conboy, 2011</xref>; <xref ref-type="bibr" rid="B18">Ljungström et al., 2018</xref>), therefore results using this technique report only the Haemonchus genus. Factors studied are presented in <xref ref-type="table" rid="t5">Table 2</xref>, Chi-Square tests indicated that the three factors were significant (P&lt;0.05), year time, production zone, production system; similarly for the analysis of risk factors were significant (P≤0.05) in the multivariate logistic regression model (<xref ref-type="table" rid="t6">Table 3</xref>). The results by year time showed a higher prevalence in autumn with 20.53 %, no difference was observed between winter and spring and the lowest prevalence was found in summer with 7.89 % (P&lt;0.0001).</p>
				<p>
					<table-wrap id="t5">
						<label>Table 2</label>
						<caption>
							<title>Risk factors associated with the presence of Haemonchus spp. eggs in feces of lambs in SPU located in the municipality of Culiacán, Sinaloa, Mexico</title>
						</caption>
						<table>
							<colgroup>
								<col/>
								<col/>
								<col/>
								<col/>
								<col/>
							</colgroup>
							<thead>
								<tr>
									<th align="center">Risk factor</th>
									<th align="center">N</th>
									<th align="left">Positive samples</th>
									<th align="center">Percentage</th>
									<th align="center">P1</th>
								</tr>
								<tr>
									<th align="center">Year season</th>
									<th align="left"> </th>
									<th align="left"> </th>
									<th align="left"> </th>
									<th align="center">0.0001</th>
								</tr>
							</thead>
							<tbody>
								<tr>
									<td align="center">Summer</td>
									<td align="left">380</td>
									<td align="right">30</td>
									<td align="center">7.89<sup>c</sup></td>
									<td align="left"> </td>
								</tr>
								<tr>
									<td align="center">Autumn</td>
									<td align="left">380</td>
									<td align="right">78</td>
									<td align="center">20.53<sup>a</sup></td>
									<td align="left"> </td>
								</tr>
								<tr>
									<td align="center">Winter</td>
									<td align="left">380</td>
									<td align="right">50</td>
									<td align="center">13.16<sup>b</sup></td>
									<td align="left"> </td>
								</tr>
								<tr>
									<td align="center">Spring</td>
									<td align="left">380</td>
									<td align="right">46</td>
									<td align="center">12.11<sup>bc</sup></td>
									<td align="left"> </td>
								</tr>
								<tr>
									<td align="center">Production zone</td>
									<td align="left"> </td>
									<td align="left"> </td>
									<td align="left"> </td>
									<td align="center">0.0001</td>
								</tr>
								<tr>
									<td align="center">High</td>
									<td align="left">183</td>
									<td align="right">7</td>
									<td align="center">3.83<sup>b</sup></td>
									<td align="left"> </td>
								</tr>
								<tr>
									<td align="center">Valleys</td>
									<td align="left">1337</td>
									<td align="right">197</td>
									<td align="center">14.73<sup>a</sup></td>
									<td align="left"> </td>
								</tr>
								<tr>
									<td align="center">Production system</td>
									<td align="left"> </td>
									<td align="left"> </td>
									<td align="left"> </td>
									<td align="center">0.0001</td>
								</tr>
								<tr>
									<td align="center">Extensive</td>
									<td align="left">437</td>
									<td align="right">112</td>
									<td align="center">25.63<sup>a</sup></td>
									<td align="left"> </td>
								</tr>
								<tr>
									<td align="center">Semi-intensive</td>
									<td align="left">248</td>
									<td align="right">50</td>
									<td align="center">20.16<sup>a</sup></td>
									<td align="left"> </td>
								</tr>
								<tr>
									<td align="center">Intensive</td>
									<td align="left">835</td>
									<td align="right">42</td>
									<td align="center">5.03<sup>b</sup></td>
									<td align="left"> </td>
								</tr>
							</tbody>
						</table>
						<table-wrap-foot>
							<fn id="TFN5">
								<label><sup>1</sup></label>
								<p>Probability values of the Chi-square test. <sup>abc</sup> Different literals in the percentages of positive samples in each risk factor indicate statistical difference (P ≤ 0.01).</p>
							</fn>
						</table-wrap-foot>
					</table-wrap>
				</p>
				<p>
					<table-wrap id="t6">
						<label>Table 3</label>
						<caption>
							<title>Odds ratios for risk factors associated with the presence of Haemonchus spp. eggs in lamb feces in SPU located in the municipality of Culiacán, Sinaloa, Mexico</title>
						</caption>
						<table>
							<colgroup>
								<col/>
								<col/>
								<col/>
								<col/>
							</colgroup>
							<thead>
								
							
							<tr>
									<th align="center">Risk factor</th>
								<th align="center">Odd ratio</th>
								<th align="center">CI 95 %</th>
								<th align="center">P Value</th>
								</tr>
							</thead>
								<tbody>
								<tr>
									<td align="center">Year season S-W-S Otoño</td>
									<td align="center">Reference 2.38</td>
									<td align="center">1.69-3.34</td>
									<td align="center">0.001</td>
								</tr>
								<tr>
									<td align="center">Production season High Valleys</td>
									<td align="center">Reference 2.70</td>
									<td align="center">1.21-6.02</td>
									<td align="center">0.016</td>
								</tr>
								<tr>
									<td align="center">Production system: Intensive-Semi Extensive</td>
									<td align="center">Reference 4.81</td>
									<td align="center">3.38-6.85</td>
									<td align="center">0.0001</td>
								</tr>
							
							</tbody>
						</table>
						<table-wrap-foot>
							<fn id="TFN6">
								<p>S=Summer, W=Winter, S=Spring; CI = Confidence interval; P = Probability.</p>
							</fn>
						</table-wrap-foot>
					</table-wrap>
				</p>
				<p>The results of the study showed that when comparing the different seasons of the year, there is a 2.38 times higher risk of presenting Haemonchus spp. in autumn than in the rest of seasons (P&lt;0.001). The results of the present investigation in relation to the summer season with 7.89 % are close to those described in England with 10.5 % (<xref ref-type="bibr" rid="B5">Broughan &amp; Wall., 2007</xref>), the low prevalence in summer can be attributed to the high temperatures that occur at this time in the area described, which is why the larvae decrease their activity, due to the negative phototropism to intense light (<xref ref-type="bibr" rid="B31">Soca et al., 2005</xref>), in another study related to year times in India reported the presence of the order Strongylida with 63.2 % in summer and 58.4 % in autumn, 52.77 % in winter and 61.3 % in spring (<xref ref-type="bibr" rid="B33">Tramboo et al., 2015</xref>), denoting difference with the current work, since in autumn there was a prevalence of 20.52 % being higher than that of summer with 7.89 %, this can be interpreted by the maximum temperatures that occur in summer in the study area, in addition to the increased humidity in the pastures in the autumn season that favor larval migration by positive hydrotropism (<xref ref-type="bibr" rid="B31">Soca et al., 2005</xref>), regarding winter and spring, differences were also found between the two studies, since in India the prevalence increased from winter to spring, this is attributed to the precipitation that favors the humidity of the pastures for the presence of the parasite. Contrary to the present result, there was no significant difference from winter to spring in relation to the nematode presence, this is interpreted to the state of hypobiosis in which the helminth enters, in an unfavorable period nutritionally, so it tends to lower its metabolism and activity (<xref ref-type="bibr" rid="B31">Soca et al., 2005</xref>); in a study conducted in Iran (<xref ref-type="bibr" rid="B22">Moghaddar, 2008</xref>), sampled lambs under five months, during the four seasons of the year, it was reported the presence of nematodes 25.9, 22.3, 50 and 53.1 % for autumn, winter, spring and summer, respectively. The differences that stand out among the studies is the report of nematodes in general and therefore a higher percentage of positive lambs, another factor that indicates a difference between the prevalence between seasons is precipitation. In the case of Iran, there is more rainfall in March and April, so there are more nematodes in spring and summer, and in the study region of Culiacán, rainfall occurs in August and September, favoring the conditions for Haemonchus in autumn, coinciding with a study conducted in the same area with the protozoan Cryptosporidium spp. in lambs, showing 2. 2 times more risk of presenting the parasite in autumn than in summer (<xref ref-type="bibr" rid="B6">Castro et al., 2017</xref>), although they are taxonomically classified in different phylum the climatic conditions at this time favor both.</p>
				<p>When analyzing the geographic zone of the region, the results indicate a higher prevalence for the valley with 14.73 % as opposed to the highland zone with 3.83 % (P&lt;0.0001), and 2.70 times higher risk of presenting the nematode in lambs in the valley zone (P&lt;0.016). 016), presenting similarity to what was found in Ethiopia the difference that was reported in general were gastrointestinal nematodes, in valley production zone was higher than the high zone, with 95 and 68.6 % respectively and coincide in terms of higher risk of presenting Haemonchus in the valley production zone (<xref ref-type="bibr" rid="B2">Asmare et al., 2016</xref>), likewise in Switzerland in high zones a low presence of the parasite was reported in comparison with medium and low zones in Italy and Ireland (<xref ref-type="bibr" rid="B28">Rinaldi et al., 2015</xref>), the water source is one of the key characteristics for the survival and dissemination of nematodes such as Haemonchus (<xref ref-type="bibr" rid="B24">Musella et al., 2011</xref>; <xref ref-type="bibr" rid="B28">Rinaldi et al., 2015</xref>), which occurred more in valley areas mainly because of dams, these areas are lower areas that can carry contaminants through water tributaries, including parasite eggs from production units or wild animals that live in higher areas, favoring the dissemination of these when this water is used for irrigation, animal consumption, among other activities of common use. Gastroenteric parasites and especially Haemonchus have managed to adapt to different ecosystems, their ability to adapt and survive different environments allow the infection of new hosts (<xref ref-type="bibr" rid="B23">Munguía et al., 2018</xref>).</p>
				<p>According to the production system the presence of Haemonchus spp was found 25.63% in extensive production system, 20.13 % in semi-intensive system and 5.03% in intensive system (P&lt;0.0001) and when analyzing the association of parasitosis this was 4.81 times more risk of occurrence in lambs under an extensive production system (P&lt;0.0001). The results differ from those performed by <xref ref-type="bibr" rid="B36">Zapata et al. (2016)</xref> and <xref ref-type="bibr" rid="B14">Herrera et al. (2013)</xref> in which no statistical difference was found among the three production systems analyzed. The conditions of the present study in animals under extensive systems are not systematized, they did not manage a deworming schedule, which agrees with <xref ref-type="bibr" rid="B21">Mederos et al. (2010)</xref> who indicate that the highest levels of gastrointestinal parasites occur in production units where there is no routine deworming management; in addition to the type of grazing-based feeding facilitates the ingestion of the parasite larvae present in the vegetation, and allows transmission as the animals themselves contaminate the grazing area (<xref ref-type="bibr" rid="B3">Belina et al., 2017</xref>; <xref ref-type="bibr" rid="B1">Akyüz et al., 2019</xref>); on the other hand, in the semi- intensive and intensive systems, deworming management was programmed and feeding was operated with diets prepared mainly in the intensive system which favored a lower percentage of the parasite presence in these systems due to the positive impact given by better quality diets on health; <xref ref-type="bibr" rid="B7">Cériac et al. (2019)</xref> and <xref ref-type="bibr" rid="B25">Naeem et al. (2021)</xref> point out that quality nutrition supplemented with high protein, amino acids stimulates the expression of host resistance and resilience, stimulates immunity, decreases parasite proliferation.</p>
			</sec>
			<sec sec-type="conclusions">
				<title>CONCLUSION</title>
				<p>The autumn season, valley area and extensive production system are the edaphoclimatic factors associated with the prevalence of Haemonchus spp (13.42%) in lambs in Culiacán municipality, Sinaloa; therefore, these aspects should be taken into account to develop strategies for the prevention and control of parasitosis. H. contortus is recognized as one of the main parasites affecting sheep, which makes it necessary to consider this agent as a possible cause of productive disorders even in early stages of the animals' age, as well as a possible infection source from young animals to the rest of the flock.</p>
			</sec>
		</body>
		<back>
			<ack>
				<title>ACKNOWLEDGMENTS</title>
				<p>To the Association of Sheep and Goat Breeders Culiacán AC. and the National Council of Science and Technology (CONACyT) Mexico, for the economic support for the training of human resources in this project.</p>
			</ack>
			<fn-group>
				<fn fn-type="other" id="fn2">					
					<p>Code: e2021-49.</p>
				</fn>
			</fn-group>
		</back>
	</sub-article>
</article>