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BioMed Research International
Volume 2013 (2013), Article ID 162158, 11 pages
http://dx.doi.org/10.1155/2013/162158
Review Article

Immune Responses Associated with Resistance to Haemonchosis in Sheep

Departamento de Ciencias Biológicas, Facultad de Estudios Superiores Cuautitlán, Universidad Nacional Autónoma de México, Km. 2.5 Carretera Cuautitlán-Teoloyucan, 54714 Cuautilán Izcalli, MEX, Mexico

Received 18 July 2012; Revised 19 September 2012; Accepted 28 September 2012

Academic Editor: Luis I. Terrazas

Copyright © 2013 Fernando Alba-Hurtado and Marco Antonio Muñoz-Guzmán. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This paper examines the known immunological and genetic factors associated with sheep resistance to infection by Haemonchus contortus. Such resistance is an inheritable genetic trait ( , 0.22–0.63) associated with certain sheep breeds. Resistant sheep do not completely reject the disease; they only harbor fewer parasites than susceptible sheep and therefore have a lower fecal egg count. Protective immune response to haemonchosis is an expression of genetic resistance. Genes associated with resistance and susceptibility are described. Genetically resistant sheep have nonspecific mechanisms that block the initial colonization by Haemonchus contortus larvae. These sheep also have an efficacious Th2 type response (e.g., increases in blood and tissue eosinophils, specific IgE class antibodies, mast cells, IL-5, IL-13, and TNFα) that protects them against the infection; in contrast, susceptible sheep do not efficiently establish this type of immune response. Finally, the main reported antigens of H. contortus were reviewed.