Differences in immune parameters are associated with resistance to Haemonchus contortus in Caribbean hair sheep

Abstract

Caribbean hair sheep are more resistant to gastrointestinal nematodes than conventional wool breeds, but mechanisms that confer resistance are not fully understood. This study compared immune effector cell populations and antibody concentrations in 12 hair and 12 wool lambs infected with the abomasal parasite Haemonchus contortus and sacrificed at 3 or 27 days post-infection (p.i.) and 14 uninfected animals of each breed. Faecal egg counts were over 2.5-fold higher (P = 0.12) and packed cell volumes approximately 8% lower (P < 0.10) in infected wool lambs. Abomasal lymph nodes were heavier in infected animals (P < 0.05) and infected hair sheep had larger lymph nodes than infected wool sheep (P < 0.05). Tissue eosinophil concentrations were likewise larger (P = 0.07) in hair compared with wool sheep at 3 days p.i. Circulating levels of IgE and IgA in uninfected lambs were higher in hair sheep (P < 0.05) and during infection, hair sheep had higher serum IgA than wool sheep at 3, 5, and 21 days p.i. (P < 0.05). Serum IgE in infected lambs did not differ between breeds, but concentrations of IgE in lymph nodes were higher (P < 0.01) at 27 days p.i. in infected hair sheep.

Phenotypic expression of parasite susceptibility to Haemonchus contortus in Pelibuey sheep

“…This result suggested that exposure to L 3 larvae of H. contortus triggered an acquired immune response that may have impacted both newly acquired larvae and adult worms. Support for this hypothesis is provided by results of MacKinnon et al (2010MacKinnon et al ( , 2015 and Jacobs et al (2016), who documented that a secondary exposure of St. Croix lambs to L 3 larvae of H. contortus initiated a cascade of protective immune responses within 3 days of infection.…”

The effect of ovine peripheral blood mononuclear cells on Haemonchus contortus larval morbidity in vitro

“…St. Croix (STC) hair sheep demonstrate a remarkable ability to clear a parasitic infection of Haemonchus contortus without anthelmintic drug treatment and, therefore, are considered parasite‐resistant . These sheep are not considered desirable commercial sheep due to low carcass weights and slow growth rates compared to conventional wool breeds.…”

Galectins and collectinis expression are increased in Haemonchus contortus-infected corriedale sheep

“…Host immunity against helminth infections is dependent on innate and acquired immune responses (STEAR & WAKELIN, 1998) and the interaction of these responses confers protection by inducing eosinophilic inflammation, mastocytosis and activation of Th2 responses, with increased expression of interleukin (IL) -4, IL-5 and IL-13 in target tissues and production of IgE and IgA (MACKINNON et al, 2009(MACKINNON et al, , 2010. In contrast, animals susceptible to infection develop Th1 responses, with secretion of cytokines such as IL-2, interferon-gamma (IFNG) and tumor necrosis factor (GILL et al, 2000).…”