Immune response of sheep naturally infected with Haemonchus spp. on pastures with two different nutritional conditions

Abstract

Parasitic nematodes in the gastrointestinal tract of small ruminants are considered one of the main causes of economical and productive losses. Haemonchus contortus is characterized as the major parasite affecting sheep worldwide. This study was designed to evaluate immunological responses in sheep naturally infected with Haemonchus spp. in two different feed grounds: native and cultivated pasture. Fecal and blood samples were collected weekly from fifteen Corriedale sheep, ages 8 to 12 months, to determine the counting of eggs per gram of feces (EPG), and the concentration of haematocrit, eosinophils, and cytokines during an 84-day experiment. Bromatological analysis of the two pasture treatments (types) showed levels of crude protein and non-fibrous carbohydrates of 9.7% and 12.3% in the native pasture and 14.3% and 23.7% for the cultivated pasture, respectively. No significant difference in haematocrit concentration was found during the experiment between different pastures (p < 0.05). However, significant differences were found in EPG, eosinophils, interleukins, and immunoglobulins levels after 21 days in the cultivated (nutritionally-enhanced) pasture. These data suggest that immune response was characterized in sheep by significantly higher peripheral eosinophilia and an increase in serum concentrations of IgE, IgA, IgG, TNF-?, IFN-?, and IL-6. Likewise, the improvement in forage condition resulted in a reduction of EPG and an increase of elements that improve a sheep’s immune system response against Haemonchus spp. infection.