Evaluation of immune response to artificial infections of Haemonchus contortus in Gulf Coast Native compared with Suffolk lambs.

The Gulf Coast Native (Native) breed of sheep among many others is identified as being relatively resistant to Haemonchus contortus, an abomasal nematode parasite of small ruminants. Understanding the mode of immune response that helps these breeds of sheep control infection could help design and implement appropriate control programs. In this experiment, the components of the immune response during the early infection period in resistant Native lambs were evaluated and compared with susceptible Suffolk breed of sheep. Groups (n=5) of six month old Native and Suffolk lambs were given infective larvae as one time (single) or trickle experimental infections. Fecal, blood, and serum samples were collected on days 0, 2, 7, 14 and 21 post-infection. Abomasal mucosa and regional lymph node samples were collected at the time of necropsy on days 14 and 21. There was no significant difference in number of worms recovered at necropsy but the ratio of adult versus larvae was significantly greater in single infected Suffolk than Native lambs. Native lambs had significantly greater numbers of mast cells and eosinophils in the abomasal mucosa and serum IgG production was significantly greater compared to Suffolk lambs. Native lambs also showed a trend of increased level of serum IgA and IgE compared to Suffolk lambs.