STUDIES ON THE HOST-PARASITE RELATIONSHIP BETWEEN TRICHOSTRONGYLUS-COLUBRIFORMIS AND SUSCEPTIBLE AND RESISTANT SHEEP

This study examined whether infective larvae (L(3)) of Trichostrongylu s colubriformis could establish throughout the small intestine and wer e not restricted to the anterior duodenum in susceptible and resistant sheep. The location of worms was similar in susceptible animals given doses of T. colubriformis between 10,000 and 80,000 T. colubriformis larvae, with 90% of worms located in the proximal 3 m of the small int estine. Those Norms recovered from resistant sheep were also found in the first 9 m of the intestine. However, worms recovered from immune s heep were significantly (P=0.0074) relocated posteriorly from the firs t 3 m into the next 6 m of the intestine. By the surgical introduction of norms, it was found that T. colubriformis could establish at any s ite in the small intestine and to some extent in the caecum. Immunity was generated principally in the site of predilection in the anterior 3 m of the small intestine and effectively expelled challenges given a t distal sites and the caecum, indicating dissemination of immunity th roughout the gastrointestinal tract. Moreover, the rejection episode h ad removed worms from the entire small intestine within 2 h of introdu ction through the pylorus. Copyright (C) 1996 Australian Society for P arasitology. Published by Elsevier Science Ltd.