PHYSIOLOGY OF 2 STRAINS OF TRICHOSTRONGYLUS-COLUBRIFORMIS RESISTANT AND SUSCEPTIBLE TO THIABENDAZOLE AND MUCOSAL RESPONSE OF EXPERIMENTALLYINFECTED-RABBITS

Two strains of Trichostrongylus colubriformis of ovine origin, one res istant and one susceptible to thiabendazole, were compared during expe rimental infection in rabbits, Groups of rabbits were infected with 50 00 infective larvae (L3) of either the resistant or the susceptible st rain, On days 21 and 42 post-infection (p.i,), 5 rabbits of each group were killed and the small intestine divided into three sections for w orm counts and histological or biochemical analysis. Faecal egg counts were performed twice a week from day 15 to day 42 p.i. The physiology of the worms was characterised by in vitro acetylcholinesterase secre tion of adult worms. The host inflammatory response was determined by peroxidase activity in mucosal homogenates and by histological counts of mast cells and eosinophils. Infectivity was not significantly diffe rent between the two strains. However, egg production was delayed and was significantly lower for the resistant strain. Conversely, in vitro secretion of resistant worms was significantly higher than the suscep tible ones. The mucosal homogenetates of rabbits infected with the res istant strain had significantly higher levels of peroxidase activity i n the duodenum on days 21 and 42 p.i. Mast cell counts were also signi ficantly higher in the duodenum on day 42 p.i., in rabbits infected wi th the resistant strain. No difference was observed in the eosinophil counts, These results suggest that genetic variation in the nematode, such as anthelminthic resistance, is associated with variations in wor m biology and physiology as well as differences in the inflammatory re sponse of the host.