A preliminary study on intestinal eosinophil cell responses in lambs experimentally infected with Ascaris suum

To estimate the intestinal eosinophil cell responses in a paratenic host of the nematode Ascaris suum, lambs were infected orally with 1000 infective Ascaris suum eggs at day 0 of the experiment. The small intestine of contro l and infected lambs was examined histologically. Data obtained showed a hi gher number of intestinal eosinophils in infected lambs compared with contr ols. The increase of intestinal eosinophils coincided with the appearance o f A. suum larvae in intestinal tissues at day 14 after infection. On day 21 of the experiment the highest incidence of A. suum larvae was reported. Th ereafter no larvae could be detected, while a marked and uniform increase o f intestinal eosinophils was evident. The peak numbers of eosinophil cells was at day 35. At the end of the experiment a decline of eosinophil numbers was associated with no or a low incidence of A. suum larvae. The uniform i ncrease of intestinal eosinophil numbers, in the absence of parasitic larva e from the small intestines of infected lambs, suggested that these cells s eem to be a measure of general immune response of the host rather than an i ndication of helminthosis.