Location and distribution of Trichostrongylus colubriformis in the small intestine of sheep during the prepatent period, and the development of villus atrophy

Abstract

Eight lambs were each infected with 80 000 larvae of Trichostrongylus colubriformis and were killed in pairs 3, 8, 12 and 16 days later. The development and the distribution of worms, and the intestinal morphology were examined. Worms were parasitic 3rd stage larvae 3 days after infection (DAI), in the late 4th stage 8 DAI, early 5th stage 12 DAI and were fully developed adults 16 DAI. At all times after infection populations were densest in the first, second or third metre of intestine, and there was no evidence of population shifts with time. By 3 DAI some shortening of villi and elongation of crypts was evident in heavily infected gut. Eight DAI villi were short and had “shoulders” from which enterocytes appeared to slough. Subtotal to severe villus atrophy with leaks and erosions in the epithelium were seen 12 DAI. Severe villus atrophy with extensive erosions was evident 16 DAI.