Trichostrongylus colubriformis: effects on villi and crypts along the whole small intestine in infected rabbits.

In control and Trichostrongylus colubriformis-infected rabbits histological samples were taken from the small intestine at 25-cm intervals from the pylorus. Length of villi, surface of glands of Lieberkühn, and number of epithelial cells per unit length were measured with a digitized table. Two zones were so delimited along the parasitized mucosa: in the proximal part of the gut, both shortened villi and dilated crypts were found; in the distal region of the intestine, which was also the area with the lowest density of parasites, dilatation of crypts was associated with an increase in the size of villi. In both regions, the size of enterocytes was unchanged. Correlation coefficients calculated between worm burdens and relative variation in length of villi were significant and negative. Conversely, the same coefficients were significant and positive between worm burdens and surface of crypts. The possibility of local and general actions of Trichostrongylus colubriformis on both villi and crypts is evoked to explain the changes in the two zones. The functional importance of the hypertrophy in the distal region is still to be investigated during a T. colubriformis infection.