Histopathologic and histochemic changes in the small intestine of calves infected with Trichostrongylus colubriformis

The pathologic effects of Trichostrongylus colubriformis on the small intestine of 8-week-old calves were studied. Morphologic and enzymic alterations were confined to the proximal third of the small intestine, which was shown to be the principal habitat of the nematode. Changes in the mucosa varied according to the acuteness of the infection rather than the duration. Villous atrophy, infiltrations of the lamina propria with plasma cells and lymphocytes, infiltrations of glandular tissue with eosinophils, and necrosis and erosions of the surface epithelial cells were present. Enzymic changes were related to the extent of cellular injury. Alkaline phosphatase and leucine aminopeptidase were more severely reduced, while nonspecific esterase and succinic dehydrogenase were less affected. Enzymic activities in the distal areas were nor influenced by the lesions in the proximal region.