[Enterocolitis in spontaneous cryptosporidiosis infections in calves]

The pathology of lesions in the intestines of 48 calves with spontaneous cryptosporidiosis was studied by histological examination and by scanning electron-microscopy (SEM). The animals were 7 to 21 days old, emergency-slaughtered mostly for dehydration and diarrhoea. Identical lesions were observed in the jejunum and ileum. The villi, often infected by cryptosporidia on a mass scale, were shortened, atrophic, markedly curved and shrunk in their ultrastructure, often as a result of the regression of groups of enterocytes with cryptosporidia, the adjacent tissue being affected, at the same time, by nodular hyperplasia. The enterocytes harbouring the protozoans exhibited cuboidal up to squamous metaplasia; in ultrastructure they had not hexagonal shape and showed signs of microvillus regression. The cryptosporidiosis of the small intestine was always accompanied by hyperaemia and inflammatory reactions in lamina propria, mostly non-purulent, with numerous eosinophils. Signs of typhlitis in the caecum--more frequent and intensive than in other parts of the large intestine infected by cryptosporidia--were characterized, in most cases, by lesions in the covering epithelium and by mostly non-purulent inflammatory infiltration with a large admixture of eosinophils in lamina propria. No inflammatory lesions were found in the colon and rectum. Severe cryptosporidial infections of large parts of intestine and the nature of pathological lesions lead to a considerable reduction in the total absorption surface of the intestine and are potential causes of diarrhoea from malabsorption.