Distribution of cryptosporidia within the gastrointestinal tract of young calves.

Natural cryptosporidial infection of the gastrointestinal tract was recognised in four young calves by light microscopy and correlated with scanning and transmission electron microscopy in two of the calves. Seven to 10 sites of the small intestine were examined in each calf and cryptosporidia were most numerous in the posterior 50 per cent. None were found in the anterior 20 per cent of the small intestine, the abomasum or the colon, but they were present in the mucosa of the caecum of three calves.