Abomasal cryptosporidiosis in cattle.

A 6-week-old calf and nine feedlot steers shed oocysts similar to Cryptosporidium muris-like oocysts. There were massive populations of this Cryptosporidium in the peptic glands of most of these animals. The oocysts were larger and more oval than the frequently reported type which is generated in the intestines of many animal species and thought to be similar to Cryptosporidium parvum. The pattern of shedding of this newly discovered Cryptosporidium in the steers was continuous over a period of months whereas the C. parvum-like oocysts cease to be shed 1 to several weeks after onset. The nature of the host-parasite interaction in abomasal cryptosporidiosis is yet to be determined. Morphologic changes that resulted from the interaction were an approximate 10% increase in abomasal mucosal thickness, widening of gland lumens in the middle region, and atrophy of epithelium in the same region.