Pathological features of Cryptosporidium andersoni-induced lesions in SCID mice.

To assess the infectivity and the istopathological features of Cryptosporidium andersoni (C. andersoni) in laboratory animals, SCID mice were orally inoculated with oocysts of C. andersoni. Starting one week after inoculation, the SCID mice began shedding oocysts, and this continued for ten weeks. Histopathologically, myriads of C. andersoni were observed on the apical surface of the epithelium in the gastric pit of the glandular stomach. There were few lesions in the gastric epithelium except C. andersoni adhesion. In the lamina propria of the affected mucosa, minimum infiltration of inflammatory cells was observed. Immunohistochemically, C. andersoni demonstrated a positive reaction to a number of primary antibodies of Cryptosporidium parvum. In the experiment described here, few increases were seen in apoptotic epithelial cells in the affected mucosas of the SCID mice, and the nuclear augmentation was not enhanced. It was hypothesized that the absence of apoptosis and cell division were due to a lack of inflammatory cell reaction in the lamina propria.