ABSTRACT
The present work was planned to study the possible mechanism[s] of diarrhea in cryptosporidiosis Stool eluates and intestinal homogenates from naturally and experimentally infected animals together with purified sporozoites were examined utilizing using chamber to demonstrate their possible enterotoxic effects Besides the histopathological changes in experimentally infected mice were studied to assess the possible underlying mechanism[s] of diarrhea in cryptosporidiosis. Characterization of the enterotoxic activity associated with cryptosporidiosis may have a great impact on the development of effective strategies for its treatment. The results of the present study revealed that in intestinal cryptosporidiosis enterotoxic substances are secreted which likely induce diarrhea. They induce an increase in the transepithelial potential difference [DIsc] to reach its maximum after 15 minutes and then slowly decrease to reach the baseline after 55 minutes [for stool eluates] and 35 minutes [for intestinal homogenates] On the other hand the purified sporozoites showed an increase in DIsc after 9 minutes and then a decrease after that to become maintained at relatively high level. The enterotoxins were found to be time and dose dependent and heat labile. The osmotic gap showed that the mechanism of diarrhea is rather secretory. In experimentally infected mice, shedding of oocysts first appeared in stools 3 days postinoculation [PI], reaching a peak 9 days [PI] and disappeared 15 days PI. Although the infected mice showed mild to severe degree of intestinal inflammation [marked villous atrophy and crypts hyperplasia], the stool was semiformed. Besides, the present study showed marked validity of mouse as an in vivo model to study the pathophysiology of cryptosporidial diarrhea. This model is inexpensive and serves as a suitable alternative to neonatal calves for efficient oocyst propagation