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In experimentally infected laboratory-bred white rats, Cryptosporidium infection rate was higher among immunosuppressed (75%) than immunocompetent ones (37.5%) with statistically insignificant difference. Cryptosporidiosis was found to be a fatal disease especially in immunosuppressed rats (50%). There was also marked flourishing of the infection as revealed by high intensity of infection in immunosuppressed than the immunocompetent rats (363 and 82.7 oocysts/pellet respectively). In spite of the severe disease, cyclophosphamide appeared to have no effect on the prepatent period. In both immunosuppressed and immunocompetent infected rats, there was a decrease in the total leucocytic count with marked lymphocytopaenia. This indicates decreased resistance to infection, thus higher oocyst counts in the pellets.

By scanning electron microscopy (SEM), T. vaginalis surface appeared pleated with crater-like depressions. All the flagella appeared to start off in a single bundle from a shallow depression with a prominent rim. The side carrying the undulating membrane is extensively ruffled having a mulberry-like appearance to which flocculent material was frequently adherent. T. vaginalis nutrition appeared to proceed through pseudopodia-like extensions and phagocytosis by a constant deep invagination at the anterior pole which seems to be a cytostome. The mulberry-like surface may serve adhesion of T. vaginalis to the host cells and probably increases the surface area for exchange of nutrients, metabolites and parasite-derived factors.