Experimental infection of elaphid snakes with Cryptosporidium serpentis (Apicomplexa: Cryptosporidiidae).

The shedding pattern of fecal Cryptosporidium serpentis oocysts, histopathologic changes in the gastric region, and the effect of spiramycin treatment were investigated in 6 experimentally infected, captive black rat (Elaphe obsoleta obsoleta), 4 yellow rat (Elaphe obsoleta quadrivittata), and 2 corn snakes (Elaphe guttata guttata). Feces were monitored for up to 2 years postinfection (PI). No significant (P > 0.07) differences were observed between expected and observed numbers of PI oocyst-positive feces. Two of 5 control animals acquired natural infections of C. serpentis over the period of study. No morphological differences were observed between oocysts from experimental and natural infections. Clinical signs included postprandial regurgitation in 5 of 13 (38%) snakes, not coinciding with the shedding of fecal oocysts. Midbody swelling and self-cure were not observed. Spiramycin treatment of 4 of 12 experimentally infected animals resulted in negative fecal examinations in 2 snakes and reduced the percentage of oocyst-positive feces in 2 other snakes from 75.5% to 24.5% and from 83.9% to 33.6%. Biopsies and necropsies revealed stages of Cryptosporidium in the gastric mucosa of all spiramycin-treated animals. The gastric mucosa was thickened and edematous, with focal necrosis, mucosal petechiae, and brush hemorrhages. Fibroplasia of lamina propria associated with chronic mucosal inflammation were common. Examination of direct fecal smears was found not to be a reliable technique for diagnosis of cryptosporidial infections in snakes.