Experimental cryptosporidiosis in a primate model.

Cryptosporidium causes a disease in infant macaques that is clinically, histologically, and microbiologically indistinguishable from that seen in young children. A reproducible experimental model of cryptosporidiosis has been developed in pigtailed macaques (Macaca nemestrina) and used to studied the infectious dose of oocysts and the effect of inoculum size on severity of disease. Inoculation with either 2 x 10(5) or 10 oocysts via nasogastric tube resulted in clinical enteritis and the fecal passage of large numbers of cryptosporidial oocysts in all four primates studied. The size of the inoculum had no apparent effect on the severity or duration of disease. Rechallenge 2 weeks after resolution of the primary infection demonstrated partial acquired immunity. The small inoculum size coupled with the passage of large numbers of oocysts contributes to the highly contagious nature of cryptosporidiosis among captive primates and may be relevant to the epidemiology and control of cryptosporidiosis in humans.