Cryptosporidiosis in animals and humans

Abstract

The protozoan Cryptosporidium (family Cryptospiridiidae), which was identified in 1907, has only recently been shown to be an important cause of enterocolitis and diarrhea in a number of mammalian species. The disease in humans was initially reported to occur in immunologically compromised individuals, but a recent study among hospital patients with gastroenteritis indicated that the infection is common in immunologically normal patients. The organism lacks host specificity, a characteristic uncommon among other enteric coccidia, and is therefore a potential zoonosis. It is extremely resistant to the action of common laboratory disinfectants and to antimicrobial agents tested so far. A preliminary serological survey indicates that the infection is prevalent among and within populations of 10 mammalian species examined. Field outbreaks of diarrhea attributed to Cryptosporidium infection have so far been reported in calves, lambs, deer, and goats and the disease has been reproduced experimentally in lambs, calves, and piglets. Sporadic cases of illness in other species have also been reported, and in birds it has been shown to cause upper respiratory tract infection. The organism infects the entire bowel but most commonly the lower small intestine, where extensive mucosal changes occur. The organism completes its life cycle on the mucosal lining by adhering to the brush border of enterocytes. Cryptosporidium causes partial atrophy, fusion, and distortion of villi, resulting in maldigestion in the brush border and malabsorption.