|Thompson, R.c. Andrew|
Submitted to: International Journal for Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2002
Publication Date: 1/1/2003
Citation: Morgan, U., Fall, A., Ward, L.A., Hijjawi, N., Sulaiman, I., Fayer, R., Thompson, R., Olson, M., Lal, A., Xiao, L. 2003. Cryptosporidium hominis n. sp. (apicomplexa: cryptosporidiidae) from humans, homo sapiens. International Journal for Parasitology. 49:433-440. Interpretive Summary: Cryptosporidium is a protozoan parasite, transmitted by a microspoic, an egg-like stage in feces of humans and animals. It contaminates food and water causing diarrhea in humans and animals. Based strictly on the size and shape of the oocyst, one species of Cryptosporidium has been reported to infect over 150 species of mammals- Cryptosporidium parvum. Because oocysts from humans failed to transmit infection to a variety of mammals, caused little or pathology in pathogen-free piglets, and had a gene sequence different from that of C. parvum, it was determined to be a separate species and was named C. hominis. The identification and naming of this parasite as a separate species will provide more accurate identification and facilitate epidemiologic data related to outbreaks. It will clearly distinguish between human and livestock sources of infections in humans and animals.
Technical Abstract: Based on biological and molecular data, the species of Cryptosporidium infecting the intestine of humans is considered a new species for which the name Cryptosporidium hominis is proposed. The structure and infectivity of the oocysts of C. hominis from the feces of humans are described. Oocysts are indistinguishable from those of Cryptosporidium parvum. Oocysts of C. hominis are passed fully sporulated, lack sporocysts, and measure 4.6 ¿ 5.4 m (mean = 5.0) X 3.8 ¿ 4.7 m (mean = 4.3 m) with a length to width ratio 1.16 (n=50). Oocysts were not infectious for ARC Swiss mice, nude mice, Wistar rat pups, puppies, kittens or calves, but were infectious to neonatal gnotobiotic pigs. Pathogenicity studies in gnotobiotic pigs revealed significant differences in site of infection and oocyst output between C. parvum and C. hominis. In vitro cultivation studies revealed growth differences between the two species. Multi-locus analysis of numerous unlinked loci, including a preliminary sequence scan of the entire genome demonstrated this species to be distinct from C. parvum and also demonstrates a lack of recombination, providing further support for species status.