Cryptosporidium hominis

Cryptosporidium hominis
Scientific classification
Domain:	Eukaryota
Kingdom:	Chromalveolata
Superphylum:	Alveolata
Phylum:	Apicomplexa
Class:	Conoidasida
Subclass:	Coccidiasina
Order:	Eucoccidiorida
Suborder:	Eimeriorina
Family:	Cryptosporidiidae
Genus:	Cryptosporidium
Species:	C. hominis
Binomial name
Cryptosporidium hominis

Cryptosporidium hominis, along with Cryptosporidium parvum, is among the medically important Cryptosporidium species.^[1] It is an obligate parasite of humans that can colonize the gastrointestinal tract resulting in the gastroenteritis and diarrhea characteristic of cryptosporidiosis. Unlike C. parvum, which has a rather broad host range, C. hominis is almost exclusively a parasite of humans. As a result, C. hominis has a low zoonotic potential compared to C. parvum. It is spread through the fecal-oral route usually by drinking water contaminated with oocyst laden feces.^[2]

Characteristics

C. hominis shares many similar characteristics with C. parvum including identical oocyst morphology and life-cycle. As a result, C. hominis is most easily differentiated from C. parvum through genetic analysis at specific loci.^[3][4]

In The Netherlands, C. hominis is responsible for an autumnal spike in cases of cryptosporidiosis, though reasons for this spike remain unclear.^[5]

Life cycle

The life cycle of Cryptosporidium hominis is similar to that of others of the genus with infective sporozoites from ingested oocysts invading gut epithelium. From there, they undergo merogony and generate merozoites, which escape and can reinvade additional cells and form a secondary meront. The secondary meront then releases secondary merozoites which reinvade and undergo gametogony forming micro and macrogametocytes. The gametocytes can then fuse, forming a zygote, which starts the cycle again.

Treatment

Though symptoms in most immunocompetent persons will resolve without treatment, Nitazoxanide has been approved for treatment of diarrhea resulting from cryptosporidiosis. The effectiveness of Nitazoxanide in immunocompromised patients, however, is uncertain and current treatments revolve around boosting the host immune system to aid in symptom resolution.^[6] Current avenues for treatment include scanning the Cryptosporidium hominis genome for possible targets for vaccine development.^[7]

References

1. ^ Leoni F, Amar C, Nichols G, Pedraza-Díaz S, McLauchlin J (June 2006). "Genetic analysis of Cryptosporidium from 2414 humans with diarrhoea in England between 1985 and 2000". J. Med. Microbiol. 55 (Pt 6): 703–7. doi:10.1099/jmm.0.46251-0. PMID 16687587. http://jmm.sgmjournals.org/cgi/pmidlookup?view=long&pmid=16687587. 
2. ^ Fayer R (December 2004). "Cryptosporidium: a water-borne zoonotic parasite". Vet. Parasitol. 126 (1–2): 37–56. doi:10.1016/j.vetpar.2004.09.004. PMID 15567578. http://linkinghub.elsevier.com/retrieve/pii/S0304-4017(04)00406-6. 
3. ^ Morgan-Ryan UM, Fall A, Ward LA, et al. (2002). "Cryptosporidium hominis n. sp. (Apicomplexa: Cryptosporidiidae) from Homo sapiens". J. Eukaryot. Microbiol. 49 (6): 433–40. doi:10.1111/j.1550-7408.2002.tb00224.x. PMID 12503676. 
4. ^ Cacciò SM, Thompson RC, McLauchlin J, Smith HV (September 2005). "Unravelling Cryptosporidium and Giardia epidemiology". Trends Parasitol. 21 (9): 430–7. doi:10.1016/j.pt.2005.06.013. PMID 16046184. http://linkinghub.elsevier.com/retrieve/pii/S1471-4922(05)00188-1. 
5. ^ Wielinga PR, de Vries A, van der Goot TH, et al. (June 2008). "Molecular epidemiology of Cryptosporidium in humans and cattle in The Netherlands". Int. J. Parasitol. 38 (7): 809–17. doi:10.1016/j.ijpara.2007.10.014. PMID 18054936. http://linkinghub.elsevier.com/retrieve/pii/S0020-7519(07)00388-8. 
6. ^ http://www.cdc.gov/NCIDOD/DPD/parasites/cryptosporidiosis/factsht_cryptosporidiosis.htm#10; CDC Cryptosporidiosis Fact Sheet. Retrieved on 18 April 2008
7. ^ http://www.hominis.mic.vcu.edu/index.html; Virginia Commonwealth University CSBC Cryptosporidium Research Website. Retrieved on 18 April 2008