Cryptosporidium parvum

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Animal and human

Fecal-oral, ingestion of contaminated food or water, swallowing recreational water contaminated with Crypto, touching your mouth with contaminated hands, and contact with infected persons or animals. [1]

2-10 days, average 7 days

Mortality in immunocompetent patients is generally low. In immunodeficient individuals, the infection can be persistent and severe. [2]
The mortality rate for children less than five years of age was 2.6/10,000/day during the outbreak[3]
In one study in the UK, 19% of AIDS patients with cryptosporidiosis were thought to have died from the infection.,[4]
Another study compiled case reports of cryptosporidiosis and found a mortality rate of 46% in AIDS patients and 29% in patients with other immunodeficiencies. [5]

In the United States, an estimated 748,000 cases of cryptosporidiosis occur each year[1] An estimated 30% of the adult population of the United States is seropositive for cryptosporidium[6] During 2006 - 2008, the number of reported cases of cryptosporidiosis increased from 6,479 in 2006 to 11,657 in 2007, and then decreased to 10,500 in 2008. A greater number of case reports were received for children aged 1--9 years and for adults aged 25--39 years than were received for persons in other age groups. Peak onset of illness occurred annually during early summer through early fall[7]

In 1993 an estimated 403,000 of the greater Milwaukee, Wisconsin area became ill with cryptosporidiosis among 880,000 possible exposures (An attack rate of about 45.8%)[8]

Internationally (including Latin America, Africa, the Middle East, and South Asia), about 13% of stool samples analyzed for parasites in developing countries reveal Cryptosporidium oocysts (Cabada, M, et al. 2011).

Duration of Infectiousness and disease


Excretion Rates (see Exposure)


A microscopic parasite that causes the diarrheal disease cryptosporidiosis; The oocysts are the infective stage and are about 5 microns in size[9]

They are highly resistant to chlorine, and can survive for months in cold lakes/streams, as well as freezing at -15C for 8-24h (AWWA 1999)


Blair, K. (1995) “Cryptosporidium and Public Health” Water Quality and Health. Retrieved on 1-23-12 from

  1. 1.0 1.1 CDC (2011) “Parasites – Cryptosporidium (also known as “Crypto”): Epidemiology & Risk Factors” Centers for Disease Control and Prevention. Retrieved on 1-23-12 from
  2. Ungar, B. L., Burris, J. A., Quinn, C. A., & Finkelman, F. D. (1990). New mouse models for chronic Cryptosporidium infection in immunodeficient hosts. Infection and Immunity, 58(4), 961–969.
  3. Mach O, Lu L , Creek T, Bowen A, Arvelo W, Smit M, Masunge J, Brennan M, and Handzel T. (2009) Population-Based Study of a Widespread Outbreak of Diarrhea Associated with Increased Mortality and Malnutrition in Botswana, January–March, 2006. Am. J. Trop. Med. Hyg., 80(5): 812–818 Full Text
  4. Connolly, G. M., Dryden, M. S., Shanson, D. C., & Gazzard, B. G. (1988). Cryptosporidial diarrhoea in AIDS and its treatment. Gut, 29(5), 593–597.
  5. Ungar, B. L. P., Soave, R., Fayer, R., & Nash, T. E. (1986). Enzyme Immunoassay Detection of Immunoglobulin M and G Antibodies to Cryptosporidium in Immunocompetent and Immunocompromised Persons. Journal of Infectious Diseases, 153(3), 570–578. doi:10.1093/infdis/153.3.570
  6. Cabada, M. Burke, C. (2011) “Cryptosporidiosis” Medscape Reference: Drugs, Diseases & Procedures: Cryptosporidiosis. Retrieved on 1-23-12 from
  7. Yoder, JS, Harral, C., and Beach MJ. (2010) “Cryptosporidiosis Surveillance — United States, 2006–2008. MMWR.” Centers for Disease Control and Prevention. 59 (No. SS-6): 1-14. Retrieved on 1-23-12 from
  8. Neil J. Hoxie, et al. (December 1997), "Cryptosporidiosis-Associated Mortality Following a Massive Waterbome Outbreak in Milwaukee, Wisconsin", American Journal of Public Health 87 (12): 2032–2035. Retrieved on 1-23-12 from