Cryptosporidium parvum

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Cryptosporidium parvum (Cryptosporidiosis)


Animal and human

Transmission/Exposure Routes

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]

Incubation Times

2-10 days, average 7 days

Case Fatality Ratios

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 (Fayer & Ungar, 1986).

Burden of Disease

In the United States, an estimated 748,000 cases of cryptosporidiosis occur each year (CDC, 2011). An estimated 30% of the adult population of the United States is seropositive for cryptosporidium (Cabada, M, et al. 2011). 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 (Yoder, JS. 2010).

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%) (Hoxie, N. 1997 & Blair, K. 1995).

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 (wikipedia)

Environmental Survival

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)

Recommended Dose Response Model

Dose response models for Cryptosporidium
Exponential, k is 0.057
Exponential model.png

References Blair, K. (1995) “Cryptosporidium and Public Health” Water Quality and Health. Retrieved on 1-23-12 from
Cabada, M. Burke, C. (2011) “Cryptosporidiosis” Medscape Reference: Drugs, Diseases & Procedures: Cryptosporidiosis. Retrieved on 1-23-12 from
CDC (2011) “Parasites – Cryptosporidium (also known as “Crypto”): Epidemiology & Risk Factors” Centers for Disease Control and Prevention. Retrieved on 1-23-12 from
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
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

  1. CDC
  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.