Sharon Roy, Michele C. Hlavsa, Michael Beach

Infectious Agent

• Protozoan parasite Cryptosporidium.
• Many species of Cryptosporidium exist that infect humans and a wide range of animals. The most common species infecting humans are C. hominis and C. parvum.

Mode of Transmission

Transmission occurs by—

• Ingesting fecally contaminated food or water, including water swallowed while swimming.
• Exposure to fecally contaminated environmental surfaces and objects.
• Fecal–oral, person-to-person contact (e.g., diaper changing, caring for an infected person).

Occurrence

• Cryptosporidiosis transmission occurs worldwide; it is a common cause of childhood diarrhea, especially in developing countries.
• Cryptosporidiosis outbreaks have been reported in North America, Europe, Latin America, Australia, and Asia. Outbreaks have been traced to contaminated recreational water, drinking water, and food; contact with animals (especially calves); hospitals; and daycare settings.

Risk for Travelers

For travelers to developing countries, risk of infection is highest for those with the greatest exposure to potentially contaminated food or water.

Clinical Presentation

• Symptoms usually begin 3–14 days after becoming infected with the parasite and are generally self-limiting.
• The most common symptom is watery diarrhea. Other symptoms can include abdominal cramps, vomiting, dehydration, fever, and weight loss. Some people infected with Cryptosporidium have no symptoms at all.
• In immunocompetent persons, symptoms usually last 1–2 weeks but may persist for a month, or rarely, up to 4 months. Some persons may experience a recurrence of symptoms after a brief period of recovery before the illness resolves; symptoms that come and go generally resolve within a month.
• In immunosuppressed persons, such as those with AIDS or patients taking immunosuppressive medications, cryptosporidiosis can become chronic and can be fatal.

Diagnosis

• Tests for Cryptosporidium are not routinely done in most laboratories; therefore, health-care providers should specifically request testing for this parasite.
• Because detection of Cryptosporidium can be difficult, patients may be asked to submit several stool samples over several days.
• Most often, stool specimens are examined microscopically by using different techniques (e.g., acid-fast staining, direct fluorescent antibody [DFA]—the gold standard) and/or enzyme immunoassays for detection of Cryptosporidium spp. antigens).
• Molecular methods (e.g., polymerase chain reaction) are increasingly used in reference diagnostic laboratories, since they can be used to identify Cryptosporidium spp. at the species level.

Treatment

• Most immunocompetent persons will recover without treatment. Diarrhea should be managed with adequate fluid replacement to prevent dehydration.
• Nitazoxanide (Alinia, Romark Laboratories, Tampa, FL, USA) has been   FDA approved for treatment of diarrhea caused by Cryptosporidium in immunocompetent persons and is available by prescription for patients 1 year of age and older. However, the effectiveness of nitazoxanide in immunosuppressed individuals is unclear.

Preventive Measures for Travelers

• No vaccine is available.
• To prevent infection, travelers should be advised to follow strict food precautions. Additionally, travelers should practice good hygiene (e.g., frequent handwashing), avoid swallowing water while swimming, and avoid fecal exposure during sexual activity.
• Cryptosporidium is poorly inactivated by chlorine or iodine disinfection. Water can be treated effectively by boiling or filtration with an absolute 1-micron filter. Specific information on preventing cryptosporidiosis through filtration can be found in Cryptosporidiosis: A Guide to Water Filters at www.cdc.gov/crypto/factsheets/filters.html.

References

1. Guerrant RL. Cryptosporidiosis: an emerging, highly infectious threat. Emerg Infect Dis. 1997;3(1):51–7.
2. Kosek M, Alcantara C, Lima AA, et al. Cryptosporidiosis: an update. Lancet Infect Dis. 2001;1(4):262–9.
3. Warren CA, Guerrant RL. Clinical disease and pathology. In: Fayer R, Xiao L, editors. Cryptosporidium and cryptosporidiosis. 2nd ed. Boca Raton (FL): CRC Press; 2008. p. 235–53.
4. Roy SL, DeLong SM, Stenzel SA, et al. Risk factors for sporadic cryptosporidiosis among immunocompetent persons in the United States from 1999 to 2001. J Clin Microbiol. 2004;42(7):2944–51.
5. Smith H. Diagnostics. In: Fayer R, Xiao L, editors. Cryptosporidium and cryptosporidiosis. 2nd ed. Boca Raton (FL): CRC Press; 2008. p. 173–207.
6. Fox LM, Saravolatz LD. Nitazoxanide: a new thiazolide antiparasitic agent. Clin Infect Dis. 2005;40(8):1173–80.
7. Yoder JS, Beach MJ; CDC. Cryptosporidiosis surveillance—United States, 2003–2005. MMWR Surveill Summ. 2007;56(7):1–10.
8. American Public Health Association. Cryptosporidiosis. In: Heymann DL, editor. Control of communicable disease manual. 18th ed. Washington D.C.: American Public Health Association; 2004. p. 138–42.
9. White, CA Jr. Nitazoxanide: a new broad spectrum antiparasitic agent. Expert Rev Anti Infect Ther. 2004;2(1):43–9.