Chapter 3Infectious Diseases Related To Travel
Sharon L. Roy, Michele C. Hlavsa
Cryptosporidiosis is a diarrheal illness caused by the protozoan parasite Cryptosporidium. Many species of Cryptosporidium exist that infect humans and a wide range of animals. The most common species infecting humans are Cryptosporidium hominis and C. parvum.
MODE OF TRANSMISSION
Transmission occurs by ingesting fecally contaminated food or water, including water swallowed while swimming. Infection can also occur after exposure to fecally contaminated environmental surfaces and objects and from person-to-person contact, such as diaper changing, caring for an infected person, and sexual contact. Humans can also be infected after contact with infected animals, particularly cows.
Cryptosporidiosis transmission occurs worldwide. From 1996 through 2005, 1.2 per 1,000 returned travelers seeking medical care at GeoSentinel-associated medical centers around the world were diagnosed with cryptosporidiosis. This proportion likely underestimates the disease incidence, because Cryptosporidium requires special staining techniques for diagnosis that are not routinely available in many laboratories. Cryptosporidiosis was most commonly diagnosed in travelers returning from the Middle East, Central America, and South America, although travelers returning from South Asia, sub-Saharan Africa, and the Caribbean were also affected. Cryptosporidiosis was diagnosed most frequently in missionaries and volunteers but was also diagnosed in tourists, business travelers, and travelers visiting friends and relatives. Overall, however, cryptosporidiosis is a small contributor to travelers’ diarrhea in the relatively few detailed etiologic studies that have been done in travelers.
Symptoms usually begin 3–14 days after infection with the parasite and are generally self-limited. The most common symptom is watery diarrhea. Other symptoms can include abdominal cramps, vomiting, dehydration, fever, and weight loss. In immunocompetent people, symptoms usually last 1–2 weeks but may persist for a month or, rarely, up to 4 months. Some people may experience a recurrence of symptoms after a brief period of recovery before the illness resolves; symptoms that come and go generally resolve within 1 month. In immunosuppressed people, such as those with AIDS or patients taking immunosuppressive medications, cryptosporidiosis can become chronic and occasionally is fatal. Some people infected with Cryptosporidium have no symptoms at all.
Tests for Cryptosporidium are not routinely included in ova and parasite testing in most laboratories. Therefore, clinicians should specifically request testing for this parasite, when suspected. Because Cryptosporidium can be difficult to detect, patients may need to submit more than one specimen over several days. Diagnostic techniques include microscopy after modified acid-fast staining or direct fluorescent antibody (considered the gold standard). Enzyme immunoassays to detect Cryptosporidium antigens are commercially available. Molecular methods (such as PCR) are increasingly used in reference diagnostic laboratories, since they can be used to identify Cryptosporidium at the species level.
Most immunocompetent people will recover without treatment. Diarrhea should be managed with adequate fluid replacement to prevent dehydration. Nitazoxanide has been approved by the Food and Drug Administration to treat diarrhea caused by Cryptosporidium in immunocompetent people and is available for patients aged ≥1 year. However, the effectiveness of nitazoxanide in immunosuppressed people is unclear.
PREVENTIVE MEASURES FOR TRAVELERS
No vaccine is available to prevent cryptosporidiosis, and there is no recommended chemoprophylaxis. Food and water precautions are the main preventive measures (see Chapter 2, Food and Water Precautions). More detailed information about cryptosporidiosis can be found on the CDC website (www.cdc.gov/parasites/crypto). Cryptosporidium is poorly inactivated by chlorine or iodine disinfection. Water can be treated effectively by boiling or filtration with an absolute 1-µm filter. Specific information on preventing cryptosporidiosis through filtration can be found in Cryptosporidiosis: A Guide to Water Filters (www.cdc.gov/parasites/crypto/gen_info/filters.html).
- American Public Health Association. Cryptosporidiosis. In: Heymann DL, editor. Control of communicable disease manual. Washington, DC: American Public Health Association; 2004. p. 138–42.
- Greenwood Z, Black J, Weld L, O’Brien D, Leder K, Von Sonnenburg F, et al. Gastrointestinal infection among international travelers globally. J Travel Med. 2008 Jul–Aug;15(4):221–8.
- Kosek M, Alcantara C, Lima AA, Guerrant RL. Cryptosporidiosis: an update. Lancet Infect Dis. 2001 Nov;1(4):262–9.
- Roy SL, DeLong SM, Stenzel SA, Shiferaw B, Roberts JM, Khalakdina A, et al. Risk factors for sporadic cryptosporidiosis among immunocompetent persons in the United States from 1999 to 2001. J Clin Microbiol. 2004 Jul;42(7):2944–51.
- Smith H. Diagnostics. In: Fayer R, Xiao L, editors. Cryptosporidium and Cryptosporidiosis. 2nd ed. Boca Raton, FL: CRC; 2008. p. 173–207.
- Swaminathan A, Torresi J, Schlagenhauf P, Thursky K, Wilder-Smith A, Connor BA, et al. A global study of pathogens and host risk factors associated with infectious gastrointestinal disease in returned international travellers. J Infect. 2009 Jul;59(1):19–27.
- Warren CA, Guerrant RL. Clinical disease and pathology. In: Fayer R, Xiao L, editors. Cryptosporidium and Cryptosporidiosis. 2nd ed. Boca Raton, FL: CRC; 2008. p. 235–53.
- White CA Jr. Nitazoxanide: a new broad spectrum antiparasitic agent. Expert Rev Anti Infect Ther. 2004 Feb;2(1):43–9.
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