Protozoan parasites in the genus Cryptosporidium, most commonly Cryptosporidium hominis and C. parvum.
Oral-fecal, primarily through contaminated food or water, including water swallowed while swimming, or through contact with an infected person or animal, most notably pre-weaned calves.
Distributed worldwide. Cryptosporidium caused only a small proportion (6%) of cases of travelers’ diarrhea in North American travelers to Mexico.
Symptoms usually begin 7–10 days (range, 2–26 days) after infection and are generally self-limited. The most common symptom is watery diarrhea. Other symptoms can include abdominal cramps, vomiting, weight loss, fever, decreased appetite, fatigue, joint pain, and headache. In immunocompetent people, symptoms most frequently resolve within 2–3 weeks; patients might experience a recurrence of symptoms after a brief period of recovery before complete symptom resolution. Clinical presentation of cryptosporidiosis in HIV-infected patients varies with level of immunosuppression, ranging from no symptoms or transient disease to relapsing or chronic diarrhea or cholera-like diarrhea, which can lead to life-threatening wasting and malabsorption. Extraintestinal cryptosporidiosis (in the biliary or respiratory tract or rarely the pancreas) has been documented in people who are immunocompromised.
Tests for Cryptosporidium are typically not included in routine ova and parasite testing. Therefore, clinicians should specifically request testing for this parasite, when suspected. Because Cryptosporidium can be excreted intermittently, multiple stool collections (3 stool specimens collected on separate days) increase test sensitivity. Diagnostic techniques include direct fluorescent antibody (considered the gold standard), EIA testing, rapid immunochromatographic cartridge assays, and microscopy with modified acid-fast staining. False-positive results might occur when using rapid immunochromatographic cartridge assays, and confirmation by microscopy should be considered.
Most immunocompetent patients will recover without treatment. Diarrhea should be managed with fluid replacement. Nitazoxanide is approved to treat cryptosporidiosis in immunocompetent patients and is available for those aged ≥1 year. Nitazoxanide has not been shown to be an effective treatment of cryptosporidiosis in HIV-infected patients. However, dramatic clinical and parasitologic responses have been reported in these patients after the immune system has been reconstituted with active combination antiretroviral therapy. Protease inhibitors might have direct anti-Cryptosporidium activity.
Food and water precautions (see Chapter 2, Food & Water Precautions) and handwashing. Cryptosporidium is extremely tolerant to halogens (such as chlorine or iodine), and alcohol-based hand sanitizers are not effective against the parasite. Water can be treated effectively by heating it to a rolling boil for 1 minute or filtering with an absolute 1-µm filter. More prevention recommendations can be found at www.cdc.gov/parasites/crypto/gen_info/prevent.html.