Potential Bioterrorism Agent: Category B
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Laboratory: Report by IDSS, facsimile, mail or phone
Physician: Report by facsimile, mail or phone
Local Public Health Agency (LPHA): Follow-up Required
Iowa Department of Public Health
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Cryptosporidiosis refers to disease caused by Cryptosporidium, a coccidian protozoan. Many species of Cryptosporidium exist that infect humans and a wide range of animals. Cryptosporidium parvum and Cryptosporidium hominis, are the most prevalent species causing disease in humans, infections by C. felis, C. meleagridis, C. canis, and C. muris have also been reported. Cryptosporidium was not recognized as a cause of human illness until 1976.
B. Clinical Description
Symptoms: The most common symptom of cryptosporidiosis is profuse and watery diarrhea, which may be preceded by anorexia and vomiting in children. The diarrhea is associated with cramping abdominal pain. Other signs and symptoms include weight loss, stomach cramps, nausea, vomiting, and low-grade fever. Some people with cryptosporidiosis will have no symptoms at all. While the small intestine is the site most commonly affected, Cryptosporidium infections could possibly affect other areas of the digestive or respiratory tract. Asymptomatic infections are common and often serve as a source of infection for others.
Complications: Symptoms often wax and wane, but improve in fewer than 30 days in most immunocompetent people (average is 10 days). Immunodeficiency, especially in HIV infection, is associated with an inability to clear the parasite, and the disease may have a prolonged and fulminant clinical course, leading to death.
Treatment: FDA licensed nitazoxanide (Alinia®) for the treatment of diarrhea caused by Cryptosporidium in immunocompetent individuals >1 years of age.
Common reservoirs: The reservoirs for the Cryptosporidium species that infect humans are humans, cattle, and other domesticated animals, including pets.
D. Modes of Transmission:
Spread: Transmission is fecal-oral, which includes person-to-person, animal-to-person, waterborne and foodborne.
Survivability: The oocyst of the parasite can survive in feces for a prolonged length of time and is resistant to chlorination.
Person-to-person: Many persons are infected by hand-to-mouth transfer of oocysts from the feces of an infected person, especially in institutions and child care centers. Transmission can also occur person-to-person through sexual contact, particularly oral-anal contact. Infected animals and people excrete large numbers of oocysts in stool and, although the infectious dose is not certain, it is probably very low.
Waterborne/Foodborne: Oocysts are relatively hardy and can survive in the environment for weeks or months. They are resistant to concentrations of chlorine and other disinfectants commonly used for drinking water or swimming pool treatment. Large outbreaks traced to contaminated drinking water have been reported, including an outbreak in Milwaukee that reportedly affected 400,000 people. Localized outbreaks may occur from fecally contaminated water, such as streams/lakes and swimming pools open to contamination by human and animal feces. Outbreaks have resulted from eating food contaminated by animal feces (e.g., unpasteurized apple cider). An infected food worker could be a source of foodborne transmission. There have also been outbreaks associated with “recreational water”, meaning water used for swimming such as municipal swimming pools, lakes, etc.
Zoonotic: Transmission can occur through contact with feces from infected animals (a risk for livestock handlers, dairy farmers and veterinarians). People are not infected through contact with blood.
E. Incubation period
The incubation period is not precisely known; 1 - 12 days is the likely range, with an average of about 7 days.
F. Period of Communicability or Infectious Period
The disease is communicable for as long as the infected person excretes Cryptosporidium oocysts. Excretion generally begins at the onset of symptoms. Oocysts continue to be excreted in the stool for several weeks after symptoms subside, and they may remain infective outside the body for 2 - 6 months in a moist environment.
Cryptosporidiosis has a worldwide distribution. Cases occur year-round with a peak during summer and early fall. Prior to 2006, approximately 70 cases were reported each year in Iowa. In recent years the number of cases reported in Iowa has dramatically increased with 364 cases in 2011, 328 cases reported in 2012 and 1505 cases in 2013. In developed countries, the prevalence of infection ranges from < 1% to 4.5% of individuals surveyed by stool examination. The prevalence is significantly higher in developing regions of the world. Cryptosporidiosis is among the most common causes of persistent diarrhea in patients with AIDS in the United States. Children under two years of age, animal handlers, travelers to endemic areas, men who have sex with men, and close contacts of infected individuals are most likely to be infected. Outbreaks have been reported in child care centers and have been associated with public drinking water; swimming in contaminated pools, lakes and ponds; and drinking unpasteurized cider made from apples contaminated with cattle manure. It is estimated that 50% of dairy calves shed oocysts and that the parasite is present on >90% of dairy farms.
H. Bioterrorism Potential
Category B Agent: Cryptosporidium parvum is identified as a Category B bioterrorism agent, seen particularly as a water safety threat by the CDC. If acquired and properly disseminated, Cryptosporidium parvum could cause a serious public health challenge because the protozoans are moderately easy to disseminate, result in moderate morbidity rates and low mortality rates, and require specific enhancements of CDC's diagnostic capacity and enhanced disease surveillance.
I. Additional Information
The Council of State and Territorial Epidemiologists (CSTE) surveillance case definitions for Cryptosporidiosis can be found at: wwwn.cdc.gov/NNDSS/script/casedefDefault.aspx
CSTE case definitions should not affect the investigation or reporting of a case that fulfills the criteria in this chapter. (CSTE case definitions are used by the state health department and the CDC to maintain uniform standards for national reporting.)
American Academy of Pediatrics. 2003 Red Book: Report of the Committee on Infectious Diseases, 26th Edition. Illinois, American Academy of Pediatrics, 2003.
CDC website, Cryptosporidium Available at: www.cdc.gov/parasites/crypto/
Heymann, D.L., ed. Control of Communicable Diseases Manual, 20th Edition. Washington, DC, American Public Health Association, 2015.