NAME: Cryptosporidium parvum
CHARACTERISTICS: Cryptosporidium parvum is an intracellular protozoan parasite of the family Cryptosporidiidae and phylum Apicomplexa Footnote 1Footnote 3. It has a complex lifecycle with sexual and asexual cycles taking place in a single host Footnote 4. Oocysts are thick-walled and are the extracellular and environmental stage Footnote 1Footnote 3. Oocysts are 4-6 μm, nearly spherical, which when ingested by the host, excyst within the lumen of the small intestine to release four infective sporozoites and invade surrounding cells Footnote 1Footnote 3. Sporozoites become trophozoites and subsequently type 1 meronts which reproduce asexually and release type 1 merozoites Footnote 4. Type 1 meronts develop into type 2 meronts and release type 2 merozoites which initate the sexual cycle Footnote 4.
PATHOGENICITY/TOXICITY: Infection causes acute gastroenteritis. Symptoms include diarrhea without red blood cells, abdominal pain, cramps, fever, vomiting, myalgia, flatulence, nausea, anorexia, malaise, and fatigue Footnote 5-7. In immunocompetent individuals, illness is self-limiting with symptoms lasting for up to three weeks Footnote 5. Immunocompromised individuals can develop prolonged and chronic cryptosporidiosis Footnote 5. Cryptosporidiosis in immunocompromised patients may lead to more severe clinical manifestations such as severe weight loss, cholangitis, pancreatitis, sclerosing cholangitis, and liver cirrhosis, and has also been associated with an increased rate of morbidity and mortality Footnote 5. This organism is categorized as a Class B bioterrorism agent by the U.S. Department of Homeland Security Footnote 8.
EPIDEMIOLOGY: C. parvum occurs worldwide and is ubiquitous in the environment Footnote 1Footnote 9. Cryptosporidiosis is in the top five most common causes of infectious diarrhea around the globe Footnote 9. Prevalence varies based on climate and level of development, accounting for 0.1-2% of diarrheal illness in cooler and developed areas and 0.5-10% in warmer and developing countries Footnote 9. Settings involving close contact with infected persons, including day-care centres, which increase transmission Footnote 10. Outbreaks have been associated with contaminated food, drinking, and recreational water. One outbreak linked to contaminated drinking water affected over 400,000 individuals in Milwaukee, Wisconsin Footnote 3.
INFECTIOUS DOSE: The median infectious dose in healthy adult volunteers is 132 oocysts Footnote 6. However, the infectious dose for humans is as low as 1-5 oocysts Footnote 11Footnote 12. Infectious dose is dependent on the immune status of the host, with immunodeficient persons being much more susceptible Footnote 13.
INCUBATION PERIOD: 7 to 10 days Footnote 9.
RESERVOIR: Environment and many mammalian species Footnote 9.
ZOONOSIS: Yes – Mainly from domestic and wild ruminants Footnote 1.
VECTORS: Flying insects can act as a mechanical vector Footnote 14.
DRUG SUSCEPTIBILITY: Susceptible to nitazoxanide Footnote 1 (not available in Canada).
SUSCEPTIBILITY TO DISINFECTANTS: C. parvum is susceptible to high concentration (> 6%) of hydrogen peroxide and ethylene oxide, ozone Footnote 15. It is resistant to low concentration of hydrogen peroxide, peracetic acid, sodium hypochlorite, phenolic, quaternary ammonium compound, 2% glutaraldehyde, ortho-phtalaldehyde, and 70% ethanol Footnote 16.
PHYSICAL INACTIVATION: Inactivated by moist heat Footnote 17(e.g. 121°C for 18 minutes), freezing (-70°C for seconds or -20°C for 24 hours), desiccation Footnote 3Footnote 16, and UV light Footnote 18. Use of “absolute” 1 μm filters.
SURVIVAL OUTSIDE HOST: Can survive for 6 months at 20°C in the environment Footnote 3.
FIRST AID/TREATMENT: Illness is generally self-limiting in immunocompetent patients. Rehydration and electrolyte therapy may be used in cases with severe diarrhea. Nitazoxanide is approved for treatment of cryptosporidiosis in children aged 1 to 10 years in the USA Footnote 19. It has also showed promise in immunocompromised individuals Footnote 1Footnote 2. Immunocompromised patients are often treated with paromomycin, letrazuril and azithromycin Footnote 2. Highly active antiretroviral therapy (HAART) is currently considered the best treatment option for life-threatening cryptosporidiosis in AIDS patients Footnote 1Footnote 2.
LABORATORY-ACQUIRED INFECTIONS: Yes, at least 16 cases of cryptosporidiosis have been reported Footnote 20.
SOURCES/SPECIMENS: Stool, intestinal biopsy specimens from humans or animals and environmental water Footnote 1.
SPECIAL HAZARDS: Contact with naturally and experimentally infected animals Footnote 4.
RISK GROUP CLASSIFICATION: Risk Group 2.
CONTAINMENT REQUIREMENTS: Containment Level 2 facilities, equipment, and operational practices for work involving infectious or potentially infectious materials, animals, or cultures Footnote 22.
PROTECTIVE CLOTHING: Lab coat. Gloves when direct skin contact with infected materials or animals is unavoidable. Eye protection must be used where there is a known or potential risk of exposure to splashes Footnote 22.
OTHER PRECAUTIONS: All procedures that may produce aerosols, or involve high concentrations or large volumes should be conducted in a biological safety cabinet (BSC). The use of needles, syringes, and other sharp objects should be strictly limited. Additional precautions should be considered with work involving animals or large scale activities Footnote 22.
SPILLS: Allow aerosols to settle and, wearing protective clothing, gently cover spill with paper towels and apply an appropriate disinfectant, starting at the perimeter and working towards the centre. Allow sufficient contact time before clean up Footnote 22.
DISPOSAL:Decontaminate all wastes that contain or have come in contact with the infectious organism by autoclave, chemical disinfection, gamma irradiation, or incineration before disposing Footnote 22.
STORAGE: The infectious agent should be stored in leak-proof containers that are appropriately labelled Footnote 22.
REGULATORY INFORMATION: The import, transport, and use of pathogens in Canada is regulated under many regulatory bodies, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment Canada, and Transport Canada. Users are responsible for ensuring they are compliant with all relevant acts, regulations, guidelines, and standards.
UPDATED: December 2011
PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada.
Although the information, opinions and recommendations contained in this Pathogen Safety Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.
Copyright © Public Health Agency of Canada, 2011 Canada