Cryptosporidium parvum – Pathogen Safety Data Sheet

Cryptosporidium parvum (C. parvum) is ubiquitous in our environment. Humans, 152 species of mammals, fish, amphibians, reptiles, and birds can carry and spread the parasite by depositing oocysts in their faeces. Both sexual and asexual lifecycles can take place in a single host. The parasite produces oocysts which are thick-walled, nearly spherical, range in size from 4-6μm in size, and survive in the small intestine of their hosts. Oocysts are found in water affected by sewage, swimmer contamination and stormwater runoff. Humans can be infected with as few as 1-5 oocysts and immunocompromised persons are more susceptible to infection. Infection causes acute vomiting and diarrhea lasting up to three weeks. Immunocompromised individuals can develop chronic cryptosporidiosis.  Cryptosporidiosis is in the top five most common causes of infectious diarrhea around the globe, causing up to 2% of diarrheal illness in developed areas and 10% in developing countries. 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.

Cryptosporidium is killed by moist heat (e.g. 121°C for 18 minutes), freezing (-70°C for seconds or -20°C for 24 hours), desiccation, and UV light. Oocysts can survive outside the host for 6 months at 20°C in the environment.

Drinking water treatment: Both microfiltration and ultrafiltration are the most cost-effective methods to remove C. muris and C. parvum from water. 20 valid cryptosporidiun species have been recognized.

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CHARACTERISTICS: Cryptosporidium parvum is an intracellular protozoan parasite of the family Cryptosporidiidae and phylum Apicomplexa Footnote1Footnote3.  It has a complex lifecycle with sexual and asexual cycles taking place in a single host Footnote4. Oocysts are thick-walled and are the extracellular and environmental stage Footnote1Footnote3. 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 Footnote1Footnote3. …

SECTION II – HAZARD IDENTIFICATION

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 Footnote5-7. In immunocompetent individuals, illness is self-limiting with symptoms lasting for up to three weeks Footnote5. Immunocompromised individuals can develop prolonged and chronic cryptosporidiosis Footnote5. 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 Footnote5. …

EPIDEMIOLOGY: C. parvum occurs worldwide and is ubiquitous in the environment Footnote1Footnote9. Cryptosporidiosis is in the top five most common causes of infectious diarrhea around the globe Footnote9. 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 Footnote9. Settings involving close contact with infected persons, including day-care centres, which increase transmission Footnote10. 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 Footnote3.

HOST RANGE: Humans, 152 species of mammals, fish, amphibians, reptiles, and birds Footnote3Footnote9.

INFECTIOUS DOSE: The median infectious dose in healthy adult volunteers is 132 oocysts Footnote6. However, the infectious dose for humans is as low as 1-5 oocysts Footnote11Footnote12. Infectious dose is dependent on the immune status of the host, with immunodeficient persons being much more susceptible Footnote13.

MODE OF TRANSMISSION: Transmitted through the fecal-oral route, direct contact with infected humans or animals, contaminated food or water and aerosols Footnote1Footnote2Footnote4.

INCUBATION PERIOD: 7 to 10 days Footnote9.

COMMUNICABILITY: Highly contagious. Human-to-human transmission is common Footnote5. Oocysts can be excreted up to 50 days after cessation of diarrhea Footnote10.

SECTION III – DISSEMINATION

RESERVOIR: Environment and many mammalian species Footnote9.

ZOONOSIS: Yes – Mainly from domestic and wild ruminants Footnote1.

VECTORS: Flying insects can act as a mechanical vector Footnote14.

SECTION IV – STABILITY AND VIABILITY

DRUG SUSCEPTIBILITY: Susceptible to nitazoxanide Footnote1 (not available in Canada).

SUSCEPTIBILITY TO DISINFECTANTS: C. parvum is susceptible to high concentration (> 6%) of hydrogen peroxide and ethylene oxide, ozone Footnote15. It is resistant to low concentration of hydrogen peroxide, peracetic acid, sodium hypochlorite, phenolic, quaternary ammonium compound, 2% glutaraldehyde, ortho-phtalaldehyde, and 70% ethanol Footnote16.

PHYSICAL INACTIVATION: Inactivated by moist heat Footnote17(e.g. 121°C for 18 minutes), freezing (-70°C for seconds or -20°C for 24 hours), desiccation Footnote3Footnote16, and UV light Footnote18. Use of “absolute” 1 μm filters.

SURVIVAL OUTSIDE HOST: Can survive for 6 months at 20°C in the environment Footnote3.

SECTION V – FIRST AID / MEDICAL

SURVEILLANCE: Detection usually by direct microscopic observation of oocysts in stool specimens. Nucleic acid and antigen detection methods have also been developed Footnote1Footnote2Footnote5.

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 Footnote19. It has also showed promise in immunocompromised individuals Footnote1Footnote2. Immunocompromised patients are often treated with paromomycin, letrazuril and azithromycin Footnote2. Highly active antiretroviral therapy (HAART) is currently considered the best treatment option for life-threatening cryptosporidiosis in AIDS patients Footnote1Footnote2.

IMMUNIZATION: None

PROPHYLAXIS: None

SPECIAL HAZARDS: Contact with naturally and experimentally infected animals Footnote4.

Copyright © Public Health Agency of Canada, 2011 Canada

References:
Enteric Protozoa: Giardia and Cryptosporidium, pdf file

Page 10: Guidelines for Canadian Recreational Water Quality – Third Edition, pdf file

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