Bioterrorism

Profiles for Health Care Workers (Fact Sheets) - "B" Agents

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Cryptosporidiosis

Causative Agent:
Cryptosporidiosis is a parasitic infection caused by Cryptosporidium parvum.

Route of Exposure:
Fecal-oral, which includes person to person, animal to person, waterborne, and foodborne transmission.

Infective Dose & Infectivity:
Less than 10 organisms, and presumably one organism, can initiate an infection. All people are believed to be susceptible, though people with intact immune systems may be asymptomatic. Individuals with impaired immunity and children ages 1 to 5 years old are most likely to become infected.

Incubation Period:
The incubation period is not precisely known; 1-12 days is the likely range, with an average of about 7 days.

Clinical Effects:
Asymptomatic infections are common and constitute a source of infection for others. The major symptom in humans is diarrhea, which may be profuse and watery, preceded by anorexia and vomiting in children. The diarrhea is associated with cramping abdominal pain. General malaise, fever, anorexia, nausea and vomiting occur less often. Symptoms often wax and wane but remit in fewer than 30 days in most immunologically healthy people. In patients who are immunocompromised, cryptosporidiosis usually causes chronic diarrhea; however, rarely, lung and biliary tract disease also occurs.

Lethality:
Cryptosporidiosis is rarely lethal in healthy people. In persons with severely weakened immune systems, chronic gastrointestinal illness or more disseminated disease can lead to complications and death.

Transmissibility:
It is transmitted by ingestion of fecally contaminated food or water, including water swallowed while swimming; by exposure to fecally contaminated environmental surfaces; and by the fecal-oral route from person to person (e.g. while changing diapers caring for an infected person, or engaging in certain sexual behaviors).

Primary Contamination & Methods of Dissemination:
In a terrorist attack, C. parvum would most likely be disseminated through the intentional contamination of food or water supplies.

Secondary Contamination & Persistence of organism:
Secondary transmission can result from exposure to the stool of infected individuals, both patients with acute infection and asymptomatic carriers. Oocysts, the infectious stage, appear in the stool at the onset of symptoms and are infectious immediately upon excretion. Oocysts continue to be excreted in the stool for several weeks after symptoms resolve; outside the body, they may remain infective for 2-6 months in a moist environment. Oocysts are highly resistant to chemical disinfectants used to purify drinking water.

Decontamination & Isolation:

  • Patients – No decontamination necessary. Patients should be treated with standard precautions, with contact precautions for diapered or incontinent patients. Hand washing is of particular importance. For hospitalized patients, enteric precautions in the handling of feces, vomitus, and contaminated clothing and bed linen; exclusion of symptomatic individuals from food handling and from direct care of hospitalized and institutionalized patients; release to return to work in sensitive occupations when asymptomatic.
  • Equipment, clothing & other objects – Infection control is difficult because of oocyte resistance to common disinfectants. Heating to 113º F (45º C) for 5-20 minutes, 140º F (60º C) for 2 minutes, or chemical disinfection with 10% formalin or 5% ammonia solution is effective.

Laboratory Testing:
Diagnosis is made by identification of oocysts in stool samples. However, routine laboratory testing for ova and parasites will not detect C. parvum. A specific request for C. parvum testing must be made. Commercially available tests include ELISA assays for stool, and a fluorescein-tagged monoclonal antibody is useful for detecting oocysts in both stool and environmental samples.

Therapeutic Treatment:
Supportive therapy with rehydration as needed is important. Nitaxozanide suspension (Alina™, Romark Laboratories) was recently approved by the FDA for treatment of cryptosporidiosis. If the patient is taking immunosuppressive drugs, these should be stopped or reduced if possible.

Prophylactic Treatment:
No vaccine is available.

Differential Diagnosis:
The differential diagnosis for Cryptosporidium parvum includes Giardia, Isospora, microsporidia, Cyclospora, Clostridium dificile, Salmonella, Shigella, Campylobacter, Mycobacterium avium complex, cytomegalovirus, rotavirus, norovirus, and adenovirus.

References:

  • Chin J. Control of Communicable Diseases Manual, Seventeenth Edition, American Public Health Association; 2000. Center for Food Safety and Applied Nutrition. Foodborne Pathogenic Microorganisms and Natural Toxins Handbook, U.S. Food and Drug Administration

Find the PDF version of this Fact Sheet in the Zebra Manual.