Cryptosporidium parvum

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Cryptosporidium parvum

• Melissa Lamb

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Cryptosporidium parvum

• Enteric parasite
• One of the three most common diarrhea-causing
  pathogens in the world

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Prevalence

• Found in most parts of the world
• Most prevalent in Asia, Africa, Australia, South
  America
• Antibody prevalence in Peru and Venezuela 64
• 32 in Peace Corps workers
• More prevalent in rural areas of U.S.
• More animal contact

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Transmission

• Fecal-oral route
• Fomites
• Water
• Drinking water (even after treatment)
• Swimming pools
• Unpasteurized Apple Cider
• Animal contact
• Food

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Infectivity

• C. parvum has a low ID50 (9-1000 oocysts)
• Can be infected by just one oocyst
• 10 billion oocysts per gram infected feces

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Life Cycle
http//www.dpd.cdc.gov/dpdx/HTML/Cryptosporidiosis
.asp?bodyFrames/A-F/Cryptosporidiosis/body_Crypto
sporidiosis_life_cycle_lrg.htm
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Life Cycle
http//www.dpd.cdc.gov/dpdx/HTML/Cryptosporidiosis
.asp?bodyFrames/A-F/Cryptosporidiosis/body_Crypto
sporidiosis_life_cycle_lrg.htm
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Oocyst

• Double walled
• Resistant to chlorine, drying, progressive
  freezing, salt water
• Only stage in life cycle that can live ex vivo
• Imbeds itself in gut epithelium and releases
  sporozoites
• Reproduction continues sexually and asexually

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Life Cycle
http//www.dpd.cdc.gov/dpdx/HTML/Cryptosporidiosis
.asp?bodyFrames/A-F/Cryptosporidiosis/body_Crypto
sporidiosis_life_cycle_lrg.htm
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Clinical Characteristics

• Secretory diarrhea (some mucous, but no blood)
• Slight fever, fatigue, myalgia
• Oocysts may infect the lungs and trachea,
  resulting in cough
• Dehydration and extreme weight loss in
  immunocompromised

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Detection

• Acid-fast stain of infected feces
• Direct immunofluorescence antibody stain using
  monoclonal antibody to oocyst wall

http//www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/Cryp
tosporidiosis_il.htm
Modified acid-fast oocyst stain
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Treatment

• Nitazoxanide
• Interferes with folate production
• Prevents parasite replication
• Immunocompetent
• C. parvum will usually pass on its own
• Immunocompromised
• AIDS patients treat with antiretrovirals and
  strengthen immune system, no cure
• Others would not benefit from antiretrovirals
  keep hydrated

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Prevention

• Water filtration
• Filters must be lt1 um to filter oocyst
• Swimming pools
• Must be drained if infected fecal accident
• Pasteurization
• Hand washing
• Particularly in daycares

C. Parvum (left) and Giardia intestinalis (right)
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Bottled Watersnot all are created equal

• Water so labeled has been processed by method
  effective against crypto
• Reverse osmosis treated
• Distilled
• Micro-filtered
• Filtered through an absolute 1 micron or smaller
  filter
• "One micron absolute"
• Water so labeled may not have been processed by
  method effective against crypto
• Carbon-filtered
• Filtered
• Particle-filtered
• Multimedia-filtered
• Ozonated
• Ozone-treated
• Ultraviolet light-treated
• Activated carbon-treated
• Carbon dioxide-treated
• Ion exchange-treated
• Deionized

http//www.cdc.gov/NCIDOD/DPD/parasites/cryptospor
idiosis/factsht_crypto_prevent_water.htm
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Outbreaks

• Milwaukee, WI 1993 400,000 people
• Gainesville, FL 1995 day camp
• New York 1996 unpasteurized apple cider

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Summary

• Cryptosporidiosis caused by cryptosporidium
  parvum
• Transmitted via fecal-oral route
• Oocyst stage in life cycle is resilient
• Oocyst imbeds itself in gut epithelium
• Infection usually occurs from tainted water, even
  if it has been treated
• No cure in immunocompromised