Focus on pathogens: Cryptosporidium parvum

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Focus on pathogens Cryptosporidium parvum

• Epidemiology As mentioned above, C. parvum
  contamination usually originates with animal
  feces washed into watersheds by rain or by other
  means. Most cases occur in urban areas when
  water treatment methods fail. Several epidemics
  in major urban cities of the U.S. occurred over
  the last 7 years. Prevalence of outbreaks is
  greatest in coastal NE and Great Lakes region
  states. Most notable was an episode during the
  Spring of 1993 in the Milwaukee area with over
  400,000 cases 40 of these cases were elderly
  people 120 deaths resulted. Serology data
  suggests that 30 of all US residents have been
  infected with C. parvum at some time.
• Young children, pregnant women, the elderly and
  otherwise immune deficient individuals have the
  greatest incidence of disease and the greatest
  severity.
• Dairy cows have historically been the primary
  focus. Canada geese feces in 7 of 9 sites tested
  on the Chesapeake bay contained C. parvum cysts
  or trophs. Poor hygiene has also been implicated
  day care centers.

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Focus on pathogens Cryptosporidium parvum

• Pathology / clinical symptoms Infections are
  self-limiting in immune competent individuals.
  In this case symptoms are standard
  gastrointestinal with cholerae-like watery or
  mucus diarhea, and varying degrees of cramping as
  in giardiasis. Immune compromised patients,
  especially those with AIDS, develop severe
  diarhea leading to electrolyte imbalance,
  dehydration and sometimes death. Severe cases
  result in destruction of intestinal microvilli,
  although the mechanism is not known.
• In immuno-compromised patients, the extent of
  infection can extend from esophagus to rectum,
  and include hepatic and respiratory systems.

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Focus on pathogens Cryptosporidium parvum

• Laboratory diagnosis Oocysts
• - Size tiny, 4-6uM
• - Appearance spherical to ovoid, refractile,
  smooth wall
• - Concentrates well with a sugar flotation
  method
• - Formalin-preserved or fresh specimens okay
• ? - Oocysts stain red with a modified acid fast
  stain 1 of only 2 protozoan cysts that share
  this property.
• - Indirect immunofluorescence stain using
  monoclonal antibody is both sensitive and
  specific for oocysts
• - Acridine orange (a nucleic acid stain) stains
  oocysts yellow in uv light (fluorescent
  microscope )

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C. parvum oocysts
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C. parvum oocysts
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C. parvum acid-fast oocysts
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FAb immunofluorescence Acridine orange
epifluorescence
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Focus on pathogens Cyclospora cayetanensis

• Facts / life-cycle originally thought to be
  cyanobacteria, this organism was not identified
  until 1990. Humans are thought to be the only
  true host (vs Sporozoan description), but there
  is some argument about this. This organism is
  NOT thought to be a zoonosis.
• Life-cycle similar to C. parvum in all respects
  except that auto-infection is less likely (some
  say it does not happen period). Merozoite
  multiplication is insufficient for effective
  infection, and the necessity for greater than
  intestinal O2 for sporogenesis within oocysts
  prevents the auto-infective cyst option.

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Focus on pathogens Cyclospora cayetanensis

• Epidemiology other than a few local outbreaks,
  prevalence in the US is far below 1. Cases are
  limited to warm weather months (for oocyst
  germination) this also coincides with fruit
  vegetable imports from C. S. America, the
  presumed source for most infections. For some
  reason, imported raspberries and herbs such as
  basil are a major source (?). Wash your produce!
  Seasonally coincides with C. parvum cases - a
  source of confusion.