Blood and tissue protozoans

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Blood and tissue protozoans

• Sarcodina Naegleria fowleri
  Acanthamoeba species
• Mastigophora Trypanosoma brucei, Trypanosoma
  cruzi
• Leishmania species
• Sporozoa Plasmodium falciparum
• Toxoplasma gondii
• Babesia microti
• ??? Pneumocystis carinii

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Focus on pathogens Naegleria fowleri

• Facts / life-cycle N. fowleri is a free-living
  protozoan in the phylum Sarcodina. Free-living
  implies lack of necessity for a host organism,
  but this guy can be a pathogen. He has no need
  for a 2 host. Trophs multiply by simple binary
  fission, can form cysts, but can also form a
  flagellated form (?) incapable of reproduction.
  N. fowleri lives in warm fresh water and soil
  where he usually comes in contact with human
  hosts in lakes, rivers, swimming pools,
  whirlpools jacuzzis although cases have also
  been linked to cysts in dust, and to air
  conditioning units. Cysts are moderately
  chlorine resistant adding to the problem.

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Focus on pathogens Naegleria fowleri

• Epidemiology the organism is common in warm
  fresh waters worldwide, so exposure to humans is
  common. Although clusters of localized
  infections occur, there seems to be no
  correlation between areas of greatest parasite
  abundance ie. infection rates are not higher in
  equatorial warm waters as would be expected.
  Most patients have been in a swimming pool or
  natural fresh water a few days prior to symptom
  onset. Infections, at least those causing
  disease are rare, but disease causing infections
  have a high mortality rate. Of 150 reported
  cases, only 3 patients have survived. Most of
  the patients have been children and young adults.

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Focus on pathogens Naegleria fowleri

• Pathology / clinical symptoms N. fowleri causes
  a condition known as primary amoebic
  meningoencephalitis, a fulminating, rapidly fatal
  disease. The amoebas enter the brain via the
  olfactory epithelium. The disease appears with
  the sudden onset of bifrontal or bitemporal
  headache, fever, nausea, vomiting, and stiff
  neck. The affected areas fo the brain are
  necrotic and hemorhagic. Purulence from immune
  response results in rapidly escalating
  intracranial pressure. Symptoms progress rapidly
  to lethargy, confusion, and coma. In all of the
  recorded cases, the patient died within 48 to 72
  hours.

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N. fowleri laboratory diagnosis

• Trophs
• Size 7-20uM
• Single nucleus with large karyosome and no
  peripheral chromatin
• Clear halo nuclear halo often visible
• Motility very active with single or multiple
  broad blunt pseudopods
• Trophs convert to flagellated form within a few
  minutes after being exposed to clear distilled
  water
• Cyst round, with size and nuclear
  characteristics identical to troph. Cysts of
  this organism are rarely found in clinical
  specimens.

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Focus on pathogens Acanthamoeba

• Facts / life-cycle this is also a free-living
  amoeba. Several species of the Genus are human
  pathogens, and no attempt is made to distinguish
  them. His life cycle is similar to Naegleria
  except for the absence of the flagellated form.
  He is also ubiquitous in fresh waters, but can
  also be found in brackish and salt water.
  Transmission appears to be similar to Naegleria
  with added means by entry through the skin. Once
  established in the patient, Acanthamoeba can
  spread via the circulatory system to cause
  pathology in other tissues, namely eyes,
  integument and lungs.

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Focus on pathogens Acanthamoeba

• Epidemiology Similar to N. fowleri. It is
  found in the same places, and is transmitted in
  the same way, although it is more common. There
  are 1000 cases annually of granulomatous amoebic
  encephalitis and amoebic keratitis caused by
  Acanthmoeba species. Pathology of other tissues,
  including integument and lungs does occur, but
  are rare.

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Focus on pathogens Acanthamoeba

• Pathology / clinical symptoms unlike N.
  fowleri, Acanthamoeba infection is usually
  limited to chronically ill, immunocompromised or
  otherwise debilitated patients. Two types of
  clinical syndromes are involved. Granulomatous
  amoebic encephalitis (GAE), similar to the neural
  condition caused by N. fowleri, is more slowly
  progressing and chronic, but also has a high
  mortality rate, partly due to the poor condition
  of the host. AIDS patients comprise a large
  percentage of GAE patients.
• The second common syndrome is amoebic keratitis,
  a blinding inflamatory condition of the cornea.
  Contact lens use predisposes folks to this
  condition.
• Acanthamoeba species can also cause opportunistic
  lung and skin infections in immunocompromised
  patients.