Parasitology and Medical Entomology: Amoebae and Diseases

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Questions and Answers

What is the primary method of diagnosis for Acanthamoeba keratitis?

  • Brain biopsy
  • Blood test
  • Culturing of CSF
  • Wet mount of corneal scrapings (correct)

Which of the following is a clinical feature of Granulomatous amoebic encephalitis (GAE)?

  • Hypertension
  • Seizures (correct)
  • Diarrhea
  • Cardiac arrest

What is the primary site of infection for Balamuthia mandrillaris in humans?

  • Respiratory tract (correct)
  • Muscular system
  • Gastrointestinal tract
  • CNS

What is the typical outcome of Acanthamoeba keratitis if left untreated?

<p>Permanent visual impairment or blindness (C)</p> Signup and view all the answers

Which of the following is a prevention method for Acanthamoeba keratitis?

<p>Avoiding tap water to rinse contact lenses (A)</p> Signup and view all the answers

What is the shape of the trophozoite of Balamuthia mandrillaris?

<p>Irregular (A)</p> Signup and view all the answers

What is the primary cause of primary amoebic meningoencephalitis (PAM)?

<p>Naegleria fowleri (B)</p> Signup and view all the answers

Where is Naegleria fowleri typically found?

<p>Warm water (e.g. hotsprings) and soil (B)</p> Signup and view all the answers

What is the shape of the trophozoite form of Naegleria fowleri?

<p>Amoeboid (C)</p> Signup and view all the answers

What is the function of the flagellate form of Naegleria fowleri?

<p>Motile form in distilled water (A)</p> Signup and view all the answers

How does the trophozoite of Naegleria fowleri replicate?

<p>Promitosis (C)</p> Signup and view all the answers

How does the trophozoite of Naegleria fowleri migrate to the brain?

<p>Via the olfactory nerves (B)</p> Signup and view all the answers

What is the primary source of infection for Naegleria fowleri?

<p>Swimming in warm freshwater lakes and rivers (A)</p> Signup and view all the answers

What type of stain can be used to examine Naegleria fowleri?

<p>Giemsa (A)</p> Signup and view all the answers

What is the typical size of an Acanthamoeba trophozoite?

<p>20–50 μm (C)</p> Signup and view all the answers

How do humans typically acquire Acanthamoeba infection?

<p>Through inhalation of cysts or trophozoites (B)</p> Signup and view all the answers

What is the characteristic feature of Acanthamoeba cysts?

<p>They have a polygonal double wall (C)</p> Signup and view all the answers

What is the primary habitat of Acanthamoeba species?

<p>Central nervous system and eyes (D)</p> Signup and view all the answers

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Study Notes

Acanthamoeba Species

  • Produce granulomatous amoebic encephalitis (GAE) in immunodeficient patients, which can be fatal within days
  • Cause keratitis in healthy individuals, often associated with contact lens use
  • Can result in permanent visual impairment or blindness

Acanthamoeba Species Pathogenesis and Clinical Features

  • GAE: seizures, paresis, and mental deterioration
  • Acanthamoeba keratitis: corneal infection in healthy individuals

Acanthamoeba Species Diagnosis

  • GAE: trophozoites and cysts in brain biopsy, culture, or immunofluorescence microscopy
  • Acanthamoeba keratitis: cyst in corneal scrapings by wet mount, histology, or culture

Acanthamoeba Species Prevention and Control

  • Do not use tap water to rinse contact lenses

Balamuthia mandrillaris

  • Found in soil
  • Habitat: CNS
  • Morphology:
    • Trophozoite: 12-60 μm, irregular shape, motile by broad pseudopodia
    • Cyst: 6-20 μm, spherical with outer irregular wall and inner smooth wall
  • Infection through respiratory tract, skin lesions, or eyes
  • Life cycle similar to Acanthamoeba spp.

Naegleria fowleri

  • Causes primary amoebic meningoencephalitis (PAM) in healthy individuals
  • Found in warm water (e.g., hot springs) and soil worldwide
  • Habitat: CNS
  • Morphology:
    • Trophozoite: 10-20 μm, amoeboid with rounded pseudopodia and spherical nucleus
    • Cyst: spherical
  • Life cycle:
    1. Cyst
    2. Trophozoite (amoeboid and flagellate forms)
    3. Flagellated form
    4. Trophozoite replication by promitosis
    5. Trophozoite penetration of nasal mucosa
    6. Trophozoite migration to brain via olfactory nerves
  • Infection occurs through swimming, diving, or nasal irrigation in contaminated water

Naegleria fowleri Diagnosis

  • CSF examination:
    • Wet film examination for motile trophozoites
    • Fixed smear staining with Giemsa or modified trichrome stain
  • Culture
  • Molecular diagnosis: PCR on CSF specimen

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