18 Questions
What is the primary method of diagnosis for Acanthamoeba keratitis?
Wet mount of corneal scrapings
Which of the following is a clinical feature of Granulomatous amoebic encephalitis (GAE)?
Seizures
What is the primary site of infection for Balamuthia mandrillaris in humans?
Respiratory tract
What is the typical outcome of Acanthamoeba keratitis if left untreated?
Permanent visual impairment or blindness
Which of the following is a prevention method for Acanthamoeba keratitis?
Avoiding tap water to rinse contact lenses
What is the shape of the trophozoite of Balamuthia mandrillaris?
Irregular
What is the primary cause of primary amoebic meningoencephalitis (PAM)?
Naegleria fowleri
Where is Naegleria fowleri typically found?
Warm water (e.g. hotsprings) and soil
What is the shape of the trophozoite form of Naegleria fowleri?
Amoeboid
What is the function of the flagellate form of Naegleria fowleri?
Motile form in distilled water
How does the trophozoite of Naegleria fowleri replicate?
Promitosis
How does the trophozoite of Naegleria fowleri migrate to the brain?
Via the olfactory nerves
What is the primary source of infection for Naegleria fowleri?
Swimming in warm freshwater lakes and rivers
What type of stain can be used to examine Naegleria fowleri?
Giemsa
What is the typical size of an Acanthamoeba trophozoite?
20–50 μm
How do humans typically acquire Acanthamoeba infection?
Through inhalation of cysts or trophozoites
What is the characteristic feature of Acanthamoeba cysts?
They have a polygonal double wall
What is the primary habitat of Acanthamoeba species?
Central nervous system and eyes
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:
- Cyst
- Trophozoite (amoeboid and flagellate forms)
- Flagellated form
- Trophozoite replication by promitosis
- Trophozoite penetration of nasal mucosa
- 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
This quiz covers the basics of parasitology and medical entomology, focusing on amoebae and the diseases they cause, including primary amoebic meningoencephalitis and granulomatous amoebic encephalitis.
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