2. Introduction
• Only 3 genera Acanthamoeba, Balamuthia, and Naegleria cause disease in
humans & animals
• Classified under Phylum Protozoa, sub phylum Sarcodina, Super Class
Rhizopodea, Class Lobosea, Order Amoebida
• Acanthamoeba cause Chronic granulomatous Amoebic Encephalitis (GAE)
• Also cause infection of the eye, Acanthamoeba keratitis in humans - occur
naturally in a variety of animals
• More than 20 species of Acanthamoeba based on size and cyst morphology
has been described
• Nine species - A. castellanii, A. culbertsoni, A. divionensis, A. griffinii, A.
hatchetti, A. healyii, A. lenticulata, A. polyphaga, A. rhysodes have been
associated with human disease.
3. Morphology
• It exists in two forms – Trophozoite and Cyst
Trophozoite
• 15 to 45μm in size
• Nuclear characteristics similar to Naegleria
fowleri
• Produce fine tapering hyaline pseudopodia
called Acanthopodia.
• Sluggish Motility
• Flagellated stage is absent
Cyst
• Have double wall, inner wall is smooth and
outer wall – wrinkled and ragged.
• Round measures 8 to 25μm in size
• Survives in dust for many years
4. Life cycle & Pathogenesis
• Diverse habitats - soil, fresh, brackish and
sea water, dust in air, sewage and
swimming pools
• Systemic infection occurs only in
immunocompromised individuals.
• Trophozoite and cyst are infective forms
• Infection enters skin/eyes/inhalation
↓
Primary infection – skin/ lungs are involved
↓
Haematogenous spread from these sites to
brain
5. Leads to the involvement of the central nervous system
↓
Produce Granulomatous Amoebic Encephalitis (GAE) –
show multiple, ring-enhancing lesions in the brain
↓
Rarely cyst rapidly transform into trophozoites in the nasal mucosa to reach the
brain through cribriform plate along the olfactory nerve
↓
Leads to Meningoencephalitis
Biopsy/Autopsy
• Show multifocal sites of haemorrhagic necrosis
in the midbrain, thalamus, brainstem and cerebellum.
• Both trophozoites and cysts are usually seen.
6. Acanthamoeba keratitis
• occurs in healthy individuals
• Associated with corneal trauma and/or contact lens use are at an high risk.
• Corneal infection occurs because of improper maintenance of the lenses and
wearing lenses while swimming.
• Symptoms - Eye pain, redness, Blurred vision, Sensitivity to light, Sensation of
something in the eye and Excessive tearing.
• Deeper corneal invasion with perforation and
loss of vision.
• Corneal lesions are caused by A. polyphaga
• Non-ocular infections are caused by A. culbertsoni
7. Clinical Signs/Symptoms
Salient features of Granulomatous Amoebic Encephalitis
• headache, stiff neck, and mental status abnormalities
• nausea, vomiting, low-grade fever, lethargy
• cerebellar ataxia – lack of muscle coordination, visual disturbances,
hemiparesis(paralysis), seizures and coma.
Laboratory Diagnosis
Sample collection
1.CSF – GAE
2.Corneal scrapings – Keratitis
Microscopy
Detection of trophozoites/cysts in tissue visualized with haematoxylin and eosin
stains
8. • Immunohistochemical tests
• Realtime PCR
• cultured by inoculating pieces of infected tissue - brain, lung, skin,
nasopharyngeal on non-nutrient agar plate coated with Gram negative bacteria.
TREATMENT
• Keratitis responds to combination of neomycin drops, dibromopropamide
ointment and propamide isethionate drops
• No treatment for GAE
• Patients with GAE treated with pentamidine isethionate IV 4 mg/kg body
weight/24 hrs, sulfadiazine 500 mg four times a day, pyrimethamine 50 mg,
once a day - study
PREVENTION
• Removing contact lens while swimming
• Proper cleaning & disinfection of lens prevent eye infections.
