Page 24 - Medical Parasitology_ A Textbook ( PDFDrive )

16 3 Amoebae

i = Infective Stage
d = Diagnostic Stage
1 Cysts

Through the eye 1
5

Through nasal
passages to the 6
lower respiratory
tract 2
4 Amoebae (cysts and
trophozoites) can
enter humans in
various ways
7
i Through ulcerated
2 Trophozoite or broken skin 3

Cysts and trophozoites in tissue
d

1 Results in severe keratitis of the eye. 8
3
Mitosis 2 Results in granulomatous amoebic encephalitis 9
(GAE) and/or disseminated disease in 10
individuals with compromised immune systems.
3 Results in granulomatous amoebic encephalitis 9
(GAE), disseminated disease 10 or skin lesions 11
individuals with compromised immune systems.
Fig. 3.7 Life cycle of Acanthamoeba species (Reproduced from https://www.cdc.gov/dpdx/free-
livingamebic/index.html)

2. Acanthamoeba keratitis
An infection of the eye that occurs in healthy persons and develops from the
entry of the amoebic cyst through abrasions on the cornea. Most cases have been
associated with the use of contact lenses. The clinical features resemble that of
severe herpetic keratitis. The eye is severely painful in amoebic infection.
Unilateral photophobia, excessive tearing, redness and foreign body sensation are
the early signs and symptoms. Keratitis can result in permanent visual impair-
ment or blindness.

Diagnosis

1. Diagnosis of GAE

Demonstration of trophozoites and cysts in brain biopsy, culture (non-nutrient
agar plate coated with E. coli), or immunofluorescence microscopy using monoclo-
nal antibodies. CSF examination can reveal motile trophozoite forms.