Page 19 - Medical Parasitology_ A Textbook ( PDFDrive )

Naegleria fowleri 11

A few instances of GAE caused by Balamuthia spp. have also been reported.
While PAM and AK occur in previously healthy individual, GAE has been associ-
ated with immunodeficient patients.

Naegleria fowleri

Distribution

Naegleria fowleri is a thermophilic amoeba that thrives in warm water (e.g.
hotsprings) and soil. It has a worldwide distribution.

Habitat

In human, N. fowleri is found in the central nervous system (CNS).

Morphology

It occurs in 3 forms:

1. Trophozoite (2 forms)
(a) Amoeboid (Fig. 3.4a)
(b) Flagellate
2. Cyst (Fig. 3.4b)

The trophozoites can withstand moderate heat (45 °C), but die at chlorine levels
of 2 ppm and salinity of 0.7%. The amoeboid form is about 10–20 μm with rounded
pseudopodia (lobopodia), a spherical nucleus and a big endosome. It is the invasive
and the infective form of the parasite. The flagellate form is biflagellated, pear-
shaped and occurs when trophozoites are transferred to distilled water. The flagel-
late can revert to the amoeboid form.

a b

Fig. 3.4 Naegleria fowleri. (a) Trophozoite (amoeboid), (b) Cysts