[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

58
CHAPTER 3 The Amebas
Human infections are relatively rare. This ameba
is found only in select areas of the world, with
the highest prevalence occurring in Papua, New
Guinea. Infections with E. polecki have also been
reported in Southeast Asia, France, and the
United States. It is interesting to note that all
the reported cases of E. polecki documented in
the United States in 1985 occurred in Southeast
Asian refugees who settled in Rochester,
Minnesota. Ingestion of the E. polecki cyst is
most likely responsible for the onset of infection.
Human to human as well as pig to human are
the major routes of parasite transmission.
Clinical Symptoms
Most patients with E. polecki are asymptomatic.
The only documented discomfort associated with
symptomatic patients is diarrhea.
Treatment
A combination of metronidazole (Flagyl) and
diloxanide furoate (Furamide) has successfully
treated patients with E. polecki. Metronidazole
alone has also been effective.
Prevention and Control
E. polecki may be prevented by improving personal
hygiene and sanitation practices. Education
programs regarding the routes of transmitting
E. polecki infection are also essential.
Quick Quiz! 3-14
Infection with E. polecki is mainly transmitted to
humans via which of the following? (Objective 3-5A)
A. Ingestion of E. polecki trophozoite
B. Ingestion of E. polecki cysts
C. Humans do not get infected with E. polecki.
D. Touching an injected pig or monkey
Endolimax nana
(en’doe-lye’macks/nay’nuh)
Common associated disease or condition names:
None (considered as a nonpathogen).
Morphology
Trophozoites. Endolimax nana trophozoites
vary in size from 5 to 12 µm (Fig. 3-14; Table
3-9). The average trophozoite size range is 7 to
10 µm. E. nana trophozoites exhibit sluggish,
nonprogressive motility, which is accomplished
by blunt, hyaline pseudopods. The single nucleus
may or may not be visible in unstained preparations.
The karyosome is typically large and irregularly
shaped, and is often described as blotlike
in appearance. The absence of peripheral chromatin
is a key feature that aids in the identification
of E. nana trophozoites. The cytoplasm of
Quick Quiz! 3-13
Which of the following statements is not true about
the cysts of E. polecki? (Objective 3-9A)
A. Cysts vary in shape from spherical to oval.
B. Cysts contain at least four nuclei.
C. The typical cyst nucleus resembles that of E.
histolytica.
D. A diffuse glycogen mass may be present in the
cytoplasm of cysts.
TABLE 3-9
Endolimax nana
Trophozoite: Typical
Characteristics at a Glance
Parameter
Description
Size range 5-12 µm
Motility
Sluggish, nonprogressive,
blunt pseudopods
Number of nuclei
One
Karyosome
Large, irregular, blotlike
Peripheral chromatin Absent
Cytoplasm
Granular and vacuolated
Cytoplasmic inclusion Bacteria