Page 17 - Medical Parasitology_ A Textbook ( PDFDrive )

Entamoeba histolytica 9

Diagnosis

1. Diagnosis of intestinal amoebiasis
(a) Microscopic examination
Demonstration of cysts or trophozoites in stool sample. Since excretion
of cysts in the stool is often intermittent, at least 3 consecutive specimens
should be examined. Trophozoite and cyst of E. histolytica have similar mor-
phology to E. dispar and E. moshkovskii which are non-pathogens. Molecular
technique can differentiate these 3 species. Fixed stool smear can be stained
with trichrome to demonstrate cysts and trophozoites.
(b) Sigmoidoscopy for mucosal scrapings
Direct wet mount and iron haematoxylin staining to demonstrate
trophozoites.
(c) Stool culture
Stool culture is a sensitive method in diagnosing chronic and asymptom-
atic intestinal amoebiasis. However, it is not a routine method of diagnosis.
(d) Serodiagnosis
Serological test is positive only in invasive amoebiasis.
(e) Molecular diagnosis
Polymerase chain reaction (PCR) to detect E. histolytica in stool and to
differentiate between the other species that are non-pathogens (E. dispar and
E. moshkovskii).
2. Diagnosis of extraintestinal amoebiasis
(a) Microscopic examination
Demonstration of trophozoites in pus aspirated from the wall of liver
abscess. The pus obtained from the centre of the abscess may not contain
amoebae as they are confined to the wall of the abscess. Cysts are not found
in extraintestinal lesions. Stool examination rarely can detect E. histolytica
cyst.
(b) Molecular diagnosis
PCR of pus aspirated from ALA
(c) Serodiagnosis

Treatment

1. Luminal amoebicides: Diloxanide furoate, iodoquinol, paromomycin and tetra-
cycline act in the intestinal lumen but not in tissues.
2. Tissue amoebicides: Emetine and chloroquine are effective in systemic infec-
tion, but less effective in the intestine.
3. Both luminal and tissue amoebicides: Metronidazole (750–800 mg 3 times daily
for 5–10 days), tinidazole and ornidazole act on both sites.

Carriers should also be treated because of the risk of transmitting the infection to
others. Paromomycin or iodoquinol should be used in these cases. Although