Amebiasis In Ethiopia Problems In Diagnosis And Determination Of Prevalence Of Infection

Although in Ethiopia intestinal amebiasis is believed to be associated with many cases ofrndiarrhea, diagnosis is based on examination of fresh stool samples by microscopy, a methodrnthat cannot discriminate the potential invasive Entamoeba histolytica from the commensalrnEntamoeba dispar. The annual reports from Wonji Hospital and the Ethio-Netherlands AIDSrnResearch Project indicate intestinal amebiasis to be a common infection with the highestrnprevalence compared to other parasites. Despite a considerably high reporting of intestinalrnamebiasis, a twenty-year hospital records among 117080 admitted patients showed only 47rnsuspected liver abscess cases, suggesting overdiagnosis. Though the prevalence of E.rnhistolytica/E. dispar by microscopy was 24.9 % in Wonji and Akaki, the specific PCR did notrnconfirm the presence of any E. histolytica infection. Even after careful microscopic analysis,rnby using quality control measures on 246 patients with diarrhea, microscopy demonstrated 40rn% positivity of Entamoeba infection. However, application of PCR, a molecular diagnosticrnmethod that can distinguish E. histolytica from E. dispar did not confirm any E. histolytica,rnonly 9% harboured E.dispar. Coproantigen detection ELISA in the same patients showedrnclear lack of sensitivity and specificity whereby only 11.4 % specimens in the genusrnEntamoeba specific ELISA were in agreement with the PCR, and none of the eight E.rnhistolytica antigen positive was confirmed. The absence of E. histolytica infection in Wonjirnand Akaki was better justified with lower seropositivity (3 %) finding, using recombinantrnsurface antigen of E. histolytica. Further study among healthy primary-school students andrnprisoners emphasize the high occurrence of E. dispar infection. Each of these samples wasrnchecked for Entamoeba infection, by careful microscopy with ocular measurement, ofrnformol–ether concentrates. DNA was then extracted from the 213 samples (27.6%) foundrnEntamoeba-positive, and run in a real-time PCR with primers, based on the SSU-rRNA genernsequences of E. histolytica and E. dispar, that allow DNA from the two species to berndistinguished. Although E. dispar DNA was identified in 195 (91.5%), no E. histolytica DNArnwas detected. This finding is consistent with the previous investigation that many amebicrninfections in Ethiopia are incorrectly attributed to E. histolytica and then treated unnecessarly.rnIn order to further confirm the actual occurrence of E. histolytica, 110 suspectedrnhaematophagous trophozoites were collected from different hospitals and health centers. Onlyrnthree (2.7 %) E. histolytica cases were detected by real-time PCR, while 71.3 % were E.rndispar. The finding was similar among HIV/AIDS patients with diarrhea where microscopyrnrevealed 12 % E. histolytica/E. dispar, but none with E. histolytica. The tradition ofrnmicroscopy in a routine diagnostic set-up appears unsatisfactory to reliably differentiate RBCengulfingrnameba from non-invasive ameba. The public health implication of this study is thatrnpatient management and validity of epidemiological surveys are questionable as long asrnmicroscopy is the only diagnostic tool. There is also a need to continue work to establish thernaetiology of diarrhea wrongly associated with amebae and explain the enigma of patientsrnrecovering following “anti-amebic” treatment. The commonly reported complaints of bloodyrnmucoid diarrhea and association of low CD4 with E. dispar infection among AIDS patientsrnrequire alternative explanation. Training in microscopy needs improvement, if not to diagnose the infection accurately, at least to minimize the over-reporting. This work emphasizes the necessity of capacity building for important diarrheal pathogens with molecular diagnostics at referral level

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