Browsing by Author "Hailu, Asrat (Professor)"

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    Indirect Hem agglutination Assay For Diagnostic and Epidemiological Studies of Visceral Leishmaniasis in Ethiopia
    (Addis Ababa University, 2005-06) Kebede, Tadesse; Hailu, Asrat (Professor)
    Visceral leishmaniasis (VL) is potentially a fatal disease that is caused by intracellular protozoan parasites of the L. donovani spp. To date, there has been no reliable diagnostic test for active infection of VL. Therefore, there is an urgent need for a simple, rapid, and reliable diagnostic test with high sensitivity and specificity for clinical practice and VL control. To determine the diagnostic and sero-epidemiological screening performance of Indirect Hemagglutination, serum samples were obtained from endemic areas of Ethiopia and evaluated using antigens prepared from an isolate of L. donovani (MHOM/SD/68/1S) promastigote stage. Serum samples of 77 suspected VL and 51 controls for diagnostic; and for epidemiological study 1217 samples involving 57 VL suspected, and 1085 samples including 132 samples from previously treated VL patients were tested by IHA at various cut-off titers, DAT, and FAST. Spleen and/or lymph node aspiration with subsequent smear and/or culture test confirmed the presence of parasite in 37 and 19 individuals in diagnostic and epidemiological study subjects, respectively. IHA test performed for comparison was able to detect anti-leishmanial antibodies in 94.6% and 100% of the confirmed cases of VL (at 1:64 cut-off titer) in diagnostic and epidemiological study subjects, respectively. Among 1085 sera, IHA (at 1:64 cut-off titer) test was positive in 10.6% of previously untreated asymptomatic individuals. Whereas out of 132 previously treated VL patients, 72% were found to be IHA positive at 1:64 dilutions. IHA at cut-off titers 1:64 and 1:128 showed a sensitivity of 94.5% and 86.5%, a specificity of 60% and 77.5% respectively in the diagnostic study and a sensitivity of 100% and 100%, specificity of 33.3% and 50% in the epidemiological study. The result showed IHA to be sensitive, rapid, and simple test for thediagnosis and epidemiological screening of visceral leishmaniasis. Further evaluation of IHA test should be conducted with careful use of the gold standard. Keywords: Indirect Hemagglutination test; Visceral Leishmaniasis; Ethiopia; seroepidemiology
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    An Investigation into Some Aspects of the Epidemiology of Cutaneous Leishmaniasis in Saris, Addis Ababa
    (Addis Ababa University, 2006-07) Erenso, Girum; Hailu, Asrat (Professor)
    Cutaneous leishmaniasis (CL) is one of the endemic diseases in Ethiopia. It’s widespread over several parts of the highlands of the country. Currently, it is becoming a major challenge in the highlands near and/or surrounding Addis Ababa. However, there was little information on the prevalence of CL around Bulbula river basin in Saris adjoining Saris Abo, Yoseph and Worku Sefer study sites, the suburbs of Addis Ababa. A survey was carried out to describe some aspects of the epidemiology of cutaneous leishmaniasis in the surroundings of Bulbula river in Saris (Addis Ababa) especially Saris Abo, Yoseph and Worku Sefer. A house to house survey of the study population (1010 persons) was undertaken of Saris Abo, Yoseph and Worku Sefer. Clinical, smear, culture and Leishmanin skin test (LST) were used to detect Leishmania parasite. Based on this investigation; Saris Abo, Yoseph, and Worku Sefer study sites had infection rates of, 3.6%, 0.6% and 1.1%, respectively. The overall cutaneous lesihmanisis prevalence rate was 1.7% (17/1010). More active cases were found aggregated around hyrax colonies in Saris Abo site and most common in age group 10-19 years. Males were found to be the most affected by the disease as compared to females. Since the males’ activities are outdoors in the field, infection could probably have occurred near hyrax colonies (extradomiciliary transmission). Uivariate multiple and pairwise comparisons showed significant differences in age groups 10-19 and below (P= 0.03), study sites (P= 0.002) and between sex (P= 0.02). This study suggests that CL has been found to be a public health problem surrounding the Bulbula river basin, especially in the study site of Saris Abo where the highest infection rate was recorded (3.6%). Key words: Epidemiology, Cutaneous Leishmaniasis, Saris Abo, Yoseph, Worku Sefer.
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    Investigations on the parasite, vector and reservoir host of cutaneous leishmaniasis in Addis Ababa, Silti, Merabete and the Awash Region, Ethiopia
    (Addis Ababa University, 2006-07) Lemma, Wossenseged; Hailu, Asrat (Professor)
    From January 2005 to May 2006, investigations on the parasite, vector and reservoir host of cutaneous leishmaniasis in Addis Ababa, Silti, Merabete and Awash Region, were carried out in different areas of Addis Ababa, Silti, Merabete and Awash-7, Addis Ababa and Silti were discovered recently as Leishmania foci of cutaneous leishmaniasis in the highlands of Ethiopia, Awash valleys were areas where sympatric Leishmania tropica and L aethiopica were discovered for the first time from sandflies, Merabete is not very well known for cutaneous leishmaniasis in humans, but visceral leishmaniasis' was reported from children in the associated lowland. The current Leishmania epidemics in South Eastern Addis Ababa along the gorges of Bulbulla and Akaki rivers was related to settlement of people near the Bulbulla - Akaki river gorges where hyraxes and sandflies (Phlebotomus longipes) co-existed in crevices and cracks of the basalt rocks. It was the area where the zoonotic Leishmania cycle was maintained. In Silti, however, the epidemics was related to the recent increase in number of hyraxes and sandflies as a result of the ecological changes of the Kerate gorge that bisects the center of the town (Kibet) and synanthropic adaptations of the hyraxes. The possible reservoir hosts that·· were examined for natural infection of Leishmania were 79 hyr'!xes, 12 Raltus raltus,.14· Praomys spp., 41 bats, 3 mongooses and 3 genet cats. Samples from skin,: blood, liver;. spleen and bone marrow were cultured in NNN medium in addition to .Giemsa stain, Leishmania parasites were isolated in NNN medium only from three bush hyraxes (Heterohyrax brucei) in Addis Ababa. The hyraxes from the other areas were negative for .. Leishmania in NNN medium. The total infection rate of H brucei in Addis Ababa :was 6.3% (3/48) and the highest infection rate was from the Saris area, 11.1 % (2/18). The hyrax infection rates in Kality were 5.9 %(1117). No infected hyraxes were found in Kilinto (Akaki). The giemsa stains of the above· tissues were negative for amastigote stage of Leishmania in the macrophages. Leishmania infection was not found in the guts of sandflies dissected. Seasonality and age dependent infections in hyraxes were observed. Infections in hyraxes were found only in April, June and September after spring peak sandfly abundance and biting passed. In Addis Ababa, no adults (0/16) were found infected, but infections occurred only in juveniles (2/25) and sub adults (1/10).
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    Preliminary studies on Immunopathogenesis of S. mansoni in Grivet monkeys (Cercopithecus aethiops) Vaccinated with 20Krad Irradiated S. mansoni cercariae
    (Addis Ababa University, 2005-01) Torben, Workineh; Hailu, Asrat (Professor)
    In this study, we established S. mansoni infection in the primates, Cercopithecus aethiops aethiops (Grivet monkeys). Most of the clinical manifestations in human schistosomiasis like fever, bloody diarrhea, loss of appetite, and swollen lymph nodes were noted in the experimentally infected monkeys. Due to the absence of the appropriate animal models, there is little understanding of immune-response development in schistosomiasis, which has created a challenge for designing an effective anti-schistosome vaccine. Repeated intraperitonial immunization of the monkeys with 20Krad irradiated S. mansoni cercariae resulted in a relatively less granulomatous reaction and EPG (P<0.05) than in the controls. The difference in the total adult worms is statistically not significant (P>0.05) between both groups of monkeys. In primary infection, IL-4 was significantly (p = 0.03) raised in the immunized monkeys, and for the same group an insignificant (P > 0.05) increases in IL-10. However, ova excretion did not have an influence on cytokines, except for the controls both IL-4 and IL-10 are significantly increased (p < 0.05). Both IL-12 and INF- levels were lower after ova excretion in the controls, but the inflammatory TNF- has increased (P = 0.049) and these can be associated with more liver pathogenesis in the group. The immunization has minimized egg production and the development of granuloma in the liver of Grivet monkeys. Thus, this work has underlined the potential importance of the monkeys as the helpful models and provided a direction for research studies of drugs or anti-schistosome vaccines.
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    Studies on the Bionomics and Behavior of Phlebotomine Sandflies (Diptera: Psychodidae) in Visceral Leishmaniasis foci in Tahtay Adiyabo District, Northern Ethiopia
    (Addis Ababa University, 2015-06) Gebresilassie, Araya; Hailu, Asrat (Professor)
    Visceral leishmaniasis (VL) caused by Leishmania donovani is widespread in Ethiopia, particularly in the north and north-west of the country. Studies to investigate the ecology and behavior of sandflies and their epidemiological significance in the transmission of VL were conducted in Tahtay Adiyabo district, northern Ethiopia. Entomological studies were undertaken in three villages of the district between May 2011 and April 2012 to identify the sandfly fauna and determine the bionomics of Phlebotomus orientalis. Collections of sandflies were done using CDC light traps, sticky traps, and pyrethrum spray catches inside residential huts. The vectorial role of sandfly vector (s) was determined by the detection of Leishmania parasites by microscopy and Leishmania specific PCR. The host preferences of P. orientalis was examined using host choice experiments and bloodmeal analysis using cytochrome (cyt) b-PCR and reverse line blotting as well as enzyme linked immunosorbent assay. Nocturnal periodicity of P. orientalis was also investigated using light traps by replacing the collection bags at hourly intervals throughout the night. The attractiveness of nine plant species for P. orientalis was also done under field settings using unlit CDC traps. The effects of lunar phases and lunar periodicity on the performance of light traps in collecting P. orientalis were studied by sampling sandflies among the four lunar phases for seven months. In total, 100,772 sandflies, belonging to 25 species were recorded. Sergentomyia africana and P. orientalis made up 59.1% and 23.5% of the collected sandflies, respectively. The outdoor to indoor index for P. orientalis was 138:1 on sticky traps, exhibiting its pronounced exophilic behavior. P. orientalis showed marked fluctuations in seasonal density, which peaked during the months of March and April. A sharp decrease in abundance of P. orientalis was also observed from July to December. The parous rate in the unfed females was 34.05% in peri-domestic and 35.35% in agricultural fields. Out of 921 females of P. orientalis dissected, one specimen (0.11%) was found naturally infected with Leishmania promastigotes. Five pools (25 females) of unfed P. orientalis had DNA of Leishmania spp. Markedly higher mean numbers of female P. orientalis were attracted to donkey-baited tent traps than traps-baited with cow, human, dog, goat, sheep or chicken, respectively. Among the small wild animals iv tested, ground squirrels attracted significantly (P<0.05) more female P. orientalis followed by the hares, gerbils, and the spiny rats. Bloodmeal analysis also revealed that P. orientalis females feed on a range of hosts with predominant preference for bovines followed by donkeys, humans, goats, sheep, dogs, and camels. Results on diel periodicity showed that the activity of P. orientalis females increased from 18:00 to 24:00 hrs, with a peak after midnight (24:00-03:00 hrs). Four of the plant species tested in the field (Balanites aegyptiaca, Acacia seyal, A. sieberiana, and Ziziphus spina-christi) was preferred by both sexes of the sandfly. Results revealed that lunar phases had significant effects in the trapping efficiency of CDC light traps for capturing P. orientalis (ANOVA, P<0.05). The mean density of P. orientalis collected in light traps during moonlit nights was around 25% of the catch during dark nights. The findings of the present study signified that P. orientalis is the principal vector of VL, which peaks in population abundance during the dry months of March and April in the current study area. As well, this vector species exhibits predominant preference to feed on bovine outdoors with peak activities in the late night