Browsing by Author "Lemma, Wossenseged"

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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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    Visceral Leishmaniasis L. Donovani; P. Orientalis Migrant Labourers Rodents Agriculture Fields Thickets of A. Seyal Dense Mixed Forest
    (Addis Ababa University, 2015-06-09) Lemma, Wossenseged; Tekie, Habte (PhD)
    Kala-azar (visceral leishmaniasis; VL), due to Leishmania donovani, is transmitted by Phlebotomus orientalis in Metema Humera lowlands where this disease is a major health problem. The aims of this study were to determine seasonal dynamics, habitat preferences, nocturnal activities, host preferences, and Leishmania infections of P. orientalis in addition to study on sero-prevalence of L. donovani infection in migrant labourers with associated risk factors and the role of rodents as reservoir hosts of VL. Centers for Disease Control and Prevention miniature light traps (CDC traps) (John W. Hock, USA) and/or sticky paper traps were used for sand fly collections. The blood meal sources for P. orientalis were detected by reverse line blot (RLB) of cytochrome b polymerase chain reaction (PCR) amplification products using 11 probes for domestic animals. Polymerase chain reaction amplification of internal transcribed spacer 1 (ITS1) and kinetoplast DNA (kDNA) markers were used to detect Leishmania infections in P. orientalis. Blood for direct agglutination test (DAT) was sampled, randomly, from migrant labourers involved in sesame harvest to study sero-prevalence of L. donovani infection and entomological risk factors. Sherman collapsible rodent traps were used to capture rodents. The rodents were anaesthetized before sacrificed for tissue biopsies from liver, spleen, bone marrow and tip of the nose (skin) in addition to blood for screening of Leishmania infections. The species of the rodents were identified by their morphological characters. The tissues from liver, spleen and skin were macerated in Locke’s solution before transferring them into Novy-McNeal Nicolle (NNN) medium for Leishmaniacultivation. Blood and touch smears of liver, spleen, skin and bone marrow were made on microscope slide and allowed to air dry before fixing using methanol and xix staining by Giemsa stain for microscopy. Polymerase chain reaction technique was also used to identify Leishmania infection in the tissues of the rodents. The studies were conducted from May, 2011 to January, 2014. During study on bionomics of P.orientalis, a total of 376, 441 sand flies using CDC light trap (n=955) and sticky traps (n=5, 551) were collected from May 17, 2011 to June 6, 2012 from agriculture fields, thickets of Acacia seyal and dense mixed forest. Of these sand flies, 313, 055 (80.45%) were Sergentomyia species. The highest mean monthly density of P. orientalis trapped by CDC light traps was found in thickets of Acacia seyal in March (64.11 + 75.87). The corresponding highest mean monthly density of P. orientalis trapped by sicky traps was found in April (58.69 + 85.20) in agricultural field. No P. orientalis were caught in September using CDC traps and July - October using sticky traps. The overall mean monthly density of P. orientalis (female and male) trapped by CDC light traps was 15.78 + 28.93 (n=320) in agricultural field, 19.57 + 36.42 (n=255) in thickets of A. seyal, and 3.81 + 6.45 (n=380) in dense mixed forest. For sticky traps, the overall mean monthly density of P. orientalis was 14.76 ± 38.78 (n=2378) in agricultural fields, 11.45 ± 15.56 (n=1500) in the thickets of A. seyal and 0.95 ± 2.16 (n=1168) in dense mixed forest. Analysis of variance (ANOVA) result has showed statistically significant mean difference (p=0.000) for different habitats. Phlebotomus orientalis, P. papatasi, P. duboscqi, P. bergeroti, P. rodhaini, P. martini and P. alexandri were the Phlebotomus species found in the area. Phlebotomus orientalis was the dominant species (99%) in the extra-domestic study sites. During January to May, 2013 collection of P. orientalis at hourly intervals using 22 CDC light traps, the peak activities of P. orientalis were at 1.00 hr (134.0 ± 7.21) near animal shelters, 3.00 hr (66.33 ± 46.40) in agricultural fields and xx 21:00 hr (40.6 ± 30.06) in thickets of A. seyal. This species was not attracted to the different species of rodents in trials carried out in March and April, 2013. Riverse line blot PCR identified 7 human (28%), 9 mixed (human and cattle) (36%) and 2 cattle (8%) blood meals while 7 were unknown (28%). Molecular screening of 30 pools (1 pool = 5 individual P. orientalis) from dense mixed forest in July (rainy season), 2011, for Leishmania infection, was performed by targeting kDNA in a PCR assay. Five pools (5/30, 16.7%) were positive for Leishmania kDNA PCR. For March–May, 2013 dry season collections, 9/15 pools (60%) were ITS1 PCR positive. Of the total 359 labour migrants screened during October – November (2013), using DAT, 45(12.5%) were seropositive (≥1:800) for L. donovani infections with risk of VL development in 3 (0.8%) individuals who had very high titer (1:12800). Leishmania donovani infection in labour migrants seemed to correlate more with relatively higher density of P. orientalis during the June – August weeding season than the September – October harvest season. Staying in the areas both in the weeding and harvesting seasons (p=0.035; odds ratio (OR) = 2.83) and sleeping in the agricultural fields (p=0.01; OR=15.096) were positively correlated with L. donovani infection. Night harvest (p=0.028; OR=0.133) and knowledge about sign or symptoms (p=0.042; OR=0.383) were negatively associated with this infection. A total of 128 rodents such as Arvicanthis niloticus (n=68), Acomys cahirinus (n=25), Tatera (Gerbilliscus) robustus (n=21), Mastomys erythroleucus (n=3), Mylomys albipes (n=2), Rattus rattus (n=5), Paraechimus aethiopicus (Hedgehog) (n=2) and Xerus erythropus (striped ground squirrel) (n=2) were trapped and screened for Leishmania infections by parasitological, serological and PCR techniques. Of 91 rodents collected from extra-domestic habitats of Beaker and Gelanzeraf (Kafta-Humera district) and xxi analyzed by ITS1 PCR using skin, spleen, liver and bone marrow samples, 6/54 (11.1%) of Arvicanthis nilothicus were positive compared to the infection rates in Acomys cahirinus (3/17 or 17.6%) and Tarera (G) robustus (2/16 or 12.5%). Almost all the PCR infections were found from bone marrow samples (8/48 or 16.7%) compared with 1/91(1.1%) liver, 2/87(2.2%) spleen and 0/87 (0%) skin. Different organs on the same rodent were not found infected. These rodents were negative with NNN-medium, microscopy (Giemsa stains) and direct agglutination tests (DAT) except 2 Arvicanthis niloticus NNN-medium positives spleen samples from Baeker. The remaining 37 Arvicanthis niloticus,Acomys cahirinus, Tatera (G) robustus, Mastomys erythroleucus, Mylomys albipes,Paraechimus aethiopicus (Hodge hoge), Rattus rattus and Xerus erythropus (striped ground squirrel) collected from Baeker, Ademiti, Mayhas and Adijamus (western Tigray)screening using NNN-medium, Giemsa stain and DAT were negative. Agricultural fields and thickets of A. seyal habitats are the breeding sites for P. orientalis in extra-domestic habitats of Kafta Humera lowlands where female P. orientalis can bite humans at any hour of the night with peak biting after mid night. Sleeping in open agricultural fields was related to L. donovani infections in labour migrants. Arvicanthis niloticus, Acomys cahirinus and Tarera (G) robustus might play important role in the transmission cycle of zoonotic VL in endemic lowlands areas of Ethiopia. Further studies are required for L. donovani isolation from rodents in the endemic areas in addition to experimental infection for xenodiagnosis before considering these rodents as reservoir hosts of L. donovani conclusively. Access and proper use of bed nets, especially during crop growing season, are required for reducing the incidence of the infection. Key words:Visceral leishmaniasis; L. donovani; P. orientalis; migrant labourers; rodents; agriculture fields; thickets of A. seyal; dense mixed forest