Browsing by Author "Aklilu, Essayas"

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    Comparative studies on bionomics and behavior of phlebotomine sandflies in highland and lowland areas of kala-azar transmission, northwest Ethiopia
    (Addis Ababa University, 2015-06) Aklilu, Essayas; Gebre, Teshome(PhD)
    The aim of this study was to investigate and compare the bionomics, ecology and behaviors of the vector (s) of visceral leishmaniasis (VL) in two endemic and ecologically distinct areas of northwestern Ethiopia. This included species composition, population dynamics, habitat preference, host preference, vectorial potential and nocturnal activity studies in the field. Phlebotomine sandflies were collected using CDC light traps, sticky traps and pyrethrum space spray catches from Libo-Kemkem district (May 2011-April 2012) and Metema district (October 2012-September 2013). A total of 51,411 sandfly specimens were collected: 10,776 from highland and 40, 635 from the lowland areas. Seven species were found in the highland area: two Phlebotomus sandflies (P. orientalis and P. rodhaini) and five Sergentomyia species, whereas 19 species were found in the lowland area: six Phlebotomus (P. orientalis, P. rodhaini, P. bergeroti, P. duboscqi, P. papatasi and P. martini) and 13 Sergentomyia species. Of the Phlebotomus spp., P. orientalis was the predominant species in both the highland (99.9%) and lowland (93.7%) areas. In both areas, this species showed seasonal a occurrence and mainly abundant during the dry months (March-May/June) of the year and increasing in numbers till the rains began, when numbers dropped dramatically. In both areas, P. orientalis exhibits both strong exophilic and exophagic behaviors and its parous rates of the species were 45.6% and 66.2% in highland and lowland, respectively. Identification of blood meals in wild caught blood fed P. orientalis using cytochrome b polymerase chain reaction (Cyt b –PCR) and reverse iv line blotting (RLB) and enzyme linked immunosorbent assay (ELISA) showed that this species has strong predilection for bovine in both the highland (67.8%) and the lowland (49.8%) areas. A total of 1087 P. orientalis from the highland area and 344 Phlebotomus spp. from lowland area were dissected for detection of natural infection, but none of them was infected. A similar result was obtained in 347 P. orientalis females processed using PCR for detection of L. donovani from the highland area. Hourly activity period of the two populations of P. orientalis showed variation. The nocturnal activity of P. orientalis in the highland peaked between 22:00 and 23:00hours for both sexes; whereas in the lowland area, this peak was between 3:00 and 4:00hours. Although natural infection was not detected in the current study, P. orientalis is strongly implicated as vector of VL in both study areas due to its abundance and other circumstantial evidences. Therefore, control of the disease in these particular areas should involve tools that mainly target the vector of the disease by considering its seasonal abundance, ecology and behaviors in the respective areas
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    Species Composition, Seasonal Variation and Roles of Anopheles Mosquitoes in the Transmission of Malaria in Koka villages, Central Ethiopia
    (Addis Ababa University, 2008-05) Aklilu, Essayas; Gebre-Michael, Teshome(PhD)
    Entomological studies on the species composition, seasonal variation and infection rates of Anopheles mosquitoes were conducted at four selected villages of Koka area, Central Ethiopia, between December 2006 and November 2007. Collection and identification of larvae of Anopheles from various breeding habitats during the study period indicated that there are three species, namely Anopheles gambiae s.l. (84.7%), An. pharoensis (14.4%) and An. squamosus (0.9%). Similarly, a total of 8, 279 adult anophelines mosquitoes representing three species were collected through indoor (7784) and outdoor (495) samplings. Overall, An. gambiae s.l. was the predominant species, making 90.1% of all collections followed by An. pharoensis (9.6%). Both species were abundant after the short rainy season and remained high through the wet season, and declined in the dry season. Peak indoor resting density was observed in May. The ratio of fed to half gravid and gravid combined for An. gambiae s.l. in indoor resting collection was 4.9:1, indicating high degree of exophily in the study area. This was also supported by high number of half-gravid and gravid An. gambiae s.l. in outdoor collection than indoor. Similarly, high exophilic behavior (3.5:1) for An. pharoensis was also observed. Of 662 An. gambiae s.l. and 246 An. pharoensis dissected from all collections; the average parous rate was 31.4% and 28.0%, respectively. None of the 208 parous An. gambiae s.l and 69 parous An. pharoensis analyzed by ELISA to detect sporozoite antigen of P. falciparum and P. vivax were found infected. This seems to support the parasitological data during the study period. Although no sporozoite infection rates was detected An. gambiae s.l. (presumably An. arabiensis) seems the principal vector of malaria in the area.
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    Species Composition, Seasonal Variation and Roles of Anopheles Mosquitoes in the Transmission of Malaria in Koka villages, Central Ethiopia
    (Addis Ababa University, 2008-05) Aklilu, Essayas; Gebre-Michael, Teshome(PhD)
    Entomological studies on the species composition, seasonal variation and infection rates of Anopheles mosquitoes were conducted at four selected villages of Koka area, Central Ethiopia, between December 2006 and November 2007. Collection and identification of larvae of Anopheles from various breeding habitats during the study period indicated that there are three species, namely Anopheles gambiae s.l. (84.7%), An. pharoensis (14.4%) and An. squamosus (0.9%). Similarly, a total of 8, 279 adult anophelines mosquitoes representing three species were collected through indoor (7784) and outdoor (495) samplings. Overall, An. gambiae s.l. was the predominant species, making 90.1% of all collections followed by An. pharoensis (9.6%). Both species were abundant after the short rainy season and remained high through the wet season, and declined in the dry season. Peak indoor resting density was observed in May. The ratio of fed to half gravid and gravid combined for An. gambiae s.l. in indoor resting collection was 4.9:1, indicating high degree of exophily in the study area. This was also supported by high number of half-gravid and gravid An. gambiae s.l. in outdoor collection than indoor. Similarly, high exophilic behavior (3.5:1) for An. pharoensis was also observed. Of 662 An. gambiae s.l. and 246 An. pharoensis dissected from all collections; the average parous rate was 31.4% and 28.0%, respectively. None of the 208 parous An. gambiae s.l and 69 parous An. pharoensis analyzed by ELISA to detect sporozoite antigen of P. falciparum and P. vivax were found infected. This seems to support the parasitological data during the study period. Although no sporozoite infection rates was detected An. gambiae s.l. (presumably An. arabiensis) seems the principal vector of malaria in the area.