Department of Biology
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Browsing Department of Biology by Author "Abate Alemayehu"
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Item The Response pof Glossina Pallidipes (Diptera: Glossinidae) Towards Different Trap Designs and Odour Baits At Nechisar National Park, Southern Ethiopia(Addis Ababa University, 2001-06) Abate Alemayehu; Girma Melaku (PhD)Investigations were carried out in the Nechisar National Park, southern Ethiopia, to determine the preferences of Glossina pallidipes (Diptera: Glossinidae) towards different trap types and odour baits, and to standardize the best bait system for catching this fly. Epsilon, F3 and NG2G traps were evaluated in different vegetation types. In experiment two and experiment three, acetone (450mglh), cow urine (858mglh) and octenol (1.5mglh) were dispensed (both separately and in blends) near traps from glass bottles, plastic bottles and sachets, respectively. The results of all experiments showed that NG2G trap was more effective in catching G. pallidipes than Epsilon and F3 traps. No significance difference was observed between Epsilon and F3 traps. Among odour attractants tested in blends, acetone + cow urine + octenol and acetone + cow urine were highly attractive to G. pal/idipes than acetone + octenol and cow urine + octeno!' The combinations of cow urine and octenol were found to be more attractive than acetone + octeno!' The relatively higher catches obtained by using NG2G traps and cow urine suggests that NG2G trap and cow urine are the best baits for community- based tsetse management. NG2G trap offers some advantages over the other traps used because it is less expensive and is easier to deploy. The availability of cow urine in large quantities with no cost to the rural communities will make fly trapping potentially feasible. Higher percentages of female flies were caught than male flies. All unbaited trap types caught a smaller propoltion of older flies of both sexes. Epsilon, F3 and NG2G traps baited with acetone, cow urine and octenol caught a smaller propoltion of female flies at their older ages and a higher proportion of male flies. NG2G taps deployed with different combinations of acetone, cow urine and octenol caught a higher propOliion of older flies of both sexes. Tabanidae did show a strong response to blends of odour baits, especially to cow urine + octeno!' Biting flies of the sub-family Stomoxyinae respond highly to odour baits and their response varies with vegetation type.Item Studies on the Impact of Bendiocarb Indoor Residual Spraying on Insecticide Resistance of Anopheles Arabiensis Patton and Other Entomological Determinants of Malaria Transmission In the Upper Blue Nile River Basin, Bahirdar Zuria District, Northwestern Ethiopia(Addis Ababa University, 2018-04-06) Abate Alemayehu; Getu Emana (Professor)Studies on the Impact of Bendiocarb Indoor Residual Spraying on Insecticide Resistance of Anopheles arabiensis Patton and other Entomological Determinants of Malaria Transmission in the Upper Blue Nile River Basin, Bahirdar Zuria District, Northwestern Ethiopia Alemayehu Abate Department of Zoological Sciences, Addis Ababa University, 2018 In Ethiopia, malaria vector control using indoor residual spraying has been used against Anopheles arabiensis Patton for decades. However, data for the effective residual life of the insecticides used for indoor residual spraying on sprayed surfaces and the impact of these interventions on different entomological risk factors for malaria transmission is insufficient or absent. Therefore, a comparative study was carried out in Andassa and nearby villages, Bahir Dar Zuria District, Upper Blue Nile River Basin, Northwest Ethiopia to estimate the effective residual life of bendiocarb on treated surfaces and the impact of the application of indoor residual spraying on insecticide resistance status, host preferences, sporozoite and entomological inoculation rate, abundance and resting habits of An. arabeinsis Patton. The effects of indoor residual spraying on the composition and abundance of other Anopheles mosquitoes were also assessed. Susceptibility of Anophels arabiensis to the insecticide used for indoor residual spraying and its residual life on sprayed surfaces was evaluated based on World Health Organization test procedures. Adult mosquitoes were collected from houses located iv nearby mosquito breeding sites using Center for Disease Control and preventions light trap, pyrethroid spray sheet collection and artificial pit shelters made nearby pyrethroid spray sheet sampling houses. Collected mosquitos were sorted into species using their external morphology and sibling species of the Anopheles gambiae complex were identified by Polymerase Chain Reaction based molecular methods. Enzyme-linked immunosorbent assay was run to determine blood meal sources and Plasmodium infection rates in Anopheles arabiensis. The effective residual life of bendiocarb on treated surfaces was higher on plastered wall surfaces than on non-plastered wall surfaces. Resistance to bedndiocarb was suspected in Anophels arabiensis (95%) after three successive spraying cycles within three-year‟s time in Andassa, while the vector remained susceptible (99%) in Tikurit, which received only one round spray. Susceptibility status of the vector to fenithrothion, primiphosmethyl and propoxur was unaffected (100%) due to the application of bendiocarb indoor residual spraying. Susceptibility of the vector to DDT, delthamethrin and malathion was improved progressively at both study sites. East African kdr mutation (kdr-e) was detected in Anopheles arabiensis Patton sampled from both study groups. In total, 8,859 Anopheles mosquitoes were collected among which 70.15% (n = 6, 215), 21.99% (n = 1,948) and (7.86%, n = 696) of them were Anopheles arabienesis, Anopheles pharoensis and Anopheles coustani, respectively. The abundance of Anopheles arabienesis drastically declined after spray, while indoor residual spraying did not influence its resting habits. General estimating equation model showed that indoor residual and time (month and years) played significant role to affect mosquito abundance. The model also showed that sampling methods had significant effect on the number of v mosquitoes caught. In contrast, the role of the number of human hosts who slept the previous night in mosquito sampling houses was not significant. The relative adjusted reduction in Plasmodium falciparum infection and entomological inoculation rate in Anopheles arabiensis was 100% after indoor residual spraying, while the reduction in human blood meal index was between 3% and 10%. In conclusion, bendiocarb was effective to reduce vector density, sporozooite rate and entomological inoculation rate in Anopheles arabiensis without affecting the resting habits of the vector. However, effective residual life of bendiocarb is too short on non-plastered wall surfaces to cover the main malaria transmission season; wall plastering is, therefore, recommended to increase insecticide persistence on treated surfaces. East African kdr mution is widely distributed in populations of the main malaria vector signifying the need to implement insecticide resistance management to restore susceptibility of the vector to DDT/pyrethroid and maintain the efficacy of long-lasting insecticide treated mosquito nets that have been used as frontline defense in the control of malaria vectors in Ethiopia in general and the present study site in particular. Resistance to bendiocarb was suspected after three spraying cycles within three-year times, while efficacy to DDT and pyrethroid was not restored within three years‟ time implying that prevention is better than restoration of insecticide resistance in disease vectors. Therefore, insecticide restitance management should be in place in time.