Ecology and Distribution Pattern of Anopheles Mosquitoes and Malaria Transmission in Ghibe River Basin, Southwestern Ethiopia

Getachew, Dejene (2017) Ecology and Distribution Pattern of Anopheles Mosquitoes and Malaria Transmission in Ghibe River Basin, Southwestern Ethiopia. PhD thesis, Addis Ababa University.

[img] PDF (Ecology and Distribution Pattern of Anopheles Mosquitoes and Malaria Transmission in Ghibe River Basin, Southwestern Ethiopia)
Dejene, Getachew.pdf - Accepted Version
Restricted to Repository staff only

Download (1MB) | Request a copy


Malaria is a leading public health problem in Ethiopia. Though malaria prevalence showed high reduction in many parts of the country, its transmission is likely to be more and more focal with some areas still having substantial risk of malaria. There was paucity of information on the malaria vectors and malaria transmission pattern in the study area. So that, the objective of this study was to investigate the species composition and monthly distribution of Anopheles mosquitoes, their blood meal sources, sporozoite infection rates and level of insecticide susceptibility in the Ghibe River basin, southwestern Ethiopia. Study on Anopheles mosquitoes distribution and malaria transmission was conducted in two study sites. Longitudinal larval and adult Anopheles mosquitoes collections were carried out monthly from November 2014 to October 2016. Late instar larvae were morphologically identified. Habitats containing Anopheles larvae were identified and their environmental variables were recorded. Adult Anopheles mosquitoes were collected from selected houses near to or far from the river with CDC light traps, pyrethrum spray catches, pit shelter and mouth aspirator. Adult female Anopheles mosquitoes were morphologically identified and their parity rate, blood meal sources and malaria infections were analysed using Enzyme-linked immunosorbent assay (ELISA). Anpheles larvae and pupae were collected from their breeding sites, allowed to emerge into adult, morphologically identified, and exposed to insecticides using WHO discriminating concentrations. Awarness of the communities towards malaria prevention and control were also investigated. Multiple regression analysis was used to identify the most predictor larval habitat environmental variables with the occurrence of Anopheles larvae. Human blood index (HBI) was calculated as the ratio of blood-fed mosquitoes that had fed on human to the total tested expressed in percent. Sprorozoite rate was expressed as the proportion of mosquitoes with sprorozoite to the number of mosquitoes tested. Insecticide susceptibility was determined based on mean mortality of the four replicates after 24 hour exposure. In total, 9,277 larvae of Anopheles mosquitoes were sampled. Mean Anopheles larval densities were higher in the pools in drying river beds (35.2 ± 7.9 larvae/dip), borrow pits (14.3 ± 8.6 larvae/dip) and pools at river edges (13.0 ± 2.1 larvae/dip) in Darge, and in borrow pits (11.2 ± 6.3 larvae/dip) and rain pools (11.9 ± 5.1 larvae/dip) in Ghibe. From totally identified Anopheles mosquitoes larvae more than 95% of them were An. gambiae s.l. Temperature at the time of collection (p = 0.03) and emergent vegetation (p = 0.003) were the best predictors of Anopheles larval density. In total, 2,669 adult female Anopheles mosquitoes were collected and morphologically identified. In Ghibe, mean density of An. gambiae s.l. (=An. arabiensis) using CDC light trap was higher outdoors (1.8/CDC light trap/night) as compared to indoors (0.7/CDC light trap/night) but in Darge 0.125/CDC light trap/night indoor and 0.07/CDC light trap/night outdoor. In Ghibe, the HBI for An. arabiensis was 58.0% from CDC light trap collections indoors and 16.0% outdoors but in Darge it was 14.0% indoors and 13.0% outdoors. Overall sporozoite rates of An. arabiensis for P. vivax and P. falciparum were 0.06% each. Anopheles arabiensis developed insecticide resistance to all the insecticide classes tested with, except fenitrotion. Study on awareness showed, there was knowledge gap in the communities towards the way malaria is transmitted. In conclusion, An. arabiensis is the predominant species of malaria vector in the study area. Malaria prevalence and vectors infection rates were very low. However, the outdoor abundance and the development of resistance to the major insecticides need to look for alternative control options in addition to LLINs and IRS.

Item Type: Thesis (PhD)
Uncontrolled Keywords: Anopheles gambiae s.l., CDC light trap, Darge, Ghibe, human blood index, larval habitat, sporozoite rate.
Subjects: Q Science > Q Science (General)
Q Science > QH Natural history > QH301 Biology
Q Science > QL Zoology
Divisions: Africana
Depositing User: Selom Ghislain
Date Deposited: 01 Oct 2018 12:04
Last Modified: 01 Oct 2018 12:04

Actions (login required)

View Item View Item