Malaria Vectors And Transmission Intensity In An Epidemic Prone Area Of Bure District West Gojam Northwestern Ethiopia

Malaria is one the leading health problem in Ethiopia. In the past few decades’ placesrnlocated above 2,000 meters elevation were considered as malaria free areas. However,rnthe major malaria epidemics were seen up to 3,000 meters due to climate and land-usernchanges (ecological changes). Currently, due to the mass distribution of long lastingrninsecticide treated nets (LLINs) and nationwide implementation of Artemisinin BasedrnCombination Therapy (ACT) and case management, the reduction of malaria morbidityrnand mortality have observed throughout Ethiopia. Regardless of these tremendousrnefforts, still malaria is one of the health problems of some highland parts of the country.rnIn the study area, there was no any information on the diversity, abundance and spatiotemporalrndistribution of both the adult and larva of Anopheles mosquitoes. Hence, thernobjective of this study was aimed to investigate the species composition and abundance,rnblood feeding pattern, parous rates, longevity, entomological inoculation rates ofrnAnopheles mosquitoes in Bure district, Northwestern Ethiopia. Similarly, speciesrncomposition and distribution of the larva of Anopheles were studied and habitats werernidentified and characterized in each month. Entomological study of Anophelesrnmosquitoes was conducted longitudinally in each month, from July 2015 to June 2016 inrnthree villages, Bukta, Workimdr and Shnebekuma. Adult Anopheles mosquitoes wererncollected by Light Traps, Pyrethrum Spray Catches and Artificial Pit Shelters.rnIdentification of Anopheles species was done using morphological keys and speciesspecificrnpolymerase chain reaction. Parous rates were determined by dissecting of thernabdomen of unfed mosquitoes and then longevity was calculated from parous rates (p)rnusing . Blood meal origins and circumsporozoite proteins were analyzed byrnEnzyme-Linked Immuno Sorbent Assay (ELISA). The human blood index (HBI) wasrncalculated as the proportion of the mosquitoes fed on human blood meal of the totalrnmosquitoes tested. Sprorozoite rate was expressed as the proportion of mosquitoes withrnCircum-sporozoite protein (CSP) to the total numbers of mosquitoes tested. Larvae werernrncollected from different breeding habitats using 350ml white dipper (and graduatedrnpipette) and habitats were characterized; and morphologically 3rd and 4th stages of thesernlarvae were identified to species level using keys from July 2015 - June 2016.rnIndependent-Samples T-Test and One-way- ANOVA were applied to evaluaternmosquitoes densities difference between villages and species, indoor and outdoor hostrnseeking mosquitoes, overall human and bovine blood indices and environmentalrnvariables. Nine adult species were identified (Anopheles demeilloni, An. arabiensis, An.rnfunestus, An. coustani, An. squamosus, An. cinereus, An. pharoensis, An. rupicolus, andrnAn. natalensis). Of 4703, An. demeilloni (50.7%, n = 2383) was the most dominant thanrnothers (p < 0.05). Spatially, the largest numbers of adult Anopheles mosquitoes wererncollected in non-irrigated village (Shnebekuma) (2.39 ± 0.10 adults/CDC-LT) thanrnirrigated (Bukta) (1.35 ± 0.11 adults/CDC-LT) (p < 0.05). The overall (single plusrnmixed) HBIs of An. arabiensis, An. funestus, An. coustani, An. squamosus and An.rncinereus were equal to the overall BBIs of the correspondent species (p > 0.05). ThernCSP-ELISA test revealed that only sporozoite infected Anopheles mosquitoes werernfound only in non-irrigated villages (Shnebekuma and Workmidr). Overall sporozoiternrates of An. funestus, An. coustani, An. arabiensis for P. vivax and P. falciparum werern0.57%, 0.23% and 0.2%, respectively. Morphologically, seven species of Anophelesrnlarvae were identified (An. demeilloni, An. gambiae s.l, An. funestus s.l, An. coustani s.l,rnAn. squamosus, An. cinereus and An. pharoensis). Of 3490, An. demeilloni (34.8%) wasrnthe most dominant than others (p < 0.05). The density of Anopheles larva wasrnstatistically insignificant in the three villages (p > 0.05). In conclusion, three of the mostrnimportant malaria vectors of Ethiopia were identified; An. arabiensis, An. funestus andrnAn. pharoensis. Most of the adults and sporozoite infected Anopheles mosquitoes werernfound only in non-irrigated villages. All these results implying that, irrigation activity hasrnnot any influence on the abundance, composition of Anopheles mosquitoes andrnprevalence of malaria in the three villages. Generally, vectors infection and malariarntransmission rates were very low. Thus, breeding habitat management must be inrnincorporated into control program and applied throughout the year together with LLINsrnand IRS, especially for non irrigated villages.

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