The effects of irrigation on species abundance and entomological inoculation rate of anophelines mosquito in Bure District, Northwestern Ethiopia

Irrigation has been playing a tremendous role by improving agricultural production, food security, and the livelihood in many developing countries, including Ethiopia. However, evidences indicate that irrigation might increase the risk of malaria disease in Africa. This study was designed to assess the effect of irrigation on species abundance and entomological inoculation rate of anophelines mosquito in Bure district, Ethiopia. Adult mosquitoes were collected from July 2015 to June 2016 using light trap catches, pyrethrum spray catches, and artificial pit shelters. Mosquitoes were morphologically identified. Following this, Anopheles gambiae sensu lato was identified molecularly. Head-thorax sporozoite infectivity of the adult female Anopheles mosquitoes was assessed using enzyme-linked immunosorbent assays. The greater number of adult Anopheles mosquitoes were collected in Shnebekuma village than Workmidr and Bukta villages (p < 0.0001). Three of Anopheles species, An. arabiensis, An. funestus, and An. coustani were found to be infected with Plasmodium falciparum and Plasmodium vivax. The overall Plasmodium infective rate in the district was 0.31%. The overall estimated EIR of Anopheles mosquitoes was 5.7 infective bites/person/year for both Plasmodium falciparum and Plasmodium vivax in the district. The presence of sporozoite infected An. coustani in Bure district is the fourth report in Ethiopia and the first in Amhara region, which indicates this species is the other responsible vectors to transmit the malaria parasite. Annual P. falciparum-EIR of An. arabiensis, P. vivax-EIR of An. funestus, and P. vivax-EIR of An. coustani were higher in non-irrigated villages than irrigated village. Therefore, long-lasting insecticide nets and indoor residual spraying could be implemented exhaustively in the non- irrigated villages throughout the year to cut the vector abundance and the entomological inoculation rate of each infected species.