High human blood meal index of mosquitoes in Arba Minch town, southwest Ethiopia: an implication for urban vector-borne diseases transmission

Abstract Background Unplanned population shifts in urban areas are expected to increase the prevalence of vector-borne diseases. This study was conducted to investigate the role of urban vectors and their blood meal sources in the spread of malaria. Methods Indoor resting adult mosquitoes were collected using Prokopack and host-seeking mosquitoes using Centers for Disease Control and Prevention light traps in Arba Minch town and identified using a morphological key. Larval collection from artificial containers was done in those houses selected for adult mosquito collection. Anopheles adults collected and emerged from larvae were identified morphologically using a key. ELISA was used to identify blood meal sources in freshly fed Anopheles and Culex mosquitoes, and CSP of Anopheles mosquitoes. Results A total of 16,756 female mosquitoes were collected. Of these, 93% (15,571) were Culex, 6% (1,016) were Anopheles, and 1% (169) were Aedes. Of the 130 adults raised from larval, An. rhodesiensis accounted for 20%, while Aedes accounted for 80%. The container-breeding Anopheles mosquito identified was An. rhodesiensis. Anopheles stephensi was not documented. Out of 823 mosquitoes tested for blood meal origins, 86.3% (710/823) tested positive for human blood, 2.2% (18/823) tested positive for bovine blood, and 11.5% (95/823) were negative for human and bovine antibodies. Anopheles gambiae complex had a human blood meal index (HBI) of 50% (90/180; CI: 42.3–57.5%) and a bovine blood meal index (BBI) of only 0.5% (95% CI 0.01–3.1%). Culex HBI was 96.7% (620/641), and its BBI index was 2.4% (15/641). While it was low (0.8%) in Culex, the proportion of An. gambiae complex with unidentified blood meal sources was 49.5%: 95 CI%: 41.9–56.9%). Among the 1016 Anopheles mosquitoes tested, a single An. gambiae complex (0.1%; 1/1016) was positive for P. vivax CSP. Conclusions The high HBI indicates frequent contact between humans and vectors. To reduce human exposure, personal protection tools should be implemented.