First report of co-occurrence of Anopheles gambiae and An. arabiensis (Diptera: Culicidae): comparative blood meal sources and infection rates in Ethiopia

Abstract

Entomological surveillance is critical for understanding the species composition, behavior, and transmission roles of malaria vectors to guide evidence-based control strategies. This study aimed to determine the species composition, blood meal sources, and infection rates of the Anopheles gambiae complex in three regions of Ethiopia. Surveillance was conducted from July to November 2024 in six sites across three regions (Southwest, Gambella, and Oromia) of Ethiopia. Mosquitoes were collected using human landing catches, CDC light traps, and Prokopack aspirators. Specimens were identified morphologically, followed by species-specific PCR. Blood meal sources and Plasmodium infection rates were determined using PCR and Circumsporozoite Enzyme-linked Immunosorbent Assay (CSP-ELISA), respectively. Of 284 morphologically identified An. gambiae s.l., PCR identified 39.8% as An. gambiae, 26.7% as An. arabiensis , and 6% as An. amharicus (27.8% non-amplified). Anopheles gambiae was present in all sites, with the highest prevalence in Godere (96.2%) and South Bench (60%). In contrast, An. arabiensis predominated in Seka Chekorsa (67.9%). Blood meal analysis results showed that the human blood index (HBI), bovine blood index (BBI) and goat blood index (GBI) for An. gambiae was 41.8%, 18.2% and 14.5% respectively while HBI, OBI and GBI for An. arabiesnsis was 0%, 28% and 71.4%, respectively. An. gambiae infection rates for Plasmodium falciparum and P. vivax were 2.8% and 0.9%, respectively and no Plasmodium infection was detected for An. arabiensis . This study provides the first report of An. gambiae in three regions of Ethiopia and its co-occurrence with the major malaria vector, An. arabiensis was also documented for the first time in Ethiopia. The high HBI and infection rates suggest that An. gambiae could contribute to local malaria transmission in Ethiopia. Hence, the national control/elimination program should prioritize indoor residual spraying (IRS) and insecticide-treated nets (ITNs) to target this indoor-resting species ( An. gambiae ) in these areas.