Population dynamics, biting activities and resting behavior of Anopheles mosquitoes in Jabi Tehnan district, Northwest Ethiopia

implications for indoor malaria vector control

Abstract

Background: Effective malaria control programs rely on the implementation of evidence-based interventions. Careful assessment of Anopheles mosquito behavior like population dynamics, biting and resting behavior of mosquito vectors strengthen the sustainability and efficacy of the deployed vector control tools.

Methods: The study was conducted from September 2016 to August 2017.Adult mosquitoes were collected both indoors and outdoors in selected villages of Jabi Tehnan District, North West of Ethiopia. Adult mosquitoes were collected from indoor and outdoor using human landing catch (HLC) ,and  CDC light traps (CDC-LT);, from indoor using pyrethrum spray catch (PSC) () and outdoor using pitfall shelters (PS)..   A total of 35 houses were selected for sampling mosquitoes, 10 houses each for CDC-LT, PSC and PS, and five houses for HLC. Mosquito collection was carried out twice a month for 12 months.

Results: In the 12 months sampling period, 9,258 mosquitoes were collected and morphologically identified to species level using standard keys. Of these, 5,098 (55.1%) were Anopheles mosquitoes belonging to five species, and the rest 4,160 (44.9%) were Culex spp. The five Anopheles species comprised Anopheles gambiae s.l. (58.5%, n=2,982), An. phroensis (11.9%, n=605), An. funestus (3.4%, n=176), An. coustani (15.2%, n=774) and An. cinereus (11%, n=561). The peak biting time for An. gambiae s.l. was between 22:00 to 00:00 hours. However, the activity decreased sharply after 23:00 - 24:00 hours and stopped completely after 04:00. Anopheles gambiae s.l., An. pahroensis and An. coustani s.l exhibited different peak biting activities throughout the night. Anopheles gambiae s.l. was the most abundant malaria vector species in the district. The Anopheles mosquito population peaked right after the long rains in October and during the short rainy season in March.

Conclusions: The results indicate that An. gambiae s.l. (primarily An.arabiensis) is the most abundant malaria vector in Jabi Tehnan District and showed marked high biting activities during peak sleeping hours. Thus, in addition to the indoor-based interventions (LLINs and IRS) in place, additional vector control methods should be designed to address the problem of outdoor biting mosquitoes.