Persistently high proportions of plasmodium-infected Anopheles funestus mosquitoes in two villages in the Kilombero valley, South-Eastern Tanzania

Mapua, S. A., Hape, E. E., Kihonda, J., Bwanary, H., Kifungo, K., Kilalangongono, M., Kaindoa, E. W., Ngowo, H. S. and Okumu, F. O. (2022) Persistently high proportions of plasmodium-infected Anopheles funestus mosquitoes in two villages in the Kilombero valley, South-Eastern Tanzania. Parasite Epidemiology and Control, 18, e00264. (doi: 10.1016/j.parepi.2022.e00264) (PMID:35959316) (PMCID:PMC9357827)

Abstract

Background: In south-eastern Tanzania where insecticide-treated nets have been widely used for >20 years, malaria transmission has greatly reduced but remains highly heterogenous over small distances. This study investigated the seasonal prevalence of Plasmodium sporozoite infections in the two main malaria vector species, Anopheles funestus and Anopheles arabiensis for 34 months, starting January 2018 to November 2020. Methods: Adult mosquitoes were collected using CDC-light traps and Prokopack aspirators inside local houses in Igumbiro and Sululu villages, where earlier surveys had found very high densities of An. funestus. Collected females were sorted by taxa, and the samples examined using ELISA assays for detecting Plasmodium circumsporozoite protein in their salivary glands. Results: Of 7859 An. funestus tested, 4.6% (n = 365) were positive for Pf sporozoites in the salivary glands. On the contrary, only 0.4% (n = 9) of the 2382 An. arabiensis tested were positive. The sporozoite prevalence did not vary significantly between the villages or seasons. Similarly, the proportions of parous females of either species were not significantly different between the two villages (p > 0.05) but was slightly higher in An. funestus (0.50) than in An. arabiensis (0.42). Analysis of the 2020 data determined that An. funestus contributed 97.7% of all malaria transmitted in households in these two villages. Conclusions: In contexts where individual vector species mediate most of the pathogen transmission, it may be most appropriate to pursue a species-focused approach to better understand the ecology of the dominant vectors and target them with effective interventions to suppress transmission. Despite the ongoing efforts on tackling malaria in the two study villages, there is still persistently high Plasmodium infection prevalence in local populations of An. funestus, which now carry ~97% of all malaria infections and mediates intense year-round transmission. Further reduction in malaria burden in these or other similar settings requires effective targeting of An. funestus.

• Item Type: Articles
• Additional Information: This work was supported by the Wellcome Trust International Masters Fellowship in Tropical Medicine & Hygiene (Grant No. 212633/Z/18/Z) awarded to SAM. This work was also supported by Bill and Melinda Gates Foundation (Grant Number: OPP1177156) and Howard Hughes Medical institute (Grant number: OPP1099295) both awarded to FOO.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Ngowo, Halfan and Okumu, Professor Fredros
• Authors: Mapua, S. A., Hape, E. E., Kihonda, J., Bwanary, H., Kifungo, K., Kilalangongono, M., Kaindoa, E. W., Ngowo, H. S., and Okumu, F. O.
• College/School: College of Medical Veterinary and Life Sciences; College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
• Journal Name: Parasite Epidemiology and Control
• Publisher: Elsevier
• ISSN: 2405-6731
• ISSN (Online): 2405-6731
• Published Online: 03 August 2022
• Copyright Holders: Copyright © 2022 The Authors
• First Published: First published in Parasite Epidemiology and Control 18: e00264
• Publisher Policy: Reproduced under a Creative Commons License