Insights into the biology and insecticide susceptibility of the secondary malaria vector Anopheles parensis in an area with long-term use of insecticide-treated nets in northwestern Tanzania

• Published in: Parasites & vectors 2024-12, Vol.17 (1), p.549-9, Article 549
• Main Authors: Mapua, Salum Abdallah, Nambunga, Ismail Hassan, Odero, Joel Ouma, Mkandawile, Gustav, Masalu, John Paliga, Kahamba, Najat Feruz, Hape, Emmanuel Elirehema, Matowo, Nancy Stephen, Tripet, Frederic, Okumu, Fredros Oketch
• Format: Article
• Language: English
• Subjects: Animals; Anopheles; Anopheles - classification; Anopheles - drug effects; Anopheles - physiology; Anopheles parensis; Brief Report; Carbamates; Disease susceptibility; Enzyme-linked immunosorbent assay; Feeding Behavior; Female; Health aspects; Humans; Insecticide Resistance; Insecticide-Treated Bednets; Insecticides - pharmacology; Malaria; Malaria - transmission; Medical research; Medicine, Experimental; Mosquito Control - methods; Mosquito Vectors - physiology; Permethrin; Plasmodium spp; Tanzania
• ISSN: 1756-3305; 1756-3305
• DOI: 10.1186/s13071-024-06634-6

The Anopheles funestus group includes at least 11 sibling species, with Anopheles funestus Giles being the most studied and significant malaria vector. Other species, like Anopheles parensis, are understudied despite their potential role in transmission. This article provides insights into the biology and insecticide susceptibility of An. parensis, with observations of its densities in northwestern Tanzania. Mosquitoes were collected in three villages in Misungwi district, northwestern Tanzania, using CDC light traps and battery-powered aspirators indoors and human-baited double net traps outdoors. Female Anopheles adults were morphologically sorted and identified by PCR, and a subset was tested by ELISA for vertebrate blood meal sources and Plasmodium sporozoite infections. Insecticide susceptibility was assessed using the WHO protocol (2nd edition, 2018). Unfed females were dissected to assess parity, gonotrophic status and insemination status, while blood-fed females were monitored for oviposition to estimate egg counts. The prevalence of An. parensis was generally < 24% across all sites, except in Ngaya village, where it unexpectedly constituted 84% of PCR-amplified An. funestus sensu lato. This species was present in both indoor and outdoor collections, yet the females exclusively fed on non-human vertebrates, with no human blood meals detected. Parity rates were approximately 49% for resting and 46% for host-seeking females, with slightly higher percentages of both parous and inseminated females in the dry season compared to the wet season. Most parous females had oviposited once or twice, with those in the dry season ovipositing significantly more eggs. The average wing length of female An. parensis was 2.93 mm, and there was no significant impact of body size on parity, fecundity or insemination. The An. parensis mosquitoes were fully susceptible to pyrethroids, carbamates, organophosphates and organochlorides. The prevalence of An. parensis was generally < 24% across all sites, except in Ngaya village, where it unexpectedly constituted 84% of PCR-amplified An. funestus sensu lato. This species was present in both indoor and outdoor collections, yet the females exclusively fed on non-human vertebrates, with no human blood meals detected. Parity rates were approximately 49% for resting and 46% for host-seeking females, with slightly higher percentages of both parous and inseminated females in the dry season compared to the wet season. Most parous fe