Proportional decline of Anopheles quadriannulatus and increased contribution of An. arabiensis to the An. gambiae complex following introduction of indoor residual spraying with pirimiphos-methyl: an observational, retrospective secondary analysis of pre-existing data from south-east Zambia

• DOI: 10.1186/s13071-018-3121-0
• Publication Date: 2018-10-11T01:08:23Z
• Authors: Dingani Chinula; Busiku Hamainza; Elizabeth Chizema; Deogratius R. Kav...; Chadwick H. Sikaala; Gerry F. Killeen
• Keywords: Anopheles gambiae; Indoor residual spraying; Mosquito control; Entomology; Sibling species

Across most of sub-Saharan Africa, malaria is transmitted by mosquitoes from the Anopheles gambiae complex, comprising seven morphologically indistinguishable but behaviourally-diverse sibling species with ecologically-distinct environmental niches. and An. arabiensis are mostly widely distributed major vectors within while quadriannulatus sparsely distributed. Indoor residual spraying (IRS) organophosphate pirimiphos-methyl (PM) was conducted four times between 2011 2017 in Luangwa Valley, south-east Zambia. were repeatedly collected indoors several experiments various objectives this study area 2010 onwards. mosquito collection methods included human landing catches, Centres for Disease Control Prevention miniature light traps back pack aspirators. complex identified to level using taxonomic keys, molecular polymerase chain reaction. These multi-study data collated so that time trends composition could be assessed. The proportion indoor accounted declined 95.1% 69.7% following two application PM-IRS rounds an emulsifiable concentrate formulation 2013, insecticidal net utilisation remained consistently high throughout period. This trend continued after further a longer-lasting capsule suspension 2015 2016/2017, which only 4.5% complex. During same interval there correspondingly steady rise proportional contribution 3.9 95.1%, nominate stable at ≤ 0.9%. It seems likely not more behaviourally resilient against IRS than gambiae, also populations exhibiting indoor-feeding, human-feeding nocturnal behaviours unusual species. Routine, programmatic entomological monitoring dynamic vector population guilds will critical guide effective selection deployment control interventions, including supplementary measures tackle persisting transmission like arabiensis.