Smallest Anopheles farauti occur during the peak transmission season in the Solomon Islands

Abstract

Background Malaria transmission varies in intensity amongst Solomon Island villages where Anopheles farauti is the only vector. This variation in transmission intensity might be explained by density-dependent processes during An. farauti larval development, as density dependence can impact adult size with associated fitness costs and daily survivorship. Methods Adult anophelines were sampled from six villages in Western and Central Provinces, Solomon Islands between March 2014 and February 2017. The size of females was estimated by measuring wing lengths, and then analysed for associations with biting densities and rainfall. Results In the Solomon Islands, three anopheline species, An. farauti , Anopheles hinesorum and Anopheles lungae , differed in size. The primary malaria vector, An. farauti , varied significantly in size among villages. Greater rainfall was directly associated with higher densities of An. farauti biting rates, but inversely associated with body size with the smallest mean sized mosquitoes present during the peak transmission period. A measurable association between body size and survivorship was not found. Conclusions Density dependent effects are likely impacting the size of adult An. farauti emerging from a range of larval habitats. The data suggest that rainfall increases An. farauti numbers and that these more abundant mosquitoes are significantly smaller in size, but without any reduced survivorship being associated with smaller size. The higher malaria transmission rate in a high malaria focus village appears to be determined more by vector numbers than size or survivorship of the vectors. Electronic supplementary material The online version of this article (10.1186/s12936-019-2847-2) contains supplementary material, which is available to authorized users.

Human exposure to Anopheles farauti bites in the Solomon Islands is not associated with IgG antibody response to the gSG6 salivary protein of Anopheles gambiae

“…Mosquito and human blood surveys took place during the dry and wet seasons in the villages of Jack Harbour, Tuguivili, Saeragi, and New Mala in Western Province, Solomon Islands [5, 13]. Human biting rates were estimated twice in the dry season (May and August 2016) and twice in the wet season (November 2016 and February 2017).…”

Humidity – The overlooked variable in the thermal biology of mosquito‐borne disease

“…Instead of measuring humidity directly (Box 1), many studies use related variables, like seasonal precipitation or land cover to predict mosquito population dynamics or pathogen transmission (Abdelrazec & Gumel, 2017; Chandy et al, 2013; Chaves & Kitron, 2011; Johansson et al, 2009; Nosrat et al, 2021; Sang et al, 2017; Soti et al, 2012). Mosquito‐borne diseases generally peak during, or following, periods of highest rainfall (Chowdhury et al, 2018; Karim et al, 2012; Magombedze et al, 2018; McLaughlin et al, 2019). Rainfall can matter as a standalone variable, since standing water is essential for mosquitoes' ontogenetic development.…”

Evaluation of the malaria reporting system supported by the District Health Information System 2 in Solomon Islands

“…There were also 109 deaths due to malaria [ 1 ]. Anopheles farauti is the primary vector and secondary vectors are Anopheles punctulatus and Anopheles koliensis [ 3 , 4 ].…”