Alteration of plant species assemblages can decrease the transmission potential of malaria mosquitoes

Abstract

Knowledge of the link between a vector population's pathogen-transmission potential and its biotic environment can generate more realistic forecasts of disease risk due to environmental change. It also can promote more effective vector control by both conventional and novel means.This study assessed the effect of particular plant species assemblages differing in nectar production on components of the vectorial capacity of the mosquito , an important vector of African malaria.We followed cohorts of mosquitoes for three weeks in greenhouse mesocosms holding nectar-poor and nectar-rich plant species by tracking daily mortalities and estimating daily biting rates and fecundities. At death, a mosquito's insemination status and wing length were determined. These life history traits allowed incorporation of larval dynamics into a vectorial capacity estimate. This new study provided both novel assemblages of putative host plants and a human blood host within a nocturnal period of maximum biting.Survivorship was significantly greater in nectar-rich environments than nectar-poor ones, resulting in greater total fecundity. Daily biting rate and fecundity per female between treatments was not detected. These results translated to greater estimated vectorial capacities in the nectar-rich environment in all four replicates of the experiment (means: 1,089.5 ± 125.2 vs. 518.3 ± 60.6). When mosquito density was made a function of survival and fecundity, rather than held constant, the difference between plant treatments was more pronounced, but so was the variance, so differences were not statistically significant. In the nectar-poor environment, females' survival suffered severely when a blood host was not provided. A sugar-accessibility experiment confirmed that is a nectar-poor plant for these mosquitoes. This study, assessing the effect of particular plant species assemblages on the vectorial capacity of malaria mosquitoes, highlights the likelihood that changes in plant communities (e.g. due to introduction of exotic or nectar-rich species) can increase malaria transmission and that a reduction of favourable nectar sources can reduce it. Also, plant communities' data can be used to identify potential high risk areas. Further studies are warranted to explore how and when management of plant species assemblages should be considered as an option in an integrated vector management strategy.

Semi-field evaluation of the cumulative effects of a “Lethal House Lure” on malaria mosquito mortality

“…A further limitation is that the study used experimental huts rather than real houses and it is possible that mosquito entry rates and contact rates with insecticide, might differ between small experimental huts and real houses. These differences could result from differences in the structures [6, 21, 44, 45], complexity of the natural environment including availability of alternate blood and sugar sources [46–49], and in human behaviour [50, 51]. In addition, the current experiments compared treatments at the equivalent of 100% coverage (i.e., 2 control huts vs 2 treated huts).…”

Not Just from Blood: Mosquito Nutrient Acquisition from Nectar Sources

“…Plant nectar is the only food source for male mosquitoes, making their survival, insemination rates, and swarming ability highly dependent on nectar availability [20,21]. Males are polyandrous and their reproductive success depends on the number of females that they can inseminate before semen depletion [22].…”

“…When considering the mosquito population density, extrinsic incubation period of malaria, mosquito mortality, and biting rate, the vector capacity of An. gambiae is estimated to increase significantly when nectar sources are plenty (Figure 3) [20]. We expect this to vary depending on the pathogen as well as the interaction between genetic and environmental factors, such as vector immunity, temperature, and access to nutrients in larval and adult mosquitoes [92][93][94][95].…”

Glucose-mediated expansion of a gut commensal bacterium promotesPlasmodiuminfection through alkalizing mosquito midgut

“…Feeding on the preferred plants increases mosquito's life span and improves its fecundity (Manda et al, 2007a;Stone et al, 2012;Yu et al, 2016). The sugars from different plant species also influence the capability of Anopheles to transmit malaria parasite (Ebrahimi et al, 2018;Gu et al, 2011;Hien and Dabire, 2016) . Although we have no access to the natural plants in malaria endemic area, using the sugar meals simulating the composition of 4 favorite and 1 less favorite plant saps as mosquito diets, we demonstrate that the composition of sugars determines the vector capacity and such determination is associated with the ability of them to promote the proliferation of A. bogorensis.…”

“…The diversity of natural plants affects the capacity of Anopheles mosquito to transmit Plasmodium parasites (Ebrahimi et al, 2018;Gu et al, 2011;Hien and Dabire, 2016). We hypothesized that the ability of different sugar composition to promote the growth of A. bogorensis might vary and such variation might influence the vector competence of Anopheles mosquitoes.…”