Temporally consistent predominance and distribution of secondary malaria vectors in the Anopheles community of the upper Zambezi floodplain

Abstract

Regional optimisation of malaria vector control approaches requires detailed understanding both of the species composition of Anopheles mosquito communities, and how they vary over spatial and temporal scales. Knowledge of vector community dynamics is particularly important in settings where ecohydrological conditions fluctuate seasonally and inter-annually, such as the Barotse floodplain of the upper Zambezi river. DNA barcoding of anopheline larvae sampled in the 2019 wet season revealed the predominance of secondary vector species, with An. coustani comprising > 80% of sampled larvae and distributed ubiquitously across all ecological zones. Extensive larval sampling, plus a smaller survey of adult mosquitoes, identified geographic clusters of primary vectors, but represented only 2% of anopheline larvae. Comparisons with larval surveys in 2017/2018 and a contemporaneous independent 5-year dataset from adult trapping corroborated this paucity of primary vectors across years, and the consistent numerical dominance of An. coustani and other secondary vectors in both dry and wet seasons, despite substantial inter-annual variation in hydrological conditions. This marked temporal consistency of spatial distribution and anopheline community composition presents an opportunity to target predominant secondary vectors outdoors. Larval source management should be considered, alongside prevalent indoor-based approaches, amongst a diversification of vector control approaches to more effectively combat residual malaria transmission.

Future malaria environmental suitability in Africa is sensitive to hydrology

“…We also recognize that sub-Saharan vector species vary in their larval habitat requirements ( 27 ) and often use small, shallow, sunlit, and water-filled depressions such as hoof prints, wheel ruts, and puddles for breeding sites (e.g., Anopheles gambiae sensu stricto and A. arabiensis ), although even here habitat hydrology and geomorphology have been shown to control the distribution of malaria vector larva ( 28 ). Conversely, other major vectors (e.g., A. funestus ) require semipermanent freshwater bodies such as swamps, ponds, and lake edges ( 27 ), and secondary vectors such as A. coustani and A. squamosus breeding in large, vegetated floodplains connected to rivers can be locally and regionally important ( 29 , 30 ). Local variability in vector ecology presents a challenge to any geographically uniform approach to modeling malaria suitability ( 31 ), although the inclusion of both local runoff and large-scale water fluxes in the composite hydrological metric (Q_PE) is an attempt to ensure that both habitat types are represented.…”

Spatio—Temporal distribution of a vector of cutaneous leishmaniasis: Pintomyia longiflocosa, in a population from the Colombian Andean Mountains

“…The dynamics of insect populations and their behaviors are affected by climate, and in the same way, they affect the transmission cycles of pathogens vectors of these arthropods [25][26][27][28][29]. For this reason, elucidating the environmental conditions and habitat attributes fostering PLOS NEGLECTED TROPICAL DISEASES elevated sand fly population density is crucial.…”