Prediction of mosquito vector abundance for three species in the Anopheles gambiae complex
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Background
The dynamics of vector borne disease transmission depend on the abundances of vectors. The dominant malaria vector species complex of Anopheles gambiae sensu lato is a target of vector control strategies designed to reduce and eliminate malaria transmission. The three most widely distributed dominant malaria vectors within the species complex are An. arabiensis, An. coluzzii and An. gambiae sensu stricto.
Methods
Previous studies across the extent of the species complex range have been restricted to predictions of relative abundance for each species or aggregates of the species. This study incorporated relative abundance data at the species level and abundance data at the species complex level to estimate and predict the carrying capacities of each species. Statistical models with interpretable parameters were used to gain insight into how factors such as meteorological conditions and human density affect the spatial and temporal predictions.
Results
At the continental scale, precipitation and temperature were found to be important spatially and temporally varying predictors of equilibrium abundances of these three dominant malaria vector species in Africa. The equilibrium abundance of An. gambiae sensu stricto was predicted to have increased across much of its range during the period 2002–2020, and particularly so in the Lake Victoria basin. In contrast, An. arabiensis was predicted to have decreased around Lake Victoria and southeastern Africa but increased elsewhere in eastern Africa. A predicted increasing inter-annual trend for An. coluzzii was possibly caused by changing species identification methods over the observational period.
Conclusion
The predicted equilibrium abundances of the three species showed potentially high levels of geographical overlap, niche overlap, and evidence for stable coexistence despite substantial interspecific competition. Improving collection of longitudinal species abundance data across the spatial range of the An. gambiae species complex will facilitate future explorations of causal hypotheses that relate vector abundance to control measures, malaria interventions and climate conditions.
