An overview of malarial Anopheles mosquito survival estimates in relation to methodology

BackgroundThe transmission of malaria is known to be sensitive to the survival (longevity, mortality) of its mosquito vector, yet there have been few reviews of estimates of this important population parameter in the malaria-carrying genus Anopheles.MethodsWe carried out a systematic search for and meta-analysis of survival estimates, framed around the methods of estimation, under the major groupings of ?vertical' (based on stable age or stage frequencies), ?horizontal' (based on recaptures of marked and released cohorts), and ?parasitological' (proportion of infectious mosquitoes). Because of the intricacies of the estimation process we provide an outline of these methods.ResultsBy meta-analysis we quantify the average of the distribution of daily survival p for vertical (0.83, 95% CI: 0.80-0.86), horizontal (0.73, 95% CI: 0.66-0.79) and parasitological (0.92, 95% CI: 0.86-0.95) methods.ConclusionsThe meta-analysis demonstrates the anticipated result that horizontal estimates are lowest because they estimate apparent survival (survival and non-emigration) rather than true survival. On the other hand, vertical methods make strong assumptions about the stability or stationarity of the underlying populations. Further potential sources of methodological bias are mentioned. The substantial differences in estimates between methods indicates that methodological biases need to be considered when making use of available survival estimates.