Why is the effect of malaria parasites on mosquito survival still unresolved?

Despite almost a century of effort, the question of whether malaria parasites kill their mosquito vectors remains open. Some direct comparisons of the longevity of infected and uninfected mosquitoes have found malaria-induced mortality, whereas others have not. Here, we use meta-analysis to show that, overall, malaria parasites do reduce mosquito survival. However, mortality effects are more likely to be detected in unnatural vector-parasite combinations and in studies of longer duration. Until these factors are systematically investigated, no firm generalities are possible.