Rapid evaporative ionisation mass spectrometry can age field caught Anopheles gambiae malaria vectors

Reliable estimates of the age structure of malaria mosquitoes would aid evaluation of the efficacy of vector control and inform models of malaria transmission. We have previously shown that rapid evaporative ionisation mass spectrometry (REIMS) could determine the age and species of laboratory reared mosquitoes and culicine mosquitoes from a river estuary in the United Kingdom. Here we investigated the robustness of this methodology by introducing additional environmental, genetic and physiological diversity in experiments using laboratory reared and field collected Anopheles gambiae mosquitoes. REIMS reliably separated mosquitoes into 3 or 5 age groups with > 80% accuracy using mosquitoes of mixed physiological status reared in insectaries or collected from semi-field stations in Burkina Faso. In addition, REIMS could distinguish mosquitoes that were nulliparous from those that had undergone one or two oviposition cycles with an accuracy of 87%. In a proof of principle experiment REIMS readily distinguished mosquitoes infected with Plasmodium berghei from non-infected. Furthermore, we show that age grading is possible using only mosquito abdomens, leaving biomass for further molecular biological experiments. Finally, we used the model generated from mixed field collections to estimate the age structure of mosquitoes collected from inside houses.