Age structure and parity status determination of Afrotropical malaria vectors using MALDI-TOF MS

The age structure of a mosquito population helps estimate the proportion of vectors capable of transmitting malaria. Many malaria transmission models rely on mosquito longevity as key parameter. However, these are rarely measured in the field due to lack of a reliable and scalable age-grading method. An accurate method could improve predictions of malaria risk and the impact assessment of interventions. This study aimed to investigate the use of Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) for malaria vector age-grading using insectary-reared and wild-caught mosquitoes. Anopheles gambiae s.s. mosquitoes were reared in the insectary to different known physiological and chronological ages to evaluate if MALDI-TOF MS could be used to distinguish between different age groups. Wild mosquitoes were collected from Mozambique and Kenya and dissected to determine their parity status. Reference spectra were obtained from mosquito's cephalothorax and used to create predictive databases which were validated using independent samples. MALDI-TOF MS identified the physiological and chronological age of insectary-reared mosquitoes with 94.52% and 77% accuracy respectively. Field-collected mosquitoes were primarily An. funestus s.s. and An. gambiae s.s. Parity prediction accuracy was between 81% and 87%. MALDI-TOF MS was able to distinguish and differentiate mosquitoes based on their age structure (chronological and physiological) and parity status.