Mosquito Age Grading and Vector-Control Programmes

• Published in: Trends in parasitology Vol. 36; no. 1; pp. 39 - 51
• Main Authors: Johnson, Brian J., Hugo, Leon E., Churcher, Thomas S., Ong, Oselyne T.W., Devine, Gregor J.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.01.2020
• Subjects: Aedes; Age Factors; age grading; Animals; Anopheles; Culicidae - classification; Culicidae - physiology; dengue; Humans; malaria; mosquito; Mosquito Control - methods; Vector Borne Diseases - prevention & control; Vector Borne Diseases - transmission; vector control; Anopheles; age grading; malaria; Aedes; dengue; vector control; mosquito
• ISSN: 1471-4922; 1471-5007
• DOI: 10.1016/j.pt.2019.10.011

An ability to characterize the age of mosquito populations could provide cost-effective and compelling entomological evidence for the potential epidemiological impacts of vector control. The average age of a mosquito population is the most important determinant of vectorial capacity and the likelihood of disease transmission. Yet, despite decades of research, defining the age of a wild-caught mosquito remains a challenging, impractical, and unreliable process. Emerging chemometric and existing transcriptional approaches may overcome many of the limitations of current morphological techniques, but their utility in terms of field-based monitoring programmes remains largely untested. Herein, we review the potential advantages and disadvantages of new and existing age-grading tools in an operational context. New guidelines on evaluating vector-control tools highlight the need for entomological-based measures that predict epidemiological outcomes.Mosquito survivorship is the key variable in epidemiological models of vector-borne disease, but existing morphological measures of age are technically demanding, subjective, and have little utility for arbovirus vectors.Emerging techniques in spectroscopy and existing transcriptional approaches may overcome many of the problems of conventional morphological techniques but their true utility has yet to be tested.Future studies on age grading must focus on the ability of the new technologies to estimate the age of wild-caught adults and provide convincing field validations, replicated across field sites. This will require blinded trials against existing correlates of age (e.g., parity, infection, or the recapture rates of released mosquitoes).