Submitted to: American Journal of Tropical Medicine and Hygiene
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/6/2009
Publication Date: 9/1/2009
Publication URL: www.ars.usda.gov/SP2UserFiles/Place/54300520/408NondestructivedeterminationofageandspeciesAnophelesgambiaes.l.usingNIRS.pdf
Citation: Mayagaya, V.S., Michel, K., Benedict, M.Q., Killeen, G.F., Wirtz, R.A., Ferguson, H.M., Dowell, F.E. 2009. Non-destructive Determination of Age and Species of Anopheles gambiae s.l. Using Near-Infrared Spectroscopy. American Journal of Tropical Medicine and Hygiene. 81(4):622-630. Interpretive Summary: Each year 350-500 million cases of malaria occur worldwide, and over one million people die. Controlling malaria by reducing human-insect contact has been one of the most successful approaches to reduce transmission. An obstacle to the control of malaria transmission in sub-Saharan Africa is that several of the most important vector species, which have distinct behavior, ecology and response to control, cannot be readily identified without the application of relatively expensive and sophisticated methods. Thus, there is a need for a rapid species identification technique. In addition, estimation of the age of malaria vectors is of prime importance for the measurement of transmission and control success. Because only relatively old malaria vectors are capable of transmitting malaria, knowledge of the age distribution of these populations is essential for prediction of the proportion of potentially infectious vectors, and how this changes over time and in response to control measures. Here, we evaluate the potential of a near-infrared spectroscopy for rapid species and age identification of two members of the An. gambiae species complex, An. arabiensis and An. gambiae s.s. This non-destructive technique predicted the species of field-collected mosquitoes with about 80% accuracy, and the relative age of females as young or old with about 80% accuracy. For applications in which rapid assessment of the general age structure and species composition of wild vector populations is needed, NIRS offers a valuable alternative to traditional methods.
Technical Abstract: Determination of the species and age of malaria vectors is crucial for the measurement of malaria risk. Although different in ecology and susceptibility to control, the African malaria vectors Anopheles gambiae sensu stricto and An. arabiensis are morphologically similar and can be differentiated only by molecular techniques. Furthermore, few reliable methods exist to estimate the age of these vectors, which is a key predictor of malaria transmission intensity. We evaluated the use of near-infrared spectroscopy (NIRS) as a tool for rapid and reliable determination of the species and age of these vectors. This non-destructive technique predicted the species of field-collected mosquitoes with about 80% accuracy, and the relative age of females as “young” (< 7 days) or “old” (=7 days) with about 80% accuracy. For applications in which rapid assessment of the general age structure and species composition of wild vector populations is needed, NIRS offers a valuable alternative to traditional methods.