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Title: Use of Near-Infrared Spectroscopy to Age-Grade and Identify Siblings of Anopheles Gambiae Complex

Author
item Dowell, Floyd
item MAYAGAYA, VALELIANA - Ifakara Health Institute
item MICHEL, KRISTIN - Kansas State University
item FERGUSON, HEATHER - University Of Glasgow
item BENEDICT, MARK - International Atomic Energy Agency (IAEA)
item WIRTZ, ROBERT - Centers For Disease Control And Prevention (CDC) - United States

Submitted to: American Society of Tropical Medicine and Hygiene
Publication Type: Abstract Only
Publication Acceptance Date: 11/14/2008
Publication Date: 11/14/2008
Citation: Dowell, F.E., Mayagaya, V., Michel, K., Ferguson, H., Benedict, M., Wirtz, R. Use of Near-Infrared Spectroscopy to Age-Grade and Identify Siblings of Anopheles Gambiae Complex. Meeting abstract. American Society of Tropical Medicine and Hygiene 57th Annual Meeting; December 7-11, 2008; New Orleans, LA

Interpretive Summary:

Technical Abstract: We used near-infrared spectroscopy (NIRS) to rapidly and non-destructively determine species and age of Anopheles gambiae ss (G3, Mali-NIH, Kisumu, ZANU, and Ifakara strains) and An. arabiensis (Dongola, KGB, and Ifakara strains). We developed NIR calibrations using mosquitoes reared and scanned at Kansas State University, the Centers for Disease Control, and the International Health Institute, Ifakara, Tanzania. For species identification, calibrations were tested by classifying wild insects collected from the Kilombero Valley, Tanzania. Species was confirmed by PCR. For age-grading, we used spectra collected from 1 to 19 day old males and females of one strain to predict the ages of two other strains or species. We used a field-portable Analytical Spectral Devices spectrometer (400-2500nm) to collect all spectra. For species identification, we showed that calibrations developed from laboratory-reared insects could be used to predict the species (An. gambiae or An. arabiensis) of wild insects with a correct classification rate of about 80%. For age-grading, we developed calibrations using spectra collected from Ifakara and G3 An. gambiae strains, and KGB An. arabiensis strain. Results showed that very young mosquitoes could easily be distinguished from very old mosquitoes, and generally we could classify into young (=4 days), middle age (7 days) and old (=10 days) age groups. This was generally true for males and females, and we could use calibrations developed for one species or strain to predict the age of other species or strains. Thus, we were able to use this rapid, nondestructive, and portable NIR technique to determine species and age of mosquitoes. Scanning requires only a few seconds per insects, and thus thousands of insects can be analyzed per day. The technique uses no consumables and no cost is involved after the instrument has been purchased.