Near-infrared spectroscopy discriminates mass-reared sterile and wild tsetse flies

In the frame of the Pan African Tsetse and Trypanosomosis Eradication Campaign, an integrated pest management approach has been adopted to manage tsetse fly populations using a sterile insect technique (SIT).. Monitoring the efficacy of the SIT programs requires the discrimination between wild and sterile males collected in monitoring traps. The discrimination between sterile and wild males relies mainly on marking of sterile males with a fluorescent dye powder (before the releases) and their identification using a fluorescence camera and /or a fluorescence microscope. However, the accuracy of this method remains limited with defective marking and wild flies contaminated with a few dye particles in the monitoring traps. The molecular techniques developed to discriminate doubtful flies are costly for endemic countries. Here, we investigate the ability of a new generation monitoring tool, the near-infrared spectroscopy (NIRS) to discriminate between lab-reared Glossina palpalis gambiensis and their counterparts in the field. NIRS technique discriminates wild flies males with 86% accuracy to Glossina palpalis gambiensis males reared in an insectarium. Interestingly, the prediction accuracy between wild and laboratory-reared flies improved to 88% when the Glossina lab colony flies were irradiated. In light of these results, NIRS can discriminate tsetse flies even when identification with the UV camera is doubtful. However, more investigations integrating some natural variables are required before the validation of the technical as a complementary method for potential future tsetse eradication programs.