Evaluation of the efficacy of a topically administered combination of imidacloprid and permethrin against Phlebotomus perniciosus in dog.

The phlebotomine sand fly Phlebotomus perniciosus is one of the main vectors of Leishmania infantum, responsible for human and canine leishmaniasis in the Mediterranean Basin. The objective of this study was to evaluate the repellent and insecticidal efficacy of imidacloprid 10% (w/v)/permethrin 50% (w/v) spot-on against sand flies (P. perniciosus) on dogs. The dogs used in this trial were laboratory-bred beagles: eight were impregnated with the solution (treated group), while the other eight were left untreated (control group). On day 0 the animals in the treatment group received 0.1 ml/kg body weight of the combination imidacloprid/permethrin spot-on. Dogs were exposed for 1h to about 100 female sand flies at weekly intervals for a period of 4 weeks, on day 1, 7, 14, 21, and 28 after applying the product. The repellency criterion was based on the feeding rate of sand flies in the treated compared to the untreated group. The insecticidal efficacy criterion was based on comparison of the survival rate of sand flies between the two groups. The product had an insecticidal efficacy on female sand flies of 53.2% (day 1), 49.4% (day 7), 15.1% (day 14), 13.2% (day 22), and 2.9% (day 29). The product showed a repellent effect of 97.7% (day 1), 96.3% (day 7), 96.5% (day 14), 92.7% (day 22), and 74.0% (day 29). Within the first week of application the insecticidal effect was significant; however it did not surpass 50%. On the other hand, the product showed a potent anti-feeding effect of over 90% during the first 3 weeks of this trial. Therefore, the application of this product every 3 weeks would be a good tool to significantly reduce sand fly bites over the period of transmission of vectorial diseases such as leishmaniasis and several arbovirosis such as Toscana virus.