Susceptibility of Lutzomyia longipalpis (Lutz & Neiva, 1912) to Fludora® FusionPM, a combination of clothianidin and deltamethrin – Field and laboratory bioassays

Background Insecticides remain a cornerstone in the control of vector-borne diseases. In Brazil, Alfatek® 200SC—a pyrethroid (alphacypermethrin)—is recommended for controlling phlebotomine sand flies, the vectors of leishmaniases. For mosquitoes such as Aedes aegypti , a combination of deltamethrin and clothianidin (Fludora® FusionPM) is endorsed. This study evaluated the efficacy of Fludora® FusionPM against phlebotomine sand flies. Methods Laboratory bioassays were conducted using Fludora® FusionPM-impregnated filter papers stored either at room temperature (25 ± 2°C) or under cold conditions (3 ± 1°C). In field trials, painted (PS) or unpainted (US) masonry-plastered walls in selected households were treated with the insecticide. Alfatek® 200SC was used as a reference, following the same procedures. Lutzomyia longipalpis females (n = 25 per replicate, in triplicate) were exposed for 60 minutes using the cone test. Mortality was assessed 24 hours post-exposure and quarterly over one year. Structured questionnaires were administered to the agent responsible for spraying and household residents to document perceived adverse effects. Results In the laboratory, the residual activity expressed by average mortality rates over one year of paper impregnation was of 97.6% for Fludora® FusionPM) and 91.7% for Alfatek® 200SC). In the field, average mortality rates were 97.3% for Fludora® FusionPM and 94.6% for Alfatek® 200SC for PS. On US walls, Fludora® FusionPM maintained high mortality rate (97.8%) whereas Alfatek® 200SC parameter was reduced to 80.7%. Adverse effects were informed by three of five residents for Alfatek® 200SC and by one of four residents for Fludora® FusionPM. The community endemic agent (CEA) reported side reactions after Alfatek® 200SC spraying. Conclusions Fludora® FusionPM was highly toxic to Lu. longipalpis and outperformed Alfatek® 200SC under field conditions, particularly on unpainted surfaces. Combining insecticides with complementary modes of action may enhance rotational strategies, reduce costs and resistance risk, and optimize control of multiple vector-borne diseases simultaneously.