Development of flame retardant slow release insecticides paint and testing its efficacy for four years against dengue and malaria vectors

Insecticide based paint formulations have been available since years, however the concept of using such paint products at household level did not get attention due to various reasons. The advancement in insecticidal paint technology has steered toward the development and evaluation of such formulations for use against arthropod vectors. The improved insecticidal paint formulations may contain two or more active agents, hence could display different type of activity against the target vectors. In the present study, optimum concentrations of deltamethrin (1%), chlorpyriphos (0.5%) and pyriproxyfen (0.075%) were used as active ingredients (AIs) to develop flame retardant slow-release insecticides paint (FRSRIP) formulation. The developed formulation was tested for physico-chemical properties, toxicity and efficacy against two important mosquito vectors. The formulation was glossy, smooth, uniform and scratch proof. Furthermore, the formulation was flame retardant and conformed to class-A according to the guidelines. Acute oral, dermal and inhalation toxicity suggested that the formulation is safe for use in human dwellings. The formulation was evaluated against Ae. aegypti and An. stephensi mosquitoes in laboratory upto four years. It was found that KDT₅₀ after 24 months (T24) was 14.8 ± 0.8 min and 17.1 ± 1.0 min, while after 48 month (T48) was 21.3 ± 2.0 min and 22.4 ± 1.4 min in both Ae. aegypti and An. stephensi respectively. KDT₅₀ was found varying during the different time intervals (T6 to T48) in both Ae. aegypti (p = 0.01) and An. stephensi (p = 0.0003). Furthermore the corrected mortality (CM) also found statistically declined during the period of evaluation (T6 to T48) in both the test species (F ≥ 42. 4; p ≤ 0.0001). Ae. aegypti mosquitoes that survived FRSRIP exposure exhibited overall decline in total eggs laid, eggs hatched, pupae formed and adult emerged at different time intervals upto T21. Behavioural experiments showed that both the tested species elicited negative response to the test formulation. The concentrations of all the three active agents were estimated by HPLC after different time intervals, however only deltamethrin (0.24%) was found after T48. The developed formulation was stable, safe and effective against mosquito vectors for a considerably longer time. In the pretext of continuous toll of vector borne diseases and trans-boundary expansion of mosquito vectors into new geographical areas, the idea of using insecticidal paint could be a game changer.