Effects of piperonyl butoxide on the toxicity of the organophosphate temephos and the role of esterases in the insecticide resistance of Aedes aegypti

Introduction The effects of piperonyl butoxide (PBO) on the toxicity of the organophosphate temephos (TE) and the role of esterases in the resistance of Aedes aegypti to this insecticide were evaluated. Methods A. aegypti L4 larvae susceptible and resistant to TE were pre-treated with PBO solutions in acetone at concentrations of 0.125, 0.25, 0.5, 1, and 2% for 24h and subsequently exposed to a diagnostic concentration of 0.02mg/L aqueous TE solution. The esterase activity of the larvae extracts pre-treated with varying PBO concentrations and exposed to TE for three time periods was determined. Results At concentrations of 0.25, 0.5, 1, and 2%, PBO showed a significant synergistic effect with TE toxicity. High levels of esterase activity were associated with the survival of A. aegypti L4 larvae exposed to TE only. Conclusions The results of the biochemical assays suggest that PBO has a significant inhibitory effect on the total esterase activity in A. aegypti larvae. .

Control of mosquito vectors of tropical infectious diseases: (2) pyrethroid susceptibility of Aedes aegypti ( l) collected from different sites in Thailand.

Four strains (SS, BS, A and B) of Aedes aegypti collected from different sites in Bangkok and at different times were examined for their pyrethroid susceptibility. Mosquito coils containing dl, d-T80-allethrin, d, d-T-prallethrin and methoxymethyl-tetrafluorobenzyl tetramethyl-cyclopropanecarboxylate (K-3050) with or without a synergist were tested by the 25 m3 semi-field test method. One strain (SS) was the most susceptible with KT50 values of about < 30 minutes for all mosquito coils, while the other three strains (BS, A and B) were found to be around 10 to 20 times more tolerant to pyrethroids than the SS strain. A similar tendency for the pyrethroid susceptibility of the four strains was obtained with tests by topical application method. In field efficacy tests, mosquito coils with d, d-T-prallethrin 0.20% plus N-(2-ethylhexyl)bicycle-[2,2,1]- hept-5- ene-2,3-dicarboxyimide as a synergist exhibited a repellent effect of about 85%, while those with K-3050 0.10% plus the synergist exhibited a greater repellent effect of about 90%. In contrast, the repellent effect of commercial dl, d-T80-allethrin 0.20% coils was as low as about 50%. The d, d-T-prallethrin and K-3050 coils with the synergist were confirmed to be highly effective in repelling Ae. aegypti.

Efficacy of piperonyl butoxide (PBO) as a synergist with deltamethrin on five species of mosquitoes.

Development of insecticide resistance has been a challenging problem for a long time and new solutions are yet to emerge. In this regard, the use of synergist with the insecticide is thought to play a key role in reducing the resistance levels. Present study demonstrates the efficacy of PBO with deltamethrin against the field collected mosquito larvae of five species of Aedes, Anopheles and Culexfrom in and around Mysore.