Susceptibility to chemical insecticides of two Brazilian populations of the visceral leishmaniasis vector Lutzomyia longipalpis (Diptera: Psychodidae)

Abstract

Summaryobjectives To investigate the insecticide susceptibility of two geographically separated Lutzomyia longipalpis populations (Lapinha and Montes Claros) with different histories of insecticide exposure (i.e. no exposure and repeated exposure, respectively).methods (i) Bioassay monitoring of sand fly survival over time when exposed to a range of insecticides; and (ii) analysis of the level of insecticide detoxification enzymes in individual sand flies caught at both study sites. Insecticides tested were the organophosphates malathion and fenitrothion and the pyrethroids k-cyhalothrin, permethrin and deltamethrin.results Survival analyses showed that whilst there was no overall significant difference in susceptibility of both populations to organophosphates, Lapinha sand flies were significantly more susceptible to pyrethroids than those from Montes Claros. Multiple regression analyses also showed that insecticide susceptibility in both locations varied with sand fly sex. The relative susceptibilities of the two sand fly populations to tested insecticides were also compared. Thus, Montes Claros sand flies were most susceptible to malathion, followed by fenitrothion, deltamethrin and permethrin. Those from Lapinha were most susceptible to k-cyhalothrin, followed by malathion, permethrin, deltamethrin and fenitrothion. Biochemical analyses demonstrated that Montes Claros sand flies had significantly lower insecticide detoxification enzyme activity than Lapinha sand flies.conclusions Our results are the first record of significantly reduced susceptibility to the insecticides used in control of wild populations of Lu. longipalpis. They demonstrate the importance of evaluating chemicals against this species by conventional bioassay and microplate assays before and during spraying programmes.

DDT-based indoor residual spraying suboptimal for visceral leishmaniasis elimination in India

“…There is an urgent need to establish the susceptibility status of the Indian vector to a range of insecticides that could potentially be used as alternatives to DDT for IRS (47). Susceptibility to deltamethrin and organophosphates has been claimed (27); however, the numbers of insects tested in these studies are low.…”

Delayed mortality effects cut the malaria transmission potential of insecticide-resistant mosquitoes

“…This study did not test for such additional indirect impacts; however, preliminary data indicate a reduction in the feeding success of exposed IR mosquitoes. In this and other studies (30,31), it was observed that the legs of mosquitoes can become detached when trying to feed through nets, which would be one mechanism to explain their subsequent reduction in blood feeding. Further work is needed to quantify this phenomenon and other indirect fitness consequences of LLIN exposure in IR mosquitoes to calculate their combined impact on transmission (13).…”

Concentraciones diagnósticas de tres insecticidas de uso en salud pública en una cepa experimental de Lutzomyia longipalpis (Diptera: Psychodidae) en Colombia

“…En las pruebas con los insecticidas deltametrina y lambdacialotrina, al finalizar el tiempo de exposición y retirar las hembras de L. longipalpis, se observó un gran número de patas desprendidas en la superficie de la botella, efecto que se ha observado en otros estudios tras la exposición de esta especie a los piretroides (20,30).…”

“…En Venezuela, Mazzari, et al (19), detectaron mayores tiempos letales medios (TL 50 ) en los insecticidas metilpirimifos, fenitrotión y permetrina en una población de L. longipalpis expuesta a insecticidas con propósitos agrícolas, comparada con una cepa sensible de laboratorio. En Brasil se registraron valores de TL 50 para los piretroides permetrina y deltametrina, significativamente más altos en una población de L. longipalpis expuesta frecuentemente a piretroides para el control de la leishmaniasis visceral que los encontrados en una población de L. longipalpis geográficamente distante y sin evidencia de exposición a insecticidas, lo que se confirmó con análisis bioquímicos de la actividad de las enzimas de desintoxicación de insecticidas (20).…”