A field evaluation study on the effects of residual spray of Bifenthrin and Deltamethrin on Anopheles minimus population in Mae Hong Son Province, northern Thailand.

Abstract

A field study was conducted to evaluate the effects of indoor residual house spraying of Bifenthrin and Deltamethrin on malaria vector population of Anopheles minimus s.l., from April 1999 to April 2001 at rural vil- lages in Mae Hong Son province, northern Thailand. Nine villages in Mae Hong Son province were selected for the present study (three villages for control and three villages each for insecticide spray). The residual spray of Bifen- thrin (25 mg/m 2 ) showed greater adulticiding effects on An. minimus s.l. population than Deltamethrin (20 mg/m 2 ). In Bifenthrin treated villages, a clear decrease in biting density of An. minimus s. l. was found in human bait col- lection as well as animal bait collection after the insecticide spray. In all of the three villages, the average density after insecticide spray was significantly lower than that observed before the spray. The effects of Deltamethrin on An. minimus s. l. density was found only in one village out of the three treated villages. A significant decrease in parous rate after insecticide spray was found in all the villages sprayed with Bifenthrin, whereas no significant changes were observed in control villages. The average parous rate in the villages treated with Deltamethrin be- came significantly higher after the insecticide spray. These results clearly suggested that the residual spray of Bifenthrin (25 mg/m 2 ) was more effective than Deltamethrin (20 mg/m 2 ).