Susceptibility of malaria vectors to insecticides in Gadchiroli district (Maharashtra), India.

insecticides 9–10 . In the morning hours (0600 to 0800 hrs) with the help of suction tube, An. culicifacies Giles, An. fluviatilis James and An. annularis Van der Wulp were collected from cattlesheds, human dwellings and mixed dwellings of different villages of Murumgaon PHC. The collected female mosquitoes were provided with 10% glucose solution soaked in cotton pads and transported in caged cloth to the field laboratories at the PHC of Murumgaon, Gadchiroli district. Insecticide-impregnated papers with different diagnostic doses received from University Sans Malaysia were used for detection of resistance to DDT (4%), malathion (5%) and deltamethrin (0.05%). Only full-fed and semi-gravid mosquitoes were used to determine the susceptibility status. Mosquitoes were exposed against the diagnostic doses of insecticides for an hour, as per standard WHO technique 9,10 . Three to four replicates of each vector species containing 15–25 female mosquitoes were taken simultaneously for each insecticide. Two replicates for control were also held parallel to each test. The mosquitoes were exposed for 1 h and kept for observation for 24 h.The percent mortalities were scored after 24 h of recovery period and if the control mortality remained within 5–20%, test mortality was corrected using Abbott’s formula 11 and expressed as corrected percent mortality. If the mortality is >20%, the tests were discarded. Results of susceptibility tests on An. culicifacies, An. fluviatilis and An. annularis against DDT (4%), malathion (5%) and deltamethrin (0.05%) are given in Table 1. The corrected percent mortality of adult An. culicifacies, An. fluviatilis and An. annularis to DDT (4%) ranged between 21 and 36.66%; to malathion (5%) between 90.52 and 96%; and to deltamethrin (0.05%) between 94 and 96.42%. These results indicate that the tested mosquito species are resistant to DDT but tolerant to malathion and