FIELD EFFICACY OF A NEW REPELLENT, KBR-3023, AGAINST AEDES-ALBOPICTUS(SKUSE) AND CULEX-QUINQUEFASCIATUS (SAY) IN A TROPICAL ENVIRONMENT

Two new repellent formulations, KBR 3023 10% and 20% from Bayer AG, Ge rmany, were evaluated together with DEET 10% and 20% as standard repel lent formulations. Evaluation was based on two separate field studies: a daytime study (0900-1700 hr) in a forested orchard on Penang Island and a nighttime study (2100-0100 hr) in a squatter residential area o n the adjacent mainland of peninsular Malaysia. Both studies were carr ied out by exposing humans with bars arms and legs to mosquitoes landi ng/biting for an eight hour period. Right arms and legs of the human b aits were treated with different repellent formulations (KBR 3023 10%, 20% and DEET 10%, 20%) and the left limbs were left untreated to act as controls. The daytime study indicated that all four formulations we re equally effective (P < 0.05) as repellents against the predominant Aedes albopictus with greater than 88.5% reduction in landing/biting i n the first four hours and not less than 65.0% in the next four hours of the assessment period. In the night study, all four formulations we re also found to be equally effective (P < 0.05) in repelling Culex qu inquefasciatus, the predominant species. All four formulations provide d complete protection against Cx. quinquefasciatus in the first two ho urs of exposure. The percentage reduction values were maintained above 90.0% for the next six hours of the assessment period. In conclusion, both the KBR 3023 and DEET formulations were found to be equally effe ctive (P < 0.05) in providing along-lasting reduction in human-mosquit o contact in both the day and night field studies.