Laboratory & field evaluation of controlled release formulation of the insect repellents N,N-diethyl-m-toluamide (DEET) & N,N-diethyl phenylacetamide (DEPA) against mosquito vectors

Background & objectives : Repellents can play a useful role in reducing the man-vector contact and help in interrupting disease transmission. Newer formulations are necessary to improve the efficacy of the repellent on the treated sites for enhanced protection. Methods : To determine the comparative efficacy, 20 per cent liposphere lotion formulation and 20 per cent alcohol solution of two insect repellents DEET and DEPA were evaluated for the extent of protection on rabbits against Aedes aegypti during the day in the laboratory and on human volunteers during the night against Culex quinquefasciatus in the urban areas of Pondicherry, India. Results : In the laboratory, the lotion formulations of DEPA and DEET were found to enhance the repellency by 1.5 (4.00 to 6.00 h) and 1.25 (4.00 to 5.00 h) times respectively compared to the alcohol solution of the repellents against Ae. aegypti at the application rate of 0.5 mg/cm(2). In the field, the lotion formulation of DEPA at 0.3 mg/cm(2) could increase the protection time from 6.30 to 8.36 h (1.3 times) whereas the lotion formulation of DEET at 0.3 mg/cm(2) could increase the protection time from 6.54 to 8.42 h (1.2 times). Interpretation & conclusion : In laboratory and field tests, the lotion formulations of both repellents were found to give a higher protection compared to alcohol solution. The lotion formulations of DEET and DEPA were found to be equally effective.