[Evaluation of a DEET-based repellent on 3 vectors of malaria in central Africa]

As part of the framework of studies on personal protection against disease-transmitting mosquitoes, a field evaluation was carried out in a forest area of Cameroon on human subjects to assess the efficacy of a common repellent: DEET (a 50% active ingredient formulation). One ml of DEET applied to the legs of resting persons gave an 85% reduction in Anopheles bites during the 5 hours following application. The repellent effect decreased gradually with time. The effect was more than 90% maximum after 3 hours, 50% by about the seventh hour and declined to 0% from the fifteenth hour onwards. No difference was found between the three Anopheles species: Anopheles gambiae ss, An. nili and An. funestus. The longevity and infectivity of Anopheles populations caught on humans with repellent and on untreated controls were similar. Thus the reduction of biting rate can be considered equivalent to the reduction in malaria transmission. The effect of sweating on the loss of the applied repellent was studied. Moderate sweating, corresponding to normal activity, did not reduce the efficacy of the repellent. More profuse sweating did not significantly reduce repellent efficacy. We conclude that the tested formulation of DEET has the same efficacy as commercial formulations already on the market. Protection did not last the whole night, which is the time required for protection against malarial infection. However, good protection levels lasted more than 5 hours.(ABSTRACT TRUNCATED AT 250 WORDS)