Evaluation of a lethal ovitrap for control of Aedes aegypti (L.) (Diptera: Culicidae), the vector of dengue in Costa Rica
Under laboratory conditions, lethal ovitraps have been effective in killing Ae. aegypti adults and larvae. These traps consist of a black plastic cup with a strip of deltamethrin-treated paper clipped to the inside. The insecticide on the strips slowly leaches from the strips into 10% hay infusion water that fills the traps. The traps attract gravid female Ae. aegypti which lay their eggs on the rough surface of the insecticide-treated paper. The mosquitoes die shortly after ovipositing and, more importantly, the first-instar larvae that hatch from the eggs die in the hay infusion water. To determine if these ovitraps could be effective in controlling Ae. aegypti in neighborhoods in dengue-endemic areas in Costa Rica, 5 traps were placed inside and 5 were placed outside of homes in the cities of Puntarenas and Siquirres. Control homes did not have ovitraps. House and Container Indices as well as the average number adult mosquitoes captured per house were not different between treated and control houses. When treated strips were tested for deltamethrin content, unused strips contained an averageof O.95 ± 0.15 mg deltamethrin per strip. Used strips from outdoor traps contained an average of 122.3 ± 46.2 [Mu]g deltamethrin per strip and used strips from indoor traps contained an average of 123.5 ± 38.0 [Mu]g deltamethrin per strip. When tested in the laboratory, unused strips killed all first-instar larvae for 27 d. Used strips from both 3-week and 4-week replicates of the Costa Rican field trials killed all first-instar larvae within 96 h. Oviposition activity within these traps was also examined. Eighty percent fewer eggs were laid by Aedes aegypti (L. in traps inside houses. Thirty-three percent more of the outdoor traps had Ae. aegypti eggs laid in them than indoor traps. Ae. aegypti larvae were found in fifty-five percent more outside traps. Deltamethrin on the strips of both outdoor and indoor containers was essentially identical (122.3 [Mu]g outdoors, 123.5 [Mu]g indoors).