Abstract
A limited field trial was undertaken in Labuan Island Sabah to determine if larvicidal treatment of open containers of stored water could achieve effective control of Aedes aegypti, a vector of dengue fever and dengue haemorrhagic fever. The insecticide used was abate 1% sand granules and the method of evaluation was the single-larva-per-container method. The lethal effect on Ae. aegypti of each application of abate at a concentration of 1ppm lasted 3 to 3.5 months and was clearly reflected in the resurgence and reinfestation of the species. A higher proportion of the larvae collected from indoor containers were Ae. aegypti. Ae. albopictus larvae in outdoor water collections tended to increase markedly during the trial. The mean Breteau index of aegypti was reduced from 83.6 before larviciding to 24.7 four months after. The final Breteau index after 11 months was 10.5 and the mean premise index fell from 52.9% to 7.6%. Ae. aegypti comprized 64.8% of the larval collections, Ae. albopictus 28.3% and other species, principally Culex pipiens fatigans 6.9%. The single-larva-per-container technique provided a useful quantitative measure of the larval densities in the treated areas.
