These results demonstrate that wet heat is the principal dormancy release mechanism for P. aculeata when conditions are hot and wet. They also highlight the potential importance of microclimate in driving the population dynamics of such species.

Objective To compare the efficacy of seven pyrethroid insecticides for impregnation of mosquito nets, six currently recommended by WHO and one candidate (bifenthrin), under laboratory conditions. Methods Tests were conducted using pyrethroid-susceptible and pyrethroid-resistant strains of Anopheles gambiae and Culex quinquefasciatus. Knock-down effect, irritancy and mortality were measured using standard WHO cone tests. Mortality and bloodfeeding inhibition were also measured using a baited tunnel device. Findings For susceptible A. gambiae, alpha-cypermethrin had the fastest knock-down effect. For resistant A. gambiae, the knockdown effect was slightly slower with alpha-cypermethrin and much reduced following exposure to the other insecticides, particularly bifenthrin and permethrin. For susceptible C. quinquefasciatus, the knock-down effect was significantly slower than in A. gambiae, particularly with bifenthrin, and no knock-down effect was observed with any of the pyrethroids against the resistant strain. Bifenthrin was significantly less irritant than the other pyrethroids to susceptible and resistant A. gambiae but there was no clear ranking of pyrethroid irritancy against C. quinquefasciatus. In tunnels, all insecticides were less toxic against C. quinquefasciatus than against A. gambiae for susceptible strains. For resistant strains, mortality was significant with all the pyrethroids with A. gambiae but not with C. quinquefasciatus. Inhibition of blood-feeding was also high for susceptible strains of both species and for resistant A. gambiae but lower for resistant C. quinquefasciatus; bifenthrin had the greatest impact. Conclusions Efficacy for impregnation of mosquito nets against A. gambiae was greatest with alpha-cypermethrin. Bifenthrin is likely to have a significant comparative advantage over other pyrethroids in areas with pyrethroid resistance because of its much stronger impact on the nuisance mosquito, C. quinquefasciatus, despite its slower knock-down effect and irritancy. Selection of pyrethroids for mosquito vector control and personal protection should take into account the different effects of these insecticides, the status of pyrethroid resistance in the target area, and the importance of nuisance mosquitoes, such as C. quinquefasciatus. Voir page 331 le re´sume´en français. En la pa´gina 331 figura un resumen en españ ol. IntroductionThe widespread distribution of insecticide-impregnated mosquito nets is a major component of the WHO global strategy for malaria control, especially in sub-Saharan Africa, where more than 90% of malaria cases are reported annually (1). To date, six pyrethroid insecticides -the only group of insecticides currently considered suitable for impregnation of mosquito nets -have been evaluated by the WHO Pesticide Evaluation Scheme (WHOPES) and recommended for this purpose: alpha-cypermethrin, cyfluthrin, deltamethrin and lambdacyhalothrin (alpha-cyano pyrethroids), and etofenprox and permethrin (non-cyano pyrethroids) (2-4).Pyrethroid resistance of malaria vecto...

The Northern Territory (NT) of Australia is currently free of the dengue mosquito Aedes (Stegomyia) aegypti (L). However, on 17 February 2004, two Ae. aegypti adults were captured in two routine CO2‐baited encephalitis virus surveillance traps in Tennant Creek, located 990 km south of Darwin in the NT. The detection triggered an immediate survey and control response undertaken by the NT Department of Health and Community Services, followed by a Commonwealth of Australia‐funded Ae. aegypti elimination program. This report details the methods and results of the detection and subsequent elimination activities that were carried out between 2004 and 2006, returning the NT to its dengue vector‐free status. There have been very few successful Ae. aegypti elimination programs in the world. This purposeful mosquito elimination for Australia was officially declared on 5 April 2006.

Aedes aegypti is the mosquito vector of dengue worldwide and also occurs in far northern Queensland, where cases of dengue occur annually. Aedes aegypti from colonies established from Townville, Queensland, Australia, and Dili, Timor-Leste, were exposed in bottle bioassays to determine their susceptibility to three pyrethroids, the organophosphate, malathion and two commercial pyrethroid-based products: Reslin® (50 g/l bioresmethrin) and Aqua-K-Othrine® (20 g/l deltamethrin) both containing the synergist, piperonyl butoxide. Aedes aegypti from Dili, Timor-Leste, were resistant to permethrin, lamda-cyhalothrin and resmethrin, but were susceptible to malathion and the two pyrethroid products. Biochemical microplate assays were used to measure activity levels of three enzymes (oxidase, esterase and glutathione-S-transferase), and there were no significant increases in the activity of oxidase and glutathione-S-transferase, but an increase in esterase activity in A. aegypti from Dili was detected. The study showed that mosquitoes originating in Timor-Leste are tolerant of pyrethroid insecticides used in Australia and monitoring of insecticide susceptibility in A. aegypti introduced into Australia needs to be maintained to ensure that adequate control of dengue vectors is achieved.

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