Six months of Aedes aegypti control with a novel controlled-release formulation of pyriproxyfen in domestic water storage containers in Cambodia.

A field evaluation of a novel, 5% controlled-release formulation of pyriproxyfen was carried out in 400-500 liter concrete water storage jars, the most common and important larval habitat of the dengue vector, Aedes aegypti, in Cambodia. The formulation consisted of cylindrical resin strands, 3 mm in diameter and 40 mm in length. Pyriproxyfen was applied to 100 jars at a target dose of 0.03-0.04 mg of active ingredient (a.i.) per liter (30-40 ppb) in households in Phum Thmei, a village near the capital city of Phnom Penh, in April 2005. Inhibition of adult emergence (IE) in field populations ofAe. aegypti was measured every 2 weeks for 34 weeks. IE in treated jars exceeded 90% for 20 weeks, and remained above 80% until the end of the study. In 25 untreated jars, failure of pupae to metamorphose into viable adults remained below 4%. No alteration of taste or other undesirable effects of the treatment were reported by householders. This single treatment provided control of Ae. aegypti in water jars for the length of the main dengue transmission season in Cambodia that normally extends from May to November.

Efficacy of Bacillus thuringiensis israelensis, VectoBac WG and DT, formulations against dengue mosquito vectors in cement potable water jars in Cambodia.

This study reports the evaluation of Bacillus thuringiensis israelensis (Bti), a biological larvicide, in cement jars holding river, well and rain water. Two Bti formulations, VectoBac WG and VectoBac DT, were evaluated in a village in Phnom Penh. Thirty-one households with cement jars supporting the colonization of Ae.aegypti immatures were chosen. In each house 3 jars were aligned next to each another and filled with the same type of water. One of the 3 jars was treated with VectoBac WG at 0.4 g per 50 liters, a second jar was treated with VectoBac DT at 1 tablet per 50 liters, and a third jar was an untreated control (UTC). The jars were not covered, kept outdoors and not subjected to water exchange activity. The efficacy of VectoBac to control natural Ae.aegypti infestation was measured by Ae.aegypti pupae surveillance, conducted 3 days per week for 3 months post-treatment (June-September 2004). All pupae were removed, allowed to emerge in the Cambodia National Malaria Center insectarium and the emerged adults were identified and counted. The VectoBac treatments were more effective in river water, followed by well and rain water. The VectoBac treatments significantly reduced the pupae numbers for a minimum of 3 months in the river water and 2.5 months in the well water (p < 0.05). In the rain water, the pupae densities in the VectoBac WG and DT treated jars were not significantly different from the untreated jars, although the treated jars yielded 2.0 to 5.2 fold less pupae, respectively, than in the untreated jars during the 3 months post-treatment. The efficacy of VectoBac WG to control Ae.aegypti was similar to the efficacy of VectoBac DT in the 3 water types (p > 0.05). It was also observed that VectoBac WG and DT were target specific, without any adverse effects on aquatic predatory insects common in well and rain water. VectoBac WG and DT were found to be easy-to-use formulations, with no need to repackage them prior to use in the containers. The amounts of VectoBac WG and DT used were 12.5 fold less by weight than temephos (Abate 1.0% SG).