Adaptability is key when monitoring insecticide resistance

and quality of insecticide formula- tions and local laboratories cannot alter the discriminating dose to deal, for example, with smaller, more fragile mosquito species. In comparison to the WHO assay, some of the components of the bottle assay are more readily and cheaply available but existing protocols require the use of technical grade (pure) insec- ticide, which is expensive and difficult to access locally. Other stipulations of the bottle assay may be regionally problematic; acetone is used as the carrier with which to coat the bottles with insecticides but, in parts of South America, its purchase is restricted because of its role in the purification of cocaine. 9 In common with the WHO assay, the recommended discrimina- tory doses listed for the bottle assay will mask low-level resistance in some species. 7,9