Critical Examination of Aedes aegypti Indices: Correlations with Abundance

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  • Tropical Health Program, Queensland Institute of Medical Research, University of Queensland Medical School, Brisbane, Australia

The following immature stage indices for Aedes (Stegomyia) aegypti surveillance were evaluated in four north Queensland, Australia towns with respect to their relationship to immature and adult female densities: Breteau, House, Container, Larval Density, Stegomyia (and modifications thereof), and a newly created Adult Productivity Index. Spearman's correlations of indices that considered larval or immature (larvae and pupae) numbers had a better relationship with immature abundance but this was not necessarily the case against adult abundance. To examine the robustness of the indices, data from 758 premises in Townsville, Charters Towers, Ravenswood, and Mingela were pooled and 30 random subsamples, each consisting of 50 premises were taken. After each subsample was taken, the premises selected were reintroduced into the original data bank of 758 premises, and therefore, were available for further selection, i.e., sampling with replacement. Indices were calculated for each of the 30 subsamples and the coefficients of variation of each index were estimated from these. The Breteau, Adult Productivity, House, and Adult density indices proved to have the smallest coefficients compared with index size. No alternate index was regarded as being superior to the Breteau, including the Adult Productivity Index measuring both container type frequency and immature density. For this reason and in view of the labor intensiveness of estimating immature indices that incorporate productivity, it is recommended that new and cost-effective methods of adult surveillance be pursued.