Assessing the Relationship between Vector Indices and Dengue Transmission: A Systematic Review of the Evidence

Abstract

BackgroundDespite doubts about methods used and the association between vector density and dengue transmission, routine sampling of mosquito vector populations is common in dengue-endemic countries worldwide. This study examined the evidence from published studies for the existence of any quantitative relationship between vector indices and dengue cases.Methodology/Principal FindingsFrom a total of 1205 papers identified in database searches following Cochrane and PRISMA Group guidelines, 18 were included for review. Eligibility criteria included 3-month study duration and dengue case confirmation by WHO case definition and/or serology.A range of designs were seen, particularly in spatial sampling and analyses, and all but 3 were classed as weak study designs. Eleven of eighteen studies generated Stegomyia indices from combined larval and pupal data. Adult vector data were reported in only three studies. Of thirteen studies that investigated associations between vector indices and dengue cases, 4 reported positive correlations, 4 found no correlation and 5 reported ambiguous or inconclusive associations. Six out of 7 studies that measured Breteau Indices reported dengue transmission at levels below the currently accepted threshold of 5.Conclusions/SignificanceThere was little evidence of quantifiable associations between vector indices and dengue transmission that could reliably be used for outbreak prediction. This review highlighted the need for standardized sampling protocols that adequately consider dengue spatial heterogeneity. Recommendations for more appropriately designed studies include: standardized study design to elucidate the relationship between vector abundance and dengue transmission; adult mosquito sampling should be routine; single values of Breteau or other indices are not reliable universal dengue transmission thresholds; better knowledge of vector ecology is required.

Re-Model the Relation of Vector Indices, Meteorological Factors and Dengue Fever

“…Failure to consider these factors may lower the prediction accuracy for DENV. Furthermore, administrative inconsistency among different spatial units may also cause geographical differences of the vector and dengue case data, which can mask potential relationship [19]. An ideal study design that considers the spatial and temporal aspects of these variables should provide better understanding on the relationship between A. aegypti population densities, DENV transmission, and disease incidence.…”

Virological surveillance of Aedes (Stegomyia) aegypti and Aedes (Stegomyia) albopictus as support for decision making for dengue control in Medellín

“…Varios autores han determinado que más de 80 % de los adultos de Aedes spp. provienen de menos del 20 % de los depósitos (18)(19)(20), y señalan que los índices aédicos tradicionales no deben considerarse como indicadores del riesgo epidemiológico (19,20). Por ejemplo, en el 2010, durante la mayor epidemia de dengue registrada en Medellín, no se observó relación entre los índi-ces entomológicos tradicionales y la incidencia de la enfermedad (21).…”

Imported chikungunya cases in an area newly colonised by Aedes albopictus: mathematical assessment of the best public health strategy

“…Here, we used the most popular way of vector-borne disease modelling (asymmetric frequency-dependent transmission). However, we could also show that another way of modelling this transmission force, through a symmetric frequency-dependent process, can result in the absence of a relationship between vector density and size of the epidemic (data not shown; details can be obtained from the corresponding author and are also available at https://sites.google.com/site/rocheben/ sochakiEtAlAppendix_V3.docx*), as empirical data suggest for dengue [22]. Nevertheless, the only qualitative change arising with this other kind of transmission force is the influence of vector density.…”