Effectiveness of environmental interventions to reduce entomological indices of dengue, Zika, and chikungunya vector

Vector-borne diseases are a major public health problem. Amongst them, dengue, Zika and chikungunya illnesses are increasing their incidence and geographical expansion. Since vector control is the main measure to prevent these diseases, this systematic review aims to determine the effectiveness of environmental interventions for the prevention of the transmission of these three diseases, as well as for the reduction of their burden. Experimental studies of environmental management interventions aimed at vector control were included. The outcome variables of interest were disease burden indicators and entomological indicators. Of the 923 references initially retrieved, after discarding those that were duplicated or didn't comply with the inclusion criteria, a total of 7 articles were included. All included studies carried out environmental manipulation interventions and only 1 carried out an environmental modification intervention. Regarding the outcome variables, all used entomological indicators (larval or pupae indices). Of those, pupae indices are better indicators of vector abundance. In 4 out of the 6 studies, there was a statistically significant reduction of the pupae indices related to the elimination of small containers, manipulation of large tanks and cleaning outdoor spaces. These interventions are easy to implement and involve little resources, which acquires special importance regarding areas with limited resources. Although it is assumed that a reduction of mosquitoes would lead to a reduction or the risk of transmission, a little evidence proving this has been published. It would be advisable that, in addition to entomological indicators, epidemiological, environmental and sociodemographic factors would be taken into consideration, bearing in mind that mosquito density is one of the many factors that influence the transmission of these viruses. None of the papers included used disease indicators, not allowing to demonstrate if environmental interventions contribute to reduce disease burden.