Dengue vector management using insecticide treated materials and targeted interventions on productive breeding-sites in Guatemala

Nidia Rizzo,Byron Arana,Pablo Manrique-Saide,Axel Kroeger,Max Petzold,Rodrigo Gramajo,Maria Cabrera Escobar

doi:10.1186/1471-2458-12-931

Abstract

BackgroundIn view of the epidemiological expansion of dengue worldwide and the availability of new tools and strategies particularly for controlling the primary dengue vector Aedes aegypti, an intervention study was set up to test the efficacy, cost and feasibility of a combined approach of insecticide treated materials (ITMs) alone and in combination with appropriate targeted interventions of the most productive vector breeding-sites.MethodsThe study was conducted as a cluster randomized community trial using “reduction of the vector population” as the main outcome variable. The trial had two arms: 10 intervention clusters (neighborhoods) and 10 control clusters in the town of Poptun Guatemala. Activities included entomological assessments (characteristics of breeding-sites, pupal productivity, Stegomyia indices) at baseline, 6 weeks after the first intervention (coverage of window and exterior doorways made of PermaNet 2.0 netting, factory treated with deltamethrin at 55 mg/m2, and of 200 L drums with similar treated material) and 6 weeks after the second intervention (combination of treated materials and other suitable interventions targeting productive breeding-sites i.e larviciding with Temephos, elimination etc.). The second intervention took place 17 months after the first intervention. The insecticide residual activity and the insecticidal content were also studied at different intervals. Additionally, information about demographic characteristics, cost of the intervention, coverage of houses protected and satisfaction in the population with the interventions was collected.ResultsAt baseline (during the dry season) a variety of productive container types for Aedes pupae were identified: various container types holding >20 L, 200 L drums, washbasins and buckets (producing 83.7% of all pupae). After covering 100% of windows and exterior doorways and a small number of drums (where the commercial cover could be fixed) in 970 study households, tropical rains occurred in the area and lead to an increase of the vector population, more pronounced (but statistically not significant) in the control arm than in the intervention arm. In the second intervention (17 months later and six weeks after implementing the second intervention) the combined approach of ITMs and a combination of appropriate interventions against productive containers (Temephos in >200 L water drums, elimination of small discarded tins and bottles) lead to significant differences on reductions of the total number of pupae (P = 0.04) and the House index (P = 0.01) between intervention and control clusters, and to borderline differences on reductions of the Pupae per Person and Breteau indices (P = 0.05). The insecticide residual activity on treated curtains was high until month 18 but the chemical concentration showed a high variability. The cost per house protected with treated curtains and drum covers and targeting productive breeding-sites of the dengue vector was $ 5.31 USD. The acceptance of the measure was generally high, particularly in families who had experienced dengue.ConclusionEven under difficult environmental conditions (open houses, tropical rainfall, challenging container types mainly in the peridomestic environment) the combination of insecticide treated curtains and to a less extent drum covers and interventions targeting the productive container types can reduce the dengue vector population significantly.

Highlights

In view of the epidemiological expansion of dengue worldwide and the availability of new tools and strategies for controlling the primary dengue vector Aedes aegypti, an intervention study was set up to test the efficacy, cost and feasibility of a combined approach of insecticide treated materials (ITMs) alone and in combination with appropriate targeted interventions of the most productive vector breeding-sites
As there is no drug or vaccine available, dengue vector control remains at present the only way of preventing disease transmission and reducing the burden of disease
Characteristics of the study population The study population consisted of 20 neighborhoods with 1,835 households and a population of 8,875 inhabitants: 865 households (4,111 people) within the 10 control clusters and 970 households (4,764 people) in the 10 intervention clusters (Figure 1, Table 1)

Summary

Introduction

In view of the epidemiological expansion of dengue worldwide and the availability of new tools and strategies for controlling the primary dengue vector Aedes aegypti, an intervention study was set up to test the efficacy, cost and feasibility of a combined approach of insecticide treated materials (ITMs) alone and in combination with appropriate targeted interventions of the most productive vector breeding-sites. There are a number of chemical or non-chemical vector control tools available [2] which are effective if correctly applied [3,4] Their efficacy is limited because they are either not applied in an efficient way by vector control services [5,6], applied in vertical programs without involvement of communities and other partners [7,8,9,10,11] or over-stress ULV (Ultra Low Volume) fogging [12] as one of the most prominent “technocratic” approaches [13]. This is why, user friendly and costeffective, new tools/interventions for dengue vector management such as targeting only the most productive (for adult vector development) water container types [14] and insecticide treated materials (ITMs) [15,16,17] are being tested to complement and enhance current dengue vector control.

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Results

Discussion

Conclusion