Cost-effectiveness of annual targeted larviciding campaigns in Cambodia against the dengue vector Aedes aegypti

Schneider Institutes for Health Policy, Heller School, Brandeis University, Waltham, MA 02454-9110, USA.
Tropical Medicine & International Health (Impact Factor: 2.33). 10/2007; 12(9):1026-36. DOI: 10.1111/j.1365-3156.2007.01889.x
Source: PubMed


To assess the cost-effectiveness (CE) of annual targeted larviciding campaigns from 2001 to 2005 against the dengue vector Aedes aegypti in two urban areas of Cambodia with a population of 2.9 million people.
The intervention under analysis consisted of annual larviciding campaigns targeting medium to large water storage containers in households and other premises. The CE compared the intervention against the hypothetical alternative of no intervention. The CE was calculated as the ratio of disability adjusted life years (DALYs) saved to the net cost of the intervention (in 2005 US dollars) by year. A sensitivity analysis explored the range of study parameters.
The intervention reduced the number of dengue cases and deaths by 53%. It averted an annual average of 2980 dengue hospitalizations, 11,921 dengue ambulatory cases and 23 dengue deaths, resulting in a saving of 997 DALYs per year. The gross cost of the intervention was US $567,800 per year, or US $0.20 per person covered. As the intervention averted considerable medical care, the annual net cost of the intervention was US $312,214 (US $0.11 per person covered) from a public sector perspective and US $37,137 (US $0.01 per person covered) from a societal perspective. The resulting CE ratios were: US $313/DALY gained from the public perspective and US $37/DALY gained from the societal perspective. Even under the most conservative assumption, the intervention remained cost effective from both perspectives.
Annual, targeted larviciding campaigns appear to have been effective and cost-effective medium-term interventions to reduce the epidemiologic and economic burden of dengue in urban areas of Cambodia.

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    • "Neighbouring countries have also tried a number of vector control strategies for DF prevention. In Cambodia, for example, larvicidal and insecticidal controls have been tested, including the use of larvivorous fish (Poecilia reticulate) in rural communities to control Ae. aegypti in water storage containers (Seng et al., 2006, 2008a, 2008b, 2008c; Suaya et al., 2007). "
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    ABSTRACT: Entomological surveillance and control are essential to the management of dengue fever (DF). Hence, understanding the spatial and temporal patterns of DF vectors, Aedes (Stegomyia) aegypti (L.) and Ae. (Stegomyia) albopictus (Skuse), is paramount. In the Philippines, resources are limited and entomological surveillance and control are generally commenced during epidemics, when transmission is difficult to control. Recent improvements in spatial epidemiological tools and methods offer opportunities to explore more efficient DF surveillance and control solutions: however, there are few examples in the literature from resource-poor settings. The objectives of this study were to: (i) explore spatial patterns of Aedes populations and (ii) predict areas of high and low vector density to inform DF control in San Jose village, Muntinlupa city, Philippines. Fortnightly, adult female Aedes mosquitoes were collected from 50 double-sticky ovitraps (SOs) located in San Jose village for the period June-November 2011. Spatial clustering analysis was performed to identify high and low density clusters of Ae. aegypti and Ae. albopictus mosquitoes. Spatial autocorrelation was assessed by examination of semivariograms, and ordinary kriging was undertaken to create a smoothed surface of predicted vector density in the study area. Our results show that both Ae. aegypti and Ae. albopictus were present in San Jose village during the study period. However, one Aedes species was dominant in a given geographic area at a time, suggesting differing habitat preferences and interspecies competition between vectors. Density maps provide information to direct entomological control activities and advocate the development of geographically enhanced surveillance and control systems to improve DF management in the Philippines.
    Preview · Article · Nov 2013 · Geospatial health
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    • "There are a number of chemical or non-chemical vector control tools available [2] which are effective if correctly applied [3,4]. However, 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 [7-11] or over-stress ULV (Ultra Low Volume) fogging [12] as one of the most prominent “technocratic” approaches [13]. "
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    ABSTRACT: Background In 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. Methods The 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. Results At 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. Conclusion Even 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.
    Full-text · Article · Oct 2012 · BMC Public Health
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    • "Figures on the costs related to routine vector control are even scarcer. The few papers published report, each for a particular mix of activities, yearly cost per capita ranging from 0.20 USD in Cambodia, to 32.0 USD in Cuba (Suaya et al. 2007; Armien et al. 2008; Baly et al. 2009, 2011; Tun-Lin et al. 2009). To our knowledge, no study has integrated information on the economic cost of routine dengue control in nonepidemic periods with figures on incremental costs for vector control and case management during outbreaks. "
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    ABSTRACT: Objective: To assess the economic cost of routine Aedes aegypti control in an at-risk environment without dengue endemicity and the incremental costs incurred during a sporadic outbreak. Methods: The study was conducted in 2006 in the city of Guantanamo, Cuba. We took a societal perspective to calculate costs in months without dengue transmission (January-July) and during an outbreak (August-December). Data sources were bookkeeping records, direct observations and interviews. Results: The total economic cost per inhabitant (p. i.) per month. (p. m.) increased from 2.76 USD in months without dengue transmission to 6.05 USD during an outbreak. In months without transmission, the routine Aedes control programme cost 1.67 USD p. i. p. m. Incremental costs during the outbreak were mainly incurred by the population and the primary / secondary level of the healthcare system, hardly by the vector control programme (1.64, 1.44 and 0.21 UDS increment p. i. p. m., respectively). The total cost for managing a hospitalized suspected dengue case was 296.60 USD (62.0% direct medical, 9.0% direct non-medical and 29.0% indirect costs). In both periods, the main cost drivers for the Aedes control programme, the healthcare system and the community were the value of personnel and volunteer time or productivity losses. Conclusions: Intensive efforts to keep A. aegypti infestation low entail important economic costs for society. When a dengue outbreak does occur eventually, costs increase sharply. In-depth studies should assess which mix of activities and actors could maximize the effectiveness and cost-effectiveness of routine Aedes control and dengue prevention.
    Full-text · Article · Sep 2011 · Tropical Medicine & International Health
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