Long-Lasting Insecticidal Hammocks for Controlling Forest Malaria: A Community-Based Trial in a Rural Area of Central Vietnam

Abstract

BackgroundIn Vietnam, malaria remains a problem in some remote areas located along its international borders and in the central highlands, partly due to the bionomics of the local vector, mainly found in forested areas and less vulnerable to standard control measures. Long Lasting Insecticidal Hammocks (LLIH), a tailored and user-friendly tool for forest workers, may further contribute in reducing the malaria burden. Their effectiveness was tested in a large community-based intervention trial carried out in Ninh Thuan province in Central Vietnam.Methods and FindingsThirty villages (population 18,646) were assembled in 20 clusters (1,000 individuals per cluster) that were randomly allocated to either the intervention or control group (no LLIH) after stratification according to the pre-intervention P. falciparum antibody prevalence (<30%; ≥30%). LLIH were distributed to the intervention group in December 2004. For the following 2 years, the incidence of clinical malaria and the prevalence of infection were determined by passive case detection at community level and by bi-annual malariometric surveys. A 2-fold larger effect on malaria incidence in the intervention as compared to the control group was observed. Similarly, malaria prevalence decreased more substantially in the intervention (1.6-fold greater reduction) than in the control group. Both for incidence and prevalence, a stronger and earlier effect of the intervention was observed in the high endemicity stratum. The number of malaria cases and infections averted by the intervention overall was estimated at 10.5 per 1,000 persons and 5.6/100 individuals, respectively, for the last half of 2006. In the high endemicity stratum, the impact was much higher, i.e. 29/1000 malaria cases and 15.7 infections/100 individuals averted.ConclusionsLLIH reduced malaria incidence and prevalence in this remote and forested area of Central Vietnam. As the targets of the newly-launched Global Malaria Action Plan include the 75% reduction of the global malaria cases by 2015 and eventually the elimination/eradication of malaria in the long term, LLIH may represent an additional tool for reaching such objectives, particularly in high endemicity areas where standard control tools have a modest impact, such as in remote and forested areas of Southeast Asia and possibly South America.Trial RegistrationClinicalTrials.gov NCT00853281

Human Infections and Detection of Plasmodium knowlesi

“…This would involve the use of insect repellents, but these are prohibitively expensive for subsistence farmers, hunters, logging camp workers, and other rural people whose daily activities take them to the forest and forest fringe. The use of insecticideimpregnated hammocks has been successful for controlling forest malaria in Vietnam (143), but hammocks are not traditionally used in Malaysian Borneo, where most P. knowlesi cases occur, and so such a control measure would be difficult to implement successfully.…”

Cross-Border Malaria: A Major Obstacle for Malaria Elimination

“…The benefits of sleeping under LLINs need to be highlighted through education, and LLINs being made available through social marketing, as has been done for refugees from Afghanistan in Pakistan (Rowland and Nosten, 2001). Alternative approaches such as the provision of insecticide-treated hammocks for people frequenting forest areas in border areas (Magris et al, 2007;Thang et al, 2009), deltamethrin-sprayed tarpaulins or tents, and premethrin-treated blankets and top sheets provide more promising options for people overnighting in the forest (Graham et al, 2002;Rowland and Nosten, 2001). These protective measures achieve the goal of reducing exposure to infected vectors for populations who do not live in traditional housing each night, a feature common to people in border areas.…”

Malaria cases in Switzerland from 2005 to 2015 and recent rise of imported Plasmodium vivax malaria

“…The use of insecticide-treated hammock nets or long-lasting insecticidal hammocks has been shown to have protective efficacy against P. vivax and P. falciparum in South America (30) and in the Mekong region (31,32). In parts of Asia, the use of topical repellents, treated materials and treated clothing has been effective, especially when these measures are used in combination (33,34); however, other studies have found uncertainty about protective effects (32,35). In Ethiopia, the combined use of ITNs and repellents was found to be protective against both P. falciparum and P. vivax (36).…”