Abstract
BackgroundLymphatic filariasis (LF) in Uganda is caused by Wuchereria bancrofti and transmitted by anopheline mosquitoes. The mainstay of elimination has been annual mass drug administration (MDA) with ivermectin and albendazole, targeted to endemic districts, but has been sporadic and incomplete in coverage. Vector control could potentially contribute to reducing W. bancrofti transmission, speeding up progress towards elimination. To establish whether the use of long-lasting insecticidal nets (LLINs) can contribute towards reducing transmission of W. bancrofti in a setting with ongoing MDA, a study was conducted in an area of Uganda highly endemic for both LF and malaria. Baseline parasitological and entomological assessments were conducted in 2007, followed by high-coverage LLIN distribution. Net use and entomological surveys were carried out after one year, and final parasitological and entomological evaluations were conducted in 2010. Three rounds of MDA had taken place before the study commenced, with a further three rounds completed during the course of the study.ResultsIn 2007, rapid mapping indicated 22.3% of schoolchildren were W. bancrofti antigen positive, and a baseline survey during the same year found age-adjusted microfilaraemia prevalence was 3.7% (95% confidence interval (CI): 2.6-5.3%). In 2010, age-adjusted microfilaraemia prevalence had fallen to 0.4%, while antigenaemia rates were 0.2% in children < 5 years and 6.0% in ≥ 5 years. In 2010, universal coverage of mosquito nets in a household was found to be protective against W. bancrofti antigen (odds ratio = 0.44, 95% CI: 0.22-0.89). Prevalence of W. bancrofti larvae in anopheline mosquitoes had decreased significantly between the 2007 and 2010 surveys, but there was an apparent increase in vector densities.ConclusionA marked reduction in W. bancrofti infection and infectivity in humans was observed in the study area, where both MDA and LLINs were used to reduce transmission. The extent to which LLINs contributed to this decline is equivocal, however. Further work investigating the impact of vector control on anopheline-transmitted LF in an endemic area not benefitting from MDA would be valuable to determine the effect of such interventions on their own.
Highlights
Introduction ofinsecticide-treated net (ITN) resulted in reduction of overall mosquito density by 22.6% Annual transmission potential was reduced by 92% Annual infective biting rate was reduced by 95% [21]An. gambiae, In case-control study, individuals using untreated mosquito net had higher odds of Lymphatic filariasis (LF) than those Not specified using ITNs Cambodia [22]Use of untreated mosquito nets was associated with reduced odds of W. bancrofti antigenaemia An. farauti, Papua New [23]and microfilaraemiaAn. punctulatus, GuineaIndividuals using untreated mosquito nets had lower odds of hydrocoele than non-users Cx. annulirostris, The aim of the present work was to investigate whether large-scale distribution of long-lasting insecticidal nets (LLINs) could contribute towards the mass drug administration (MDA)-based transmission control of LF
In the 2007 and 2010 surveys, individuals who had been resident in the sub-county for less than two years were excluded (n = 144 in 2007, n = 169 in 2010), while families that had been resident in the village for fewer than seven months, the time since the LLIN distribution, were excluded from the 2008 survey (n = 6)
Six months after the LLIN distribution in 2008, households had an average of 2.8 nets, and 55.5% had achieved universal coverage
Summary
Individuals using untreated mosquito nets had lower odds of hydrocoele than non-users Cx. annulirostris, The aim of the present work was to investigate whether large-scale distribution of LLINs could contribute towards the MDA-based transmission control of LF. Maintaining high coverage of MDA over several years is challenging, in resource constraint settings [12], and has to proceed with caution or not at all in areas where the parasitic worm Loa loa is prevalent, due to the increased risk of severe adverse events [9,13] Due to these limitations of MDA, vector control is increasingly being considered as a complementary tool for LF elimination [14,15,16], in locations where Anopheles mosquitoes are the vector and malaria is co-endemic
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