Abstract
BackgroundThe Global Programme to Eliminate Lymphatic Filariasis recommends the transmission assessment survey (TAS) as the preferred methodology for determining whether mass drug administration can be stopped in an endemic area. Because of the limited experience available globally with the use of Brugia Rapid™ tests in conducting TAS in Brugia spp. areas, we explored the relationship between the antibody test results and Brugia spp. infection as detected by microfilaremia in different epidemiological settings.MethodsThe study analyzes the Brugia Rapid™ antibody responses and microfilaremia in all ages at three study sites in: i) a district which was classified as non-endemic, ii) a district which passed TAS, and iii) a district which failed TAS. Convenience sampling was done in each site, in one to three purposefully selected villages with a goal of 500 samples in each district.ResultsA total of 1543 samples were collected from residents in all three study sites. In the site which was classified as non-endemic and where MDA had not been conducted, 5 % of study participants were antibody positive, none was positive for microfilaremia, and age-specific antibody prevalence peaked at almost 8 % in the 25–34 year-old age range, with no antibody-positive results found in children under eight years of age. In the site that had passed TAS, 1 % of participants were antibody positive and none was positive for microfilaremia. In the site which failed TAS, 15 % of participants were antibody positive, 0.2 % were microfilaremic, and age-specific antibody prevalence was highest in 6–7 year olds (30 %), but above 8 % in all age levels above 8 years old.ConclusionsThese results from districts which followed the current WHO guidance for mapping, MDA, and implementing TAS, while providing antibody profiles of treated and untreated populations under programmatic settings, support the choice of antibody prevalence in the 6- and 7-year-old age group in TAS for making stopping MDA decisions. Since only one study participant was microfilaremic, no conclusions could be drawn about the relationship between antibodies and microfilaremia and further longitudinal studies are required to understand this relationship.
Highlights
The Global Programme to Eliminate Lymphatic Filariasis recommends the transmission assessment survey (TAS) as the preferred methodology for determining whether mass drug administration can be stopped in an endemic area
Non-endemic site In Payakumbuh, a total of 23 (5 %) study participants were antibody positive; none was positive for microfilaremia
A better understanding of antibody responses in all ages is critical for determining the appropriateness of current World Health Organization (WHO) guidelines in Brugia spp. areas
Summary
The Global Programme to Eliminate Lymphatic Filariasis recommends the transmission assessment survey (TAS) as the preferred methodology for determining whether mass drug administration can be stopped in an endemic area. Lymphatic filariasis Lymphatic filariasis (LF), known as elephantiasis, is a parasitic disease caused by three species of parasitic worms – Wuchereria bancrofti, Brugia malayi, and Brugia timori – and transmitted by mosquitoes It can cause clinical complications of lymphedema and hydrocele, making it one of the most disabling diseases in the world. This guidance introduced the transmission assessment survey (TAS), an impact survey designed to determine whether prevalence has been lowered to such a level that MDA could be stopped and recrudescence would not occur. This infection level is likely to be reached after five to six annual MDA rounds with effective coverage of at least 65 % of the total population. The TAS uses a population-based cluster-sampling methodology to estimate prevalence among 6–7 year old children in an evaluation unit
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