Towards elimination of lymphatic filariasis in southeastern Madagascar: Successes and challenges for interrupting transmission

Abstract

IntroductionA global strategy of mass drug administration (MDA) has greatly reduced the burden of lymphatic filariasis (LF) in endemic countries. In Madagascar, the National Programme to eliminate LF has scaled-up annual MDA of albendazole and diethylcarbamazine across the country in the last decade, but its impact on LF transmission has never been reported. The objective of this study was to evaluate progress towards LF elimination in southeastern Madagascar.MethodsThree different surveys were carried out in parallel in four health districts of the Vatovavy Fitovinany region in 2016: i) a school-based transmission assessment survey (TAS) in the districts of Manakara Atsimo, Mananjary, and Vohipeno (following a successful pre-TAS in 2013); ii) a district-representative community prevalence survey in Ifanadiana district; and iii) a community prevalence survey in sentinel and spot-check sites of these four districts. LF infection was assessed using the Alere Filariasis Test Strips, which detect circulating filarial antigens (CFA) of adult worms. A brief knowledge, attitudes and practices questionnaire was included in the community surveys.Principal findingsNone of the 1,825 children sampled in the TAS, and only one in 1,306 children from sentinel and spot-check sites, tested positive to CFA. However, CFA prevalence rate in individuals older than 15 years was still high in two of these three districts, at 3.5 and 9.7% in Mananjary and Vohipeno, respectively. Overall CFA prevalence in sentinel and spot-check sites of these three districts was 2.80% (N = 2,707), but only two individuals had detectable levels of microfilaraemia (0.06%). Prevalence rate estimates for Ifanadiana were substantially higher in the district-representative survey (15.8%; N = 545) than in sentinel and spot-check sites (0.8%; N = 618). Only 51.2% of individuals surveyed in these four districts reported taking MDA in the last year, and 42.2% reported knowing about LF.ConclusionsAlthough TAS results suggest that MDA can be stopped in three districts of southeastern Madagascar, the adult population still presents high CFA prevalence levels. This discordance raises important questions about the TAS procedures and the interpretation of their results.

Coverage Validation survey for lymphatic filariasis treatment in Itang special district of Gambella regional state of Ethiopia; Cross sectional study

“…A strategy of MDA, following the 1997 World Health Assembly resolution to eliminate LF, has led to one of the most ambitious and successful interventions against a neglected tropical disease. Under sufficient level of intervention coverage, transmission of LF can be interrupted within five years (13).…”

“…The coverage in school age children (5)(6)(7)(8)(9)(10)(11)(12)(13)(14) shows significant difference with treatment coverage in individuals aged 15 and above (p<0.001) in the last mass drug administration campaign and this fact can be explained by the fact that most of the respondents were school age children and that there was a wrong assumption that the treatment is not given for adults while the treatment strategy include all individuals aged 5 and above and other reasons were also considered such as change of living area and not being around during the mass drug administration.…”

“…MDA offered against LF and its association with gender, age and school attendance(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) among individuals 5 years and above in Itang special woreda of Gambella (integrated approach),…”

Systematic sampling of adults as a sensitive means of detecting persistence of lymphatic filariasis following mass drug administration in Sri Lanka

“…MX is more sensitive than TAS but technically more difficult to perform. As noted in the Introduction, recent studies in India, American Samoa and in Madagascar where LF is transmitted by Culex have also documented significant persistence of LF in adults in areas that met school-TAS targets [15, 17, 18]. In addition to its value for post-MDA surveillance, adult-TAS may also be superior to the current practice of performing Mf surveys on convenience samples of adults in a small number of sentinel locations and for assessing the presence of LF in areas believed to be non-endemic that are adjacent to formerly endemic areas, because it samples more people in more locations.…”

“…While TAS provides information on recent transmission events in children, it has not been rigorously validated as a tool for detecting persistent LF in post-MDA settings. Recent post-MDA surveillance studies performed in Sri Lanka, India, American Samoa, and in Madagascar have documented significant persistence of filarial infection in adults and evidence for ongoing transmission in areas with <2% antigen prevalence in children [12–18]. School-TAS based on WHO guidelines employs children as sentinels for detecting recent transmission of the infection.…”