Assessment of transmission in areas of uncertain endemicity for lymphatic filariasis in Brazil

Author summary Lymphatic filariasis is a parasitic disease that can cause incapacity and chronic complications. The World Health Organization aims to eliminate lymphatic filariasis as a public health problem worldwide by 2020. Four municipalities in the Metropolitan Region of Recife (Brazil) are endemic, of which three have undergone mass drug administration (MDA). However, the epidemiological status of filariasis in nine adjoining areas is unknown. Therefore, a literature review was conducted to identify reports of the vector and human cases in these nine municipalities. A review of data starting in 1967 from eight scientific reports highlighted the circulation of microfilaremia, infection of Culex quinquefasciatus with Wuchereria bancrofti, and morbidity owing to lymphatic filariasis. However, no surveillance was proposed in these areas. Therefore, in 2016, a survey of 17,222 children aged 6-10 years and enrolled in urban schools in the nine municipalities was conducted. One child from a municipality in which MDA was conducted tested positive for lymphatic filariasis, but no other case was diagnosed in her family. Our results showed no transmission of lymphatic filariasis in these nine municipalities. However, population migration and socioenvironmental conditions that favor mosquito breeding grounds indicate the need for surveillance in these areas. Background The objective of the Global Program to Eliminate Lymphatic Filariasis (GPELF) is to phase out this endemic disease as a public health problem by 2020. Validation of elimination is obtained from the World Health Organization through evidence of non-transmission in countries that have already been subjected to mass drug administration (MDA) and in places adjoining these endemic areas. While three municipalities in Brazil have completed MDA, the epidemiological situation remains uncertain in nine adjoining municipalities. To determine the epidemiological status, this study was to perform a review of the literature and a school-based survey to describe the past and recent endemicity of lymphatic filariasis (LF) theses nine municipalities in Brazil. Methodology/Principle findings For review of the literature, both formal and informal literature sources were accessed since the first reports of filariasis in the Metropolitan Region of Recife, Brazil. We conducted a school-based survey in 2016 using immunochromatographic card tests (ICTs) among schoolchildren aged 6-10 years living in nine municipalities contiguous with the endemic areas in which MDA was conducted. Our review of the literature identified eight studies involving surveys demonstrating that microfilariae had been circulating in eight of the municipalities since 1967, with a low prevalence of microfilaremia, isolated autochthonous cases, and treatment of individual cases. The school-based survey included 17,222 children in 185 urban schools in the nine areas of Brazil with uncertain endemicity. One child affected by allochthonous transmission was antigen positive based on ICT and lived in a municipality adjacent to Recife; this child's family came from Recife, but no other case was diagnosed within the family.