Effectiveness of annual single doses of diethylcarbamazine citrate among bancroftian filariasis infected individuals in an endemic area under mass drug administration in Brazil.

The Global Program to Eliminate Lymphatic Filariasis has achieved extraordinary success in reducing transmission and preventing morbidity through mass drug administration (MDA) to the population at-risk. Brazil is the only currently using diethylcarbamazine citrate (DEC) alone for MDA, so an assessment of its effectiveness is needed. We report the trends of filarial markers in a cohort of 175 individuals infected with Wuchereria bancrofti in areas that underwent MDA in the city of Olinda, Northeastern Brazil. The prospective study was conducted between 2007 and 2012 (corresponding to five annual MDA rounds). The quantification of microfilaraemia (QMFF) was assessed by filtration. Circulating filarial antigen (CFA) was detected through immunochromatographic point-of-care test (POCT-ICT) and Og4C3-ELISA whereas antifilarial antibody titres (IgG4) were assessed through Bm14 assay. The CFA and IgG4 titres were measured by Optical Density (OD). The main characteristics at baseline, MDA coverage and the trend of filarial infection markers during follow up were described. The trend of filarial markers in relation to time (years of MDA), sex and age were analysed through Generalized Estimating Equations (GEE) models. The models demonstrated a significant decrease in all markers during MDA. The probability of remaining positive by QMFF and POCT-ICT diminished 70% and 46%, respectively, after each MDA round. There was a significant annual drop in CFA (-0.290 OD) and IgG4 antibodies titres (-0.303 OD). This study provides evidence that MDA with DEC alone can be effective in the elimination of LF in Brazil.