Abstract
BackgroundControl of lymphatic filariasis (LF) in most of the sub-Saharan African countries is based on annual mass drug administration (MDA) using a combination of ivermectin and albendazole. Monitoring the impact of this intervention is crucial for measuring the success of the LF elimination programmes. This study assessed the status of LF infection in Rufiji district, southeastern Tanzania after twelve rounds of MDA.MethodsCommunity members aged between 10 and 79 years were examined for Wuchereria bancrofti circulating filarial antigens (CFA) using immunochromatographic test cards (ICTs) and antigen-positive individuals were screened for microfilaraemia. All study participants were examined for clinical manifestation of LF and interviewed for drug uptake during MDA rounds. Filarial mosquito vectors were collected indoor and outdoor and examined for infection with W. bancrofti using a microscope and quantitative real-time polymerase chain reaction (qPCR) techniques.ResultsOut of 854 participants tested, nine (1.1%) were positive for CFA and one (0.1%) was found to be microfilaraemic. The prevalence of hydrocele and elephantiasis was 4.8% and 2.9%, respectively. Surveyed drug uptake rates were high, with 70.5% of the respondents reporting having swallowed the drugs in the 2014 MDA round (about seven months before this study). Further, 82.7% of the respondents reported having swallowed the drugs at least once since the inception of MDA programme in 2000. Of the 1054 filarial vectors caught indoors and dissected to detect W. bancrofti infection none was found to be infected. Moreover, analysis by qPCR of 1092 pools of gravid Culex quinquefasciatus collected outdoors resulted in an estimated infection rate of 0.1%. None of the filarial vectors tested with qPCR were found to be infective.ConclusionAnalysis of indices of LF infection in the human population and filarial mosquito vectors indicated a substantial decline in the prevalence of LF and other transmission indices, suggesting that local transmission was extremely low if occurring at all in the study areas. We, therefore, recommend a formal transmission assessment survey (TAS) to be conducted in the study areas to make an informed decision on whether Rufiji District satisfied WHO criteria for stopping MDA.
Highlights
Control of lymphatic filariasis (LF) in most of the sub-Saharan African countries is based on annual mass drug administration (MDA) using a combination of ivermectin and albendazole
Rufiji District was purposively selected for the study due to its history of high LF prevalence before the start of elimination activities based on ivermectin and albendazole MDA in 2002
LF prevalence and disease burden A total of 854 individuals above five years-old in five villages of Rufiji District were examined for circulating filarial antigens (CFA), MF, hydrocele and elephantiasis
Summary
Control of lymphatic filariasis (LF) in most of the sub-Saharan African countries is based on annual mass drug administration (MDA) using a combination of ivermectin and albendazole. It is estimated that one billion people are at risk of infection and 120 million are affected by LF Of those at risk of infection, 65% reside in the Southeast Asia, 30% in Africa, and the remainder live in other parts of the tropical world [2, 3]. The programme had a principle objective of interrupting the transmission of W. bancrofti and Brugia malayi through the application of annual mass drug administration (MDA) to the entire at-risk population as well as management and prevention of LF-related disabilities [8]. It has been suggested that after four to six consecutive rounds of MDA, microfilariae load in the endemic population is expected to fall below 1%, and this reduction in microfilaraemia will lead to the reduced acquisition of new infections [10]
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