Abstract
BackgroundLymphatic filariasis (LF) elimination program in Tanzania started in 2000 in response to the Global program for the elimination of LF by 2020. Evidence shows a persistent LF transmission despite more than a decade of mass drug administration (MDA). It is advocated that, regular monitoring should be conducted in endemic areas to evaluate the progress towards elimination and detect resurgence of the disease timely. This study was therefore designed to assess the status of Wuchereria bancrofti infection in Culex quinqefasciatus and Anopheles species after six rounds of MDA in Masasi District, South Eastern Tanzania.MethodsMosquitoes were collected between June and July 2019 using Center for Diseases Control (CDC) light traps and gravid traps for indoor and outdoor respectively. The collected mosquitoes were morphologically identified into respective species. Dissections and PCR were carried out to detect W. bancrofti infection. Questionnaire survey and checklist were used to assess vector control interventions and household environment respectively. A Poisson regression model was run to determine the effects of household environment on filarial vector density.ResultsOverall, 12 452 mosquitoes were collected of which 10 545 (84.7%) were filarial vectors. Of these, Anopheles gambiae complex, An. funestus group and Cx. quinquefasciatus accounted for 0.1%, 0.7% and 99.2% respectively. A total of 365 pools of Cx. quinquefasciatus (each with 20 mosquitoes) and 46 individual samples of Anopheles species were analyzed by PCR. For Cx. quinquefasciatus pools, 33 were positive for W. bancrofti, giving an infection rate of 0.5%, while the 46 samples of Anopheles species were all negative. All 1859 dissected mosquitoes analyzed by microscopy were also negative. Households with modern latrines had less mosquitoes than those with pit latrines [odds ratio (OR) = 0.407, P < 0.05]. Houses with unscreened windows had more mosquitoes as compared to those with screened windows (OR = 2.125, P < 0.05). More than 80% of the participants own bednets while 16.5% had no protection.ConclusionsLF low transmission is still ongoing in Masasi District after six rounds of MDA and vector control interventions. The findings also suggest that molecular tools may be essential for xenomonitoring LF transmission during elimination phase.
Highlights
Lymphatic filariasis (LF) elimination program in Tanzania started in 2000 in response to the Global program for the elimination of LF by 2020
The current findings indicate that, Cx. quinquefasciatus is a dominant vector of W. bancrofti in Masasi District, which accounted for 99.2% of the filarial vectors sampled
LF low transmission is still ongoing in Masasi District after six rounds of mass drug administration (MDA) and vector control interventions which are in place
Summary
Lymphatic filariasis (LF) elimination program in Tanzania started in 2000 in response to the Global program for the elimination of LF by 2020. DEC is not recommended in some countries of sub-Saharan Africa due to the co-endemicity with onchocerciasis. After five rounds of annual MDA, the prevalence of microfilaria (MF) in endemic settings was expected to fall below 1% and reducing the potential for new transmission by mosquitoes [11] The success of this strategy is evidenced in Western Pacific Region including Cambodia, Cook Islands, Egypt, Maldives, Marshall Islands, Niue, Sri Lanka, Thailand, Tonga, and Vanuatu where the MF prevalence fell below 1% after several rounds of implementing MDA with DEC and ALB [12,13,14]. Togo was declared as the first country in sub-Saharan Africa to achieve LF elimination following six rounds of MDA with ivermectin and albendazole using a network of community health workers [15]
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