Factors influencing sustained transmission of lymphatic filariasis in school children after eight rounds of mass drug administration: A case of Mafuriko village in north-eastern Tanzania

Abstract

Background: The program to eliminate lymphatic filariasis in Tanzania is based on Mass Drug Administration (MDA) with ivermectin and albendazole once per year for 4-6 years in order to interrupt transmission. One of the indicators used to measure the impact of MDA is the prevalence of circulating filarial antigen in children born within the intervention period. It is thought that at a good coverage of ≥ 80% and more than 4 rounds of MDA these children are not expected to have infection (WHO, 2005). High prevalence of circulating filarial antigen of 6.4% has been reported in Tanga despite 8 rounds of MDA in the region (Simonsen et al 2011). This suggests that there is an ongoing transmission of lymphatic filariasis in Tanga.

Objective: This study was designed to determine factors influencing sustained transmission of lymphatic filariasis in Tanga based on the findings of high prevalence of circulating filarial antigen in children born within the elimination program.

Methodology: A descriptive cross-sectional study involving individuals aged 6 years and above was conducted at Mafuriko village along the coast of Tanga. The study had three parts, an entomological component that included collection and determination of infection and infectivity rates in vectors, parasitological component that involved night blood examination for microfilaria detection and quantitative studies to assess community knowledge and awareness of the LF elimination program, to determine the proportion of individuals who took drugs during the last round of MDA and to assess the rate of insecticide treated bed net utilization. The study recruited 317 study participants.

Results: The microfilaria prevalence among the study participants was 6%. The prevalence was high among males (4.7%) than females (1.3%). The most affected age group was the youth below 26 years of age with the prevalence of 19.2% p=0.09. History of ever participated in MDA was found to be protective [AOR=4.6, 95%CI (1.6-13.9)]. Only two mosquitoes out of 555 were found to harbour L1 and L2 and all collected vectors were Culex quinquefasciatus.

Ninety one percent (91%) of study participants were aware of lymphatic filariasis (LF) and 79% were aware of the LF elimination program, 99.3% had good knowledge about LF elimination program and 54% swallowed the drugs in the last cycle of treatment. 76.7% participants reported to possess an ITN, among these 93.4% used the ITN the night before the interview.

Conclusion: Presence of infected individuals, infected mosquitoes, poor compliance to treatment, low levels of knowledge on LF elimination program, transmission and prevention are the main factors that may influence high prevalence of CFA in school children at Mafuriko village.