Prevalence and Correlates of Lymphatic Filariasis Infection and Its Morbidity Following Mass Ivermectin and Albendazole Administration in Mkinga District, North-Eastern Tanzania

Abstract

Lymphatic filariasis (LF) is a neglected tropical disease targeted for elimination as public health problem through morbidity management and preventive annual mass drug administration (MDA). This cross-sectional community-based surveillance assessed the prevalence and correlates of LF infection in Mkinga district, Tanga-region, Tanzania. A total of 4115 individuals (49.7% males, 35.2% children) were screened for circulating filarial antigens (CFA), microfilaremia (mf) and disease manifestations in 15 villages between November 2018 and January 2019. MDA uptake in the previous year was assessed. Overall prevalence of CFA-positivity was 5.8% (239/4115; 95% CI: 5.1-6.6), with significant heterogeneity between villages (range 1.2% to 13.5%). CFA-positivity was higher in males (8.8%) than females (3.3%), and correlated with increasing age (p < 0.001). Prevalence of mf among CFA-positives was 5.2%. Only 60% of eligible inhabitants in the study area took MDA in the previous year, and CFA-positivity was 2-fold higher in those who missed MDA (p < 0.0001). Prevalence of scrotal enlargement, hydrocele, arms or legs swelling, lymphoedema and lymphadenopathy was 6.4%, 3.7%, 1.35%, 1.2% and 0.32%, respectively. Compared to baseline data, 16 years of MDA intervention significantly reduced LF transmission and morbidity, although the intended elimination target of <1% mf and <2% antigenemia to level where recrudescence is unlikely to occur by the year 2020 may not be attained. The finding of hotspots with ongoing transmission calls for intensified control measures.

Keywords: Tanga; Wuchereria bancrofti; albendazole; antigenemia; circulatingfilarial antigen; ivermectin; lymphatic filariasis; mass drug administration; microfilaremia; microfilariae.

Figure 1

Map of the study site. Left is the map of Tanzania located in the Eastern part of Africa. The top-right figure shows the map of Tanga region, where the Mkinga district is located. The bottom-right figure shows the map of wards in the Mkinga district, whereby villages in these wards participated in this study. The study site map was originally generated using ArcGIS software version 10.7.1 [28].

Figure 2

Prevalence and 95% CI of circulating filarial antigens (CFA) positivity stratified by age group (A) and by age group and sex (B).

Figure 3

Proportion compliance of villages with mass drug administration (MDA) coverage.

Figure 4

Proportion of individuals who did not use MDA in the last round of distribution by age group (A) and by villages (C); and prevalence of CFA by age group (B) and by village of residence (D). The color bands represent Boma, Doda, Kwale, Manza, Maramba, and Mayomboni wards.

Figure 5

Distribution of hydrocele in males and swelling of arms or legs in both males and females by age group (A) and by village (B).