Spatial Clustering of Lymphatic Filariasis in Relation to Potential Mansonia Mosquito Habitats in Endemic Communities of Belitung Regency, Indonesia

Abstract

Background

Lymphatic filariasis (LF) remains endemic in several island communities in Indonesia despite mass drug administration (MDA) campaigns. Investigating the spatial relationship between human cases and potential mosquito breeding sites may help explain the persistence of LF transmission.

Methods

A cross-sectional survey was conducted in 2019 across four sub-villages in two LF-endemic villages in Belitung Regency, Indonesia: Suak Gual village (Suak Gual sub-village) and Lasar village (Batumana, Dudat, and Ulin sub-villages). Thick blood smears were collected at night from 671 participants and were examined microscopically. GPS coordinates were recorded for the residence of all study participants, regardless of their infection status, as well as for each water body exhibiting characteristics consistent with a potential Mansonia habitat. Distance analysis, buffer zone evaluation, the Clark-Evans test, and cross-K function analysis were used to characterize the spatial relationship between cases and habitats.

Results

Case clustering was robust in two of the four sub-villages, Suak Gual (R = 0.380, p < 0.001) and Batumana (R = 0.432, p < 0.001), with significance maintained after Bonferroni correction across all boundary-window widths tested. Ulin showed nominally significant clustering (R = 0.654, p = 0.026) that did not survive Bonferroni correction (p = 0.106) or a narrower boundary window and is reported as a weaker, less consistent finding. Dudat showed no deviation from spatial randomness (R = 0.856, p = 0.434), which is consistent with its comparatively dense and widespread habitat. Just over three-quarters of cases, 76.5% (n = 26), lived within 500 m of the nearest habitat, indicating a geographic link between residence and vector breeding sites.

Conclusions

Filariasis cases in Belitung tend to cluster near potential Mansonia habitats. These findings provide programme planners with a quantitative basis for prioritizing habitat-focused interventions alongside ongoing mass drug administration. Direct entomological surveys are still needed to confirm vector presence and test the effectiveness of spatially targeted control.