Spatial Analysis of Lymphatic Filariasis Transmission Clusters in Anambra State Using Transmission Assessment Survey Data

Transmission assessment surveys are used to determine whether lymphatic filariasis transmission has been interrupted following mass drug administration, and spatial analysis of survey data can identify residual transmission hotspots requiring targeted intervention. This study performed spatial clustering analysis of lymphatic filariasis transmission assessment survey data collected from 30 evaluation units in Anambra State, Southeast Nigeria. Circulating filarial antigen prevalence data from 3,600 children aged 6 to 7 years tested using the filariasis test strip were geo-referenced by community. SaTScan software and ArcGIS spatial statistics tools were applied to identify statistically significant transmission clusters. Age-adjusted antigen prevalence ranged from 0 to 3.4 percent across evaluation units, with 73.3 percent of units meeting the less than 2 percent threshold for transmission interruption. Spatial analysis identified three statistically significant high-prevalence clusters in riverine communities of Ogbaru and Onitsha North local government areas. Proximity to the Niger River and suboptimal mass drug administration coverage in preceding rounds were significant spatial predictors. The identified residual transmission foci require geographic targeting with intensified mass drug administration and supplementary vector control to prevent recrudescence of endemic transmission in otherwise elimination-threshold communities. Keywords: lymphatic filariasis, spatial analysis, transmission assessment survey, elimination, Anambra State.