Long-Term Environmental Persistence and Phylogenetic Evidence of Burkholderia pseudomallei in a Melioidosis Case Cluster in Taiwan.

OBJECTIVES

Melioidosis, caused by Burkholderia pseudomallei , is an environmentally acquired disease endemic to Southeast Asia and northern Australia, and increasingly recognised as an important but underdiagnosed tropical infection. In Taiwan, the spatial distribution and environmental reservoirs of this pathogen remain poorly understood.

METHODS

We analysed 796 melioidosis cases reported between 2003 and 2024 and identified a recurrent, statistically significant cluster zone using SaTScan, especially during 2009-2013 and again in 2024. To investigate environmental persistence, we conducted long-term surveillance across 46 GIS-defined grid squares within the cluster zone from 2012 to 2024.

RESULTS

This zone accounted for 61%-72% of national cases, with annual incidence rates ranging from 0.3 to 4.0 per 100,000 people. Three adjacent squares (31-33) consistently showed high soil PCR positivity (68.4%-85.5%). During rainy seasons, DNA concentrations in aerosols and stagnant surface water followed similar temporal patterns, influenced by rainfall and wind gusts. A heavy rainfall event in 2024 increased soil PCR positivity from 77.7% to 97.4%. Seventeen viable B. pseudomallei isolates were cultured from soil, surface water, aerosols and cattle shed wastewater. All belonged to ST58, ST1115 or ST1354, with ST58 prevalent across environmental sources. Core genome single nucleotide polymorphism (SNP) analysis revealed close phylogenetic relatedness between environmental and clinical ST58 isolates, indicating localised environmental-to-human transmission.

CONCLUSIONS

These findings provide insights into the environmental persistence and transmission dynamics of B. pseudomallei , supporting more effective risk assessment and public health strategies for melioidosis in endemic tropical regions.