# Evidence of populational Burkholderia pseudomallei exposure in Madagascar

## TL;DR

This study found evidence of Burkholderia pseudomallei exposure in Madagascar, particularly in the Mahajanga region, suggesting the need for better disease surveillance and public health interventions.

## Contribution

The study identifies HCP1 and CPS I as promising diagnostic targets and provides the first large-scale serological evidence of Bp exposure in Madagascar.

## Key findings

- Seroprevalence was highest in Mahajanga, especially for HCP1 and CPS I antigens.
- Bp DNA was detected in a water sample from Mahajanga, confirming environmental presence.
- Blood donor samples proved effective for large-scale serological surveillance in low-resource settings.

## Abstract

Burkholderia pseudomallei (Bp), the causative agent of melioidosis, poses a significant health risk in endemic regions. This study aimed to characterize six previously identified Bp antigens for exposure monitoring in potential endemic setting of Madagascar and to assess potential exposure and reactivity across Madagascar to inform diagnostic strategies and understand regional exposure patterns.

Six highly reactive Bp antigens, CPS I, LPS types A and B, HCP1, AhpC, and GroEL, were characterized using the protein BLAST (BLASTp) algorithm against the NCBI non-redundant protein database to evaluate conservation and specificity. Serological reactivity was analyzed in 5,736 serum samples from six regions of Madagascar using Luminex bead-based multiplex assays. Principal Component Analysis was conducted to identify co-reactivity patterns. Environmental sampling in Mahajanga assessed the presence of Bp DNA in soil and water samples via real-time PCR.

Antigen conservation varied, with HCP1 and CPS I demonstrating the highest specificity, suggesting their potential for targeted serological detection. Seroprevalence and co-seroprevalence were highest in the Mahajanga region, particularly for HCP1 and CPS I (p < 0.0001). PCA revealed distinct antigen-specific immune response profiles. Environmental sampling confirmed the presence of Bp DNA in a water sample from Mahajanga, indicating local bacterial presence in the environment.

These findings suggest human exposure to Bp occurs in multiple regions in Madagascar. HCP1 and CPS I emerged as promising targets for diagnostic applications, and environmental detection of Bp underscores the need for targeted public health interventions in higher-risk regions like Mahajanga.

Melioidosis is a serious and potentially fatal infectious disease caused by the environmental bacterium Burkholderia pseudomallei (Bp), which is naturally found in soil and surface water. The disease primarily affects individuals with underlying conditions such as diabetes and can lead to severe illness or death if not promptly diagnosed and treated. Despite its clinical severity, melioidosis often goes undiagnosed in low-resource settings due to the need for specialized laboratory diagnostics.

In Madagascar, only a handful of human cases have been officially reported, but the true extent of exposure across the population has remained unknown. To address this gap, we conducted a large-scale serological survey, analyzing blood samples from more than 5,000 healthy blood donors across five regions of the country. By screening for antibodies indicative of past infection, we uncovered a significantly higher seroprevalence in the coastal region of Mahajanga, pointing to localized transmission. Supporting these findings, we also detected B. pseudomallei DNA in surface water samples from the same region, providing environmental evidence of exposure risk.

These results suggest that melioidosis may be more widespread in Madagascar than previously recognized. Our study underscores the importance of strengthening disease surveillance and environmental monitoring while raising awareness of this neglected tropical disease. It also highlights the potential of using blood donor samples as a cost-effective and scalable tool for uncovering hidden infectious threats in resource-limited settings.