Glanders and the risk for its introduction through the international movement of horses.
Authors: Kettle A N B, Wernery U
Journal: Equine veterinary journal
Summary
Glanders, caused by the bacterium *Burkholderia mallei*, represents a significant biosecurity concern for international equine trade despite its eradication from most Western countries in the early 20th century. Recent re-emergence in previously disease-free regions has prompted investigation into diagnostic reliability; whilst the World Organisation for Animal Health recommends the complement fixation test (CFT) for screening horses in international commerce, this test demonstrates variable sensitivity and specificity depending on antigen preparation and methodology used. Kettle and Wernery's 2016 review highlights a critical vulnerability: *B. mallei* can establish latent infections akin to those caused by *Burkholderia pseudomallei*, meaning infected horses may test negative on current diagnostic protocols yet remain infectious, presenting a genuine risk of disease reintroduction through animal movement. False negatives pose a greater threat to global equine health than false positives (which primarily affect individual owners), particularly given the documented emergence of glanders in areas where it had been eradicated. With international horse movement increasing, practitioners and regulatory bodies must recognise that existing CFT protocols may be insufficient as sole screening tools, warranting consideration of supplementary or alternative diagnostic methods and enhanced epidemiological surveillance for horses imported from endemic regions.
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Practical Takeaways
- •Be aware that glanders may present as latent infections in imported horses that escape detection by standard CFT screening, requiring heightened clinical vigilance in recently imported equids
- •Understand that current diagnostic tests have limitations; false positives can create unnecessary trade restrictions while false negatives allow disease re-entry into previously free regions
- •Recognize that increased international horse movement combined with diagnostic gaps and re-emerging glanders in new geographic areas represents an ongoing biosecurity risk requiring updated protocols
Key Findings
- •Glanders has re-emerged in areas where it was previously eradicated over the last 10-20 years
- •B. mallei can produce latent infections that may not be detectable by current diagnostic tests
- •The OIE-recommended complement fixation test (CFT) has varying sensitivities and specificities depending on antigen and methodology
- •False negatives in diagnostic testing pose a major risk for reintroduction of B. mallei into disease-free areas through international equid movement