Re-emergence of equine glanders in Mongolia based on region-wide serosurveillance.

Overview

• This study conducted a nationwide survey to measure the prevalence and distribution of glanders, a bacterial disease affecting horses, in Mongolia.
• Findings reveal a significant resurgence of glanders compared to previous data, indicating the disease is spreading again across various regions.

Background and Purpose

• Glanders is a zoonotic disease caused by the bacterium Burkholderia mallei, primarily affecting horses but also transmissible to humans.
• The disease had been controlled in Mongolia for decades but recently re-emerged, raising concern among animal health authorities.
• The purpose of the research was to assess the current prevalence of glanders over a wide geographic area through serological testing to guide control and prevention efforts.

Study Design and Methods

• Timeframe: The study was conducted from 2021 to 2024.
• Sampling:
  • Used random 3-stage cluster sampling to achieve a representative sample across Mongolia.
  • Collected a total of 3,001 serum samples from horses belonging to 332 herds.
  • Sampling spanned 46 soums (Mongolian administrative districts similar to counties) in 13 provinces as well as 3 districts in Ulaanbaatar city.
• Testing Strategy:
  • Initial screening using the complement fixation test (CFT), a standard serological test for glanders antibody detection.
  • Positive samples then confirmed by immunoblotting and ELISA, ensuring specificity and reliability of positive results.

Key Findings

• Overall seroprevalence of glanders antibodies was 1.03% (95% confidence interval: 0.7% to 1.5%), indicating exposure to the pathogen in the horse population.
• Geographic Distribution:
  • Positive cases were detected in 69.2% of the provinces.
  • Detected in roughly one-third (34.8%) of the soums sampled.
  • Detected in 7.2% of individual herds tested.
  • The highest seroprevalence was in the eastern part of Mongolia, especially in Sukhbaatar province, which had a 4.5% prevalence.
• Clinical Observation:
  • None of the seropositive horses exhibited clinical signs of glanders, indicating either subclinical infection or early exposure stages.
• Comparison with Past Data:
  • The seroprevalence in this study is approximately 5 times higher than the 0.19% found in a 2011 nationwide surveillance effort.
  • This substantial increase signals a clear resurgence of glanders in the horse population in Mongolia over roughly a decade.

Interpretation and Implications

• Possible Causes of Resurgence:
  • Reduced veterinary oversight may have led to decreased disease monitoring and control.
  • Unrestricted movement of horses for racing and breeding likely facilitates transmission across regions.
  • Geographic and environmental factors could be contributing to the spread or persistence of the bacterium in certain areas.
• Control Recommendations:
  • Emphasize continuous and systematic surveillance to monitor infection trends.
  • Implement movement controls based on laboratory testing results to reduce spread between herds and regions.
  • Increase awareness and education among herders about glanders risks and preventive measures.
  • Strengthen veterinary services and enhance reporting and response mechanisms for glanders cases.
• Overall, the study highlights an urgent need for enhanced public and animal health interventions to prevent further spread of glanders, protecting both equine and human populations in Mongolia.