Horses in Asia Found Infected with H5N1 Avian Influenza

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A recent study has revealed that horses in Asia have been infected with H5N1 avian influenza,
with these infections occurring undetected.  

The research, led by Professor Pablo Murcia from the MRC-University of Glasgow Centre for Virus Research, in collaboration with an international team of scientists from the US and Mongolia, involved antibody testing on horse herds in Mongolia.  The findings, published in Emerging Infectious Diseases, reveal asymptomatic infections in Mongolian horse herds.

 

The researchers tested horse herds in two distinct Mongolian regions: a wetland area with a high population of wild birds and a dry area with low bird density. The results showed higher exposure rates in the wetland region. Importantly, there were no reports of previous respiratory disease outbreaks among the horses, suggesting that the infections were acquired asymptomatically.

 

These findings confirm that avian influenza can spread to other species, including horses. While equine influenza is typically caused by the H3N8 subtype, the detection of H5N1 highlights the potential for avian influenza to infect horses.

The study raises concerns about cross-species transmission, particularly in agricultural environments where horses may be exposed to infected livestock. Since March 2023, the rapid spread of H5N1 in US dairy cattle has amplified the risk of horses contracting avian influenza.

Coinfection with H5N1 and equine influenza (H3N8) could result in genetic reassortment, potentially creating new influenza strains with unpredictable consequences for animals and humans. Professor Murcia noted parallels to the 2009 swine-origin influenza pandemic, emphasizing the importance of preventing such reassortment events.

The researchers conclude by recommending serologic surveys in premises that keep horses. Such studies, they say, would aid early virus detection, provide a comprehensive picture of the changing ecology of avian influenza viruses, and inform the design of control measures to prevent influenza emergence.

This study highlights the need for:

1. Enhanced surveillance of influenza infections in horses, particularly in regions with high wild bird densities or significant interaction with infected livestock.
2. Strengthened biosecurity measures to reduce interspecies transmission in agricultural settings.
3. Further research into the mechanisms of avian influenza spillover and the potential for new virus emergence.

For more details, see: 

 

Batchuluun Damdinjav, Savitha Raveendran, Laura Mojsiejczuk, Ulaankhuu Ankhanbaatar, Jiayun Yang, Jean-Remy Sadeyen, Munir Iqbal, Daniel R. Perez, Daniela S. Rajao, Andrew Park, Mafalda Viana, and Pablo R. Murcia (2025)

Evidence of Influenza A(H5N1) Spillover Infections in Horses, Mongolia.

Emerging Infectious Diseases, 31(1) 

https://doi.org/10.3201/eid3101.241266 

https://www.gla.ac.uk/news/headline_1134067_en.html