Equine Herpesvirus Myeloencephalopathy (EHM)

Equine herpesvirus myeloencephalopathy (EHM) is caused by Equine herpesvirus type 1 (EHV-1) and is a significant concern in the equine industry worldwide. It poses a substantial threat to horse health, performance, and welfare. As a professional animal disease CRO, BioVenic has an in-depth understanding of all aspects of EHM to help customers develop effective prevention, diagnostics, and management strategies.

Etiology and Epidemiology

EHV-1 is a highly contagious virus belonging to the family Herpesviridae and the genus Varicellovirus that primarily targets the respiratory and nervous systems. The exact mechanisms of how EHV-1 leads to neurological damage are still not fully understood. It is believed, however, that the virus damages the central nervous system by causing inflammation and vascular damage.

Fig. 1 Schematic structural representation of equine herpesvirus type 1 (EHV-1).¹

The epidemiology of EHM highlights the significance of the disease. EHV-1 infection spreads rapidly within horses, particularly in environments where horses come into close contact, such as training facilities, shows, and racetracks. The virus can persist in latent form within infected horses, making it challenging to detect and control.

Transmission

Transmission of EHV-1 occurs when horses direct contact with each other, inhale respiratory secretions, or come into contact with contaminated equipment or surfaces. Another important route of transmission of EHV-1 is from mare to foal, even if the mare has been vaccinated. Infected horses spread the virus even without clinical signs. It is crucial to implement strict biosecurity measures to prevent the spread of EHV-1. We strongly recommend the following measures,

• Isolation: Separate newly arrived horses from the resident population for a quarantine period to monitor for any signs of illness.
• Hygiene: Practice proper hygiene by cleaning and disinfecting equipment, shared spaces, and high-contact surfaces regularly.
• Vaccination: We develop a vaccination plan tailored to your horse's needs.
• Travel management: Minimize horse movement and avoid mixing horses from different populations during outbreaks.
• Testing: Consider regular testing for EHV-1 to identify carriers and implement appropriate management strategies.

Fig. 2 Pathogenic mechanisms of EHV-1 in horses.²

Why Should We Care About EHM?

EHM is a condition that affects horses of all ages and breeds. It can occur sporadically or in the form of outbreaks, which have been reported in several countries including the United States, Canada, Europe, and Australia. These outbreaks have had significant impacts on the equine industry, leading to quarantine measures, event cancellations, and economic losses. Therefore, biological companies, veterinarians, and farmers must pay close attention to EHM to prevent and manage outbreaks.

Signs and Symptoms

Clinical symptoms of EHM vary but often present with respiratory symptoms and neurologic deficits, including,

Diagnosis

BioVenic provides customers with complete EHM laboratory diagnostics solutions, including immunodiagnostics and molecular diagnostics.

• For aborted horses, tissue from aborted foals is usually used as a sample to detect EHV-1 by virus isolation, PCR, and LAMP.
• In cases of horses with obvious respiratory symptoms, pharyngeal or nasal secretions can be collected to identify EHV-1 by PCR and LAMP.
• For serum samples, an indirect ELISA method is used to detect specific IgG antibodies against EHV-1.

Treatment

Currently, no specific antiviral therapy exists for EHV-1.Treatment for EHM focuses on supportive care, including anti-inflammatory medications, fluid therapy, and nursing care to help affected horses recover.

EHM Vaccines

EHV-1 vaccines control respiratory, and abortive symptoms and limit spread among horses. However, none of these vaccines has been recognized as effective in preventing EHM. To address this, both universities and research institutes are currently studying existing vaccines to determine their effectiveness in preventing EHM. Additionally, new EHM vaccines are also being researched. BioVenic is actively committed to helping customers develop vaccines that can effectively prevent EHM.

BioVenic is committed to promoting equine health and supporting the industry in the fight against EHM. We provide our customers with EHV-1 diagnostics solutions to help diagnose the disease accurately and promptly. At the same time, our experienced research teams collaborate with veterinary researchers to develop effective vaccines and treatment strategies. For more information, please contact us today.

References

1. Oladunni, Fatai S, et al. "EHV-1: A constant threat to the horse industry." Frontiers in microbiology 10 (2019): 2668.
2. Laval, Kathlyn, et al. "The pathogenesis and immune evasive mechanisms of equine herpesvirus type 1." Frontiers in Microbiology 12 (2021): 662686.