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Viral Diseases of Horses

Author(s):
Johns I.C.
In: EVC - Voorjaarsdagen - Amsterdam, 2009 by European Veterinary Conference - Voorjaarsdagen
Updated:
APR 25, 2009
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Viral diseases of horses, in particular Equine influenza (EI) and Equine herpesvirus myeloencephalopathy (EHM) continue to have a major impact on the global equine industry. The international movement of horses is now almost commonplace, and this can increase the risk of dissemination of viruses throughout the world.

Equine Influenza

• Highly contagious respiratory disease caused by the EI virus (EIV).
• Clinical signs: fever, coughing, tachypnoea, weight loss, +/- more severe clinical signs eg secondary bacterial pneumonia
• Up to 100% morbidity in susceptible populations
• Two subtypes of EIV:
     • A/equine 1 (H7N7): not isolated for more than two decades
     • A/equine 2 (H3N8): associated with all recent outbreaks
• H3N8 evolved into two subfamilies:
     • American lineage
     • European lineage
     • Both lineages currently co-circulate in Europe and the USA

Equine Herpesvirus

• Two predominant types: EHV-1 and EHV-4
• Most horses infected around the time of weaning
• Latent infection established in lymph nodes, circulating leukocytes and neurones of the trigeminal ganglia
• Ubiquitous throughout the global equine population
     • Up to 80% of adult horses likely to be latently infected
• Reactivation of latent virus can follow transport, handling, re-housing and weaning
• Disease syndromes:
     • Upper respiratory disease
     • Abortion
     • Neonatal disease
     • Neurologic disease (EHM) 

EHM

• Primarily caused by EHV-1
• Recent increase in the frequency of reported EHM outbreaks in the UK, Europe and the USA
• Majority of EHV isolates associated with EHM caused by a genetic variant resulting from a single point mutation of the DNA polymerase gene (involved in viral replication)
• Viraemia after infection (new infection or reactivation of latent infection)
• Virus infects endothelial cells within CNS – vasculitis, thrombosis and ischaemic degeneration
• Clinical signs - hind limb paresis/paralysis, recumbency, urinary and faecal retention
• Remain contagious - isolate [...]

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How to reference this publication (Harvard system)?

Johns, I. (2009) “Viral Diseases of Horses”, EVC - Voorjaarsdagen - Amsterdam, 2009. Available at: https://www.ivis.org/library/evc/evc-voorjaarsdagen-amsterdam-2009/viral-diseases-of-horses (Accessed: 17 September 2024).

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Every spring the European Veterinary Conference Voorjaarsdagen used to organize. Important goals of the Voorjaarsdagen Conference were to build friendships between veterinarians at a national and international level, to enhance the quality and availability of veterinary medicine and surgery, and to foster the exchange of scientific information among veterinarians.  The activities of the European Veterinary Conference have ceased with the last meeting in 2019.

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