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Equine Herpes Virus Myeloenceophalopathy (EHV 1)

Equine Herpesvirus, Type 1 (EHV-1) is a virus that causes rhinopneumonitis and equine abortions.  Rhino is a viral “cold” horses catch from other horses.  Horses at risk are those that have contact with many other horses or are in stressful situations, such as show barns or at the track.In recent years we have seen a mutation occasionally occur in the EHV-1 virus.  This mutation allows the virus to infect the central nervous system of horses, causing severe neurological symptoms in addition to the traditional symptoms of fever and an upper respiratory infection.

Both forms of the virus are transmitted by the same means (nose-to-nose contact) and both are highly contagious.

This form of herpes emerged decades ago, and in recent years we have seen an increase in the frequency and severity of occurrence.  In 2003, 2004, 2005, 2006, and 2007 significant pockets of the disease have been documented.  In 2006-2007 alone, Florida, Connecticut, California, Minnesota, New Hampshire and Maine all saw cases.

In Maine, the first case of EHV-1 was diagnosed on a farm in Rome.  The horse confirmed to have the disease was euthanized.  A stable mate had died several days previous, and it is assumed based on symptoms that that horse died from EHV-1.  The farm was quarantined.

Two horses from that farm moved to a farm in Wales prior to the confirmed diagnosis (and the implementation of the quarantine.  One of those horses developed symptoms eight days after moving to Wales.  The farm in Wales was immediately quarantined.

Horses on both farms were monitored for symptoms, and swabs of nasal secretions and blood samples were tested for the presence of the virus.  So far, no further cases have been detected.

So what does this mean for horses in Maine?  How safe are we?

There are several vaccines available that provide protection against the abortions and rhinopneumonitis seen with EHV infection.  Their ability to protect against the neurological form is unknown, though early use suggests that the vaccine provides some increased protection. We at Maine Equine Associates use FluVac innovator by Fort Dodge.  We feel this is a safe vaccine that balances the risk of vaccination with the risks of acquiring the disease.

Equine Herpesvirus Myeloencephalopathy is a disease most often identified in the winter and early spring.  The virus likes cool damp dark places, and the dry warm sunny conditions of summertime quickly reduce the risk of infection.

Even though your horse is vaccinated, you should exercise caution around other horses.  Nose-to-nose contact is the way the disease is spread.  This means if you pet another horse’s nose, then return to your hose, you have facilitated nose-to-nose contact.

Above all, call or email us with your questions and concerns.  We are constantly in contact with our colleagues here and around the country, and we are always happy to share that information with you.



-David A. Jefferson, DVM

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