Horse Health: What is EHV and EHM?

Exactly what is Equine Herpes Virus (EHV) or the mutated EHM -- and what are the symptoms? Equine Herpes Virus (EHV) is a common DNA virus that occurs in horse populations worldwide.Exactly what is Equine Herpes Virus (EHV) or the mutated EHM -- and what are the symptoms? Equine Herpes Virus (EHV) is a common DNA virus that occurs in horse populations worldwide.

Story originally posted by: by Dr. David L. Biehl, DVMwww.heartlandvetsupply.com

Exactly what is Equine Herpes Virus (EHV) or the mutated EHM — and what are the symptoms?

Equine Herpes Virus (EHV) is a common DNA virus that occurs in horse populations worldwide. The two most common strains are EHV-1, which causes abortion in pregnant mares, respiratory disease and neurologic disease; and EHV-4, which usually causes respiratory disease only but can occasionally cause abortion.

Respiratory disease caused by EHV is most common in weaned foals and yearlings, often in autumn and winter. Older horses are more likely than younger ones to transmit the virus without showing signs of infection.

Although EHV-1 causes outbreaks of abortion, EHV-4 has only been associated with single occurrences and is not considered a risk for contagious abortions.

EHV-1 myeloencephalitis results from widespread vascular injury after damage to the vascular endothelium of the blood-brain barrier. Neurologic signs result from vasculitis, thrombosis, and necrosis of neurologic tissue.

Herpesvirus myeloencephalitis cases occur singly or as outbreaks affecting 20-50% of the population. They may or may not be associated with a previous or ongoing EHV-1 respiratory disease outbreak.

Clinical Signs and Symptoms:

Fever – commonly precedes other clinical signs, but may be the only clinical sign and goes undetected, therefore, temperature monitoring twice a day is suggested. Persistent Temperatures of 101.5 should be of concern in horses 3 months and older unless it is really warm out .Take temps first thing in the morning for the most accurate readings

Respiratory disease

Coughing and nasal discharge

Weakness

Jaundice – yellowing of gums and area around the eyes

Respiratory distress

Central Nervous System (CNS) signs: stumbling or difficulty getting up (death commonly occurs within 3 days)

— Neonatal foals infected in utero are usually abnormal from birth

— Older foals show nasal discharge

Abortion

Usually no warning signs of impending abortion

Typically occurs late pregnancy (8+ months); occasionally as early as 4 months.

Neurologic disease: EHM

— Incoordination of the hind (and occasionally fore) limbs

Usually unable to get there back legs to work then spreads to the front legs

— Urine retention/dribbling

— Bladder atony difficult urination

— Recumbency – lay on their side and can't get up

— Neurologic signs may be preceded by fever and respiratory signs

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Dr. Biehl has been an Equine Practioner in Nebraska for 35 years and continues in Equine practice as an Equine Healthcare Consultant for Heartland Veterinary Supply and Pharmacy. Visit them here to find out more: www.heartlandvetsupply.com