APHIS
Factsheet
Veterinary Services
May 2007
Questions and
Answers: Equine
Herpesvirus
Q. What is equine herpesvirus type 1?
A. Equine herpesvirus type 1 (EHV-1) causes a dis-
ease of horses called equine rhinopneumonitis. It is
found in horses worldwide but does not affect humans.
EHV-1 usually causes respiratory symptoms with
fever, but it can also cause abortion, nervous system
(neurologic) disease, or death.
Q. Are there different types of EHV-1?
A. EHV-1 has several different strains, and new
strains can develop from natural mutations. These
strains or mutations are thought to cause outbreaks of
the disease. The neurologic form of the disease can
cause a wide variety of symptoms, including incoor-
dination, weakness or paralysis of the hind limbs and
tail, incontinence, and loss of skin sensation. The
horse may lie down and not be able to get up. The
paralysis can be progressive and in some cases, the
animal may die.
Q. How is EHV-1 spread?
A. The virus can spread via contact with an infected
animal, through the air, via contaminated equipment,
or via a handler’s clothing and hands. An infected
animal can be latently infected and sporadically shed
the virus, or show only mild clinical signs.
Q. Why is there a concern about EHV-1?
A. The neurologic form of disease caused by EHV-1
is emerging worldwide with outbreaks having a higher
frequency than has been reported previously. Recent
outbreaks may be related to a mutation of the EHV-1
virus that allows it to multiply more efficiently. More
horses are dying from this form than would normally
be expected, and the disease also demonstrates the
ability to affect horses of all breeds, ages, and vacci-
nation status. This new form therefore has the poten-
tial to cause high losses in the U.S. horse population.
Q. What is the Federal role in addressing EHV-1
outbreaks?
A. EHV-1 is found throughout the United States and
outbreaks are usually handled by the States involved.
In some instances, however, shipme