Equine Rhinopneumonitis (Contagious or Viral Abortion, Snots) is
a disease caused by equine herpes virus Type 1 (EHV-1). Each
subtype produces different symptoms: Sub-type 1 is the strain
that causes abortions, respiratory, and neurologic disease, while
sub-type 2 is just a respiratory strain.
Rhinopneumonitis occurs in horses of all ages but is more common
in horses less than three years old. Sporadic outbreaks come from
inhalation of the virus particles. After incubation of two to 10
days, symptoms for the respiratory subtype are a fever of 102o to
107o F with a bacterial infection or "snots." Recovery provides
immunity for only two to three months.
Respiratory problems are more severe in foals, with infections
near birth producing weak foals that die within 24 hours.
Following a respiratory infection, the virus can cause abortions.
Death of the fetus occurs two weeks to four months after exposure
to the virus, or during the last three months of pregnancy.
Abortion storms have a sudden onset with no additional clinical
signs. The foal dies from asphyxiation by the premature
separation of the placenta.
Occasionally, the virus attacks the central nervous system,
causing mild incoordination, paralysis of the rear legs or
Two vaccines are available: a killed vaccine and a modified-live
The killed vaccine is given to pregnant mares during the fifth,
seventh and ninth months of pregnancy. The modified-live vaccine
can be given every three months. Foals should be vac-cinated at
three months of age and again at four months. Horses should be
given boosters every year.
Prevention includes isolating arrivals and dividing the
horses into small groups. The disease is difficult to confirm by
diagnostic procedures unless proper tissue and blood samples are