| Equine Diseases
Equine Viral Respiratory Diseases:
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In discussing viral respiratory disease in horses, it
is important to clear up a common confusion. Although
often administered together in the “Rhino/Flu” fall
shots, there are actually two major respiratory viruses
we are worried about. One of them is Equine Influenza
Virus. The other is Equine Herpes virus types 1 and 4,
also known as Rhinopneumonitis. Although these viruses
share many characteristics, there are several key
differences when it comes to controlling outbreaks.
Equine Influnza is the most common cause of viral
upper respiratory disease in horses. Onset is usually
sudden with only 1 to 5 days between exposure and
clinical symptoms occurring. The symptoms include fever,
dry cough, and nasal discharge, as well as secondary
signs such as anorexia and muscle pain. Healthy adult
and vaccinated horses usually have an uneventful
recovery, but foals,geriatric, and immune-suppressed
animals can become very ill or die from the disease.
Equine Influenza virus can be spread by droplets ie:
mucous, saliva, or similar from an infected horse, or by
fomites. Fomite is a scientific term for infectious
particles such as viruses that are spread from an
infected animal to a carrier object, and then from the
carrier object to the next animal. Fomite spread can
occur when buckets, lead ropes, brushes and other
equipment, barn cats and other wandering animals or
people have contact with an infected horse and then have
contact with a non-infected horse. This means that it is
not necessary to have an infected horse on the property
to spread the disease. The virus can live up to 48 hours
outside the horse, so there is a real risk of
transmission by fomites.
 Vaccinating
is the first step toward protecting your barn. The
higher the percentage of vaccinated horses in a given
population, the less likely the disease is to spread in
that population. Influenza will generally spread very
rapidly in an unvaccinated population In general; horses
that are competing or are frequently exposed to new
horses should be vaccinated every 4-6 months. The older
horse that does not travel much may be fine with an
annual vaccination, but other horses should be
vaccinated at least biannually. Pregnant mares should be
vaccinated with a killed vaccine 6-8 weeks prior to
foaling to insure adequate immunity. It is now
recommended that foals born to mares vaccinated for
influenza not get their first influenza vaccination
until they are 9-11 months old. This is because the foal
has antibodies from his mother which may interfere with
the vaccine. It is best to wait until the antibodies he
received from his mother are fading before vaccinating.
However, the foal from an unvaccinated mare should be
vaccinated early and often. Vaccination plays a big role
in preventing influenza outbreaks.
Treatment of horses with influenza is aimed at
reducing fever , due to the dangerous side effects of
high fevers in horses( laminitis, coagulation issues)
and preventing the development of more serious bacterial
infections in the lungs. Non-steroidal anti-inflammatory
drugs such as Banamine can reduce fever and accompanying
discomfort. Sometimes antibiotics will be given to treat
or prevent bacterial infections. In addition, rest and
plenty of fluids is important for the infected horse.
Generally, one week of rest for every day of fever is a
good guideline. Most previously healthy, vaccinated
adult horses will recover without any lasting problems.
 Rhinopneumonitis
is caused by equine Herpes virus types 1 and 4. It is
most common in horses less than 3 years old. It is not
as likely to result in large outbreaks as Influenza is.
The most common sign is nasal discharge. Fever, ocular
discharge, lymph node enlargement, and lethargy may also
occur. In addition, equine herpes virus infection can
cause abortion in pregnant mares. Equine herpes virus
type 1 can also cause neurologic disease that can result
in signs ranging from incoordination to inability to
rise or move.
Equine herpes virus, presents a special sort of
challenge when it comes to controlling disease. This is
because herpes viruses develop what is called latency.
This means that after infecting an animal, the virus can
live in certain body tissues and be protected from the
horse’s immune system. The virus lives undisturbed
inside the horse, and at times of stress, the horse may
develop signs of infection, or may simply secrete virus
that can infect other horses, without getting sick. This
characteristic of the herpes virus makes it very
difficult to identify potential carrier horses, and very
difficult to eradicate the disease from horse
populations. Like influenza, it can be spread from horse
to horse by droplets, or can be spread by fomites. It
may survive up to 35 days outside the horse, so
transmission between horses and farms by humans and
objects is an important source of transmission.
As with influenza, vaccination is important in
preventing outbreaks of Rhinopneumonitis. Vaccination
should be done every 4-6 months for horses that are
competing or frequently in contact with strange horses.
Rhino can affect pregnant mares and cause abortions so
vaccination at 5, 7 and 9 months with a Rhinopneumonitis
vaccine designed for pregnant mares is necessary for
broodmares. Foals should receive their first vaccination
for Rhinopneumonitis at 4-5 months of age, with two
booster shots at 6-7 and 8-9 months of age. Vaccination
is less effective at preventing the neurologic form of
the disease.
Treatment for Equine Herpes Virus infection is
similar to that for Influenza. However, horses with the
neurologic form of the disease often need intensive
treatment.
 There
are other steps you can take to minimize disease risk.
First, any new horses or horses that have been away at
events should be quarantined for at least 14 days upon
arrival to a facility. This means they have no face to
face contact with other horses. In addition, try to
handle, feed, or groom new horses last, and then wash
your hands well to decrease the risk of transfer of the
virus. Each horse should have his own bucket, lead rope,
halter, etc that are not shared. If this is not
possible, items should be disinfected prior to passing
between horses. This is especially true of items that
have face contact, such as bits. Dilute bleach is an
effective disinfectant, but items must be free of dirt,
hair etc before being disinfected. General good
management practices, such as keeping pregnant mares and
mares with young foals separated from other animals,
segregating animals by age group, and reducing stress by
preventing overcrowding and providing appropriate feed
and preventative care will all help reduce the risk of
an outbreak. You can talk to your veterinarian for more
information about protecting your horses from
respiratory disease this winter.
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Denise Bickel DVM
Whole Horse Veterinary Services
Phone # 517-474-4050
Fax # 517-764-7710
3906 Seymour Rd
Jackson, MI 49201
EMAIL US
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