COVER 1 - NMHBA SUMMER 2017 low res

“We typically
see outbreaks
of flu in young
horses two to
five years old,
in training or
congregated
for racing,
showing, etc.”
The influenza virus denudes the
epithelium, destroying the cilia and
removing that defense mechanism. “The
serious cases of influenza are the ones that
develop secondary bacterial infection in the
lungs (pneumonia),” explains Crisman.
You don’t want the horse exercising,
breathing deeply, drawing dust or debris
down into airways that cannot fully protect
against these particles getting down into
the lungs. If you exercise him too soon,
you may set him up for a more serious
respiratory infection. Many riders, especially
those with competition schedules, don’t
give the horse enough time.
“We typically see outbreaks of flu
in young horses two to five years old,
in training or congregated for racing,
showing, etc. Their job is to perform/make
money, and it’s hard to convince people
they need to rest a horse this long because
the horse feels better after just a week or
so and looks normal. But he’s not,” says
Crisman.
Prevention
There are two ways to protect your
horse—with vaccination and with attention
to biosecurity. “Vaccination is helpful, but
it simply puts a protective barrier around
the horse for a short period of time. It is
not the greatest limiting step for disease
prevention,” he says.
“I can’t emphasize enough the
importance of biosecurity, but this is
the hardest thing to get people to do.”
Keeping new arrivals separate from your
other horse for two weeks, quarantine of
sick horses, etc., is a good technique to
use for biosecurity. “New horses need to
be isolated, checked closely and monitored
to make sure they are staying healthy,
with temperature taken twice daily. Also
important is submitting nasal swab samples
if a horse does get a fever so that we know
what it is. There are many diagnostic labs
that can help us identify it. Our strategy for
treatment and care will be different if it’s
herpes or influenza,” he says.
Disinfection is equally important when
there is a sick horse, as it ensures the virus
is not spread to other horses on shared
equipment. Some people just use bleach
solutions, but organic matter, such as straw
and manure, makes bleach ineffective.
“Fortunately, the influenza virus is not
very hardy in the environment and, if it is
sitting on a surface somewhere, it won’t
last a long time. Equine Influenza is
primarily spread by nasal secretions from
one horse to the mucus membrane of the
second horse. It’s not like strangles, which
can survive in the environment or in water
buckets a lot longer,” says Crisman.
Vaccination can be helpful. For instance,
vaccination of mares can help protect their
foals. “If a mare is vaccinated during her
last trimester, she passes immunity to her
foal via colostrum. In this situation, foals
will have immunity up to about five or six
months of age. If there are other horses on
the farm traveling in and out, this could
put foals at a higher risk. Depending on
exposure risk, some people start vaccinating
their foals at five or six months of age, or
may wait until they are eight months of
age,” he says.
Influenza is a risk-based vaccine. The
horses most at risk should be vaccinated
three or four times a year. For a backyard
horse that never goes anywhere and might
only be exposed unintentionally by an
unforeseen encounter with other horses,
annual vaccination might or might not be
adequate.
“Decisions regarding influenza
vaccination should be made by the owner
in consultation with his/her veterinarian
as to how they will handle vaccination.
Influenza is a risk-based vaccine
(rather than one of the core vaccines
recommended by the AAEP for every
horse), and not very immunogenic,” says
Crisman.
“Some of the other vaccines, like
tetanus, EEE, WEE and rabies, are highly
immunogenic; the body mounts a good
The equine influenza vaccine is a cheap insurance
policy and can prevent a large medical bill should the
horse become ill.
SUMMER 2017 31