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[RC] EHV-1 A Must Read On Vaccinating Part 2 of 4 - Don Huston

                          
                          Part 2 of 4

The neurological form of the disease tends to occur in sporadic but
deadly clusters. The first horses involved tend to be some population of
horses subject to typical show or race stress. The typical stresses felt
by this population include, but are not be limited to: intermittent
travel, social isolation (stall confinement), exposure to a changing
population of equine neighbors, exposure to other communicable diseases,
performance in the face of low or moderate grade musculo-skeletal
injuries, performance enhancing medications, a diet too rich in cereal
grains but low in anti-oxidants, short or little breaks from the same
training routine and little to no time spent outside, grazing green
grass. There is often a history of a vaccination within the preceding 60
days, sometimes even for Rhinopneumonitis (EHV). Once started, infection
can spread by direct contact, aerosolized particles or mechanical
vectors. The virus is not especially long lived in the environment and
is susceptible to almost all properly applied disinfectants.

In 2004 there was an outbreak of the neurological form of EHV1 at Finley
University in Ohio. That outbreak claimed the lives of over 20 horses.
This was despite heroic 24 hour care provided by the two veterinarians
on staff. What was note worthy about that outbreak was that both the
morbidity (attack rate) and mortality (death rate) were higher in horses
vaccinated for the disease than among those never vaccinated (Dr.
Stephen Reed, Ohio State University, January, 2004, personal
communication). I am aware of
how discouraging that statement reads to Vets and the public alike. If
vaccinated horses are at, the very least, not more immune to the
neurological form of EHV1, then what options do we have? We do have
options available to us. These include the proper use of vaccines and a
larger view of health. The answer to this puzzle lies in the way
vaccines achieve their effectiveness.

Vaccines present to the body a modified form of the infectious agent
that the body can recognize as foreign and wage a brief and successful
battle. When exposed to the same infectious agent in the future (that
is, exposed to the disease), the response will be quicker and more
efficient. The body wins the battle without becoming sick at all or,
perhaps, not as sick. Each and every vaccination causes a transient dip
in the body's level of immunity as the body fights the battle and
processes the information for the future use. The more vaccines that are
grouped together in one vaccine, the more profound are the transient
negative effect upon the bodies' immune status. Grouping vaccines
together also negatively impacts the bodies' ability to respond to each
individual vaccine. For the sake of convenience and economy, most of our
equine vaccines are grouped together in batches. For example, the
commonly used 4-way vaccine contains Eastern and Western
encephalomyelitis, Influenza (flu) and tetanus. We often add other
vaccines at the same time such as Rabies or Rhino. There is now on the
market a 6-way vaccine which adds Venezuelan encephalomyelitis and Rhino
to the already over-loaded vaccine. I would advise you to try to limit
your use of these vaccines. Do not use the 6-way vaccine; the downside
is greater than the potential benefit. Try at the very least to avoid
vaccination with more than one vaccine at a time. Do not go to vaccine
clinics where horses are vaccinated for many diseases at the same time.
If your veterinarian performs your vaccinations, see if you can
influence him to not group vaccines. Perhaps if you offer to van the
horse to his place of business or allow him to send a technician over to
perform the mechanical act of giving one vaccine at a time. More effort
will lead to better results and fewer complications.

The sense of urgency that we sometimes feel as regards vaccinations is
generally due to external perceptions about the need to vaccinate. This
is often due to the need to adhere to some new requirements such as
travel to a foreign country, a different state or to a new barn that has
more stringent vaccination requirements. The most dangerous sense of
urgency comes as an urge to vaccinate because of a fear of recent
exposure to disease. The desire to vaccinate in the face of a potential
recent exposure is an understandable one. After all, we are helping him
to resist the disease, right?



                          See Part 3


Don Huston  <donhuston@xxxxxxx>