University of Vermont AAHS

Ask the Vet

By David Cross, Ph.D., D.V.M.
AAHS Vice-President for Veterinary Services
Associate Professor of Veterinary Medicine
University of Missouri School of Veterinary Medicine
Columbia, Missouri

[reproduced from Spring 2002 Caution:Horses]


Q: Our veterinarian recommended that we vaccinate for West Nile Virus and EPM.  Since we have a summer camp and use leased horses, should the owners of the horses vaccinate them before they arrive at the camp?  Should all horses receive WNV and EPM vaccinations and what is the cost?  I have seen a paste for EPM.  What is that?

A: West Nile Virus arrived in the United States about three years ago in the New York area.  It affects birds, especially crows, causing death.  It also affects horses and humans with encephalomyelitis and has been responsible for several human and equine deaths.  It is rapidly spreading west, having arrived in Missouri already.  Mosquitoes are the insect carrier of the virus.

            Fort Dodge received a provisional license last year to produce and sell a vaccine.  This means that the vaccine is safe but has not yet been proven to prevent West Nile Fever. It is the only product available.  Horses are administered an initial vaccination followed three to six weeks later by a booster.  An annual vaccination is recommended thereafter.  The cost of the vaccine varies but expect one dose to cost between $15 and $20. 

            Since this is a provisional vaccine, the decision to administer it should be made in consultation with your veterinarian.  Since West Nile is rapidly spreading and is a new disease to this country, I would vaccinate my own horses.

            There is also an EPM vaccine available, another Fort Dodge product that has a provisional license.  Again, this vaccine is safe but has not been proven to prevent EPM.  As with the WN vaccine, you should consult with your veterinarian about its use.  I believe it is more expensive than the WNV vaccine, but check with your veterinarian for details.  Please note that the vaccine will not cure a horse affected by EPM.  The EPM paste is not a vaccine but part of a treatment (Marquis).  An affected horse receives the paste daily for 28 days with a cost in the neighborhood of $700-$800. 

            Horses being moved onto any property should have already been vaccinated for Tetanus, EEE, WEE, flu and rhinopneumonitis.  Horses coming to a summer camp should have been vaccinated in the spring but should receive flu and rhinopneumonitis boosters about two weeks before being moved.  Who pays for that and veterinary care should be agreed upon between the lessor and lessee as part of the lease agreement.

Q: My farrier was talking about white line disease recently.  What is it, is it contagious and what is the treatment? 

A:   The white line is the junction of the sole with the white soft horn of the hoof wall and is the landmark used by farriers to drive horse nails.  White line disease is not contagious but is a result of chronic founder.  In a foundered horse, this area is especially susceptible to infection and abscessation because of the separation of the lamina that can be seen when the hoof is cleaned.  “Seedy toe” is another name for this condition.  Keeping the foot clean and dry might help but it is something that has to be continually examined, especially if the separation is severe.

            Another problem associated with the white line is the migration of small pieces of gravel or sand up the hoof wall causing the formation of a laminar abscess or “gravel”.  These are extremely painful and are treated by trying to open the abscess at the solar surface or allowing it to rupture at the coronary band.  Since it can be difficult to dig out a gravel in comparison to a solar abscess, soaking in warm water and Epsom salts will hasten the resolution of the problem.  If the gravel is dug out, there will be a solar defect until it grows out.  If the gravel ruptures at the coronary band, there will be a hoof wall defect until it grows out.  Consult with your farrier and veterinarian for the best approach to dealing with a gravel.  They are usually not a major problem once the abscess starts to drain and the pressure is relieved.

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