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I just attended an equine health conference at the
University of Florida, Gainesville. It is put on by the American Quarter Horse
Association. It's a wonderful program.
Anyway, we discussed WNV at length with Dr. Maureen
Long. It is a virus that gets into the central nervous system and can cause
death very quickly. Young horses and horses with compromised immunity are most
susceptible. Even horses who received the vaccination have gotten seriously ill
and or died. Overall though, any horse is at risk.
We were shown pictures and movies of horses in the
hospital who were infected and I am telling you it was sad. Because it is a
neurological virus, they can become paralyzed much like with EPM. One mare was
eating her hay, went into a blackout, (still standing) and then about 1-2
minutes later opened her eyes and began eating as if nothing ever happened. One
very young colt, 3 or 4 months old would be standing and then all of a sudden
collapse. He lived, thank God but he was one sick little horse.
I thought it was more like a flu virus. I had no
idea how bad it could be. I have not vaccinated my horses for it because last
year when the vaccine came out, it had not been tested on many horses and it
wasn't known if it actually protected the horse. The Vet who gave the lecture
said the best defense is to keep your horses in when mosquitoes feed, don't
leave any standing water on your property and spray your horses as often as you
can. (Fly spray but not with DEET) She never really came out and said to get
your horses vaccinated, or if she did I missed that. The literature did say the
best time to vaccinate is BEFORE mosquito season. Horses that have had the virus
and recover have long-term immunity against WNV and should not require
immunization.
Some of the signs to look for are lethargy, not
eating or drinking, low grade fever, periods of hyper excitability,
apprehension and or sleepiness. Also fine twitching of face (lips) and neck
muscles, temporary blindness, drooling and of course the neurological signs
like, wobbling or going down completely. If you have the slightest idea
that your horse may have it, I would call the vet immediately and have him
tested. The sooner they catch it, the better the outcome.
The criteria most important for a diagnosis of WNV
is the presence of balance problems, weakness, muscle tremors, and behavioral
changes with fever. Some of the horses we saw were so sensitive to sound and
movement it was almost like they had rabies.
One of the tests could show a positive
MAC-ELISA> 1:400 or a four-fold change in the PRNT titer. CSF analysis
demonstrating high mononuclear count and/or high protein.
The focus of therapy is to decrease brain swelling,
treat fever and provide supportive care. Medications would include Banamine,
dexamethasone, DMSO and maybe IV fluids and feeding if the horse isn't doing
either on it's own.
I still have not vaccinated my herd. If this season
shows that the horses who have been vaccinated were indeed protected, and not a
large percentage of them became ill from the vaccine, then next year I will
probably get the shots.
You can call any large animal hospital and talk to
the extension vet to get info on the disease in your area.
I hope this helped.
Lisa Salas, The Odd FArm
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