1. How do the horses become infected with West Nile virus?
The same way humans become infected-by the bite of infectious mosquitoes. The virus is located in the mosquito’s salivary glands. When mosquitoes bite or “feed” on the horse, the virus is injected into its blood system. The virus then multiplies and may cause illness. The mosquitoes become infected when they feed on infected birds or other animals.
2. How does the virus cause severe illness or death in horses?
Following transmission by an infected mosquito, the virus multiplies in the horse’s blood system, crosses the blood brain barrier, and infects the brain. The virus interferes with normal central nervous system functioning and causes inflammation of the brain.
3. I have a new horse with no vaccination history, how should I proceed?
If no history is known it is safest to assume previous vaccinations have NOT been given and give the two shot series of the Fort Dodge or one of the Vetera to establish protective titers. In some cases a simple phone call to the previous owner to establish past vaccination history can be helpful in creating a vaccination protocol for your new horse.
4. Can pregnant mares be vaccinated?
Yes, there is NO scientific evidence that West Nile vaccinations cause abortions or deformities.
5. What age should I begin vaccinating foals?
The American Association of Equine Practitioners (AAEP) recommends that foals start the vaccination series for West Nile at 5 months.
6. My horse is vaccinated against eastern equine encephalitis (EEE), western equine encephalitis (WEE), and Venezuelan equine encephalitis (VEE). Will these vaccines protect my horse against West Nile virus infection?
No. EEE, WEE, and VEE belong to another family of viruses for which there is no cross-protection.
7. Is West Nile infection treatable?
There are several treatments aimed at minimizing symptoms and arresting progression. At this time there is no specific cure for the disease. While some horses make a complete recovery, others survivors may have long term deficits. Approximately 33% of horses that contract West Nile disease will die or be euthanized.
8. There is a horse in my barn diagnosed with West Nile, is my horse at greater risk?
The virus is not transmitted from horse to horse. Horses are known as “dead-end hosts”. This means that horses do not create enough virus particles for mosquitoes to transmit West Nile virus from an infected horse to a healthy horse. However the conditions in your area may be right for local birds to carry the disease. Your best protection is proper vaccinations and strict mosquitoe control measures.
Dr. Garfinkel is a graduate of the highly regarded College of Veterinary Medicine at North Carolina State University. She has been practicing in the East County of San Diego since 2000, and has built a reputation of providing high quality and compassionate care.
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