Mostly transmitted during the later stages of summer, the West Nile Virus (WNV) causes one of the deadliest viral infections to horses. In recent years, confirmed cases of this equine infection have been going up across many regions in the US.
Among the first major steps you can take to help safeguard your equine stock from this dangerous virus is working to reduce the number of mosquitoes in your horses’ environment, as well as destroying their possible breeding locations.
According to equine experts from the James L. Voss Veterinary Teaching Hospital at Colorado State University (CSU), the two most important ways you can help your horses avoid WNV infection include:
- Reducing their exposure to mosquitoes, and
- Vaccinating them against the WNV virus.
How to reduce your horses’ exposure to mosquitoes
- Stall your horses during the peak mosquito activity periods, especially at dawn and dusk.
- Do away with all the areas of stagnant water, including disposing of any discarded tires and changing birdbath water and your horse’s water in tanks at least once per week.
- Use fans built for agricultural or outdoor use on horses when stabled.
- Make use of insect repellants specially designed for horses. A fly sheet and mask will also help minimize equine exposure to mosquitoes.
- Install incandescent bulbs around your horse’s stable perimeter.
- Eliminate any dead birds from your property; they are part of the virus cycle. Wear rubber gloves (or turn a plastic bag inside out and use it) when picking up a dead bird. For more information on how to test birds for the WNV virus, consult a public health officer.
Vaccinating your horses against WNV
Based on safety research conducted for protection against WNV as well as their efficacy, currently only 4 vaccine formulations have been licensed for equine use. The American Association of Equine Practitioners recommends all horses to be vaccinated against WNV at least once per year, whatever their geographical location in the US, with this vaccination going side by side with the preventive strategies against mosquitoes that we’ve highlighted above.
NOTE: Vaccinating your horses against other causative agents of equine encephalitis such as Eastern, Western or Venezuelan equine encephalitis DOES NOT safeguard them from WNV.
Make sure your horses get their first WNV vaccination series (or booster vaccine) before exposure to the virus. This means that they should have been vaccinated prior to the setting in of the mosquito season. And if your mare is pregnant, contact a vet for the most effective and secure method of WNV vaccination. Generally, reproductive specialists recommend avoiding all kinds of vaccines during the first 40 days of a pregnancy.
According to recent studies, a 3-month old foal is grown enough to receive vaccination against WNV safely. Actually, vaccinating them early helps build stronger immunity against the virus.
Diagnosis and treatment of West Nile Virus
Key clinical indicators and symptoms of WNV infection include fever, inco-ordination or ataxia), anorexia, twitching of muscles, head-pressing, hyper-excitability, lethargy, recumbency or inability to rise, and finally death.
Diagnosis involves a combination of observation of these signs and positive diagnostic tests on a suspected horse’s blood and/or cerebrospinal fluid.
While WNV treatment is basically supportive with some involvement of a number of licensed anti-inflammatory drugs and fluids, some horses may need to be hospitalized. In some cases, a horse may also need to be assisted with a sling in order to be able to remain standing. You can also consult your vet about the use of clinical products that provide antibodies against the virus.
NOTE: It’s also not true that an infected horse can infect other horses in the neighboring stalls or even people with WNV because the virus is only spread via an infected mosquito’s bite, never through contact with the affected horse.
In conclusion, vaccinating your horse against WNV is very important. Work with your vet to determine the most appropriate plan for a mare in foal, as well as other horses if need be. Your vet will also be best placed to help with advice on the best WNV strategy with very young horses. Finally, remember that WNV can only be transmitted via mosquito bites.
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