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Equine Neurological Viruses

What you need to know!

With the recent Diagnoses of several equine neurological diseases in Southern Ontario this past year, its no wonder that many horse owners are concerned. In this season's Newsletter we'll discuss the different neurological diseases ( also known as "Sleeping Sicknesses") and untangle some of the mysteries around them. Neuro diseases can be fatal, but with education and prevention, we can decrease the risk of your equine companion becoming affected!

What are the neurological disease viruses that affect horses?

In Southern Ontario there are four main neurological diseases that can be seen in horses: Eastern Equine Encephalitis (EEE), West Nile Virus (WNV), Equid Herpesvirus 1 (EH1), and Rabies. While all four can appear very similar in terms of symptoms, there are some subtle differences that your veterinarian can use to help differentiate them. The main thing for owners to know is however it that if any of the following signs are in seen in their horses, they should contact there veterinarian right away.

Signs to look for are:

  • Staggering, tripping or unsteadiness on their feet

  • Pressing their head against a stall wall or other structure

  • not lifting the tail to urinate, defecate or swat flies

  • Muscle twitching

  • Over-reaction to things that normally wouldn't bother them or acting dull and non-reactive to everything

  • Difficulty eating

Now that you know what signs to look for, Let's talk about how these diseases are transmitted and how they can be prevented!

Disease Transmission - How does my horse get a neurological disease?

While all four of the aforementioned viruses can cause similar symptoms, they can be transmitted in slightly different ways. For EEE and WNV birds and mosquitos are the primary disease reservoirs, able to transmit the viruses between one another and pass along to other species like humans and horses. Horses and humans however, are considered "Dead end Hosts" meaning they can not pass on the virus to anyone else, even members of their own species EVH1 causes disease through inflammation of the veins and arteries, setting apart from other strictly neurological viruses. As such it can be transmitted from horse to horse through nasal, ocular, and reproductive secretions, making it harder to control as an outbreak. As with other species, Rabies is transmitted through the saliva of affected animals (Most commonly raccoons, Possums, and bats) that might bite a horse.

Prevention Methods - How to prevent your horse from contracting these diseases?

As with many viruses, there are very effective vaccines available for EEE, WNV and Rabies. Care must be taken however to follow the full set of vaccinations protocols including the appropriate boosters and annual re-vaccinations. the Large majority of horses that contract and die from these viruses are either unvaccinated or only received a single shot without the recommended boosters. A Vaccine for EH1 is still being developed.

Although the vaccines available are very effective, no vaccine is considered 100% protective. As such, there are several other ways to help lower the risk even further. Because mosquitos are far more likely to bite your horse than a bird is, reducing the amount of standing water in the area is an important preventative to decrease the mosquito population. Fly sheets and sprays can also be helpful. With EH1 early diagnosis followed by strict quarantine is a very important tool in preventing the spread of the virus as it can be easily passed from horse to horse. Keeping horses in at night or in pastures farther away from forested areas can help lower the risk of bites from rabid animals.

Can my horse be treated?

While prevention is by far the best way to keep your horse safe some of these viruses can be treated, though the prognosis is especially poor for those with EEE and Rabies. Those who do recover from WNV and EH1 may never return completely to normal. Treatment for any of these diseases is mainly symptomatic, meaning anti-inflammatories, fluid therapy, anti-virials and other supportive methods until the virus has run it's course.

Take home message

Neurological viruses can be a scary subject but by staying educated and using the appropriate prevention methods we can work together to lower the risk and slow the current outbreaks. Don't hesitate to contact your veterinarian today with any questions!

Written by Dr. Emily Zakrajsek

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