October 2009

Rabies in Horses

By Charlene B. Cook DVM

Remember that old movie Ole Yeller? Ole Yeller was a stray dog that became the family pet on a farm in Texas. Ole Yeller fought off a mad wolf to protect his family but then he becomes rabid. The movie ends as poor Travis has to shoot the beloved family pet. Ole Yeller would have been saved if he had been vaccinated but that would spoil the movie plot. Did you know that your horse can develop rabies? Did you know that Rabies is always fatal? Here are some of the facts and myths about Rabies that you should know to protect yourself and your horse.

Rabies is caused by a virus, specifically a Lyssavirus from the family Rhabdoviridae. Rabies virus is present worldwide except the United Kingdom, Ireland, Australia, New Zealand, Iceland and Scandinavia. Each year 55,000 people die from Rabies. 95% of all human Rabies cases are in Asia and Africa. In 2007 there were 7,258 cases of animal Rabies in the United States and 1 human case. In the United States 93% of all animal cases occur in wildlife and 7% occur in domestic animals including dogs and cats.

The majority of Rabies cases in this country occur in the eastern states from Maine to Florida, raccoons are the primary source of Rabies in our area. Skunks are an important source of Rabies in Tennessee and Kentucky. A large number of Rabies cases are also located in Texas.

Rabies is a zoonotic disease; this means that the disease may be transmitted from animals to man under natural conditions. In fact all mammals can get Rabies. Wildlife serves as the virus reservoir. The virus is transmitted when an infected animal bites another mammal. The virus replicates in the muscle tissue at the bite site. The virus then travels up the peripheral nerves to the spinal cord and finally into the brain. Once the virus enters the brain the animal will start to show clinical signs. The elapsed time from the original bite to the development of clinical signs can occur in as little as 2 weeks or take as long as 6 months. If an animal is bitten on the head the virus has a relatively short path to the brain and clinical signs will develop much sooner than if the animal were bitten on the hind foot.

 The Rabies virus does not survive in the environment. Once outside the host, the virus is rapidly deactivated by drying and ultraviolet radiation. Rabies can only be transmitted by direct contact with saliva, mucous membranes (eyes, nose or mouth) or central nervous tissue. A person that was exposed to the blood, urine or feces of a rabid animal is not at risk. Rabies cannot penetrate intact skin. In addition the virus does not survive on the coat of an animal.

Rabies has typically been classified into two forms of the disease: Dumb and Furious. Ole Yeller had the furious form, hyperexcitable, enraged, and aggressive. In the dumb form the animal may show only depression, head pressing, circling and weakness. In horses there are no set rules, a horse with Rabies can show any set of clinical signs. They may show a behavior change or blindness, ataxia and incoordination, fever, hypersalivation and drooling, paralysis, difficulty swallowing, lameness or colic. In many cases the signs are obscure and many people may be exposed to the horse before a diagnosis is reached.

Rabies is always fatal. Horses that contract Rabies will always become progressively worse and most die within 3-7 days once clinical signs begin. There is no treatment for Rabies. Rabies can mimic many other diseases including:
•    EEE - Eastern Encephalomyelitis
•    WEE - Western Encephalomyelitis
•    VEE - Venezuelan Encephalomyelitis
•    WNV - West Nile Virus
•    EHV - Equine Herpesvirus
•    Hepatic Encephalopathy
•    Brain Tumors
•    EPM.
•    Colic
•    Lameness

 There is no antemortem (before death) test for Rabies. In many cases treatment and diagnostic test are done to rule out other treatable diseases in an attempt to save the horse. A post mortem examination and testing of the brain is always required to confirm Rabies in any animal.

Rabies is preventable. A safe and effective vaccine is available. All horses should be vaccinated against Rabies. Rabies vaccine is safe for foals, pregnant mares, breeding stallions and miniature horses. The vaccine needs to be given once yearly.

There are other steps that you can take to minimize your risk of Rabies for you and your horse;
•    Vaccinate your horse yearly.
•    Minimize contact with wildlife.
•    Secure garbage and remove trash from the farm and stable.
•    Do not leave pet food outside to attract wildlife.

 For more information on Rabies you can go online and view a free webinar  “Understanding Equine Rabies” at www.TheHorse.com.

Friends We Have Lost
Tom Batten suffered a devastating loss with the death of a fine filly by his stallion King Corona out of the stakes winning mare Emma Perry. The filly was conceived by embryo transfer and everyone felt she was truly destined for greatness.

The Patrick Hilton family bid a sad farewell to their mare Tiffany after a devastating injury which ruptured her eye.

It was a very tough day for Gina Kees who laid her beloved Quarter Horse gelding Redmond to rest after a long battle with laminitis.

SBG (single blind gelding) seeks OM (older mare) to be my guide horse. Contact Susan Turner at sue1147@yahoo.com

Lonely OM (older mare) seeks new PF (pasture friend). I have a beautiful pasture to share. Contact Terry Smith at swildcatroad@windstream.net

Well that’s all for now, please stay in touch.