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Equine rabies is a fatal disease caused by a lyssavirus that affects the horse’s neurologic system and salivary glands. It is rapidly progressive and typically results in death from cardiorespiratory failure or misadventure within 10 days of clinical manifestation. Affected horses usually start displaying related clinical signs within 2-9 weeks of contraction.

The virus is prevalent throughout the continental United States and can be contracted by any mammal. Due to the relatively low body temperature of the opossum (94-97 degrees F), however, infection of this species is extremely rare. Of course, the opossum offsets this valued characteristic by being the definitive host for another equine neurologic disease known as Equine Protozoal Myeloencephalitis (EPM).

Hawaii is the only US state free of rabies. Countries considered rabies-free include Australia, Great Britain, New Zealand, Scandinavia, and Switzerland.

 

Rabies has at least six genotypes, all of which have different host ranges and pathogenicities.

The virus appears to be both unique and sophisticated when considering the fact that it is not only able to situate itself within the saliva of the host, but actually changes its host’s behavior to increase the chance of successful transmission through a bite.

 

Rabies is transmitted between animals in one of the following ways:

  • A rabid animal bites an uninfected animal

  • Saliva or blood from a rabid animal contaminates an uninfected animal’s wound.

     

Rabies is also a zoonotic disease, meaning that it can be passed from horses to humans. For this reason, extreme caution must be exercised when handling rabid horses. See below for details.

Rabies outbreaks in domestic animals typically coincide with an increase in local wildlife population. In Eastern US states, horses are most likely to contract rabies through a bite from a rabid raccoon; infected saliva is deposited under the skin (usually along the muzzle or limb). Western horses are more likely to contract rabies from an infected skunk. Other transmitters of the disease include the fox (somewhat common) and bat (less common).

 

Clinical Signs in the Horse

Clinical signs associated with rabies infection can be somewhat ambiguous and nonspecific, particularly in the early stages of the disease.

Early Symptoms-

  • Depression

  • Anorexia

  • Mild ataxia (incoordination)

  • Behavioral changes

  • Colic

  • Obscure lameness

  • Fever

     

Late Symptoms-

  • Repetitive twitching

  • Hypersensitivity to touch and sound

  • Hypermetria (a condition in which voluntary muscular movement overreaches the intended goal)

  • Proprioceptive deficits (lack of physical awareness of limbs and their placement)

  • Superlibido

  • Regional pruritus (itchiness)

  • Belligerousness

  • Periods of violence interspersed with periods of normalcy or depression

  • Normal, increased, decreased, or absent spinal function

  • Behavioral changes

  • Difficulty swallowing

  • Ataxia (incoordination)

  • Paralysis of one or more limbs

  • Hypersalivation

     

Diagnosis

Rabies can only be definitively diagnosed post-mortem using a fluorescent antibody test. Euthanasia of a suspect horse should be avoided until clinical signs become evident, however, since progression of the disease within the central nervous system is required to produce a positive result.

 

Treatment

Once rabies is contracted the prognosis for survival is grave.

Horses exposed to a rabid animal that are up-to-date on inoculations (vaccines) should be revaccinated immediately and monitored closely for a period of 90 days to see if clinical signs develop.

Unvaccinated horses that have been exposed to a rabid animal should be euthanized (if clinical signs are present) or observed for the manifestation of clinical signs for a period of six months. During that time, the horse should be only handled by people previously exposed and preferably vaccinated; exposure to new or additional humans and/or other animals should be avoided as much as possible.

A list of individuals (including veterinarians, veterinary technicians, grooms, farriers, owners, trainers, etc.) that have been in contact with an exposed animal should be updated regularly. These individuals will be notified by the state veterinarian in the event that a positive rabies test result is returned.

Any biologic sample obtained from the horse should be labeled as “rabies-suspect” to protect laboratory personnel. Gloves, face shields, masks, and eye protection should be utilized appropriately.

As previously mentioned, euthanasia of a suspect horse that has already been exposed to humans should be avoided until clinical signs become evident, since progression of the disease within the central nervous system is required to obtain a definitive diagnosis.

 

The recent use of four modified live vaccine injections successfully protected horses and cattle naturally infected with rabies during one research project, although no USDA-approved biologics for post-exposure implementation currently exist.


Prevention

Fortunately, rabies is a very preventable disease.

The incidence of equine rabies in the US has been on the gradual decline due to vaccination efforts. The majority of cases are observed in nonvaccinated animals, although some horses not vaccinated within a 12-month span have also contracted the virus.

The antigens associated with the rabies virus are very specific and consistent-in-nature. Moreover, since rabies is an excellent immunogen, vaccines against the virus tend to be very effective. Most preparations induce a strong serologic response within 45 days after single dose administration.

 

The American Association of Equine Practitioners (AAEP) advises that all horses be vaccinated for rabies on a annual basis.

  • Adult horses should receive an initial single dose and booster inoculations annually.

  • Foals born to vaccinated mares should receive an initial vaccine dose no earlier than six month of age and a second dose 4-6 weeks later followed by annual inoculation.

  • Foals born to unvaccinated mares should receive an initial vaccine dose at 3-4 months of age followed by annual inoculation.

Click LOGO below for Specific Vaccination Recommendations for Your Horse(s):

See Specific Vaccination Recommendations for Your Horse

 

Rabies is a Reportable Disease

Animal health authorities should be notified immediately in the event that:

  • A horse (with or without known rabies exposure) bites a person. The local veterinary rabies officer will quarantine the horse at home for 90 days. If the horse dies or is euthanized for any reason during that time period then testing for rabies must be performed.

  • A horse is exposed to a rabid animal.

  • A person contacts a horse suspected of rabies exposure.

 

Click HERE to review our Infectious Disease Control Guidelines

 

If you have any questions regarding Equine Rabies please call our office at (678) 867-2577. We look forward to serving you!
 
THE ATLANTA EQUINE CLINIC: 1665 Ward Road, Hoschton, Georgia 30548 - ph. 678-867-2577

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