Rabies is a fatal viral disease that can affect horses and is present in wild mammals all over the world. [1] Rabies is a zoonotic disease, which means it can be transmitted from animal to humans, and can be fatal if not addressed urgently after exposure to the virus. [2]

This disease primarily affects the central nervous system, leading to progressive and fatal encephalitis. Initial signs in affected horses include fever, colic, and lameness, followed by aggression, incoordination, recumbency and ultimately death.

The rabies virus is transmitted to horses through saliva, most commonly via bites from infected wildlife. Once a horse is infected and displays symptoms, there is no effective treatment for the disease. [3]

There is no reliable ante-mortem method to diagnose rabies in horses. If a horse displays symptoms indicative of rabies, they are often labeled as a “rabies suspect,” prompting the initiation of biosecurity and public health protocols. [4]

Regular vaccination against rabies is the primary preventive measure. Rabies vaccines for horses are both safe and effective. [5]

Rabies Virus in Horses

Rabies is caused by an RNA virus from the Rhabdoviridae family. [6][7] Horses that are infected by the rabies virus experience significant inflammation in the brain and spinal cord. This severe inflammatory response is fatal in unvaccinated horses. [6][7]

Rabies affects mammalian species. Although the virus circulates among various wildlife species, horses are deemed “dead-end” hosts, as they do not transmit it to other animals. [6][8]

According to the Centers for Disease Control and Prevention (CDC), wildlife accounts for 91% of reported rabies cases. [2] Affected animals are often called “rabid”. [1]

The primary reservoir species vary by region, but all animals can transmit the virus to both humans and horses. Notable reservoir species include raccoons, skunks, bats, and foxes. [8]

Rabies has been a nationally notifiable disease since 1938. [8] While the virus exists worldwide, certain countries like Great Britain, New Zealand, and Iceland have successfully eradicated it. [3]

In the United States, domestic animals represent 8% of all reported rabies cases. [3] Horses constitute 3 – 5% of rabies cases annually. [4]

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Clinical Signs

Clinical signs of rabies in horses can be ambiguous and vary widely. Once symptoms manifest, they intensify until the horse succumbs to the disease. [9]

Rabid animals typically exhibit symptoms that fall into two primary categories: the “dumb” form and the “furious” form. [3]

Horses predominantly exhibit the “dumb” or paralytic form of rabies. Symptoms associated with this form include pronounced depression, paralysis, drooping of the face or jaw, and excessive salivation. [1][3][4][10]

On the other hand, the “furious” form of rabies is marked by aggressive and erratic behavior or intense agitation. [10] While this form is more typical in carnivores, when it appears in horses, it poses a significant threat to both the animal and its handlers. [3][4]

Clinical signs may include any of the following: [3][9]

  • Fever
  • Poor racing performance
  • Lameness
  • Knuckling
  • Uncoordinated or stumbling gait
  • Paresis or paralysis of the hindlimbs
  • Unwillingness to rise (recumbent)
  • Colic
  • Constipation
  • Straining to pass manure
  • Dribbling urine
  • Lack of tail and anal tone
  • Erect penis in males without stimulation
  • Frequent mounting behavior
  • Self-mutilation
  • Itchiness
  • Muscle tremors
  • Unusually aggressive behavior
  • Blindness
  • Head pressing
  • Frequent bellowing
  • Hyperextension or backwards arching of the head and neck (“stargazing”)
  • Difficulty swallowing (may b