by N. Striegel1
Rabies in horses is caused by a virus of the Rhabdovirus family and causes a severe, rapidly progressive neurological disease. It is transmitted via saliva, most commonly through bite wounds from an infected wild animal bite. Symptoms can appear in as little time as two weeks but can take up to one year for clinical signs to appear. On the average, symptoms will be seen four to eight weeks after the exposure. Death usually occurs within two to four days after the horse begins to show clinical signs, although death may not occur until up to two weeks later with supportive care.
Should horses in Colorado or in other states be vaccinated? Owners will have to weigh the incidence of terrestrial wildlife rabies in their geographical location, the risk of human exposure and contracting rabies, the possible financial costs, the potential emotional loss of their horse, and the cost of the vaccination procedure. Horse owners should seek out the recommendation of their veterinarian who is a valuable resource for their horse’s health. Horse owners should also consider their equine insurance companies policies and rules, if their horse is insured – some insurance companies require the horse to be vaccinated every year, and it must be done by a licensed veterinarian.
Once the virus enters the body by a bite wound, it migrates through the peripheral nerves to the spinal cord, and then travels up the spinal cord to the brain. From the brain the virus migrates to the salivary glands where it replicates and is shed in high quantities in the saliva. At this point, the infected animal can expose others through its saliva. While the symptoms of rabies in the horse may take two weeks up to one year to appear after exposure, the animal is NOT infectious until clinical signs of rabies are becoming noticeable.
Clinical signs of rabies can also vary immensely. It does cause severe, rapidly progressive encephalitis (inflammation of the brain). Some of the signs that can be present are:
- Depression with loss of appetite
- A low-grade fever
- Lameness and / or incoordination
- Other neurological symptoms, including convulsions
- Increased sensitivity to being touched
- Abdominal pain or colic (straining to urinate or defecate)
- Swallowing problems and drooling
- Odd behavioral changes, nervousness, irritability
Once a horse shows symptoms of rabies, the disease progresses rapidly. The horse will usually die within two days to two weeks after it starts showing clinical signs of rabies.
If you look at a U.S. map of the distribution of skunk rabies, it seems to stop right at the eastern Colorado state border. That is not the case anymore. Positive skunk rabies cases have been documented in several eastern Colorado counties. The concern is that the virus is moving westward towards the Front Range of Colorado. Counties along the Front Range are more populous in people and horses and so there is a potential risk to humans, dogs, cats, livestock, and horses.
Certainly, the best recommendation is to seek the advice of your veterinarian who knows your horse management situation, the individual health of your horse, and is familiar with the incidence and risk of equine diseases in your geographical locale. Your veterinarian’s advice is based on their experience and the recommendations of experts in the field of equine preventive medicine.
The American Association of Equine Practitioners (AAEP) has recently included rabies in their “core vaccinations” and defined a recommended vaccination schedule. According to the American Veterinary Medical Association, core vaccinations are the immunizations “that protect from diseases that are endemic to a region, those with potential public health significance, required by law, virulent/highly infectious, and/or those posing a risk of severe disease. Core vaccines have clearly demonstrated efficacy and safety, and thus exhibit a high enough level of patient benefit and low enough level of risk to justify their use in the majority of patients.”
In the end, it is the horse owner’s decision whether to vaccinate or not to vaccinate. It has become a vital question to ponder for horse owners in Colorado. Rabies in horses is fairly rare but it would seem after considering the recommendations of veterinarians, the incidence of wildlife rabies, and the course of the disease, the benefits of vaccinating horses for rabies may outweigh other potential reasons for not vaccinating horses in Colorado.
Consult with your veterinarian about vaccinating your horse against rabies. Do not handle wild animals or do any feeding around the house that may attract them to come closer to your family. If you see any wild animals that are acting strange, showing neurological symptoms, or showing odd behavior such as nocturnal animals (skunks and raccoons) being active during the day – contact your animal control officials or your local public health department.
1. N. Striegel, D.V.M, Colorado State University Extension 4-H and livestock agent, Boulder County.