Extension Report

Baldwin County Extension Office

302A Byrne Street

Bay Minette, AL  36507

Telephone (251) 937-7176 or

928-0860/943-5061 ext. 2222

FAX (251) 937-7285

Ken Kelley

Regional Extension Agent/Animal Science

July 20, 2010

Healthy Horses – Part 1

We have a lot of folks who own horses in our area. Some of these folks have owned horses for years, and have a solid base of knowledge concerning horse health, nutrition, pasture production, etc. However, we also have a large group of folks who don’t have that base of knowledge...many of them being relatively new to horse ownership.

First, I would recommend finding a veterinarian. There are a lot of times when you need a vet, and often your vet needs to know your situation, i.e. a little about your horse, your farm, etc...  Your vet can work with you on planning a herd health calendar, and can help with the giving of vaccinations. However, there are some things that you can do for yourself, and some things you need to know about your horses.

First, infectious diseases. There are three infectious diseases that we commonly vaccinate for in Alabama. Let’s talk just a minute about each of these.

Tetanus. Tetanus, or lockjaw, is caused by a bacterial toxin. The bacteria is normally found in the soil and in the feces and intestinal tracts of horses. However, these bacteria can enter the horse’s tissues through a wound or the naval stump of a newborn foal. Reduced oxygen in these areas may allow the bacteria to multiply and produce toxins that result in tetanus. While tetanus is normally associated with deep puncture wounds, any wound that has healed over may produce conditions that cause tetanus.

Usually, the first symptom of tetanus is the third eyelid protruding upward from the inner corner of each eye so that it covers one-third to one-half of the eye. The horse’s head and neck may also appear stiff. As the disease progresses, the horse develops stiffness all over its body, and it has difficulty moving and turning. The horse usually stands in a “sawhorse” position with its legs extended, and it may seem nervous and excitable. Noises may cause general muscular spasms.

Most cases of tetanus in horses are fatal, but the disease can easily be prevented by a yearly vaccination with tetanus toxoid. Horses that have not been immunized can be protected temporarily by a tetanus antitoxin injection. However, the antitoxin is not a substitute for routine vaccinations. Horses may get many small, unnoticed wounds that can allow tetanus to develop.

Equine Encephalomyelitis. Equine encephalomyelitis (sleeping sickness) is a nervous system disease that can be caused by several different strains of virus. In Alabama, the eastern and western strains are the primary causes of equine encephalomyelitis. Eastern equine encephalomyelitis (EEE) and western equine encephalomyelitis (WEE) are transmitted from infected animals, such as wild birds and rodents, to healthy horses primarily by mosquitoes. The horse is considered a terminal host for WEE and EEE—that is, the disease cannot be passed on from an infected horse to another animal.

The first signs of encephalomyelitis in the horse are usually severe depression and a high fever (104 to 106 degrees F) for 1 to 2 days. The horse may then go through a period of excitement in which it appears nervous, blind, and uncoordinated. Infected horses may also show involuntary muscle tremors, yawning, and grinding of the teeth. A quiet period in which the horse appears depressed and drowsy follows the period of nervous activity. The horse may press its head against a solid object, and it eventually becomes completely paralyzed.

The mortality rate from equine encephalomyelitis varies according to the viral strain infecting the horse. Many horses that do recover are useless due to brain damage caused by the disease. Annual vaccination will prevent encephalomyelitis in horses. In areas with a long mosquito season, spring and fall vaccinations are usually recommended. Mosquito control is also helpful in preventing equine encephalomyelitis outbreaks.

West Nile Virus. West Nile Virus (WNV) causes encephalitis (inflammation of the brain) and interferes with central nervous system functioning. There are many signs of WNV infection in horses. Affected horses may be depressed and off-feed. They often have muscle tremors and may have convulsions. Some experience hypersensitivity and are easily startled by noise or touch, and others seem drowsy and less reactive than normal. Other signs include walking continuously without purpose or control, circling, exhibiting lack of coordination, and experiencing paralysis, especially in the hind legs. Signs of WNV infection are often similar to those of other diseases, including equine protozoal myelitis (EPM), eastern equine encephalomyelitis (EEE), and rabies. Any horse that seems depressed or shows any neurological signs should be examined by a veterinarian immediately.

West Nile Virus is transmitted by mosquitos. Usually the disease is passed from an infected bird to an uninfected bird via mosquito. Horses also get the disease from mosquitos. Horses are incidental (dead end) hosts because they cannot produce enough of the virus to pass the virus to another animal (mosquito, horse, human). Therefore, horses with the disease do not need to be isolated from other horses or from humans.

West Nile Virus is not as deadly to horses as are other encephalitic diseases, such as EEE. Only about 33 percent of horses that contract WNV die or are put down because of the disease. Most horses that contract the disease can recover with appropriate veterinary and nursing care. However, recovery is slow and effects of WNV infections may be present several years after contraction of the disease. The prolonged period of extra care may be costly in terms of time and money. Even though the WNV vaccine is expensive compared to many of the other commonly administered equine vaccinations, it is probably cost-effective in the long run.

Two different types of WNV vaccines are approved to give horses effective protection against the virus. It is very important that horses initially receive two doses of the vaccine at the time interval recommended by the vaccine manufacturer. Maximal protection does not occur until several weeks after the second vaccination.

Alabama's mild winters create ideal conditions for WNV to become a year-round problem with more intense outbreaks in the summer and fall (similar to EEE outbreak patterns). Most veterinarians currently recommend that horses in Alabama receive spring and fall booster vaccinations after the initial two-dose vaccine series. This procedure enables horses to maintain a high level of antibodies against WNV.

Hopefully, this is the first in a series about things you need to know as a horse owner to make sure that your horse remains healthy now and in the future. There are many other topics that we can and will cover related to horses. If you have any more questions, feel free to give me a call or an email. If there is an aspect of horse ownership that you would like covered, feel free to drop me an email and I will try to cover it. 

Email address: kellewi@aces.edu

Phone number: 937-7176 or 943-5061, 928-0860, ext. 2222

The Alabama Cooperative Extension System (Alabama A&M and Auburn Universities) in cooperation with the U.S. Department of Agriculture is an equal opportunity educator and employer.