Equine Vaccinations

Vaccines are preparations of killed microorganisms, living weakened microorganisms, etc. introduced into the body to produce immunity to a specific disease by causing the formation of antibodies. Vaccines are very delicate compounds, which if handled or administered incorrectly, will be ineffective or neutralized. Vaccines are administered initially as a two-shot series and then annually or semiannually. Foals require a three-shot series. The vaccines and vaccine protocols listed below are tailored to our practice and geographic location and follow the guidelines of the AAEP.

Eastern & Western Encephalomyelitis: Encephalomyelitis is caused by a virus which is transmitted by mosquitos. The virus causes inflammation of the brain and spinal cord. The vaccine is very effective against the disease. We recommend administering the vaccine annually.

Tetanus Toxoid: Tetanus is a disease caused by a specific toxin of a bacillus (Clostridium tetani) which usually enters the body through wounds. It is characterized by spasmodic contractions and rigidity of some or all of the voluntary muscles (especially of the jaw, face and neck). The bacteria is found in horse manure. The vaccine is very effective and administered once yearly. The vaccine is boostered in case of laceration, surgery, or penetrating wounds.

Rabies: Rabies is a viral disease that infects the nervous system of mammals. It is transmitted through contact with the saliva of infected animals. It is 100% fatal. The vaccine is given once yearly and is very effective.

West Nile Virus: West Nile Virus (WNV) causes encephalitis in birds, horses and humans. The virus is transmitted from infected birds by mosquitos. Humans and horses appear to be especially susceptible. Studies done by the U.S. Department of Agriculture show that infected horses will not transmit WNV to other horses or to people. However, care should be taken when handling blood from suspect animals.

Symptoms of disease caused by WNV may include the following:

* Flu-like signs (fever and depression)
* Skin twitching, especially around the muzzle
* Hypersensitivity to touch and sound
* Driving or pushing forward without control
* Incoordination

Because permanent neurological problems and death can occur, early recognition and initiation of treatment is important. No specific treatment protocol exists; however, most cases will resolve with supportive therapy and anti-inflammatories.

Efforts to prevent disease in horses caused by WNV is through the use of the West Nile Vaccine from Zoetis Pharmaceuticals and through actions that will reduce exposure to mosquitos. The vaccine is safe and appears to be effective. We recommend administering the vaccine annually.

The most effective way to limit the mosquito population is to destroy the mosquito larval habitat. This is done by reducing the amount of standing water. Water troughs should be cleaned at least once a week. Keeping weeds trimmed and lawns mowed helps to eliminate areas where mosquitos rest. Directly protecting horses from mosquito bites is more difficult. Fly and mosquito repellents may be helpful. Products containing pyrethroids are considered safe for horses. Spray stalls, aisle walls, and other areas such as under shade trees where horses congregate. Fans can also be used to discourage mosquitos from residing in your barn.

Rhinopneumonitis: Two distinct viruses, equine herpesvirus type 1 (EHV-1) and equine herpesvirus type 4 (EHV-4), cause two different diseases, both of which are known as rhinopneumonitis. Both cause respiratory tract problems, and EHV-1 may also cause abortion, foal death and neurological signs, which may eventually cause paralysis. Infected horses may be feverish and lethargic as well as lose appetite and experience nasal discharge and a cough. Young horses suffer most from respiratory tract infections and may develop pneumonia secondary to EHV-1. All pregnant mares must be immunized. Foals, weanlings, yearlings and young horses under stress should also be vaccinated. Immune protection is short. Therefore, pregnant mares are vaccinated at a minimum during the fifth, seventh and ninth months of gestation, and youngsters at high risk need a booster at least every six months. Some horses may require more frequent vaccinations depending on disease risks.

Influenza: Influenza is a virus that causes high fever and respiratory infection. The vaccine is not 100% effective and the protection lasts only 10-12 weeks. Horses traveling to shows, sales, racing events, etc. should be vaccinated every 3 months. Horses that do not travel should be vaccinated once a year.

Potomac Horse Fever (PHF): Potomac Horse Fever is caused by the parasite Ehrlichia risticii. Horses are infected through small land snails (they can fly) that carry the parasite. It is not contagious and occurs more commonly in wet areas. The disease causes high fever, laminitis, and severe diarrhea. The vaccine is fairly effective and is administered once a year. It is also administered annually in problem areas.

Strangles: Strangles is a bacterial disease caused by Streptococcus equi. It is highly contagious and causes the following signs: high fever, abscessed lymph nodes, and respiratory infection. Horses may develop guttural pouch infections, sinus infections, purpura hemorrhagica, laryngeal paralysis, and bastard strangles. There is an intranasal vaccine which is more effective than the intramuscular vaccine. The vaccine is given once a year except in endemic barns (that have frequent outbreaks) where semiannual vaccination is recommended.