Routine vaccinations are an integral part of a thorough preventative health care program for your horse. The AAEP (American Association of Equine Practitioners) has divided vaccines into those considered essential for all horses (termed core vaccines) and those that are considered optional (non-core vaccines), depending on risk of exposure, management practices,etc.
Core Vaccines:
1. TETANUS: Tetanus is a disease caused by a toxin produced by the bacteria, Clostridium tetani. It generally gains entrance into the body as a result of a deep or penetrating wound such as a puncture. The action of this toxin in the body of an unvaccinated animal is to inhibit the production of a special chemical necessary for the proper functioning of nerves and muscles. When the toxin is released in the horse's body it makes the muscles unable to stop their contractions resulting in prolonged, abnormal muscle firing.The horse is unable to eat or move normally, its muscles become tight and rigid and any stimulation can cause the horse to go into spasms and convulsions. Horses with tetanus will usually die. Protection against tetanus is easy and inexpensive.Foals are generally vaccinated at about 5-6 months of age followed by a booster 2-4 weeks later. Yearly boosters are then required for the life of the horse. Horses sustaining deep puncture wounds or severe lacerations should be given a booster at the time of injury.Pregnant mares should be vaccinated at about 9-10 months of gestation to pass on immunity to the newborn foal.
2. EASTERN / WESTERN ENCEPHALOMYELITIS: These are both neurologic diseases caused by viruses. The natural resevoir in the environment are birds and mosquitoes and the horse becomes infected by the bite of an infected mosquito.The horse is not a natural host for this virus so it is called a "dead end" host, meaning it does not serve as a source of infection for other horses or people (people can become infected through the bite of an infected mosquito). The effect of the virus is on the brain and causes signs such as aimless wandering, head pressing, profound depression, convulsions and death. Foals are vaccinated at 5-6 months of age with an initial injection and then boostered 2-4 weeks later. This vaccine is commonly combined with tetanus. Yearly boosters are given for the life of the horse. Pregnant mares should be vaccinated at 9-10 months of gestation.
3. RABIES: Rabies is a viral disease that is spread exclusively through the bite of an infected individual. It is always fatal and can effect all mammals including people. The resevoirs of infection in nature are primarily skunks, foxes, raccoons (most common in Vermont and New Hampshire) and bats. Any obvious bizarre changes in behavior accompanied by weakness and incoordination should be viewed with extreme caution and the veterinarian should be called. Foals are vaccinated at 5-6 months, boostered in 2-4 weeks and then yearly. At present there are no 3 year vaccines for horses as there are for dogs and cats.
4: WEST NILE VIRUS; While West Nile Virus is still considered a core vaccine by the AAEP there have not been any equine cases in Vermont of New Hampshire for several years. Incidence of the disease appears to have dramatically declined and to have moved to the west coast, especially Washington state. West Nile is a disease caused by a virus that is tranmitted by mosquitoes that have bitten infected birds. Horses and people can be thus infected and are both "dead end" hosts. Infected horses then are not potential sources of infection for other horses or people. The disease is characterized by depression,listlessness, incoordination, weakness, stumbling,convulsions and sometimes (+/- 40%) death. Foals should be vaccinated at 5-6 months of age, boostered 3-5 weeks later and then yearly.
Non-core vaccines:
1. INFLUENZA and RHINOPNEUMONITIS: Theses are both upper respiratory viral infections that are spread primarily through direct contact with infected individuals and their nasal secretions. In general they cause fever,cough and nasal discharge ("snotty nose"). The viruses are often spread throughout the barn or stable infecting many of the horses. Most of the time the disease will run its course without complications but occasionaly pneumonia or other serious complications can occur. In addition to the most common upper respiratory form of rhinopneumonitis, variants can cause abortions in pregnant mares and rarely neurologic disease (there have been several severe outbreaks of this form in the past several years in New England race tracks and showgrounds). Vaccinations against "flu" and "rhino" begin in foals at 5-6 months of age followed by a booster in 2-4 weeks, (some recent research has indicated that a third booster may offer the best protection). Depending upon the degree of exposure to other horses boosters may be given yearly,every 6 months or even every 3 months. Pregnant mares should be vaccinated against rhinopneumonitis at 3,5,7 and 9 months of gestation
2. POTOMAC HORSE FEVER: This disease is caused by an organism named Ehrlichia risticii and is acquired by the ingestion of small water insects such as mayflies,caddisflies and dragonflies. Clinical signs include fever, depression, sometimes diarrhea and laminitis.The vaccine is recommended for horse living in swampy or marshy areas or where horses are drinking from streams or springs. There is some controversy regarding the efficacy of the PHF vaccine. Horses are vaccinated at 5-6 months of age, boostered 2-4 weeks later and at least twice yearly thereafter.
3. STRANGLES: Strangles is a respiratory disease that is transmitted from one horse to another either by direct contact, through the nasal secretions or by contaminated objects (fomites). This bacterial disease is very contagious and can rapidly spread through a stable or barn. It is characterized by fever, purulent (pus) nasal discharge and painful enlargement and abscessation of the lymph nodes under the jaw possibly causing airway obstruction. Horses may be reluctant to eat or swallow. The nasal discharge can lead to an accumulation of mucous, rattling breathing noises, increasingly thick discharge and trouble breathing. The skin over the swollen nodes may ooze fluid as the abscess matures.They may break open themselves but often need to be surgically drained. The disease usually responds well to antibiotic treatment once the lymph nodes have been drained. Strangles can be an ongoing problem on a stable or farm because the organism (Streptococcus equi) can survive in the environment for long periods of time and continue to serve as a source of infection. Additionally, horses can become inapparent carriers (clinically normal) of the disease and periodically shed the organism thereby continuing to transmit the disease to other horses. Vaccination is intranasal and is begun at 5-6 months of age with an additional dose given 2-4 weeks later and then yearly. Vaccination against strangles is usually done on horses residing in stables where the disease has been present in the pase or travelling to areas or stables, shows,etc. where the previous vaccination histories of other horses is unknown.
