Vaccinations

Horse vaccines (shots) 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, stored or administered incorrectly will be ineffective or neutralized.

Vaccines are administered initially as a two- or three-shot series and then annually or semiannually.

The horse vaccines and vaccine programs listed below are tailored to our practice and geographic location and follow the guidelines of the AAEP:

Eastern & Western Equine Encephalomyelitis: Encephalomyelitis ("sleeping sickness") is caused by a virus, which is transmitted by mosquitoes. The virus causes inflammation of the brain and spinal cord.  The vaccine is very effective against the disease. We recommend administering the vaccine once a year.  A third form of this disease, called Venezuelan encephalomyelitis has been seen in some southern states, but is not considered a major threat at this time and we do not vaccinate for it.

Tetanus Toxoid: Tetanus is a disease caused by a specific toxin of a bacterium (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 are found in soil and in horse manure. The vaccine is very effective and administered once yearly. The vaccine is boostered in cases 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 in preventing death following exposure.  The AAEP now considers Rabies vaccine to be a core vaccine in any vaccination program.

West Nile Virus: West Nile virus is transmitted by mosquitoes. The virus causes inflammation of the brain and spinal cord, leading to fever, stumbling, ataxia (swaying when walking and uncoordination), muscle twitching, coma, or even death. At the peak of West Nile outbreak, we vaccinated twice a year.  Now we usually do once in the spring as the threat seems to have lessened. Veterinarians in problem areas still vaccinate twice per year.  Use of West Nile vaccines has reduced the number of reported cases in our area from 15,000 cases in 2003 to 334 cases in 2007.

Rhinopneumonitis: Rhinopneumonitis is a herpesvirus (EHV-1) which causes respiratory infections, abortions, and myeloencephalitis (inflammation of the spinal cord and brain). The vaccine is not 100% effective, and the protection only lasts 10-12 weeks.  Pregnant mares should be vaccinated at 3, 5, 7 and 9 months of gestation. Horses that are travelling to shows, races, sales, etc. should be vaccinated every 3 months. Pleasure horses that do not travel should be vaccinated once a year. The modified live Rhinomune® vaccine which we use protects against all three forms of the disease.  There is also some cross-immunity against the other forms of the virus, such as EHV-4.

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

Potomac Horse Fever (PHF): Potomac Horse Fever is caused by the parasite Neorickettsia risticii. Although first discovered in the Potomac River valley, it is also very prevalent in the Mississippi River valley.  Horses are infected by ingesting small aquatic snails or flukes that carry the parasite, or by ingesting insects such as mayflies, caddisflies, and dragonflies which carry the parasite. It is not contagious from horse to horse.  It occurs more commonly in wet areas, but many cases have been seen in dry areas also. Peak season for disease is late summer and early fall.  The disease causes high fever, laminitis (founder), and severe diarrhea. Horses may seem colicky due to the intestinal cramps caused by the diarrhea.  Some horses may recover from the diarrhea and fever, only to develop potentially life-threatening laminitis.  The vaccine is fairly effective and is administered once a year.  It is administered 2-4 times per year 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 (internal abscesses). There is a modified live intranasal vaccine which is more effective than the old intramuscular vaccine. The vaccine is given once a year except in endemic barns (that have frequent outbreaks) where semiannual vaccination is recommended.  The vaccine should not be given while the horse has strangles, or within 6 months of having the disease, as purpura hemorrhagica may result from over-stimulation of the immune system.