Springtime is almost here, which means it's time for your horses' yearly vaccinations. Although you can vaccinate any time of the year, doing so in the spring offers the best protection against mosquito, tick, and fly transmitted diseases.

   The American Association of Equine Practitioners (AAEP) recommends four core vaccines for horses in the continental United States. The American Veterinary Medical Association defines core vaccinations as those that protect from diseases that are regularly found in a region, those with public health significance, those required by law, highly infectious, and/or those posing a risk of severe disease. The 4 core diseases are: 1.Tetanus 2. Eastern/Western Equine Encephalomyelitis 3. West Nile Virus 4. Rabies.   (For those of you outside the U.S., tetanus and rabies are worldwide diseases, and West Nile is also present in parts of Europe and Asia, with similar viruses in many parts of the world)

    Tetanus is not a contagious disease, but is contracted when spores of the bacterium clostridium tetani get into an open wound. The bacteria release a neurotoxin which causes muscle spasms so severe that they are strong enough to tear the muscles and break bones. Tetanus is almost always fatal to horses. Since the spores are present in horses' intestinal tracts and can live in the soil for years, the threat of tetanus is always present. Horses should be given a yearly tetanus toxoid booster.

   Eastern/Western Equine Encephalomyelitis is actually two different forms of encephalomyelitis. As is indicated in the name, one is found in the eastern part of the US while the other is found in the west. But since the actual boundaries of the two viruses are always changing and since horses are often moved from one area into another, one inoculation is given which will combat either form of the virus. EEE/WEE are infectious diseases spread by mosquitoes (and sometimes other blood sucking insects) to horses from wild birds or rodents. The disease attacks the brain, causing neurological dysfunction and paralysis. WEE has a 50% mortality rate, while EEE has a 90% mortality rate. There is no known cure for the disease, so you certainly want to include this inoculation in your yearly plan.

   West Nile Virus is another form of encephalomyelitis. The symptoms and spread of the disease are similar to those of EEE/WEE. The mortality rate of West Nile is 33%, but of those survivors, 40% or more never regain full health. So a West Nile vaccination is another necessary yearly booster.

   Rabies is a rare disease of horses. The AAEP has classified it as a core vaccination since it is almost 100% fatal and the disease poses a public health risk. This is another disease which attacks the brain. It is spread by the bite of infected animals. In the US, the spread is usually from infected wildlife, most commonly, skunk, bat, raccoon or fox.

   No matter what region of the US I was living in, I have always been advised to give the first 3 core inoculations listed here. However, the first time I gave my horses rabies shots was when I went to California and worked on a Marine Base. We had over 60 horses for trail rides and they were turned out in a huge pasture of native chaparral, with thousands more acres of chaparral surrounding them. There was wildlife everywhere, so the odds of the horses being bitten by a rabid animal was higher than in most places where horses are kept. Most of the horses did fine with the shots, but several of them (including one of my geldings) had swelling, stiffness, and pain around the injection site. They also went off their feed and were very lethargic . These side effects cleared up completely in a couple of days. One year we did have a mare that was greatly affected by the shot. The whole side of her neck became swollen, she went off her feed, and lay down almost constantly for a couple of days. The following year, we gave Sissy her rabies shot first, and then gave her the rest of her boosters after the effects of the rabies shot had worn off. She had much less trouble the second year. So I would recommend talking to your vet about the pros and cons of a rabies shot.

   Besides the four core vaccines, there are other vaccines available which the AAEP considers risk based vaccines. For the US, some of the ones of concern for adult horses not used for breeding are: anthrax, botulism, equine herpesvirus (rhinopneumonitis), equine influenza, Potomic horse fever, snake bite, and strangles.

   Horse owners need to speak to their veterinarians to see if any of these vaccines are necessary to their particular horses. One vaccine your vet may recommend is the equine herpesvirus, especially if you board in a facility with a large turnover of horses or if you haul your horses to shows or other events where numerous horses are present, In the past, mostly only pregnant mares, or horses who were around pregnant mares were vaccinated, since rhino could cause abortion or foal death. Lately however, a mutation in the EHV-1 strain of the virus has occurred, making this a more serious disease for riding horses. The disease is generally an upper respiratory disease which most horses develop a natural immunity to. In its mutated form, the virus causes neurological symptoms such as paralysis, and is often fatal. Horses do not become immune to this form, and it is usually mature horses that die from it. So I would certainly talk to my vet about this one. The vaccine is generally given every 6 months. On the racetracks in the US, we have to give our horses a booster every 3 months.

   If you know how to give a horse a shot, you can administer most vaccines yourself. With the exception of rabies, which in many states, must be given by a licensed veterinarian, you can buy the vaccines without a prescription. Combinations are available, giving you all the core vaccinations (except rabies) and also equine influenza in one shot. Prices run about $20-25. Whether you or your vet give the shots, I would recommend doing it on a day when you will not be riding your horse. Many times horses do not feel their best after an injection. I always give my horse the following day off also, just to be sure.

  If you would like to learn more about these vaccines and the diseases they prevent, the AAEP has a website with in-depth information. Their address is www.aaep.org.