Horse

Horse Vaccines

What are you doing when you vaccinate your horse? When we vaccinate our horses we are deliberately exposing them to a portion of a disease-causing organism or exposure to a disease causing-organism, such as the bacteria or virus of a disease. This is done in a very small dose. We do this in order to cause an immune response in the horse that will hopefully protect the horse in the future from that particular disease. Generally, this is how vaccines work.

Is it a100 % guarantee that the horse will never contract the disease? No. But should the horse contract the disease that they were vaccinated against usually it is a lighter case than without the vaccination. Chances for recovery are greatly increased with the vaccination than without. Vaccines must also be stored, handled and administered properly. Not doing so can mar the effectiveness of the vaccine.

Here are some of the diseases we vaccinate horses for:


Tetanus (Lockjaw): Tetanus occurs when a specific bacteria enters a horse like a deep wound. As Tetanus grows it produces a toxin and attacks the nervous system of the horse. Tetanus is fatal.


Encephalitis: Horses can be attacked by three types of encephalitis, Eastern, Western, and Venezuelan. Mosquitoes carry this virus. Horses become infected by bites from infected mosquitoes (usually found in states close to the Mexican border). Encephalitis infects the horses' brain. If they survive they may have permanent defects as a result. Encephalitis is potentially fatal.


Rabies: Infects the nervous system with a fatal infection. Rabies is caused by a bite from an infected animal (such as bat, raccoon, or skunk). Rabies can go undiagnosed in a horse for a period of time and can actually spread the infection to humans. This can happen by contact of body fluids with broken skin (a cut on your hand).


Potomac horse fever: Generally confined to a specific geographic areas (along the Potomac River) and in areas with moderate climate and close to rivers. This disease is characterized by depression, fever, diarrhea and founder. Check with your vet or local extension agent for advice in your area.


Rotavirus diarrhea: Causing sever, potentially life-threatening diarrhea in young foals. Rotavirus it appears is carried by the mother (or passably another horse). The horses that pass the virus may not develop problems but simply pass it on. Pregnant mares can be vaccinated then they pass the antibodies to their foals in the first milk (colostrum). Check with your veterinarian about availability of this vaccine.


Influenza: This shows up like severe cold-like symptoms and high fever making it a risk for developing bacterial pneumonia. There can be periods when the virus mutates, causing epidemics to break out. Vaccines are not completely effective in preventing the disease since the virus can mutate easily. The vaccine however can reduce the severity of the symptoms. Horses that are most at risk to the flu are the very old, very young, horses under stress, horses traveling, and horses stabled where there is horse traffic.


Botulism: This is caused by toxin of a bacterium related to the one that causes tetanus. Horses are highly sensitive to it and many can die from this disease or the complications brought on by this disease. If this disease is contracted, treatment can be expensive.


Rhinopneumonitis: Also known as “rhino”. This disease is like our “common cold”. The rhino virus can invade the horses' nervous system causing paralysis, and can also cause abortion. As with influenza, the risk factors are the same. Every two months throughout pregnancy mares should be vaccinated.


Strangles: Routinely not done, strangles vaccination is recommended for horses at high risk of exposure. Risk of side effects from the intramuscular vaccine may be up to 30% for this vaccine. This may include fever, loss of appetite, local swelling, muscle stiffness and abscess formation at the vaccination site. Vaccines usually provide reliable protection from severe disease but only for a few months. It does not prevent the disease completely. Unless there is known contamination on the premises, shipping horses frequently or a lot of traffic on and off the a farm, due to the side effects and limited time it is effective, you should weigh the benefit for your situation to vaccinate for strangles or not. That being said, there is a type of strangles vaccine that is a spray into the horse's nose. Intranasal vaccine has low incidence of side effect. Protection is about the same. It is not clear if intranasal vaccine for pregnant mares gets the needed antibodies into the blood (protecting the foal with colostrum). It would be wise to use the intramuscular vaccine with mares close to foaling.


West Nile: This virus has caused many deaths in horses in recent years in United States. It is transmitted by infected mosquitoes. This virus infects the central nervous system and causes symptoms of encephalitis. Signs of encephalitis in horses include loss of appetite and depression, in addition to any combination of the following signs — fever, weakness or paralysis of hind limbs, muzzle twitching, impaired vision, incoordination, head pressing, aimless wandering, convulsions, inability to swallow, circling, hyperexcitability, or coma. It is wise to vaccinate for this disease but avoid vaccinating pregnant mares late in pregnancy. If you have a pregnant mare, contact your veterinarian for a time best to vaccinate her for your area.


Which diseases should you vaccinate your horse for? That depends. You, with the advice of your veterinarian or your local extension office, will need to make that decision. Getting the best, up to date information from these sources will help you choose wisely.

About the Author
Fran Mullens has been a barn manager, trainer and riding instructor for several years, and has worked with horses for nearly 25 years. Fran is co-author with Skimbleshanks the Farm Cat at his blog. To learn more about the farm cat go to http://skimbleshanksthefarmcat.blogspot.com/.