How do vaccines work?
Vaccines help protect horses against infectious diseases by stimulating their immune system to fight against viruses and bacteria. When horses are vaccinated, they’re given a dose of antigen (contains inactivated part of a disease making organism). The antigen is injected into the muscle and encourages the immune system to create antibodies against it; antibodies are disease defenders.After vaccination,the antibodies circulate the horse’s bloodstream, attacking invading organisms. Therefore, the horse is less likely to get sick. A newer technology that has been recently introduced is intranasal (in the nose) vaccines for respiratory diseases. They are sprayed up the horse’s nose where they stimulate immune system functions. They are now available for influenza and strangles and have proven to be more effective and have less side effects than intramuscular (in the muscle) vaccines. As technology advances, vaccines become more effective. Horse’s have complex immune systems and they involve more than just the production of antibodies for disease prevention. Another advancement is DNA vaccines, which work by injecting parts of genetic material of the organism that produces diseases rather than killed organisms. The newer vaccines are more likely to give better, long lasting immunity to diseases than older vaccines.
Do they work?
Vaccines are effective to a degree. They will either prevent the horse from becoming sick or reduce the severity and length of the disease. Though, vaccines won’t completely protect the horse against diseases in every situation.
How are vaccines approved?
For a vaccine to be approved and licensed by the USDA, it must demonstrate a certain increase in the number of antibodies following administration. Though an increase in antibodies doesn’t always effectively fight the disease. Even with USDA approval, we don’t always know whether certain vaccines will provide complete protection against diseases.
The tetanus vaccine protects the horse against Clostridium tetani, which invades open wounds and can cause life threatening paralysis. Every horse should be vaccinated for tetanus annually due to the seriousness of the disease and the amount of the disease found in the environment. If a horse suffers a wound and has not been vaccinated in the last 6 months, the vaccine should be re-administered to help protect the horse.
Easter & Western Encephalomyelitis (sleeping sickness) vaccine
This vaccine protects the horse against both eastern & western viruses. A 3rd form of sleeping sickness exists, but is only a concern for horses living near the mexican border of the U.S. These viruses are transmitted by bloddsucking insects and can cause a life threatening neurological disease. All horses should be vaccinated from EEE and WEE, but only horses living 40 from the Mexican border should be vaccinated for VEE. Horses should be vaccinated annually, but may be vaccinated twice a year if living in an area where mosquitoes are especially prevalent or the disease is common.
Influenza (flu) vaccine
This is a vaccine that protects horses against one of the most common causes of respiratory diseases. The influenza virus is spread through particles in the air or carried on solid objects. Though Influenza is rarely fatal, it can affect the horse for several weeks. Young horses should definitely be vaccinated because they are most often affected. Show horses (which are exposed to many different horses) or horses with respiratory diseases should be vaccinated. Intranasal vaccines are effective for 6 months & intramuscular injections are effective for 3 to 4 months. Horses should be vaccinated quarterly for intramuscular vaccine.
Equine Viral Rhinopneumonitis
The Rhino virus can have several different forms and cause a variety of problems (neurological diseases, respiratory diseases, abortion). It is passed from horse to horse. The vaccine will reduce the horse’s chance of becoming ill with the respiratory disease, but has no effect of fighting the neurological form. Immunity lasts 2-3 months and may be given every 6 months with the modified live vaccine, which is more effective.
West Nile Virus Vaccine
This virus attacks your horse’s nervous system. It was first identified in the U.S in 1999 and rapidly spread throughout the county. It is carried by birds and transmitted to horses & humans through mosquitoes. Signs include stumbling, lack of coordination, weakness, paralysis, and muscle twitching. Death in horses are reported to as high as 30%. Due to its efficiency and few side effects, this vaccine is recommended in the U.S annually, though it may be administered biannually if the horse is in an area where the disease has been identified.
Potomac Horse Fever Vaccine
PHF is a severe diarrheal disease caused by Erlichia ristieii (bacterial organism) and is carried by ticks. Freshwater snails can also transmit the disease. The vaccine reduces the horse’s chances of getting sick. Requirement depends on geographical location and exposure to other horses. If PHF is in the area, your horse should be vaccinated annually and in high risk areas, twice a year.
Rabies is a 100% fatal viral disease that is transmitted through wild animal bites. The vaccine is safe and effective. Geographical location and the horse’s lifestyle will determine the need for the vaccine. Given annually.
Strangles is a respiratory disease caused by streptococcusequi. This disease is characterized by large abscesses that form in the horse’s lymph nodes. It is passed from horse to horse and flies may play a role in transmission. The vaccination can result in serious side effects Purpura hemorrhagicia, an immune system reaction that may be fatal. Many vets only recommend the vaccine in a high risk exposure area. The newer intranasal vaccine may have reduced side effects.