Vaccinating your horse is just one of the steps you can take toward controlling infectious diseases in horses. You should develop a program that includes all of the important components of good managerial practices in the control of disease.
This program should:
- Reduce the horse’s exposure to infectious agents in its environment
- Minimize factors that reduce the horse’s resistance to disease
- Enhance your horse’s immunity with vaccines
Vaccination alone is often times not successful in preventing disease, but it may lessen the severity of the disease process and minimize the risk of infection. It is imperative that the vaccines be administered appropriately and at the time of most likely exposure. Not all horses are protected to the same degree or for the same duration after vaccination. Attempting to keep all horses in the same herd on a similar schedule will help increase herd resistance to infection. Accurate and precise vaccination records are very important. Once the vaccine has been administered following the manufacturer’s guidelines, there is a period of time before the horse’s body produces active immunity.
Immunity comes in both natural and acquired forms. From the time the horse is born, it begins developing acquired immunity. The term vaccine originated from immunization against smallpox virus with vaccinia virus. Vaccines work by introducing an antigen derived from an infectious agent into the animal’s system so that an animal will mount a specific immune response to the antigen and will achieve resistance to the agent. When you first introduce vaccines to a horse, you have to give at least two injections at least three weeks apart. The reason for this is so that the body can recognize the antigen the second time around, and build a more intense response. Once the initial program has been instituted, re-exposure to the antigen allows for a very strong immune response.
There are three methods of producing vaccines, which are live vaccines, modified-live vaccines, and killed vaccines. The live vaccines may stimulate a very good immune response, but pose risks of causing disease in the horse. The inactivated vaccines do not produce as good of immune response, but are very safe for animals. Administration of the vaccine does not always mean that the vaccine is going to be effective. If the animal is sub-clinically infected with the disease when the vaccine is given, the vaccine will not be protective. Animals with a suppressed immune system, such as heavily parasitized or malnourished animals, will not produce an appropriate immune response. Stress caused by fatigue and extreme heat or cold can also reduce the normal immune response.
The recommendation that vaccines should be administered by, or under direct supervision of a veterinarian comes highly when considering the possibility of an anaphylactic reaction to a vaccine. Anaphylactic shock can occur within seconds after the vaccine enters the circulation. Horses will develop severe inflammation of the upper airways, such that extreme difficulty with breathing occurs. They can become extremely agitated, nervous, get hives, and begin acting colicy due to the edema that may form in their GI tract. There are times when the reaction is so severe that cardiovascular insult leads to death