Vaccination Program Update For Horses by Gary Heusner, Extension Equine Specialist, University of Georgia A planned vaccination program for horses can prevent certain diseases or limit their severity. In the past two to three years, there have been new developments concerning vaccination programs. One of the biggest developments concerns age of the foal or weaning for initial vaccinations. Another development deals with upper respiratory disease vaccines that can now be administered intranasally and appear to be a more effective vaccine for the prevention of the disease than the injectable forms. The vaccination program of the foal should really begin in utero. That is the mare should be vaccinated four to six weeks prior to foaling. These vaccinations include Tetanus Toxoid, Eastern and Western Encephalomyelitis, Rhinopneumonitis, and Influenza. Strangles is one which is normally considered optional but many farms have made the Strangles vaccination a routine one for the prepartum broodmare due to the high incidences of strangles. The importance of vaccinating the mare four to six weeks prior to foaling cannot be overemphasized. There is no transplacental (across the placenta) transfer of immunoglobulins across the diffuse epitheliochorial placenta of the foal. Consequently, foals are born essentially without antibodies, and they must absorb passively transferred maternal antibodies from colostrum if they are to survive. The foal is capable of synthesizing antibodies at birth, but protective levels will usually not be reached until at least two to three months of age. Recent findings also indicate that foals who have received adequate levels of antibodies from the mare should not be vaccinated the first time until approximately six months of age. It has been shown that the maternal antibodies in foals will inactivate many vaccines if foals are vaccinated prior to six months of age. In other words, for many of the diseases for which a foal is vaccinated prior to six months of age, the foal will be unresponsive to the vaccine and you are wasting your effort and money and giving yourself a false sense of security. The American Association of Equine Practitioners now recommend the following vaccination times for foals from which the mare has been vaccinated four to six weeks prior to foaling. The development of intranasal vaccines for influenza and strangles seems to have improved or strengthened the immune response for these diseases. Intranasal vaccines for respiratory disease work better because the nasal cavity or pharynx are where the bacteria or virus enters the respiratory system. Researchers have shown that natural infections induce higher levels of an antibody associated with the mucous membranes lining the respiratory tract versus conventional vaccinations. The intranasal vaccines developed are also modified live vaccines which should also stimulate a stronger immune response that lasts longer than the conventional killed injectable vaccines. Therefore, by using the intranasal vaccines, you will not have to vaccinate as often. Table 1 and 2 provides a comparison of how the injectable and intranasal forms of influenza and strangles should be used. It is important to visit with your veterinarian to determine what your vaccination program should entail. Even the best vaccination program may not prevent all diseases. Vaccinations serve to minimize the risk of infection. All horses are not protected on an equal basis. In addition, it is important that vaccines are stored and handled correctly, as well as being properly administered.
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