EQUINE VACCINATIONS There is not a standard vaccine program for all horses. Instead, each individual horse requires a protocol based on the following criteria: • Risk of disease (age, breed, use, anticipated exposure, environmental factors, geographic factors, etc) • Consequences of disease (prevalence, mortality, risk of human infection) • Effectiveness of selected products • Potential for adverse reaction to vaccines • Cost of immunization vs. potential cost of disease Realistically, it should be understood that: • In the absence of good management practices for disease control, vaccination alone may not be enough to prevent infectious disease • Vaccination minimizes the risk of infection, but cannot prevent disease in all circumstances • Vaccines do not provide immediate protection to a patient, and boosters must be initially given to activate proper immunity • Primary vaccines and booster doses should be administered prior to a likely exposure • Every horse in a population is not protected to the same degree or duration with each vaccination • There is always the potential for an adverse reaction to a vaccine despite their appropriate handling and administration. Ideally, the same schedule is followed for all horses in a population. This minimizes the transmission of infectious disease in a herd and protects horses in the herd that respond poorly to vaccination (herd immunity). The American Association of Equine Practitioners (AAEP) has established core vs. non-core vaccination recommendations. A core vaccine is described as one which protects from disease that is prevalent in a region, poses a potential danger to public health, is required by law, is highly infectious, and/or poses risk of severe disease. Core vaccines have established efficacy and safety, and therefore have a high enough level of benefit to offset the risk associated with their use. The following vaccines are described as core vaccines: Eastern/ Western Equine Encephalomyelitis, Tetanus, Rabies, and West Nile Virus.
vaccinations and are regularly vaccinated. Different protocols exist for horses which have never been vaccinated, pregnant mares, and foals. Please speak to your veterinarian before instituting a vaccine protocol for these groups of horses. Eastern and Western Equine Encephalomyelitis (EWT) Eastern Equine Encephalomyelitis (EEE) is most present in the south-eastern US. Western Encephalomyelitis (WEE) is typically reported in the western and mid-western states; however, there have been sporadic outbreaks of WEE in Florida. Venezuelan (VEE) occurs in Central and South America, and has not been reported in the US for 40 years. Horses typically receive an EEE/WEE combination vaccination, which may be partially protective against VEE infection. EEE/ WEE/VEE is transmitted by mosquitoes from wild birds and rodents. Humans are also susceptible to these diseases through mosquito bites. Transmission of any of these viruses from horse to horse or from horse to human is highly unlikely. WEE has a mortality of approximately 50% and EEE of approximately 90%. Research has shown that young horses are very susceptible to disease caused by EEE virus. Since mosquitoes are active year round in Florida, vaccination for EEE/WEE is recommended every 6 months. Typically the vaccination used is a combination vaccine of EEE and WEE with tetanus, commonly called “EWT.” Tetanus Vaccination Tetanus is caused by the bacterium Clostridium tetani. C. tetani is found in the intestinal tract and feces of horses, other animals, and humans, as well as in the soil. C. tetani is a hardy bacterium, and can survive in many environments for long periods of time. Tetanus is not contagious; instead, infection is due to the bacterium infecting wounds, surgical incisions, the umbilical cord of foals, and the reproductive tract of mares after foaling. There are two types of tetanus vaccines: toxoid and antitoxin. The toxoid vaccine is what is used to regularly vaccinate horses. The antitoxin is only used in specific cases where an injured horse has never received a tetanus vaccine. Typically horses are vaccinated for tetanus with a tetanus toxoid on an annual basis. Horses that sustain a wound or undergo surgery more than 6 months following their latest tetanus booster should be immediately revaccinated with the tetanus toxoid vaccine. West Nile Vaccination
Following is a description of an ideal vaccination protocol for horses in the southeastern US. Since the southeast has an active mosquito population year round, typically horses are vaccinated more aggressively against mosquito-borne diseases in this area. The following vaccination protocol is for horses which have received the complete series of booster
West Nile Virus (WNV) is one of the leading causes of encephalitis in horses and humans in the United States. Since 1999, horses represent 96.9% of all non-human mammalian cases of WNV. WNV has been identified in the entire continental US, most of Canada and Mexico. The virus is transmitted by mosquitoes from bird hosts to horses, humans and other mammals. Humans and horses are dead-end hosts for WNV. There have not been reports
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HorseNRanchMag.com
VOLUME 6 | ISSUE 8 2020
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