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Fall Vaccines for Horses

Fall Vaccines for Horses
By Elizabeth Davis
This time of year we are all looking forward to cooler temperatures. As a horse owner, the best part about fall is knowing we won’t have to deal with as many insect-related issues—hooray! Instead, we’re starting to think about housing, nutrition, and preventive health strategies for cooler weather. One important aspect of preventing disease is the use of seasonally appropriate vaccinations—in this case, fall vaccines for horses.
The AAEP’s vaccine guidelines are integral to designing a vaccine plan for your horse. Talking with your veterinarian will help you make decisions that are specific to your horse, based on factors such as age, geographic location, use, transportation frequency, and previous vaccinations.
?Owners need to understand the difference between core and risk-based inoculations. Core vaccines include Eastern and Western equine encephalomyelitis (EEE/WEE), West Nile virus (WNV), tetanus, and rabies and should be administered to all horses at least annually following an initial two- to three-dose series. The initial dosing series frequency is based on the horse’s age at the time your veterinarian administers the initial vaccine series. Ideally, the veterinarian administers core vaccine boosters in the early months of the year (spring in the Northern Hemisphere) so horses will have mounted a robust immune response by the time exposure to the pathogen is likely to occur. 
Transmission of insect-vectored diseases is linked to climate and season. This is why we want to vaccinate early in the year to allow the horse to produce antibodies that will provide protection later in the year when potential virus-carrying mosquitoes are in highest numbers. In geographic regions where mosquito populations persist well into the fall months, additional booster vaccinations against EEE/WEE and WNV are sometimes indicated in mid- to late summer. These later boosters will help the horse sustain high levels of protective immunity later in the year, helping ward off infection.  
Risk-based vaccines protect against a variety of diseases that can affect certain horses but are not necessarily a risk for all horses and are less likely to result in death. Depending on the type of vaccine, it is not uncommon to administer risk-based vaccines more than once annually, necessitating a booster vaccine in the fall months in addition to those given in the spring. Risk-based diseases include viral respiratory pathogens such as equine influenza (EIV) and equine ­herpesviruses-1 and -4 (EHV-1/4), also termed rhinopneumonitis. Horses that compete, travel, and are exposed to horses from other farms are at a higher risk of coming into contact with these pathogens—this is why they are classified among the risk-based vaccines. When horses are infected with these pathogens, they can develop clinical signs of respiratory disease such as lethargy, high fever, mucoid (mucousy) nasal discharge, and coughing. 
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