August 01, 2017

Disease Risks Remain as Summer Comes to an End

Diseases don’t take a break, even if your horses do

DULUTH, Ga. — As the days get shorter and opportunities for equine activities dwindle, the immunity provided by some vaccinations administered earlier in the year may also be diminishing. So whether you are out on the trail enjoying fall colors or heading to a show, fall booster vaccines should be considered as a part of your overall vaccination protocol.  

A fall vaccination program may depend on what was administered previously in the spring and the area of the country. “Veterinarians may recommend boostering what they gave in the spring, including eastern and western equine encephalitis [EEE, WEE], West Nile Virus [WNV], tetanus, equine influenza virus [EIV] and rhinopneumonitis,” notes Scott Hancock, DVM, Equine Professional Services Veterinarian at Boehringer Ingelheim. He adds, “Rabies may or may not be necessary in the fall if the horse received a rabies vaccine in the spring.”

The boostering of EEE, WEE and WNV in the fall can depend on the geography and the climate.  For example, if a horse resides in, or if it is showing in, a more temperate climate with a longer mosquito season, it could be at risk for mosquito borne diseases later in the year.  

Climate and Travel, Show and Training Considerations

Mosquito-borne diseases appear to have been on the rise for the past several years. And, in areas where it has been unseasonably warm during the year, the mosquito season could be extended, according to Dr. Hancock. “In these areas, I would strongly urge horse owners to discuss the need for booster vaccinations for WNV, EEE and WEE with their veterinarians,” he says.  

Respiratory diseases such as EIV, rhinopneumonitis and strangles are not dependent on climate or location, and persist as a continual threat throughout the year. Owners should have a risk-based discussion with their veterinarians to determine if there is a need for modifying their vaccination protocols, depending on show, training, travel schedule and frequency of new horses moving in and out of the barn or training facility.

Direct Protection

Choosing the right vaccine is also important. Not all vaccines are created equal, Hancock explains, so it pays to be certain you are using a vaccine with up-to- date and relevant vaccine strains. In the case of equine influenza, the virus is subject to antigenic drift (mutations occuring within the virus). “If you use a vaccine with an influenza strain that more closely resembles what is currently circulating in the equine population, you will have better protection as compared to using a less relevant strain of flu,” he says. Vetera® XP vaccines, from Boehringer Ingelheim, are the only vaccines in the U.S. updated with influenza strains recommended by the Expert Surveillence Panel on Equine Influenza.  

“Ideally, horses will develop antibodies against the relevant vaccine strain, resulting in a significant reduction of clinical disease and nasal shedding of the virus,” points out Hancock. “Vaccines that contain outdated strains of influenza may provide only partial clinical protection, and may result in nasal shedding of the virus, oftentimes as much as an unvaccinated horse, thus putting other horses at risk.” 1,2

Vaccinating Pregnant Mares, Foals

Fall booster vaccinations also coincide with the timing for vaccinating pregnant mares against the abortive form of equine herpes, which should be considered at five, seven and nine months of pregnancy. Consult with your veterinarian to ensure the appropriate vaccine is chosen for that particular form of equine herpes.

With some breeds actually foaling very early in the spring, pregnant-mare vaccinations should be discussed with your veterinarian to offer optimum protection for the newborn foal. There are specific vaccines that have demonstrated safety and are labeled safe for use in pregnant mares. According to Dr. Hancock, foals are protected by the mother’s maternal antibiodies through the colostrum, but those antibodies start waning around 4 to 5 months of age.  Vaccinations of foals should coincide with the decline of maternal antibodies at 4 to 6 months of age, followed by boosters in three to four weeks.

For more information on vaccination and to learn about the available combinations of VETERA vaccines, visit or talk to your veterinarian.

1 Elton, D., Cullinane, A., 2013. Equine influenza: Antigenic drift and implications for vaccines. Equine Vet. J. 45, 768-769.
2 Paillot, R. Hannant, D., Kydd, J.H., Daly, J.M., 2006. Vaccination against equine influenza: quid novi? Vaccine 24, 4047-4061.

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