Do you have your horses vaccinated?

Farm Forum

The return of spring-like weather is a very welcome development around the region. Personally, the long winter lulled me into a sense of paralysis for preparing for spring. It’s hard to make springtime preparations with all the late March snowstorms we encountered.

But the calendar says springtime, and with it the seasonal changes affecting our animal populations. Springtime means the return of insects that can transmit diseases between animals, as well as the time of year we and our animals get out and mingle more with each other. Perhaps no other species is affected by this relationship between seasons and disease risk than the equine. That’s why spring is horse vaccination time.

A look through the coolers at a veterinary clinic will reveal many options for horse vaccines. The appropriate question to ask – and continually re-visit with your veterinarian – is, “Which ones do my horses need?” As with many disease prevention questions, the answer is, “It depends.”

There are a handful of conditions that every horse should be vaccinated for. Tetanus is first and foremost. Horses are perhaps the most susceptible of all the species to tetanus; it is a risk that cannot be avoided. Tetanus spores can be found everywhere in the horse’s environment. When an injury carries them into a deep wound, tetanus is a likely outcome unless the horse has been vaccinated.

I’ve written about rabies before in this column – in South Dakota, a horse is more likely to encounter rabies than many other diseases for which we vaccinate. There’s no cure for rabies and a rabid horse has the added risk of exposing people to the disease (something I know from personal experience!).

Then there are the mosquito-borne diseases. West Nile virus is a problem here. One just has to observe the numbers of human West Nile cases every summer in South Dakota to see that it hasn’t gone away. West Nile cases still occur in horses each year, but invariably in horses not current on their vaccinations – a good testament for the vaccine’s effectiveness. Eastern and Western Equine Encephalitis are mosquito-borne diseases that are also threats to our horses here.

Those five conditions are on my “core” list of vaccinations for every South Dakota horse because they can be encountered simply out on summer pasture. There are others that should be strongly considered if horses do any kind of traveling or co-mingling with horses from other farms. In recent years, one of those disease conditions has gotten a lot of press: Equine Herpesvirus.

Equine Herpesvirus currently has a lot of horse owners worried. One specific strain is associated with neurologic problems in horses, resulting in quarantines when it’s detected on a premise. This “neuropathogenic” strain of equine Herpesvirus-1 (EHV-1) is related to EHV-4 (“rhino”), which commonly causes upper respiratory problems in horses and is very contagious. Another strain of EHV-1 is associated with abortions in pregnant mares and other illness.

We have been vaccinating horses against rhino for many years. It’s necessary (along with influenza) for horses that have a high chance of encountering horses from other farms or their environments. The trouble is that current vaccines are not 100% protective against these EHV-1 neuropathogenic strains. However, horses currently vaccinated for rhino are likely better off should they become exposed to this neuropathogenic form. The limitations of current vaccines should not be an excuse to drop them from the program; rather they are a reminder of the importance of biosecurity and isolation following horse events.

We should also keep in mind that vaccines vary in their duration of protection. The first year a foal is vaccinated, he will need more than one dose of a vaccine in order to adequately charge up his immune system. Additionally, your veterinarian may recommend giving more frequent boosters of flu and rhino vaccines for horses that travel a lot.

The landscape of preventable horse diseases is changing. That means a conversation with your veterinarian prior to spring is always a good idea. Make sure your vet understands how you use your horses and how frequently they encounter other horses. That will help them design a vaccine program that ensures your horses are as well protected as possible this year.

Russ Daly, DVM, is the Extension Veterinarian at South Dakota State University. He can be reached via e-mail at or at 605-688-5171.