Spring vaccines to protect your horse

By: Megan Slamka, DVM

Getting ready to vaccinate your herd this spring? Here are some helpful insights on how vaccines work, what diseases we consider “core” vaccines and others which are risk based, as well as when vaccination is recommended based on the American Association of Equine Practitioners.

Vaccine technology is always changing and improving. At Anoka Equine, we research the Vaccine Imagebest products to use each year to assure the best protection for your horse, while minimizing the potential for adverse reactions. For example, we currently use the only Rabies vaccine made specifically for horses, greatly minimizing the number of adverse reactions we have seen in previous years.

Vaccines contain parts (antigens) of disease causing agents such as viruses and bacteria that are not strong enough to cause disease, but tell the immune system to make antibodies which protect the horse in the event their immune system is exposed to those antigens in the future. Thus, your horse will be able to develop immunity to a disease without actually having the infection.

Due to the current cases of EHV-1 that are occurring in Minnesota, and how contagious the virus is, it is recommended that your horse receive the Flu/Rhino (Calvenza) vaccine.  Like all vaccines this will not provide 100% prevention of contracting the disease.  This vaccine will not prevent the neurological form of Equine Herpes Virus, but will lower the risk of contracting the virus or decrease the effects of the symptoms, if contracted.  For more information about EHV-1 click here.


The following vaccines are considered to be “core” vaccines. These vaccinations are crucial to preventing diseases commonly found in an area, are highly contagious or cause serious health problems, those that pose a potential public health risk and those that are required by law. These vaccines have proven to be very safe and effective and their benefits are such that all horses should receive them on an annual basis. Hence, the following vaccines should be administered annually. If your horse has not been vaccinated previously, a two dose series should be administered with the second dose being administered 4-6 weeks after the first. Broodmares should be vaccinated annually and 4-6 weeks pre-partum.

          Tetanus is a bacterial infection most commonly caused by contamination of a wound or incision from soil and manure. Despite treatment, there is a very high mortality rate. A booster should be administered at the time of a penetrating injury or prior to surgery if the last dose was greater than 6 months prior.

          Eastern/ Western Encephalomyelitis (EEE/WEE) are viral diseases that cause dysfunction in the nervous system. Birds serve as a reservoir and transmission is via mosquitoes. Humans may also be infected by mosquitoes. We recommend vaccinating annually prior to the onset of mosquito season.

          West Nile Virus is also a mosquito borne virus, which causes neurologic disease in horses and humans. West Nile virus has a 30% mortality rate and symptoms often include somnolence, fever, muscle twitching, and depression. We recommend vaccinating your horse in the spring prior to the onset of mosquito season.

          Rabies is an extremely severe and fatal viral disease affecting the central nervous system. It is spread by the bite of infected animals such as skunks, bats, and raccoons. It is a zoonotic disease meaning transmission can occur between horse and human. Broodmares can be vaccinated prior to breeding or 4-6 weeks pre-partum. Otherwise, vaccination can be done annually in the fall to decrease the number of vaccines given in the spring.


Equine Herpes Virus (Rhinopneumonitis) is a viral infection that can cause respiratory disease, abortions in mares, and neurologic dysfunction. Unfortunately, there is no vaccine for the neurologic form. Pregnant mares should receive the killed vaccine (Pneumabort) at 5, 7 and 9 months of gestation. Your veterinarian may consider 6 month revaccination in horses less than 5 years of age, horses on breeding farms, horses in contact with pregnant mares, performance horses, and show horses, as they are at higher risk. Unvaccinated horses should receive a three dose series at 4-6 week intervals, then annually.

Equine Influenza Virus is a very common viral respiratory disease. Young horses appear to be more susceptible; however, horses of any age can become infected in scenarios where their immune system may be overwhelmed.  Therefore, horses that go to shows frequently or are housed with horses that attend events where large groups of horses are present should be vaccinated twice a year.

Potomac Horse Fever is a bacterial disease that can cause severe diarrhea, fever, inappetance, colic, and laminitis. Neorickettsia risticii is the causative bacteria, which is carried by cercariae (a type of parasite). Cercariae are transported by aquatic insects which can affect horses when ingested.  Therefore, horses housed near bodies of water or swamps may be at increased risk. The highest number of cases occur in late summer to early fall. We recommend annual vaccination prior to August.

Strangles (Streptococcus equi) is an extremely contagious bacterial upper respiratory infection causing nasal discharge, high fevers and abscessed submandibular lymph nodes.  Caution should be used in vaccination of horses with known exposure or in young foals due to risk of development of purpura hemmorrhagica, a life threatening complication of strangles. Horses that attend shows or other events involving large groups of horses may be at an increased risk of exposure and may be vaccinated annually or bi-annually. We use a modified live intra-nasal vaccine that has been shown to induce a high level of immunity.