Equine Vaccinations

Should I vaccinate my horses or not?

Vaccinations are an important part of any pet’s preventive healthcare routine. However, many people question whether or not they need to have their horses vaccinated, and what they need to vaccinate them against. As newly available vaccinations and updated research are accessible, protocols for equine vaccinations frequently change. This makes it hard for a horse owner to keep up with equine vaccination recommendations and determine if they should vaccinate against diseases. An increasing number of recommendations are becoming risk-based recommendations. This means equine vaccination recommendations vary based on risk and individual horse health needs. Questions to keep in mind when determining the necessary vaccines for

your horse include, 'Does your horse travel or stay at home?' 'Do your horse's pasture/barn mates travel frequently?' 'What area of the country are you located in?' 'Are there cost considerations to keep in mind?' and 'What’s the environment like at the barn and in the pastures?' Risk may not be readily identified by non-professionals; it's important to consult a veterinarian when developing a vaccination program for your horses.

Core Vaccinations

The AVMA defines core vaccinations as those “that protect from diseases that are endemic to a region, those with potential public health significance, required by law, virulent/highly infectious, and/or those posing a risk of severe disease. Core vaccines have clearly demonstrated efficacy and safety, and thus exhibit a high enough level of patient benefit and low enough level of risk to justify their use in the majority of patients.”

The following equine vaccines meet these criteria and are identified as ‘core’ in these guidelines and as such are recommended by the American Association of Equine Practitioners (AAEP) to vaccinate each horse on a yearly basis.

Eastern / Western Equine Encephalomyelitis (EEE/WEE)

Eastern Equine Encephalomyelitis (EEE) and Western Equine Encephalomyelitis (WEE) are related viral diseases that affect a horses central nervous system and is usually transmitted by mosquitos. 5-10 days after contracting WEE or EEE, the virus passes to the brain and spinal cord and begins to kill nerve cells. This results in fever and loss of appetite, progressing to incoordination, sensitivity to sound and touch, muscle twitching in the shoulder and flank, head pressing and seizures. Within another day the horse will develop paralysis followed by coma and death in 90% of cases. Because of the high mortality rate, this is considered grounds for a 'core' vaccine. The AAEP suggests each horse get this vaccine on a yearly basis.

Rabies

Rabies affects the central nervous system. While raccoons, bats, skunks, and foxes are the most common carrier of rabies, it can be transmitted by any mammal. Depending on the location of the bite, it can take anywhere from a few days to a few months for the disease to reach the brain and rabies to set it. There is no treatment for rabies, resulting in death nearly 100% of the time. Horses should get the rabies vaccine yearly.

Tetanus

Tetanus is a paralytic disease that is caused when a bacteria known as C. tetani enters a body through a puncture wound. This disease causes the muscles to spasm and lock up, resulting in paralysis and death. Even with rigorous treatment, the mortality rate for tetanus comes in at 75%. Because puncture wounds can be small and unnoticed in many cases, it's difficult to catch tetanus in a timely manner. Vaccinations are recommended to administer yearly by the AAEP.

West Nile Virus (WNV)

WNV is transmitted through infected mosquitos. Signs and symptoms may not be noticed and many horses are able to fight off the disease before it gets serious. In roughly 10% of cases, the disease reaches the central nervous system resulting in elevated fever, muscle weakness and incoordination, loss of appetite, muscle twitching of the face, behavioral changes and paralysis and recumbency. One-third of these horses will either die or need to be put down. Those that survive may take up to a year to fully recover. Based on recommendations from the AAEP, horses should receive this core vaccination yearly, preferably right before mosquito season.

*Vaccinations for EEE/WEE, Tetanus, and WNV can all be administered with a single vaccination known as EWT/WN. This will protect against Eastern and Western Encephalitis, Tetanus, and West Nile Virus. This 4-way vaccine is just as effective as administering individual shots.

Risk-Based Vaccines

Under the guidelines set forth by the AAEP, these are vaccinations included in a vaccination program after the performance of a risk-benefit analysis. The use of risk-based vaccinations may vary regionally, from population to population within an area, or between individual horses within a given population. Consult a veterinarian to determine if your horse would benefit from the following vaccines.

Anthrax

Anthrax is a septicemic disease caused by the spread and reproduction of Bacillus anthracis in the body. Infection is acquired through ingestion, inhalation or contamination of wounds by soil-borne spores. Because soil conditions need the be specific to favor the survival of the organism, Anthrax is only encountered only in particular locations. Vaccination is designed only for horses pastured in endemic areas.

Botulism

Commonly referred to as "Forage Poisoning" and "Shaker Foal Syndrom", botulism is a disease that occurs when toxins produced by the bacterium, Clostridium botulinum, enter the horse's body causing varying levels of muscle weakness which may progress to paralysis and death. 8 types of botulism toxins can be produced. There is currently a vaccine that counteracts one these toxins.

Influenza

Equine influenza is a respiratory virus that is contagious from horse to horse. While any horse can contract it, those in contact with large numbers of horses and horses 1 to 5 years old are more susceptible. Equine influenza is highly contagious and the virus is spread by infected horses coughing. The flu vaccine is particularly suggested for horses that travel a lot as they are usually in contact with many other horses.

Leptospirosis

Leptospirosis can affect any mammal. This disease is caused by a bacterium known as leptospires. Horses become infected through mucous membranes of the eyes or mouth and sometimes through broken skin by contact with infected urine, blood, or tissues. Horses can become infected by eating hay or grain that has been contaminated by infected urine, or they can contract it by drinking from standing water that has been similarly affected. There is currently one vaccine approved for use in horses.

Potomac Horse Fever

Potomac Horse Fever (PHF) is a bacterial disease that is contracted when a horse ingests mayflies and other insects that carry the bacteria. While it used to be confined to the Mid-Atlantic region of the U.S., PHF has now been reported in 43 states. A vaccine for PHF is available, but it only protects against 1 of the many strains of the disease, and in many cases doesn't prevent the disease, but rather lessens the effects once contracted.

Rhinopneumonitis/Equine Herpes Virus

Rhinopnemonitis, also known as Equine Herpes Virus (EHV) is found in many horses worldwide. Most horses have been infected and have the virus, but don't have serious side effects. It is unclear what makes the virus begin to show serious signs in the infected horses. Spread through direct contact with the virus from an infected horse, EHV can cause abortion, respiratory disease, and neurologic disease. Vaccines are available to prevent the respiratory and abortion forms of EHV, but none are labeled as effective against the neurologic form of the disease. The vaccine to protect against the pregnancy loss strain of EHV is reported to be highly effective.

Rotaviral Diarrhea

Rotavirus causes diarrhea in foals. While this is a common disease with nearly 50% of susceptible foals contracting it, rotavirus has a low mortality rate of around 1%, provided veterinary care is provided when needed. The only vaccination available is administered to mares and considered safe as it has been in use since 1996.

Snake Bite

Venomous snake bites to horses occur in several areas throughout the U.S. Pre-exposure vaccination is available for use in healthy horses to decrease the likelihood of mortality in venomous snake bites to horses.

Strangles

Strangles is a bacterial infection that causes abscessation of the lymph nodes. This leads to pus discharge from the nostrils, high fever, and a hacking/strangled sound when the horse breaths. Although it's not typically life-threatening, when the bacteria affects internal lymph nodes, airways can become swollen and prevent airflow, causing death. Use caution when considering vaccination in dealing with an outbreak, as there is a significantly increased risk of adverse reactions in exposed horses

Viral Arteritis

While Equine Viral Arteritis (EVA) is not typically life-threatening to healthy adult horses, it can cause abortion in pregnant mares and, on occasion, death to young foals. Many horses may not show any symptoms or minor flu-like symptoms. In some cases, abortion in pregnant mares is the only sign of the disease. The highest infection rate for EVA is found in Standardbreds and Warmbloods. Those who would benefit most from vaccination would include breeders, racehorse owners, and show horse owners as EVA can eliminate an entire breeding season by causing numerous mares to abort.