Vaccine Recommendations:
- centerlineequineve
- Mar 12
- 6 min read
There are many vaccine options available for horses, and while some are 'core' vaccines that all horses should have annually, there are other vaccines that are 'lifestyle' vaccines that your horse may or may not need- so let's break these down!
Core Vaccines: Rabies, EEE/WEE/WNV, Tetanus
These vaccines are frequently administered as combo vaccines- the most common combo vaccines contain EEE/WEE/WNV/and Tetanus. Rabies may be included in the combo, or given separately for horses that are sensitive to vaccines.
Rabies:
Once annually.
Very effective at preventing disease
Can only legally be given by a veterinarian.
EEE/WEE/WNV:
Eastern and Western Encephalitis, and West Nile Virus.
Once annually, boostered every 6 months for Florida travel
Very effective at preventing disease, vaccine manufacturer guarantee if given by a veterinarian.
Tetanus:
Once annually, booster after a large/deep wound if close to due for next Tetanus vaccine.
Very effective at preventing disease, vaccine manufacturer guarantee if given by a veterinarian.
Additional details on Core vaccines:
Rabies:
All horses should be vaccinated for Rabies. All. Horses. Rabies is 100% fatal to horses and humans. We have seen a scary uptick in rabies cases in the US this past year, and Pennsylvania has one of the highest rates of rabies in the country! Feral/stray barn cats that are unvaccinated can also be carriers, as can the many types of wildlife that pass through barns and pastures.
EEE/WEE/WNV:
These viruses are carried by mosquitoes. We have seen increasing cases in recent years, and there is no way to prevent mosquitoes from accessing your horse. These diseases are also incurable, and frequently fatal, causing neurological symptoms and death. It is best to vaccinate in early Spring/Summer so that the vaccine immunity is strongest while mosquitoes are most active.
Tetanus
Horses are uniquely sensitive to tetanus- while other animal species may get a scratch and get along fine with just wound care, horses are affected by tetanus at much higher rates. And we all know horses are excellent at finding things to scratch, cut, or injure themselves on! While the vaccine is labeled for 12 months, we typically recommend a booster if they receive a deep injury close to that 12 month mark.
Lifestyle vaccines: PHF, Flu/Rhino, Botulism, Strangles, Lyme
PHF:
Potomac Horse Fever
Ideally twice a year during peak bug activity: April-June and August-October
For horses living near water (streams, creeks, or ponds).
Can reduce severity of disease, but not prevent it.
Flu/Rhino (Flu/EHV):
Every 6 months for horses exposed to travel (boarding barns, show horses, sale barns, trail rides, etc).
Can reduce severity of disease, but not prevent it.
Botulism:
Once annually
For horses eating round bales/large square bales.
For horses receiving the vaccine for the first time, they need 3 boosters 4 weeks apart to be considered protected.
Not effective against Type C (spread by carcasses)
Strangles:
Annual intranasal vaccine
For horses with high risk (large horse shows, frequent travel, auction environments).
Should NOT be given to horses with an unknown history or recent exposure/illness from strangles without a titer first- high titers can cause a dangerous immune response called purpura hemorrhagica.
Can reduce severity of disease, but not prevent it.
Lyme:
Not FDA approved in horses- this is a canine vaccine used off-label in endemic areas.
Immune response is short-lived, so target vaccine to the times of the year that ticks are most active: early Spring and late Summer/early Fall.
Unknown effectiveness- studies show it produces antibody protein, but no studies to prove that the antibodies protect from disease.
Additional details on Lifestyle vaccines:
PHF (Potomac Horse Fever):
This is a vaccine that most people in Pennsylvania should plan to give their horses. Potomac Horse Fever is a severe bacterial infection that attacks the colon. It causes fever, colic/colitis, and laminitis, and can be fatal. It has a complex life cycle that involves spread by snails, mayflies, and even birds. Horses that drink out of creeks, streams, or ponds can be exposed by snails in the water or mayflies and other water-loving bugs. However, even stalled horses can be exposed by mayflies/caddisflies that are attracted by the barn lights and fall into the water buckets or hay.
The vaccine does not prevent the disease, however it has been shown to significantly reduce the severity of infection.
While attending veterinary school in Tennessee, we frequently had at least one horse in the hospital for Potomac almost year round- they get very, very sick and it is not a cheap or easy disease to treat.
Flu/Rhino (Flu/EHV):
This is a common requirement for boarding barns, trail riding groups, and horse shows/events. Equine Influenza and Equine Rhinopneumonitis (also called Equine Herpes Virus, or EHV) are spread from horse to horse. EHV received a lot of media attention this past year due to severe outbreaks out West, and some smaller outbreaks on the East coast. This vaccine is similar to the human flu virus- it does not necessarily prevent all strains of infection, but reduces severity by “priming” the immune system. Any horses that are traveling, coming into contact with new horses frequently, or who have barnmates that travel, should be vaccinated
Botulism:
This vaccine protects against the toxins associated with botulism bacteria. Botulism can be found in the soil, in rotting vegetable matter, or in decaying carcasses. Common sources of infection for horses are moldy hay/feed and dead animals (either caught in a bale of hay or in a water trough). The vaccine ONLY protects from the Type B toxin found in the soil and from decaying feed material. Horses that are fed large square bales or round bales should be vaccinated for botulism, as it is common for the center of the bale to rot/mold faster than the horses can eat it, resulting in botulism toxicity. There is no protection from the form carried by dead animal carcasses, and any hay/feed containing dead animal carcasses should be disposed of.
Botulism causes weakness, inability to swallow, stumbling, and can result in death from paralysis of the diaphragm (resulting in an inability to breathe). Treatment involves referral for hospitalization involving antitoxin and supportive care, but recovery is not guaranteed, and horses that recover can have lingering neurologic damage.
Strangles:
This is a bacterial disease spread from horse to horse. Young horses tend to be the most frequently exposed to strangles, and also the ones who most frequently become ill from strangles. The disease affects the lymph nodes and guttural pouches, which are located deep inside the throatlatch, resulting in a buildup of pus that can restrict breathing (thus, the name ‘strangles’). The vaccine is frequently used in young show horses who are traveling and exposed to large numbers of horses.
However, this vaccine carries the most risk of any that we use: if a horse has an unknown history, recent exposure, or recent illness with strangles they should NOT receive the vaccine without a titer. Strangles vaccines in a horse with a high titer can cause purpura hemorrhagica- a potentially fatal immune response where the body ‘overreacts’ to the vaccine and causes massive vascular damage. This is why we do not vaccinate in the face of an outbreak, or “just in case” unless the horse has a known vaccine/disease history.
Lyme:
There is no approved vaccine for Lyme disease in horses. Many practitioners use the canine Lyme vaccine to attempt to offer some protection for horses in areas where Lyme is endemic, such as the northeast. There are a number of studies, including one from Cornell, that show that vaccination of horses with some of the commonly available Lyme vaccines causes a rise in the titers of Osp-proteins, which are proteins associated with the immune response against Lyme disease. It is unknown at this time whether this provides the same level of protection as it does in dogs.
The Lyme vaccine does not last as long in horses as it does in dogs- the level of Osp-protein response in horses drops very rapidly, and as a result frequent boosters (every 3-4 months) are ideal for maintaining protection. Vaccine timing depends on the weather patterns in your area and are generally considered to be early spring, mid-summer, and early fall to provide an immune response before, during, and after the major activity of Lyme-carrying ticks in Pennsylvania. The highest risk for Lyme disease is early spring, when nymphs (baby ticks) emerge and begin feeding on animals and humans and mid-Fall, when the adults are taking their last blood meals before winter.
As a result, twice-a-year vaccination based in early Spring and then late Summer/early Fall would likely be sufficient in our area.
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