Vaccines protect horses from disease by increasing circulating levels of certain antibodies in the blood. Most vaccines require two doses, 2-4 weeks apart, when given for the first time in a horse’s lifetime. Thereafter, it is currently believed that boosters are required to maintain immunity each year. Below are listed the vaccines most commonly given. We recommend that all horses receive Rabies and EEE/WEE/tetanus/West Nile Virus vaccinations annually, as bare minimum protection if your horse is healthy enough to receive vaccines. Other vaccines are recommended based on the horse’s environment, travel, and other considerations.
Rabies is a deadly virus that causes fatal disease in 95% of cases. All mammals, including humans, can contract the disease, usually through a bite or contact with saliva from an infected animal. Rabies vaccine is one of the core vaccinations we recommend for all horses. All pet animals and livestock need to be vaccinated for Rabies. In horses, the vaccine must be administered every year to be considered current.
If a vaccinated animal is bitten by or comes in contact with a rabid animal, they must receive a booster Rabies vaccine within 5 days. If an unvaccinated animal is exposed to a rabid animal, NJ State recommends euthanasia. The alternative is a 6 month period of observation with strict isolation. If a horse shows signs of Rabies, and has not been currently vaccinated, upon euthanasia, legally their head must be submitted for Rabies testing, due to the human health exposure risks. The vaccine is very safe and effective, and we strongly recommend that your horses and camelids be protected by annual vaccination.
EEE/WEE/Tetanus/West Nile (EWTW)
This combination vaccine is considered to be a core vaccine – one recommended for nearly all horses. EEE (Eastern Encephalomyelitis) and WEE (Western Encephalomyelitis) are fatal viral diseases transmitted by blood sucking insects, most commonly mosquitoes. Wild birds and rodents are natural reservoirs of the diseases. Humans are susceptible to these both EEE and WEE when the virus is transmitted to them by infected mosquitoes. Signs in horses include profound neurologic disease and acute death. Multiple unvaccinated horses in New Jersey died of EEE in 2016. See http://nj1015.com.
Tetanus is a disease caused by the bacterium Clostridium tetani, and it is often fatal. Tetanus is usually associated with wounds, especially punctures. Treatment for encephalitis or tetanus is rarely successful.
Clostridium tetani can be found in the soil as well as in the intestinal tract and feces of horses, other animals and humans. Spores survive in the environment for many years, and contamination of any wound or exposed inflamed tissues with spores can lead to tetanus. The severity of the wound does not predict the risk of tetanus as is can be contracted even with superficial wounds.
West Nile virus has been identified in all of the continental United States. The virus is transmitted via mosquitoes and other blood sucking insects to horses, humans and other mammals from bird reservoir hosts. The virus is amplified in birds, which can harbor the virus for long periods of time. When mosquitoes feed on the birds, they then become carriers of the virus. Horses sick with West Nile Virus show neurologic signs that can mimic EPM or other diseases. Treatment for affected horses is symptomatic and aimed at relieving inflammation of the nervous system, maintaining hydration, and preventing secondary illnesses. About 35% of horses affected by West Nile virus die or are euthanized. Those horses that do survive the infection often have residual effects like gait abnormalities or behavioral changes for 6 months or more post infection. Although cases can be seen any time that mosquitoes are active, the majority of cases are seen in late summer and early fall.
The vaccine is safe for use in all age groups, including pregnant mares. Two doses 2-6 weeks apart are required the first year the vaccine is given, followed by an annual booster. We recommend that all horses be given this vaccine, and in cases where mosquitoes are especially bad, a booster may be necessary in the late summer to early fall to give the best protection.
EEE/WEE/Tetanus/Flu/Rhino/West Nile (EWTFRW)
This vaccine also includes Influenza and Rhinopneumonitis (see below). We recommend this combination vaccine for all of our patients who have any contact with other horses. New data shows that for most horses, a single combination vaccination shot is friendlier to the immune system than multiple separate vaccines to accomplish the same protection. This is because combination vaccines create much less exposure to adjuvant (the part of the vaccine that is made to ramp up the immune system to cause a memory response by the immune system) compared to giving multiple separate vaccines; with one combination vaccine the horse is only exposed once to adjuvant.
Influenza (aka “Flu”) and Rhinopneumonitis (aka “Rhino” or Equine Herpes Virus) are contagious respiratory diseases in horses. Vaccination for influenza and rhinopneumonitis is generally recommended for any horses that have any contact with other horses. The vaccine that we use for Influenza guarantees protection for one year, however the Rhinopneumonitis (EHV) needs to be given at least every 6 months.
Rhinopneumonitis /Equine Herpes Virus most commonly causes a respiratory illness characterized by fever, nasal discharge, and cough. Clinical disease is most commonly seen in horses that travel, show or are otherwise exposed to a changing population of horses, or under stress. In pregnant mares, exposure to EHV may cause abortion. An estimated 80% of horses over the age of 2 years are carriers of EHV, which is contracted for life. When under stress, the virus becomes active and the horse becomes ill and/or sheds virus in his nasal secretions. Because carriers can become ill repeatedly and/or spread the disease to others through nasal secretions, future outbreaks are inevitable in the horse population.
Along with abortions and respiratory disease, EHV can also cause a neurologic syndrome with weakness, ataxia (loss of balance), and hind end paralysis. A mutation in the virus occurred early in the 21st century, causing an increase in the number and severity of cases of neurologic EHV. In 2003, many horses in Ohio at a Findlay riding school were affected with the neurologic form, and since that time there have been yearly clusters of cases both on racetracks and in riding stables throughout the US. Although the majority of cases recover, 30-50% of these cases are ultimately euthanized. During the time the horses are sick, they shed virus in nasal secretions that are highly contagious.
In summary, EHV can cause abortion in pregnant mares, respiratory problems in all horses, and less commonly, neurologic disease in some horses. Vaccination cannot completely prevent illness from EHV, but can substantially lessen the incidence.
Influenza, or “Flu” is a highly contagious viral respiratory disease that causes high fever, depression, cough, and nasal discharge that can last for 2-4 weeks, but is rarely life threatening. However, the inflammation may cause a lingering cough that can curtail riding for months. Vaccination is highly effective.
Strangles (Strep Equi equi)
Strangles vaccination is only recommended for horses which will be shown frequently, have frequent contact with unfamiliar horses, travel to different premises, or reside on farms with a history of repeated Strangles outbreaks. Because the vaccine has a higher undesirable side effect rate than many of our other vaccines, we don’t recommend it except for horses with these higher risks. Strangles is a highly contagious bacterial disease characterized by high fever, thick nasal discharge, and lymph node abscessation. While only occasionally fatal, horses can require weeks of recuperation and nursing care. Sometimes internal abscessation occurs, and this can cause death after a prolonged course. The nasal secretions of sick horses contain large numbers of bacteria, which can be easily transmitted by contact with nasal secretions and abscess drainage via people, shared tack/equipment and water sources.
Potomac Horse Fever (PHF)
Potomac Horse Fever is a non-contagious disease that causes depression, fever, and loss of interest in feed, followed by diarrhea and commonly by laminitis, especially if early signs are ignored. In some areas of country in recent years, a particularly severe strain of PHF caused multiple deaths due to severe laminitis despite appropriate treatment. Treatment includes intravenous fluids, antibiotics and anti-inflammatory medications for 5-7 days. Vaccination for PHF can be effective in reducing the severity of illness, but is disappointing in entirely preventing the disease.
The bacteria Clostridium botulinum, commonly found in soil, causes this neurologic disease characterized by ascending paralysis, which can progress to death by suffocation. There is an increased prevalence of this disease among both foals and adults in the Mid-Atlantic states because preformed toxin is often present in the soil. Treatment with antitoxin plasma can help survival, but is very expensive. Supportive care, tube feeding and IV fluids are usually necessary. Foals are particularly susceptible to the effects of the botulinum toxin. The first year of vaccination, three doses one month apart must be given. In subsequent years, a single dose booster is given.
Lyme disease is caused by the spirochete bacteria Borrelia burgdorferi. It is spread by ticks. Signs of the disease are quite variable, which can make it difficult to distinguish, and blood tests are helpful to determine if treatment is warranted. Treatment is generally successful but can quite some time in some cases. Signs can include generalized stiffness, extreme sensitivity to being touched (called “hyperesthesia”), seeming sore to skin pressure, weight loss, performance decline, lameness that shifts from leg to leg, or seems better some days than others, loss of muscle tone, slight fever (less common), swollen joints (less common). Severe cases can get nervous system disease, and / or serious eye problems. There is not yet an approved vaccine for horses. However, there is more and more work being done using one of the vaccines that is approved in dogs, at a higher dose. We DO NOT recommend this vaccine to be given at the same time as other vaccines. If you wish to discuss the pros and cons of vaccination for Lyme disease please contact us.
Leptospirosis is a bacterial infection caused by spirochete bacteria that belong to the Leptospira family. Leptospirosis can cause equine recurrent uveitis – a debilitating inflammatory condition that affects the eyes. It can also infect the kidneys and lead to abortion and acute kidney failure. Horses become infected when they come in contact with the spirochetes which can be shed in infected animals urine, as well as aborted fetuses and vaginal secretions. Wildlife such as opossums, raccoons, skunks and white tailed deer all serve as maintenance hosts and can pass on the disease. The bacteria can survive for weeks in warm, moist environments, and the bacteria can penetrate mucous membranes or abraded skin. Appaloosas and Warmbloods are more severely affected than some other breeds. There is a new approved vaccine for this disease. If you would like to discuss the pros and cons for vaccination for Leptospirosis, please contact us.