10 Most Common Equine Diseases

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We dedicated this article to the “10 most common equine diseases” in honor of our equine vets and equine enthusiasts. You can read about the most common diseases that affect horses and the indications of whether an effective vaccine exists.

If you are pursuing a career in the Equine Veterinary Sciences field, you read our article about How do you become an Equine Veterinarian.

10 Most Common Equine Diseases

10 Most Common Equine Diseases

Equine Influenza (Flu)

Equestrians, veterinarians, and horse owners alike should be aware of equine influenza. The virus is highly contagious and can spread easily through droplets in the air, contact with infected horses, or contaminated surfaces.

  • Clinical signs of equine influenza: fever, coughing, nasal discharge, and a loss of appetite.
  • This is a highly contagious equine disease.
  • vaccine available. When vaccinating horses use the most recent influenza strain available.

Rhinopneumonitis/Equine Herpes Virus (EHV)

Infectious respiratory disease caused by the herpes virus. It causes an upper respiratory tract infection with a variety of clinical symptoms and is most commonly seen in horses, especially those that have been out grazing or exercising regularly. It can be severe in immunocompromised individuals such as people suffering from HIV or cancer. It’s also sometimes called Equine Herpes Virus.

  • Clinical signs of equine herpesvirus: respiratory infections, paralysis, abortion, occasionally death in young horses.
  • This is a highly contagious equine disease
  • The good news is that there is a vaccine available. EHV-4 and EHV-1 strain vaccine for all horses. For abortion protection in the pregnant mare, you should vaccinate at the 3rd, 5th, 7th, and 9th month of the gestation for EVH-1 with “Pneumobort-K”.

Equine Encephalomyelitis (Sleeping sickness)

brown horse with sleeping sickness

Some of these things are: understanding what equine encephalomyelitis is and how it affects horses; knowing where the disease can be contracted; taking precautions to avoid contracting equine encephalomyelitis.

  • Clinical signs of equine encephalomyelitis: loss of appetite, excites and compulsive behavior, walking blindly into objects.
  • This is a vector disease transmitted by mosquitos. Highly fatal.
  •  A vaccine is available.

Equine Infectious Anemia Virus (EIA)

This is a global disease that is affecting horses and other mammalian livestock. The virus is spread by blood-sucking arthropods, such as mosquitoes and ticks. The equine encephalomyelitis virus (EIA Virus) can also be transmitted by ingestion. This virus was discovered in 1922 when it was studied in horses following an epidemic of the disease in Asia and Europe called “horse sickness”.

The EIA Virus causes a disease that affects the central nervous system of the horse.

  • Clinical signs of equine infectious anemia: fever, depression, decreased appetite, fatigue, reduced stamina, rapid weight loss.
  • This is a potentially fatal viral disease.
  • No vaccine, treatment or cure available.

West Nile Virus

West Nile is a virus that can cause disease in humans, horse and other animals. It is spread by mosquitoes, so the best way to prevent it is to avoid being bitten by mosquitoes.

  • Clinical signs of West Nile Virus: loss of coordination, depression, heightened sensitivity to external stimuli, stumbling, toe dragging, paralysis, and even death in severe cases.
  • Mosquito-borne viral disease.
  • A vaccine is available.

Streptococcus Equi (Strangles)

Streptococcus Equi is the most common bacterial infection found in horses. In humans, it will usually cause an upper respiratory infection. Symptoms include fever, nasal congestion, and a sore throat.

If left untreated, Streptococcus Equi can progress to septicemia and death. The organism is typically transmitted through contact with nasal secretions or respiratory droplets from an infected horse or other equine patients.

  • Clinical signs of equine strangles include fever, discharge, cough, loss of appetite, trouble swallowing, swollen lymph nodes, impaired breathing.
  • This is a contagious bacterial disease.
  • A vaccine is available.

Tetanus (Lockjaw)

Tetanus is a serious illness that occurs when bacteria grow in the body. It can affect any part of the body and be life-threatening, especially if not treated. Horses are at risk for tetanus because they may ingest spores of tetanus bacteria while grazing on soil contaminated by animal manure or other waste. This is called “Tetanus In A Tethered Horse” or “Tethered Horse Tetanus”.

  • Clinical signs of tetanus in horses: muscle cramps, high fever, violent reactions to sudden movement or noise, sometimes death from asphyxiation.
  • Bacterial disease (Clostridium tetani).
  • A vaccine is available.
the tetanus virus under a microscope

Equine Rabies

If you’re an equine professional, it’s important to know about rabies. Rabies is a deadly and preventable virus that is transmitted through saliva. Rabies can infect all mammals including horses, cattle, cats, dogs, and humans

Rabies in horses manifests as behavioral changes such as agitation or depression. Other symptoms include asymmetrical paralysis or abnormal gait.

  • Clinical signs of equine rabies: depression, loss of appetite, low-grade fever, abdominal pain, lameness, increased sensitivity to touch.
  • Rabies is inariably fatal. If you suspect that a horse might have rabies call a veterinarian ASAP.
  • A vaccine available and recommended.

Potomac Horse Fever

Potomac Horse Fever is a viral respiratory illness that typically affects horses and, on rare occasions, humans. The disease has the potential to cause clinical signs such as fever and depression in affected animals but can be prevented with proper vaccinations.

  • Clinical signs of Potomac horse fever include characterized fever, lameness, diarrhea, occasionally death.
  • A vaccination is available and strongly recommended in endemic areas.

Equine Protozoal Myeloencephalitis

Equine Protozoal Myeloencephalitis, or EPM, is a potentially deadly disease for horses. It’s caused by the protozoan parasite Sarcocystis neurona and transmitted via the fecal-oral route. Horses can contract the disease through contact with contaminated pastures, equipment, or other horses.

EPM has been known about since 1948 when it was first described in a horse from England who had contracted EPM from another infected horse given access to his stable.

  • Clinical signs of equine protozoal myeloencephalitis include asymmetric incoordination, weakness, spasticity, which may mimic other neurological conditions.
  • No effective vaccine is currently available.