Guide to Horse Diseases: Symptoms and Treatments.

Some of the most common horse diseases, that horses are susceptible to, are preventable with the proper horse vaccines. This is why it is so important to keep up with you vaccination schedule.

Planning a good vaccination program for your horse is a very important factor when owning horses. Equine diseases can cause loss of use or even death for a horse. If your horses are like mine, they become family members. I can not imagine the guilt that I would feel if my horse became ill or died, because of something that I neglected to do.

Tetanus(lockjaw) - is a bacteria that enters the body at the sight of a wound or the umbilical cord stump in a foal. Its symptoms are early signs of colic and stiffness. Horses will develop spasms in the jaw, neck, hind legs and muscles around the wound.

If this disease goes untreated, as it worsens, the horse will develop labored breathing. Stiffness develops in the front and hind legs. The tail is held out stiffly, ears are erect and nostrils will be flared. The jaws will contract so that the horse is unable to open his mouth. In the final stage, the horse will lie down and die of respiratory paralysis.

Treatment: The wound must be opened widely, removing all infected tissue. It must be washed thoroughly and penicillin injected into the wound. Wounds must be left open to allow for drainage.

Prevention: Thoroughly clean and treat all new wounds. This will prevent most cases of tetanus. Foals should be given a tetanus shot when they are born.

Eastern(EEE)/Western(WEE) and Venezuelan Equine Encephalitis(VEE) - These are the 3 mosquito transmitted horse diseases. They attack the central nervous system of horses. EEE is the most dangerous, with a mortality rate of 70 to 90 percent. WEE is the least dangerous of the 3, its mortality rate is about 20 to 50 percent.

The first signs of these diseases are a high fever which may last for 2 or 3 days. Brain inflammation will start to occur. Signs of brain inflammation are compulsive walking, loss of coordination and apparent blindness. As the disease progresses, the horse becomes extremely lethargic and seemingly oblivious to his surroundings. This stage is referred to as “sleeping sickness”.

As it starts to affect the spinal cord, the horse will develop a staggering gait, weakness and muscle twitching.

The final stage is paralysis. The horse will develop seizures and will collapse, unable to breath.

Call your vet immediately if you suspect your horse has this disease. Intensive treatment is critical for a successful outcome.

West Nile Virus(WNV) is a mosquito-borne virus that causes encephalitis (inflammation of the brain) and/or meningitis (inflammation of the lining of the brain and spinal cord).

Typical signs include muscle trembling, skin twitching, ataxia (uncoordination, stumbling, limb weakness) that appears suddenly. In some cases it appears gradually and worsens. Sleepiness, dullness, listlessness, facial paralysis (droopy eyelids, lower lip), difficulty with urination and defecation, and an inability to rise are also signs. Some horses may develop mild fevers, blindness and seizures.

There is currently no vaccine for humans, but there is a vaccine for horses. Getting your horse vaccinated will prevent this disease.

Rabies - Is transmitted through a bite from an infected animal. It is a highly fatal infection of the central nervous system. Its symptoms include, increased saliva, excitability, disorientation and running blindly.

Equine Influenza - an upper respiratory disease that is similar to the flu in humans. Its symptoms are a nasal discharge, cough, fever and loss of appetite.

Treatment: Isolate this horse from the rest of the herd. Stall rest is very important. Butazolidin is used to control fever and muscle stiffness.

Potomac Horse Fever - is a diarrheal disease that is infrequently seen in the western U.S. Horses with symptoms will develop high fever, lethargy, loss of appetite and diarrhea. The stool is very watery and abundant.

Strangles - Strangles is a highly contagious horse disease that can spread rapidly throughout a herd. Symptoms can range from very mild to severe. These include, swelling of the lymph nodes under the jaw, nasal discharge, fever, fast breathing and lethargy.

When the lymph nodes swell, they will often abcess and drain. After dealing with a horse who has strangles, always wash your hands thoroughly before touching another horse.

Equine Herpes Virus/Rhinopneumonitis - is a serious respitory disease in young horses, ages two and under. It is highly contagious and can spread rapidly throughout a herd.

The herpes virus can cause late abortions in pregnant mares. Its symptoms are nasal discharge, cough and fever. However it is not fatal to most horses.

Equine Infectious Anemia(Swamp fever) - This is more often than not, a fatal horse disease. It is very contagious and is transmitted by blood sucking insects, such as horseflies and mosquitoes. Symptoms include rapid weight loss, fever, sweating, weakness, anemia, and swelling of the limbs. The mortality rate is very high, sometimes sudden death is the first indication.

A Coggins test detects the presence of Equine Infectious Anemia. All horses that travel into the U.S. are required to have a negative Coggins test. Once your horse has tested negative, your vet will give you a signed paper which states that your horse is negative. This document, (or a copy) should be carried with the horse wherever he travels. You should also make this a requirement before introducing any new horse into your barn.

Equine Viral Arteritis - an acute respiratory illness similar to influenza. Typically, fluid will accumulate in the hind limbs, sheath, scrotum and abdominal wall. Other signs of this horse disease include loss of appetite, dehydration, colic and diarrhea.

Cushing's Disease is a disease of the endocrine system and there is no cure. With daily medication to control symptoms, most horses can lead a somewhat normal life.

This disease normally occurs in ponies and older horses, however it has been known to happen in younger horses.

Cushing’s is caused by a tumor on the pituitary gland. The tumor causes the gland to produce excessive amounts of the hormone, cortisol.

Symptoms of Cushing’s Disease

• Long, wavy haircoat, that does not shed in the spring.
• Excessive water intake
• Increased appetite
• Weight loss, despite the decreased appetite
• Increased urination
• Will have more bouts with laminitis

It affects the nervous system by interrupting nerve transmission to the muscles, causing paralysis.

Some signs of this disease are: sudden high fever, loss of appetite, depression, and respiratory problems.

Salmonellas - Salmonella is the most common cause for infectious diarrhea in horses. This bacteria can remain alive for months or years in the soil and in manure.

The symptoms are high fever, colic and foul-smelling, watery green to brown diarrhea. The onset of this disease is sudden. The horse can get seriously ill and will rapidly dehydrate. Death can occur within 12 hours.

If you suspect your horse of having this disease, get medical attention immediately.

Colitis X - is a toxic horse disease of the cecum and large colon. It produces severe, watery diarrhea. This disease is most often fatal. Signs are sudden pain and explosive, sometimes bloody diarrhea. The horse most often dies within a matter of hours.

Anthrax - is a highly contagious, mostly fatal disease that affects all animals. Horses acquire this disease by grazing on infected pastures. This bacteria can lie dormant in the soil for up to 50 years.

The first signs of anthrax are high fever, colic and the appearance of hot swollen areas of the throat, neck and belly. A horse will develops a staggering gait, rapid breathing, coma, then death.

Because of the hazards of this disease to humans, great care must be taken when handling these animals. Because of the rapid progression of this disease, death often occurs before treatment can begin.

Vesicular Stomatitis - is a highly contagious disease affecting horse, cattle and swine. It is transmitted by the biting black fly and possibly other biting insects. It can also be transmitted from horse to human.

Some signs of this horse disease is lethargy, fever and small blisters containing clear fluid, on the mucus membranes.

Notify your vet immediately if you suspect this horse disease, as infected horses must be quarantined. Usually the horse will recover in about 2 weeks, after treatment. Insect control is the best way to combat this disease.

Histoplasmosis - this disease is caused by spores found in contaminated soil. Contamination occurs from the dung of chickens, birds and bats. Most infected horses will suffer only a mild respiratory illness.

Blastomycosis - a skin disease that forms nodules and abscesses which ulcerate and drain. A systemic form of this disease is very similar to histoplasmosis.

Cryptococcus - a fungal disease that is acquired by inhalation. This fungus usually grows well in chicken, pigeon and bird dung. Infection will start in the nasal cavity and pass through to the lower respiratory tract, where it causes pneumonia.

Coccidioidomycosis - a mild respiratory infection that can, (on rare occasions), spread to all organs of the body.

Aspergillosis - a horse disease usually contracted by the inhalation of spores from damp hay.


As you can tell by reading through these horse diseases, most of them have a lot of the same symptoms. Never try and diagnose your horse, yourself. Always contact a vet immediately, if you suspect any illness or horse disease.

Health certificates are also important. This is a signed document by your vet, stating the health of your horse within ten days of traveling. Some horse shows require a copy of a health certificate. They have to be sure that he is free from any contagious horse diseases that could be spread to the other participants.