Skip to main content

Specific Conditions

The veterinarians at Full Circle Equine Services are committed to promoting responsible horse ownership, preventative health care, and health-related educational opportunities for our clients. We offer a complete list of Care Guide topics.


The word colic describes abdominal pain, which can be caused by many different problems. It can occur suddenly or gradually over a period of days.

Horses often develop colic because their digestive systems are very long (more than 100 feet) and complex. Certain parts of their digestive system are prone to develop twists and impactions (blockages) of food material.

Horses’ digestive systems are designed for foraging, eating small amounts of food throughout the day while on the move. However, domestic horses are often fed large amounts of highly concentrated diets (e.g., grain) two or three times a day and kept in small areas without enough pasture turnout, grazing and exercise. Stress from activities such as racing or showing may also contribute to colic.

Colic can have many signs, but the most common can include Decreased eating and/or drinking. Reduced quantity of manure or decreased frequency of defecation. Change in consistency of feces (e.g., small, hard manure balls vs. large, soft manure piles. Disturbed bedding, showing that your horse has been pawing or getting up and down. Kicking at abdomen. Pawing. Looking back at the abdomen. Lying down and getting up repeatedly. Rolling or thrashing. Sweating. Increased respiration/breathing rate. Increased heart rate. Fever. Lack of gut sounds (check with stethoscope).

The most important step in treating colic is to contact your veterinarian immediately. Do not attempt to diagnose and treat colic on your own. Most colic cases can be treated at the farm by your veterinarian with the use of pain-relieving medications, muscle relaxers, laxatives, and fluids. However, some cases require more sophisticated diagnostic tests and/or surgery and will need to be transported to a clinic.

In general, the more intense the signs are of pain, the more serious the episode of colic.


Infection with Streptococcus equi equi, also commonly known as strangles, is a very contagious infection that can spread quickly among horses. It can affect one or two horses on a farm, or many horses affected in large outbreaks.

While any horse can develop strangles, young horses are more often affected. This infection is usually spread through contact with an infected horse through nasal discharge (such as nose-to-nose contact with a horse that has a runny nose) or sharing equipment (such as buckets and automatic waterers) or through contact with people handling an infected horse.

The bacterium Streptococcus equi equi infects horses’ lymph nodes, especially under the jaw and around the throat. Horses that routinely have contact with unfamiliar horses (such as at shows or other events) or that are boarded with horses that travel are more likely to develop this contagious infection.

Clinical signs usually start between 3 and 14 days after exposure to a contagious horse. An affected horse may have a fever, depression, loss of appetite, thick, yellow/whitish nasal discharge and visibly enlarged and/or draining lymph nodes have difficulty swallowing due to enlarged lymph nodes.

Horses with severely swollen lymph nodes have difficulty breathing; therefore, the disease is known as strangles.

Clinical signs can range from mild (fever and mild nasal discharge) to severe (labored breathing and death due to obstruction of the airway by enlarged lymph nodes).


Tetanus is caused by the bacterium Clostridium tetani. Spores from this bacterium can be found almost everywhere in the environment.

Tetanus is a serious, frequently fatal disease. Once the bacteria infect a wound, they release neurotoxins that can cause muscle spasms and paralysis leading to death.

The disease rarely occurs in properly vaccinated animals.

Tetanus can result from any kind of wound, even a small one, but it is most frequently associated with puncture or wire wounds in the feet or muscles, surgical wounds, and exposed tissue, such as the umbilicus of foals or the reproductive tracts of mares that have recently foaled.

Diagnosis is generally achieved by a thorough physical examination of the affected horse and blood tests. Treatment is a combination of supportive therapy, tetanus anti-toxin and medications such as antibiotics. Severely affected horses often do not survive due to complications.


Rabies is a serious disease that is 100% fatal. However, it is almost completely preventable through vaccination.

While the incidence of rabies in horses is low, it is a serious public health threat for anyone who is involved in handling horses.

The rabies virus attacks the central nervous system (brain, nerves, and spinal cord) of mammals and is transmitted through infected saliva, either through a direct bite wound or by contact with any open wound or mucous membrane.

Clinical signs vary widely and can take anywhere from weeks to months to develop after exposure. Signs frequently include behavioral changes, un-coordination, muscle tremors, seizure, paralysis, and coma. Rabid horses may present with clinical signs of colic. However, the signs are non-specific, and rabies can be extremely hard to diagnose.

There is no treatment. Once clinical signs appear, rabies is 100% fatal as well as contagious to people handling the horse or the horse’s body fluids.

West Nile Virus

Like EEE/WEE, West Nile virus is transmitted by mosquitoes. The disease is associated with a significant death rate of about 35%. Approximately 40% of horses that recover still show residual effects more than 6 months after recovery.

West Nile is currently the leading cause of encephalitis (inflammation of the brain) in horses in the United States. West Nile virus can cause potentially life-threatening encephalitis. It attacks the spinal cord and brain and can cause un-coordination, muscle twitching, depression, paralysis, and erratic behavior such as hypersensitivity to the head and neck being touched.

Horses that are severely affected may become recumbent (unable to stand) and eventually die. Diagnosis is generally achieved by a thorough physical examination and testing of blood and cerebrospinal fluid, if needed.

Treatment is primarily supportive (e.g., intravenous fluids, anti-inflammatory medication, nursing care).

Potomac Horse Fever

Potomac Horse Fever (PHF), also known as equine monocytic ehrlichiosis, is caused by the bacterium Neorickettsia risticii.

Despite its name, PHF is found throughout most regions of the United States and Canada. The disease is seasonal, generally appearing in the spring, summer and fall and is associated with pastures located near waterways.

Signs of infection vary, but may include fever, mild to severe diarrhea, laminitis and colic. As a result, the disease can result in fatal complications and has a death rate of 5% to 30%.

Eastern and Western Equine Encephalomyelitis

These two serious diseases are transmitted by mosquitoes. The risk of infection exists almost anywhere in the United States where mosquitoes can be found and during all parts of the year when they are present.

EEE is more prevalent in the eastern United States; WEE is more prevalent in the West and Midwest. Although infection is relatively rare, the disease can be catastrophic. Approximately 50% of horses infected with WEE die. The fatality rate among horses with EEE approaches 90%.

Humans can also get EEE/WEE. These viruses attack the brain and spinal cord and can cause un-coordination, muscle twitching, depression, paralysis and erratic behavior. Horses that are severely affected may die.

Diagnosis is generally achieved by a thorough physical examination and testing of blood and cerebrospinal fluid.

Treatment is primarily supportive (e.g. intravenous fluids, anti-inflammatory medication, nursing care).

Equine Infectious Anemia

The coggins test is used to detect Equine Infectious Anemia (EIA) – a highly contagious and potentially fatal viral disease of horses.

EIA is a reportable disease and is therefore regulated by the United States Department of Agriculture (USDA), but state laws vary.

A current, negative coggins test result is often required to transport horses across state lines. Horses that attend equine events are usually required to show a current, negative test result to participate, even within your home state.

In the 1970’s, veterinarian Leroy Coggins developed the test that bears his name. With no vaccine available, the only way to prevent the spread of this highly contagious disease is to identify infected horses and then separate or isolate them from non-infected horses, so the virus is not transmitted.

EIA virus is most often spread through biting insects, primarily horseflies and deerflies. It can also be transmitted through saliva and other bodily secretions, shared syringes and any objects contaminated with infected blood or fluids. Infected pregnant mares can pass the virus to their foals.

While the USDA estimates that fewer than eight in 100,000 horses become infected with EIA virus, 50% do not survive despite treatment. EIA comes in 3 forms: acute, chronic and the inapparent carrier. In the acute form, horses experience fever, lethargy and loss of appetite and many die within a few weeks even if they receive aggressive treatment. If they recover, they become chronic carriers and are contagious for life.

Chronicallly infected horses become ill, recover and then become sick again and never completely recover. They often lose weight and suffer from anemia and swollen limbs. Horses that are inapparent carriers appear healthy, but can spread the disease to other horses, or eventually become ill themselves.

Equine Protozoal Myelopathy

Equine protozoal myeloencephalitis (EPM) is a disease that causes spinal cord problems and brain inflammation in horses.

It is caused by infection with certain microorganisms, one of which is carried by opossums. In the Americas, EPM is caused by a microorganism called Sarcosystis neurona in a horse’s feed or water. Horses can be affected at any age.

Signs of EPM vary according to the location of the infection in the body. Signs are very rare in horses younger than 12 months.

Infection of the spinal cord is common, resulting in weakness, loss of coordination and wasting of the rump muscles (one side of the rump is often smaller than the other). Other signs include sudden sweating, head tilt, facial paralysis, vision problems, behavioral abnormalities and seizures. Some signs may not occur until years after infection.

Diagnosis is based on signs, cerebrospinal fluid testing and your horses response to medication. With medication, horses can recover from EPM; however, neurologic damage can be permanent. Treatment can take 28 days to 6 months, depending on the drug, which is applied as an oral paste.

Without treatment, EPM is often fatal. A vaccine is available to help prevent EPM and its effectiveness continues to be evaluated by researchers.

Equine Influenza Virus

While equine influenza is a type 2 virus is rarely fatal except in debilitated animals, it is highly contagious and can cause significant illness resulting in extended loss of training and use.

Equine influenza is marked by rapid onset of high fever, lethargy (tiredness) and cough. The virus is mainly spread through the air.

Treatment is primarily supportive care and rest. Non-steroidal anti-inflammatory drugs (NSAIDS) and antibiotics may be prescribed if the horse’s fever persists or if a purulent nasal discharge develops, which may indicate a secondary bacterial infection.

Proud Flesh

When a wound begins to heal, the new tissue is very fragile. If the wound is located near a joint where there is a lot of motion, the fragile new tissue tends to break down and rebuild several times before the wound heals completely. In some cases, an overabundance of new tissue is produced during the rebuilding phase of healing, overrunning the wound and impeding the healing process.

This exuberant granulation tissue is called proud flesh, which is common in leg lacerations – one of the most common conditions that veterinarians evaluate in horses.

Wounds should be treated as soon as possible because untreated wounds are more likely to become infected or develop proud flesh. The treatment of wounds with proud flesh usually depends on the extent of the overgrowth.

If proud flesh is detected early, its progression can be diminished by applying special wound powders, allowing normal healing to continue. More often, however, excessive proud flesh is not detected immediately and must be trimmed by a veterinarian to permit proper healing.

With proper care, the wound can then heal with little or no scarring.

Exertional Rhabdomyolysis

External rhabdomyolosis (ER), which is also called tying up, is a disorder of the metabolism of the muscle that results in muscle cramps in horses.

In severe cases, an affected horse’s urine appears red from the release of myoglobin (an oxygen-transporting protein) by damaged muscle and muscle enzyme levels are greatly increased.

Most cases of ER occur in horses that have not been in work for several days and are then exercised strenuously. Typically, an affected horse develops a stiff gait with excessive sweating and rapid breathing during or shortly after exercise. The horse’s muscles are hard and painful to the touch.

ER can often be prevented by supplementing the feed daily with an electrolyte supplement that includes at 1oz of NaCl and by ensuring that the dietary carbohydrate level is not too high.

Affected horses should be kept on a consistent exercise program.


Botulism is caused by the bacterium Clostridium Botulinum. This bacterium can be present in the soil as the spores, especially in certain areas of the United States, such as mid-Atlantic states.

The spores can germinate into active bacteria that produces a neurotoxin called botulinum toxin. Horses may be exposed by eating food contaminated with the toxin or the spores themselves (foals) or through wound contamination with soil that contains spores. This infection can occur at any time of year.

The disease is not contagious, but outbreaks may occur if a number of horses eat contaminated hay or grain. Signs of infection include difficulty chewing/swallowing and progressive weakness, culminating in recumbency (inability to stand) and death.

Diagnosis is made through physical examination and blood and/or fecal tests. Treatment is very expensive and consists of administering antitoxin and supportive care, including intravenous fluids and feeding the horse through a tube a few times per day.

Horses that are severely affected are likely to develop respiratory paralysis, leading to death.

Consider Full Circle Equine Sports Medicine and Lameness Evaluation for your horse.