Common Horse Diseases

Knowledge is the key to disease prevention. Infectious diseases are those diseases that horses can get from each other, or via an insect like mosquito, which may transmit the disease from horse to horse. Horse owners can vaccinate their horses against many of these diseases, or their veterinarian may administer the vaccinations. Some vaccines are considered "core" vaccines that cover diseases that all horses need to be immunized against. Some horses may need to be immunized only when there is significant risk that they will be exposed to the disease in their natural environment, or if they may be exposed when traveling, showing, or competing. In addition, horses must be vaccinated at different life stages. Most vaccines need to be given annually.

Although there are a large number of horse diseases, there are only a small number of diseases which are both common and serious. Horse owners who familarize themselves with the prevention and treatement of these key diseases will on average have horses that live longer and healthier lives, as well as lower veterinarian costs. The two most important important illnesses are colic and laminitis. Between them, they are responsible for appoximately a third of all horse deaths.

The word literally describes abdominal pain. There are three main types of horse colic: gas, impaction and sand. Impaction happens when digested matter builds up in the intestinal tract and does not pass through. Gas colic is whne the horse has a severe build up of gas. Sand colic occurs when a horse is allowed to eat on sandy ground.

In the horse, this can be quite dramatic and distressful, for many species-specific reasons. It can arise most commonly from impaction of ingesta or from accumulation and entrapment of gas (impaction colic, spasmodic colic, gassy colic). These types will usually resolve, especially with the help of first-aid homeopathic remedies, like Nux vomica or Colocynth.

More rarely, a case of 'surgical colic' can arise, which is, of course much more serious. This can occur as a result of abdominal growths or a twisted bowel. Homeopathic remedies will only be of limited, first-aid value, in such cases. A veterinary surgeon is usually necessary, to help diagnose the exact nature of the problem in any given case and to decide upon timely surgical intervention.

Laminitis, commonly called founder, is an acutely painful inflammation of the foot. It occurs most often in the front feet although it can affect the hind feet as well. Founder is the name given to the resultant tissue damage and complications following one or a series of acute attacks of laminitis. Symptoms include heavy breathing and glazed eyes due to pain. The feet will feel hot and the digital artery, located over the fetlock joint, will have a pounding pulse. Different situations can cause laminitis. Grazing on lush pasture (particularly overweight horses), overloading on grain, eating lawn grass clippings, or drinking large amounts of water when overheated can all cause a horse to founder.

Laminitis can be avoided by avoiding feeding excesses and keeping the horse at a reasonable weight. Watch for and avoid grass blooms on pastures; pull horses off the fields and onto dry lots if necessary. Feed hay in the morning and turn horses out after the lushness and dew is off the grass. Keep grain in closed bins and the door to the feed room closed. Give horses unlimited access to fresh, clean water...but regulate water intake immediately after exercise.

Tetanus (lockjaw)
Tetanus is caused by a bacterial toxin normally found in the soil and in the feces of horses.

The bacteria that produce the tetanus toxin need a decreased oxygen supply to multiply, so any area where there is a deep puncture wound or where a wound has healed over (such as the navel stump of a newborn foal) is an area where tetanus can thrive. Its symptoms are early signs of colic, an elevated third eyelid and stiff neck, progressing to overall muscle stiffness causing a 'sawhorse' stance. 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 end, the horse will lie down and die of respiratory paralysis. Tetanus is often fatal, but preventable with annual vaccination.

Equine Encephalomyelitis (sleeping sickness)
This is a disease that affects the nervous system, and can be caused by equine encephalomyelitis viruses (Eastern, Western, and Venezuelan), which are carried by mosquitoes. Signs include depression and a high fever, followed by a period when the horse appears blind, nervous and uncoordinated, which progresses to muscle tremors, yawning, and eventually, complete paralysis. Proper vaccination and good mosquito control are important to help prevent this disease.

Equine Influenza
Equine Influenza is a viral disease, which appears to be specific to equine animals (i.e. it is not known to cross the 'species barrier'). It is much-feared, giving rise to compulsory vaccination regimes for various forms of sporting competition and for some yards. It is highly infectious but, usually, not too severe. This viral disease is spread by inhalation of drops of infective material. Signs include a dry, hacking cough, sudden onset of fever, watery nasal discharge, weakness, stiffness, loss of appetite and depression. Infection with equine influenza is rarely fatal but can cause problems such as emphysema, pneumonia or bronchitis.

Equine Herpesvirus (rhinopneumonitis, rhino, viral abortion)
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.

There are 2 types of equine herpesvirus: EHV-1, which causes respiratory disease (fever, cough, nasal discharge), reproductive problems (abortion, stillbirth), and neurological problems (hindlimb weakness, difficulty walking, sometimes paralysis); and EHV-4, which is limited to respiratory problems and is usually only a problem in younger horses. Once a horse has been infected with EHV-1, he will always be a carrier, and the virus may re-activate within the horse during times of stress. A horse that has been infected with EHV-4 will always test positive for it also, but usually will not show clinical signs of it again after the initial infection.

West Nile Virus
West Nile Virus 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). Horses get WNV by being bitten by an infected mosquito; most horses do not show any signs and recover on their own, but in some horses the infection affects the central nervous system and causes signs including fever, weakness or paralysis of the hind limbs, impaired vision, lack of coordination, head pressing, convulsions, inability to swallow, and coma. Typical symptoms appear 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. It is a highly fatal infection of the central nervous system. Its symptoms include, increased saliva, excitability, disorientation and running blindly.

Rabies is a highly fatal viral infection of the central nervous system. Its symptoms include, increased saliva, excitability, disorientation and running blindly. Although it is not common in horses, rabies can be transmitted to horses by the bite of an infected animal such as a skunk, raccoon, fox, dog or bat. Rabies can be transmitted to people. We recommend that you check with your veterinarian regarding recommendations for rabies vaccination for your horse. Getting your horse vaccinated will prevent this disease.

Strangles (shipping fever)
Equine strangles is a respiratory disease caused by a bacterium called Streptococcus equi. Signs include a fever, thick, yellow, nasal discharge and swollen, abscessed lymph nodes under the jaws. The infection is spread by infected material from nasal discharge or abscesses contaminating stalls, feed troughs, pastures, etc. Young horses are the most susceptible to strangles and many horses seem to have a lifetime immunity after recovering from this disease. In the best cases infected horses must be isolated and rested for up to three months, at worst complications can lead to pneumonia and even death. The horse's recovery is dependent on its immune system fighting the bacteria.

Potomac Horse Fever
Potomac Horse Fever - is a diarrheal disease that is infrequently seen in the western U.S. Horses. This disease is a bacterial infection of the blood and tissues and is thought to be transmitted to horses by arthropod vectors such as ticks, lice, mites, and fleas. It is much more common in some areas of the country than others. Signs include a high fever, depression, decreased gut sounds, and a profuse, watery diarrhea that can lead to laminitis, colic, dehydration, shock, and death.

Another common condition affecting horses are worms, although not technically a disease, they are parasites.

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