Internal Medicine

Common Equine Diseases

  1. PPID (Formerly Equine Cushing's Disease)

    A disorder of the pituitary gland. It is caused by the growth of a benign tumor called a pituitary adenoma. 

    Common Symptoms

    •  suppressed immune system (delayed wound healing etc.)
    •  long curly hair (more advanced cases)
    •  decreased musculature, may have a pot-bellied appearance
    • elevated fatty acids and cholesterol in the blood stream
    •  increased risk for laminitis
    Often diagnosis is based on a blood test called ACTH. High levels of this hormone is a reliable marker for Equine Cushing's Disease. In severe cases, clinical signs may be obvious, but bloodwork may still be indicated to be able to effectively assess treatment to therapy.
    • Management with pergolide is considered the most effective. 
    • Occasionally, some horses may be responsible to an older drug, cyproheptidine.


  2. Equine Metabolic Syndrome

    A disease caused by Insulin Resistance.

    • Fat deposits on neck crest, along back and rump.
    • may still easily palpate ribs
    • "Easy-keepers"
    • High levels of circulating insulin, glucose, and fatty acids.
    • Genetic factor likely plays a role for certain breeds like Arabians, Morgans, and many pony breeds.
    • Most commonly based on clinical signs
    • Confirmation via bloodwork can be performed.
    • Likely would see elevated insulin and potentially elevated fatty acids. Glucose may be elevated as well, but is not reliable as any excitement or stress also elevates glucose. 


    • Decrease caloric intake
    • Increase exercise regimen (consult your veterinarian to help determine a good program for you and your horse)
    • Brief treatment with a thyroid supplement to improve metabolism may be recommended.
    • In more severe cases a medication known as metformin may be utilized. Thismedication reduces the amount of sugar and fatty acids in the bloodstream.
    • This is a disorder that will need to be managed for the rest of the horse's life.


  3. Equine Strangles

    Equine Strangles is an infectious disease caused by the bacteria Streptococcus Equi Equi. It is highly contagious and spreads from direct contact. It can also be spread indirectly via contaminated equipment (tack, buckets, stalls etc).

    Common Symptoms:

    • More common in young horses

    • Fever

    • Unwillingness to Eat

    • Pain and/ or swelling around the throatlatch area

    • Nasal Discharge

    • Respiratory Stress


    • Prevention is priority

    o Annual Vaccinations (especially in younger horses)

     Will help to lessen the severity of disease if infected (may not fully prevent infection)

    o Good biosecurity (no sharing of water buckets etc. especially in public)

    • Goal of treatment is to relieve respiratory distress

    • Antibiotics may be clinically indicated depending on each individual case

    o Consult with your veterinarian before administering antibiotics.

    • Abscess may form during the course of disease and may need to be lanced.

    For more information please refer to the AAEP website. Click here.


  4. Pigeon Fever/ Dryland Distemper


    A disease caused by Corynebacterium Pseudotuberculosis. It is most commonly spread by biting flies or contamination of open wounds. In the photo above, the horse has an abscess on the ventral midline of the abdomen with severe edema surrounding it.

    Clinical Signs:

    • External Abscess (most common)

    o Large swelling (most commonly on chest or abdominal region)

    o Lameness depending on location of abscess

    o May become tender over abscess area

    o May be slow for abscess to mature and rupture on its own

    • Internal Abscess (rare)

    o Fever

    o Lethargy

    o Weight Loss

    o More symptoms may be present depending on location of internal abscess

    • Lymphangitis (very rare)

    o Form that affects the lower portion of the legs

    o Hot, swollen leg (classic appearance of cellulitis)

    o May have a chronic discharge (oozing)

    o Multiple limbs may be affected

    o Lameness


    • External Pigeon Fever may be diagnosed by visual and ultrasonographic appearance

    • Internal Form and Lymphangitis may require more diagnostics

    o Thorough Ultrasound

    o Blood titers

    o Culture of internal mass or discharge of skin.

    • It is important to rule out other potential causes of these clinical symptoms as they may be vague and common for multiple different causes.


    • External Form

    o Allow to mature and drain/ lavage

    o Antibiotics may hinder/ slow the maturing process and thereby delay time to healing

    o Once abscess is opened and draining antibiotics may be clinically indicated.

    • Internal Form and Lymphangitis

    o Aggressive long term andtibiotics are likely necessary once diagnosis is established

    o Anti- inflammatories may also be clinically indicated to relieve discomfort.


    • Fly control is the most effective way to decrease the spread of disease.

    For more information pelase refer to the AAEP website. Click here


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