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Purpura hemorrhagica: a bad sequel to strangles

Quick facts

  • Purpura hemorrhagica is a swelling of the blood vessels usually after strangles

  • A common sign is swelling of the head, legs and underbelly

  • A blood test or skin biopsy can diagnose purpura hemorrhagica

  • Treatment includes corticosteroids and antibiotics

  • Most cases are mild and result in a positive outcome.

What is purpura hemorrhagica?

Purpura hemorrhagica (PH) is when blood vessels swell due to an improper immune response. PH cases usually relate to prior bouts of strangles. Unlike strangles, PH can’t spread to other horses. There are reports that some PH cases relate to other upper respiratory infections.

Signs of illness

With purpura, the immune system harms the vessel walls and causes them to leak. As blood leaks into the tissue, swelling occurs. Signs of PH include:

  • Swelling in the head, legs and underbelly

  • Red spotting on the gums and other mucous membranes from bleeds

  • Serum may seep from the skin

  • In severe cases, the skin may die and slough off

PH affects most of the body, including the lungs, muscles and kidneys. Thus it can lead to other signs including:

  • Lameness

  • Laminitis

  • Colic

  • Weight loss

  • Neurologic signs


Contact your veterinarian if you see signs of PH after a recent respiratory infection or strangles vaccine. Your veterinarian may make a diagnosis based on the history and exam findings. They may take a blood sample or skin biopsy to check for signs of PH.


A veterinarian usually starts the horse on dexamethasone, a corticosteroid, which eases the immune reaction. In addition, antibiotics will stop any other respiratory infections and prevent further infections.

The disease is often mild and the horse recovers well. In severe cases the horse may die or need to be put down. Catching PH early is key to a good outcome.


PH is hard to predict and prevent. Your veterinarian may recommend not using the strangles vaccine again if your horse reacts to it. They may want to do further testing.

Research shows that horses with high levels of antibodies to strangles may be at higher risk of PH. High antibody levels are very likely after horses are exposed to and vaccinate for strangles.

Phil Kieffer, former student, College of Veterinary Medicine

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