Seasonal Diseases: Pigeon Fever

Pigeon Fever, also known as Dryland Distemper, is an equine disease most commonly occurring in the Fall.  It is a bacterial infection, and in most cases horses will be fully recovered in a matter of weeks.

Pigeon Fever is caused by a bacteria called corynebacterium pseudotuberculosis.  The bacteria lives in soil, and makes its way into a horse’s system through open skin such as a wound or insect bite.  It is contagious and can be transmitted from horse to horse.  For that reason, proper quarantine procedures and biosecurity practices should be observed.

close-up photo of a light brown horse's swollen breast area

The first case of Pigeon Fever was reported in 1915 in San Mateo County, California.  Originally this infection was limited to the warmer southwestern states, however within the past 20 years, cases have been reported in over 25 states including Hawaii and Florida.  It has also been documented in Mexico and Canada.

The corynebacterium pseudotuberculosis bacteria’s incubation period is about 3 or 4 weeks.  That means a horse can be infected for up to one month before symptoms appear.  Symptoms can include lethargy, fever, and reluctance to move.  The primary symptom of Pigeon Fever is the appearance of large, deep, external abscesses on the muscles of the breast, abdomen, groin, and udder or sheath.  These abscesses are caused by a toxin the bacteria releases, which causes the immune system to build a thick wall around it to contain the pathogen.

In 8% of cases, internal abscesses will develop as the bacteria gets carried to the organs. In only 1% of cases, abscesses form in the lymph channels of the legs, causing extreme swelling and cellulitis in the lower limbs.

Pigeon Fever is diagnosed through a bacteria culture and lab testing.  Except for those rare cases, treatment involves letting the disease run its course.  It can take weeks, but the abscesses will drain and the wounds will heal.  It is not highly fatal, although the symptoms have a very dramatic look to them.

gloved hand treating a dark brown horse's abscess at the base of its neck

The bacteria causing Pigeon Fever can live up to 8 months in soil, and up to 2 months in hay or stall bedding.  Flies can transmit the disease, so pest management is essential.


The Facts on EHV-1

As horse owners, we want to make sure our horses stay as healthy as possible.  Part of that responsibility includes understanding common equine diseases, so that we can prevent them before they start.  Here’s some quick facts on the virus EHV-1.

cartoon horse with a cold
EHV-1 is a respiratory infection
  • EHV-1 is an abbreviation for Equine herpesvirus-1.
  • It is 1 of 4 EHV strains.
  • It is a virus, meaning it does not respond to antibiotics.
  • It routinely causes upper respiratory infection in young horses, under 2 years old.
    • Symptoms include fever, lethargy, nasal discharge, loss of appetite, and persistent cough.
    • The virus usually runs its course and horses recover without incident.
  • In rare cases, adult horses show symptoms of respiratory infection, and develop a secondary disease called equine herpes myeloencephalopathy (EHM).
  • EHM is a serious neurological disease.
    • Symptoms include lack of coordination, inability to stand, leg swelling, and inability to eliminate waste. These symptoms are also commonly found in other neurological diseases such as West Nile Virus.
  • Diagnosis is done by a veterinarian with a nasal swab test.
  • Because it is a virus, supportive care is the only treatment option.
  • EHV-1 is contagious and spread through horse-to-horse contact.
    • It is transferred through the air up to 35 feet.
    • It can survive on surfaces up to 7 days under normal circumstances, but can remain alive for a maximum of 1 month under perfect environmental conditions.
  • EHV-1 is easily killed with disinfectants.
  • At-risk farms should observe quarantine procedures for a minimum of 2 weeks, keeping horses isolated and disinfecting equipment, tack, clothing, and other surfaces.
  • Farms with confirmed cases should observe quarantine procedures for longer, about 4 weeks.
  • If there is an outbreak in your area, it is best to reduce the risk of exposure.
    • Keep your horses at their home base.
    • Don’t let your horse meet new friends.
    • Don’t share equipment, tools, etc.

To stay up to date and monitor disease outbreaks in your area, visit the Equine Disease Communication Center’s website <>.