Caused by the hardy bacteria Corynebacterium pseudotuberculosis, pigeon fever can be highly contagious if not properly managed, but is rarely fatal. The disease is seasonal, with peak incidence in the dry/fall months, and the incidence fluctuates from year to year within a site.
It is characterized by intramuscular abscesses, primarily in the pectoral area and ventral part of the abdomen, which gives the horse a puffed-out appearance similar to that of a pigeon. The infection is confirmed with a bacterial culture and by symptoms. Other symptoms are lethargy, stiffness and lameness from the pain and swelling.
Horse should be checked daily; look closely at the underside and check for swelling. In some cases, the infection can spread to the horse’s legs, causing a syndrome called ulcerative lymphangitis, which more challenging to treat.
Ruminants, such as sheep, goats and cattle, can also become infected by this bacteria.
How It Is Spread
The bacteria lives and multiplies in dry soil and manure. Hot, dry weather facilitates this bacterial growth. Horses contract the disease through an open wound or fly bite, with bacteria entering through these abrasions or wounds and, sometimes, mucous membranes.
In 2008, an Oregon veterinarian who was treating horses with pigeon fever contracted the bacteria. This case highlights the importance of wearing gloves while caring for infected horses and following disinfection protocols.
Humans can also carry the bacteria on their boots, hands, and tools. Proper disinfection protocols should be utilized to limit the spread of the bacteria. Gloves should be worn when handling infected horses. Bedding, water buckets, and any other material that might come in contact with pus should be disinfected or disposed of and not shared with other horses.
The most aggressive prevention method to help limit the spread of the bacteria is to remove the top layer of soil in the area that is contaminated by wound drainage and replace it with clean soil or bedding. Bleach and other disinfectants do not work well on organic debris (dirt or manure), so pouring disinfectants on the ground is not effective. Bleach does work well on clean surfaces, like stall mats and scrubbed walls.
Fly control (sprays, sheets and repellents) can help to limit disease risk, as can meticulous manure clean-up.
A vaccine has been developed by a Bend-area veterinarian and is expected to be available by 2016.
Treatment involves lancing and draining the absecesses and, in some cases, antibiotics. An ultrasound can help to locate deep internal abscesses and find the best place to drain them. A horse is unlikely to be contagious if all abscesses have healed.
For more information on pigeon fever, please consult with your veterinarian.