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WHETSTONE — Veterinarians are starting to see cases of pigeon fever, a bacterial infection affecting horses, striking primarily in the fall.
Pigeon fever typically manifests itself with a large, deep abscess on the horse’s chest, or pectoral area. The disease is called pigeon fever because as the abscess develops, it causes the animal’s chest to swell, resembling the prominent chest of a pigeon.
Other clinical signs of the disease can include lameness, fever, lethargy and weight loss, usually accompanied by the deep abscess. Horses will sometimes develop multiple sores along the chest, mid-line and groin area.
Mares have been known to develop abscesses on the mammary glands, while male horses can develop them on the scrotum or sheath. Abscesses also can occur internally.
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The abscesses are caused by a bacterium, corynebacterium pseudotuberculosis, which is found in the soil and can enter the animal’s body through wounds, broken skin or mucous membranes. It’s believed to be carried by flies.
Highly contagious, it is best to try and contain the disease by isolating infected horses. The abscesses should be properly treated, following a veterinarian’s guidelines, and the drainage properly disposed of.
According to a Colorado State University Web site, pigeon fever also is known as pigeon breast, breastbone fever, false strangles, dryland strangles or dryland distemper. It tends to be seasonal, with most cases occurring in the fall. There have, however, been confirmed cases during winter months, as well as other times of the year.
Equine veterinarian Dusti Prentice has treated horses with the disease in recent weeks and has spoken to several concerned horse owners over the phone.
“This is the typical time of year for pigeon fever,” Prentice said. “There seems to be an environmental contamination that ranges from Whetstone to Elgin. I’ve been treating horses and hearing about cases in those two areas.”
Whetstone resident Bob Cook owns one of the horses that Prentice is treating. Cook, who was raised around horses, now owns three horses and a mule. He said this is his first experience with pigeon fever.
“When I saw the swelling on his chest, I thought he’d been kicked by one of our other horses,” Cook said. “But after a few days I could tell it was forming an abscess.”
Cook contacted Prentice who cultured the lesion sent the sample to a lab to confirm the pigeon fever diagnosis.
“The one lesson I learned from this is, if you see a lump on your horse’s chest, don’t just conclude it’s an injury,” Cook said. “My horse (Magic) is coming along just fine now, but I’ve been treating this for a few weeks. And he needs to stay on antibiotics until the first of November.”
Equine veterinarian Lucinda Earven has not seen cases of pigeon fever so far this season, but is familiar with the disease and its treatment protocol.
“In the early stages, it’s often a large, painful swelling with a doughy feeling when touched. My biggest challenge with this disease is convincing people that it’s not ready to lance when it first appears,” Earven said.
Horse owners see the swollen area and often think the best course of treatment is to lance the abscess right away and start the animal on antibiotics. Prentice and Earven said lancing too soon or putting the horse on antibiotics inappropriately can actually prolong the disease’s course.
“We can’t do anything about the infection until the bacteria is drawn to the surface, next to the skin,” Earven said. “Once it comes to a head, it can be lanced by a veterinarian. And sometimes these abscesses will break on their own.”
Applying warm compresses to the swollen area will help draw the infection to the surface, essentially speeding up the process. Earven recommends using Epsom salts as a poultice.
Once the abscess breaks and is draining, Prentice and Earven recommend flushing it with a betadine solution at least two or three times a day, or according to the treating veterinarian’s instructions.
“Smearing the wound with Ichthammal will help it continue to drain,” Earven said.
If the horse is extremely uncomfortable, as when swellings occur on the mammary glands of mares or the sheath in males, the veterinarian may put the animal on a nonsteroidal anti-inflammatory drug such as phenylbutazone to control swelling and pain.
“This is an extremely contagious bacteria, so it’s really important that horse owners clean everything thoroughly once an abscess is draining,” Prentice advised. “The infected horse’s stable area must be properly cleaned with a disinfectant, along with all tools, equipment, brushes, halters, anything used on that horse. The owner needs to wash well after treating the horse. Fly control is huge, because flies spread this.”
The bad thing about pigeon fever, Earven said, is that it’s resistant to environmental conditions, capable of living long periods of time in the soil.
The good news is the disease is not typically life threatening.
“The prognosis is usually good, but sometimes horses will experience a recurrence,” Earven said. “I had a case last year where a horse had gone through the treatment, and then developed another abscess.”
Depending on the animal and where the infection is located, treatment can range between two weeks and three months, Prentice said.
“Horses with internal abscesses are more difficult to treat. In those cases, I put them on an intensive, long-term course of antibiotics, usually for three months. But even that can vary.”
As a service to horse owners, Colorado State University’s equine veterinarians have created a fact sheet about pigeon fever, posted on the university’s Web site at http://www.cvmbs.colostate.edu/cvmbs/service.htm.
Some of the items from the fact sheet — provided by CSU College of Veterinary Medicine and Biomedical Sciences — include the following:
• There is no vaccine for pigeon fever.
• Bacterium in the pus draining from abscesses on infected horses can survive from one to 55 days in the environment. It has also been shown to survive from one to eight days on surface contaminants and from seven to 55 days within feces, hay, straw or wood shavings. Lower temperatures prolong survival time.
• Horses may become infected, but not develop abscesses for weeks.
• The disease usually manifests in younger horses, but can occur in any age, sex and breed.
• The disease typically comes in three forms: external abscesses, internal abscesses or limb infection (ulcerative lymphangitis). The ulcerative lymphangitis rarely involves more than one leg at a time. Usually, multiple small, draining sores develop above the horse’s fetlock.
• The most common form of the disease in the United States is external abscessation, which often forms deep in the muscles and can be very large. Abscesses usually appear in the pectoral region, the ventral abdomen and the groin area. After spontaneous rupture or lancing, the wound will exude a liquid, light tan-colored, malodorous pus.
• Internal abscesses can occur, and are more difficult to treat.
• Veterinarians can collect a sample for culture at a diagnostic laboratory. It is important to isolate the bacterium to get a definitive diagnosis since pigeon fever can superficially resemble other diseases.
• Hot packs or poultices should be applied to abscesses to encourage opening. Open abscesses should be drained and regularly flushed. External abscesses can be cleaned with a 0.1 percent povidone-iodine solution.
Diana wrote on Nov 20, 2008 1:32 PM: