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Published Date: 2012-02-02 16:57:42
Subject: PRO/AH/EDR> Corynebacterium, equine - USA (02): (OK)
Archive Number: 20120202.1028113

CORYNEBACTERIUM, EQUINE - USA (02): (OKLAHOMA)
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Date: Sun 29 Jan 2012 [The delay in posting is regretted - ProMED]
Source: News 6 [edited]
http://www.newson6.com/story/16624181/potentially-deadly-horse-disease-on-the-increase-in-oklahoma

More horses are getting sick from a strain of bacteria that vets say was likely caused by the drought conditions in [Oklahoma]. It's called drought distemper or pigeon breast.

The bacteria can spread from horse to horse and are hitting a lot of horses right now and vets say it can kill them. "Most of them don't know about it until it hits their horse," Shawnee Animal Hospital veterinarian Mike Steward said. He says he has never seen so many cases of drought distemper. "In my 32 years, the 1st 30 I probably saw 10 cases. This year I've seen 60 in the Shawnee area."

The Oklahoma Humane Society tells News 9, 3 of 20 horses they've helped rescue recently have drought distemper, too. They have kept those 3 separate from the rest and Steward says that's the right thing to do. The disease is contagious and can be deadly. "It's kind of like a gopher," Steward said. "It likes to tunnel around in the tissue rather than stay in one spot."

Drought distemper or pigeon breast normally shows itself on horses' chests. There is no vaccine available, but it is treatable if horse owners can spot it. "A lot of horse owners come in complaining someone kicked their horse in the chest or whatever," Steward said. "May only be the size of a 50 cent piece or something."

If it's not treated, the bacteria can spread to the horse's liver and kidneys and they can die from it. "If you see it and you've got a big herd, you'll probably see it in 2 or 3 others," he said. Steward says it's called drought distemper because it's thought to be caused by dry or contaminated soil. He's also read some studies indicating flies or insects may be the cause.

[Byline: Jamie Oberg]

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[Pigeon fever, pigeon breast, breastbone fever, dryland distemper, dryland strangles, false strangles, or false distemper are the names by which this disease -- caused by the bacterium _Corynebacterium pseudotuberculosis_ -- is most frequently known. Geographically, it was at one time considered to be a disease of California, where it is regarded as endemic. However, it is much more widespread now, especially in the western states of the USA, but it has a worldwide distribution. It is a seasonal disease, usually appearing in late fall, but it can appear sporadically at any time of year.

The signs of pigeon fever can also initially resemble those of other diseases such as strangles. Sometimes the only initial signs are lameness and a reluctance to move. It can strike a horse of any age, sex, or breed, but usually attacks young adult animals. There is a low incidence in foals.

It has also been diagnosed in cattle, and a similar disease affects sheep and goats. The disease is not transmissible to humans, although humans can carry the infectious agent on shoes, clothing, hands or barn tools and transfer it to another animal.

Clinical signs include lameness, fever, lethargy, and weight loss, and these are usually accompanied by very deep abscesses and multiple sores along the chest, midline, and groin area and, sometimes, the back. Abscesses also can develop internally.

The disease is called pigeon fever because infected animals often develop abscesses in their pectoral muscles, which swell to make it resemble a pigeon's chest. Although the disease is considered seasonal, with most cases occurring in early fall, a number of cases have been confirmed during winter months and other times of the year as well.

The causative bacteria live in the soil and can enter the animal's body through wounds, broken skin, or through mucous membranes. In addition, some researchers believe pigeon fever may be transmitted by flies.

Of the types of disease (external abscesses, internal abscesses, or limb infection [ulcerative lymphangitis]), ulcerative lymphangitis is the commonest form worldwide and rarely involves more than one leg at a time. Usually, multiple small, draining sores develop above the 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. Usually, it appears in the pectoral region, the ventral abdomen, and the groin area. After spontaneous rupture, or lancing, the wound will exude liquid, light tan-colored, malodorous pus.
The commonest forms are external abscess and lymphangitis, with the prognosis of a full recovery being generally good. Internal abscesses can occur and are very difficult to treat.

The contagious nature of the disease means an accurate diagnosis is imperative, and treatment should be initiated as well as control of insects and the rigid practice of biosecurity.

Horse owners should be aware of the clinical signs and understand that veterinary care must be timely. Infected horses should be isolated, the abscesses properly treated, and the drainage properly disposed of. The area where the infected horse is kept must be properly cleaned and completely disinfected, because this is a very hardy bacterium. Bacteria in the pus draining from abscesses on infected horses can survive from one to 55 days in the environment. They have also been shown to survive from one to 8 days on surface contaminants and from 7 to 55 days within feces, hay, straw, or wood shavings. Lower temperatures prolong the survival time.

Pest control is extremely important. The bacteria may be transported between animals by flies.

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.

A different biotype of the organism is responsible for a chronic contagious disease of sheep and goats, caseous lymphadenitis (CL). Either biotype can occur in cattle.

Treatment in horses often consists of hot packs or poultices applied to abscesses to encourage opening. Open abscesses should be drained and regularly flushed with saline solution. Surgical or deep lancing may be required, depending on the depth of the abscess or the thickness of the capsule, and should be done by your veterinarian. Ultrasound can aid in locating deep abscesses so that drainage can be accomplished. External abscesses can be cleaned with a 0.1 percent povidone-iodine solution. Antiseptic-soaked gauze may be packed into the open wound. A nonsteroidal anti-inflammatory drug, such as phenylbutazone, can be used to control swelling and pain.

Antibiotics are controversial. Their use in these cases has sometimes been associated with chronic abscessation and, if inadequately used, may contribute to abscesses, according to one study. The most commonly used antibiotics for the treatment of this condition are procaine penicillin G, administered intramuscularly, or trimethoprim-sulfa. In the case of internal abscesses, prolonged penicillin therapy is necessary.

Buckets or other containers should be used to collect pus from draining abscesses, and this infectious material should be disposed of properly. Consistent and careful disposal of infected bedding, hay, straw, or other material used in the stall is vitally important. Thoroughly clean and disinfect stalls, paddocks, all utensils, and tack. Pest control for insects is also very important.

With treatment, recovery usually takes place between 2 weeks and 77 days. Although some animals may have recurrences, generally recovery is complete, and the prognosis is good.

Portions of this comment have been extracted from http://www.completerider.com/ucolorado/PIGEONFEVERINEQUINES.html.

Oklahoma may be located on the HealthMap/ProMED-mail interactive health map at http://healthmap.org/r/1Jc8. - Mod.TG]

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