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Published Date: 2012-11-16 02:39:27
Subject: PRO/AH> Corynebacterium, equine - USA (05): (MO)
Archive Number: 20121116.1411851

CORYNEBACTERIUM, EQUINE - USA (05): (MISSOURI)
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Date: Wed 14 Nov 2012
Source: The Horse [edited]
http://www.thehorse.com/articles/30867/drought-causes-spike-in-equine-pigeon-fever-cases-in-missouri

Drought causes spike in equine pigeon fever cases in Missouri
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The long summer drought in Missouri has ruined a large portion of this year's [2012] crop harvest, and one University of Missouri (MU) equine veterinarian says the negative effects of the dry weather can still be seen across the state.

Philip Johnson, a professor of equine medicine and surgery in the MU College of Veterinary Medicine, says he has seen a large spike in the number of Missouri horses infected with _Corynebacterium pseudotuberculosis_, a bacterium that can cause painful swelling, abscesses, and inflammation in the legs, chests, and abdominal cavities.

"Under normal conditions, this disease is uncommon in Missouri," Johnson said. "However, likely because of the extremely dry weather Missouri has experienced in the last 6 months, we have seen an abnormally large number of cases pop up throughout the state. The disease is contracted through abrasions in the skin, as well as by bites from flies and ticks."

Johnson says that horse owners should keep a wary eye on their horses for swelling in their chests or swollen abscesses and sores on their legs. He says that infected horses could also show behavioral signs of sickness such as lethargy, depression, and loss of appetite. If an infection is left unattended for too long, it could result in horse lameness and even death if the infection moves into internal organs.

"It is very important for horse owners to monitor their horses' health carefully," Johnson said. "They should call their veterinarians as soon as they see any potential sign of infection, so that the veterinarians can accurately diagnose the condition. The earlier the infection is detected, the easier and more effective the treatment will be."

Johnson also recommends that owners quarantine any horses they believe could be infected, as draining abscesses can spread the disease to healthy horses. He says that treatment typically involves draining any abscesses close to the surface of the skin and allowing them to heal. He only recommends the use of antibiotics if the abscesses are deeper under the skin or if the infection has moved to the internal organs of the horse.

[byline: Sharon Spier]

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[Pigeon fever, pigeon breast, breastbone fever, dryland distemper, dryland strangles, false strangles, or false distemper are 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, 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 commonest 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 per cent 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.

Missouri may be found on the HealthMap/ProMED-mail interactive map at http://healthmap.org/r/1zT0. - Mod.TG]

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