Published Date: 2012-01-18 14:51:19
Subject: PRO/AH> Corynebacterium, equine - USA: (TX)
Archive Number: 20120118.1013774
CORYNEBACTERIUM, EQUINE - USA: (TEXAS)
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: Sun 15 Jan 2012
Source: Denton Record-Chronicle [edited]
Pigeon fever new horse problem in Denton County
[Denton County local veterinarians state that they haven't seen a single case of pigeon fever in the horse population] in years and now in the last couple of months, it seems one to 2 cases a week are being reported.
Pigeon fever -- also known as pigeon breast, dry land distemper, and Colorado strangles -- is unpredictable and contagious.
It gets its name from the abscess lumps that often appear on the pectorals, making the horse look like it has a pigeon's breast. It is caused by bacteria called _Corynebacterium pseudotuberculosis_.
It is thought that the bacteria enter through skin abrasions and insect bites. It can also be spread through horse to horse contact, horse to cow contact, through the soil, or through a break in the skin.
Pigeon fever is more common in dryer climates and is prevalent in California, but in recent years has been spreading northward. This disease, when introduced into a conducive environment, becomes difficult to eliminate, resulting in unpredictable future outbreaks.
Rarely is this disease fatal, but recovery can take months and the disease can reoccur. It also seems that horses kept outdoors tend to be at higher risk than stabled horses.
There is no vaccine for this disease, so if a horse contracts pigeon fever, the course of action is to prevent the spread of the infection to other horses. Any time the abscess breaks open, there is a risk of the pus spreading the disease. Precautions should be taken to clean up the fluids in the stall or pen, or ground where the horse was treated.
Limiting any type of area contamination will help prevent the spread, but remember the bacteria live in the soil and probably will never be eliminated completely once introduced in an area. Early diagnosis is key, so if you suspect your horse is a carrier for pigeon fever, consult your veterinarian.
[byline: Eddie Baggs, extension agent with the Texas AgriLife Extension Service in Denton County]
[Pigeon fever, pigeon breast, breastbone fever, dryland distemper, dryland strangles, false strangles, 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 US, 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 and 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]), the 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.
Internal abscesses can occur and are very difficult to treat. The commonest forms are external abscess and lymphangitis, with the prognosis of a full recovery being generally good. Internal abscesses are much more 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 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. Flies are also being investigated in the role of instigator of this disease.
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 antibiotic for the treatment of this condition is 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.
The state of Texas can be located on the HealthMap/ProMED-mail interactive map at http://healthmap.org/r/1EZ1. Denton County in east Texas can be seen on the map at http://www.digital-topo-maps.com/county-map/texas.shtml. - Mod.TG]