Published Date: 2011-12-11 05:14:15
Subject: PRO/AH> Corynebacterium, equine - USA (LA)
Archive Number: 20111211.3566
CORYNEBACTERIUM, EQUINE – USA (LOUISIANA)
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: 8 Dec 2011
Pigeon fever cases in horses
More than 30 cases of pigeon fever in horses have been reported to the
Louisiana Department of Agriculture and Forestry, agriculture and
forestry commissioner Mike Strain, DVM, says. The Veterinary Teaching
Hospital (VTH) at the LSU School of Veterinary Medicine treated 10
cases of pigeon fever in horses and the Louisiana Animal Disease
Diagnostic Laboratory (LADDL) reported 20 positive cases from
referring veterinarians. VTH estimates that there have been at least
100 cases in Louisiana in 2011 and suspect that the number of cases
may be related to drought and heat.
Pigeon fever is the common term for an infection caused by the
bacterial organism _Corynebacterium pseudotuberculosis_ which can form
abscesses in the pectoral region and ventral abdomen of the horse. The
condition is not related to pigeons. The abscesses cause swelling and
give the horse a "pigeon-breast" appearance. The illness is also known
as dry-land strangles.
Cross-species transmission usually occurs only between horses and
cattle because they can carry the same strain of bacterium. The
bacterium rarely infects humans.
There are 3 recognized forms of the disease in horses: external
abscesses, internal abscesses, and ulcerative lymphangitis.
Horse owners should contact their veterinarians if they suspect pigeon
fever so a definitive diagnosis can be made through bacterial culture.
There is no vaccination to protect horses against pigeon fever.
Treatment usually consists of having a licensed veterinarian
surgically open the abscess to allow drainage. Affected horses should
be isolated because draining bacteria from the abscess will
contaminate the stall or pen. Horses, especially ones with open
wounds, should be sprayed with fly repellent to prevent spread of the
bacteria by flies. Humans can carry the bacteria on shoes, hands, etc,
so it is necessary to maintain good hygiene and biosecurity after
handling sick horses.
Basic hygienic and biosecurity measures include thorough handwashing
after touching each horse and wearing gloves when treating sick
horses. Medical professionals and other handlers should change clothes
and sanitize shoes after treating sick horses before moving on to
Bedding, water buckets, and any other materials that come in contact
with pus should be disinfected or discarded and never used with other
horses. Non-porous surfaces like stall mats and walls may be
disinfected with bleach. However, pouring bleach or disinfectants on
the stall's dirt floors or over manure is not effective.
Call your veterinarian for more information on this disease. More
information on pigeon fever can be found at the following website
[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
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
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. 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
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, animals usually recover between 2 weeks to 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