More Pigeon Fever in Kentucky

The bacterial disease "pigeon fever," also known as dryland distemper, usually is seen west of the Mississippi--especially in California and southwestern states--but it has been recognized in Kentucky and Florida in increasing numbers in recent years. There was a small outbreak in Kentucky in November 2002 (see article #4040 at Some affected horses are still battling the disease.

According to Doug Byars, DVM, Dipl. ACVIM, Dipl. ACVECC, of Hagyard-Davidson-McGee Associates (HDM), in Lexington, Ky., three cases were seen at HDM by Jan. 27. One pregnant mare under the care of private practitioner Steve Conboy, DVM, died of the disease after a prolonged battle. She had severe lung lesions--the lung was reported to be 1 1/2 times its normal size--and the lesions cultured positive for Corynebacterium pseudotuberculosis, the organism that causes pigeon fever.

Byars and Conboy reported that the fetus had liver lesions consistent with pigeon fever, and its lung cultured positive for C. pseudotuberculosis. Maternal transfer of the disease to a fetus has been reported before in literature, but it is rare, according to Sharon Spier, DVM, PhD, Dipl. ACVIM, of the University of California, Davis. The organism can cause abortion, but rarely.

Pigeon fever usually is associated with very deep abscesses and multiple sores on the chest (hence the name pigeon fever, as the chest swells, resembling a pigeon breast). Occasionally there are sores on the midline and abdomen, or even on the back. An ulcerative lymphangitis (causing the hind legs to swell and "bust out" in crusts) and internal abscesses also can be caused.

The majority of cases are seen when fly populations are the most intense (late summer/fall). But sporadic cases can "pop up" during other times of the year. The incubation period (from bacterial entry to formation of the abscess and subsequent immunity) is variable, which is probably why cases are still occurring in January. "Clearly more research needs to be performed to better understand the treatment and control of this ugly disease," said Spier.

See article #4110 at for more information on pigeon fever.

About the Author

Kimberly S. Brown

Kimberly S. Brown was the Publisher/Editor of The Horse: Your Guide To Equine Health Care from June 2008 to March 2010, and she served in various positions at Blood-Horse Publications since 1980.

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