HERD HEALTH
PIH-56
pork industry handbook
PURDUE UNIVERSITY • COOPERATIVE EXTENSION SERVICE • WEST LAFAYETTE, INDIANA
Swine Dysentery
(Bloody Scours, Vibrionic Dysentery, Black Scours)
Authors
D. L. Harris, Rothville, Missouri
Robert D. Glock, Casa Grande, Arizona
Lynn Joens, Arizona State University
Isabel Turney Harris, Rothville, Missouri
Reviewers
Duane and Rhonda Haufler, Boerne, Texas
Edward M. Jenkins, Tuskegee University
Kurt Wohlgemuth, North Dakota State University
Swine dysentery occurs most frequently in 8-14 week-old pigs, although all ages may be affected with the disease. Typically, the pigs pass loose stools containing blood and mucus. When swine dysentery occurs in young weaned pigs, up to 90-100% of these pigs may be affected and 20-30% may die if an effective treatment is not administered. The disease may also appear in suckling pigs or adult swine. In such cases, the disease is usually mild and may not be readily diagnosed. Often, when the disease has been present in a herd for a time, the clinical picture is less dramatic, especially when drugs are routinely used to control swine dysentery. In such cases, only sporadic diarrhea is seen.

Due to the inapparent infectiousness of the disease, the economic significance is difficult to assess. In typical outbreaks, losses result from poor rate of gain and feed efficiency, medication costs, and death. The Livestock Conservation Institute estimates that swine dysentery causes an annual loss of $64 million to the U.S. swine industry. A recent survey conducted at Iowa State University indicated that 40% of the herds in Iowa, Missouri, and Illinois were affected with swine dysentery.

Cause
An anaerobic (growing only in the absence of oxygen) bacterium, Treponema hyodysenteriae, is
the cause of swine dysentery. As the disease progresses, blood may be lost through the damaged intestinal wall. Death usually results because of dehydration and a loss of electrolytes.

Most herds of pigs harbor another type of bacterium, Treponema innocens. Although this type is identical in appearance to T. hyodysenteriae, T. innocens does not cause disease in pigs. The two types of bacteria can be identified by laboratory tests and oral innoculation into experimental pigs. A definitive diagnosis of swine dysentery should only be based on the isolation and identification of T. hyodysenteriae in a qualified laboratory.

Transmission
Treponema hyodysenteriae is present in the feces of pigs that are either affected with or have recovered from swine dysentery. After susceptible pigs ingest the organism, symptoms of swine dysentery usually occur in 2-21 days; however, longer incubation times have been reported. The incubation period is usually shortened by the ingestion of higher numbers of T. hyodysenteriae.

It has been shown that sows may harbor T. hyodysenteriae without having clinical evidence of swine dysentery. The organism lives in the feces of the sow and is transmitted to the suckling pigs. Often, it appears that most pigs are not susceptible to the
Cooperative Extension work in Agriculture and Home Economics, state of Indiana, Purdue University and U.S. Department of Agriculture cooperating. H.A. Wadsworth, Director, West Lafayette, IN. Issued in furtherance of the acts of May 8 and June 30, 1914. The Purdue University Cooperative Extension Service is an affirmative action/equal opportunity institution.