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. (Hank) Harris, Iowa State University
Robert D. dock, Colorado State University
Lynn Joens, Arizona State University
Thad B. Stanton, NADC, USDA/ARS, Ames, Iowa
Reviewers
Edward M. Jenkins, Tuskegee University
Duane Miksch, University of Kentucky
Alan B. Scheidt, Purdue University
M. J. Wannemuehler, Iowa State University
Swine dysentery occurs most frequently in 8 to 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% to 100% of these pigs may be affected and 20% to 30% may die if an effective treatment is not administered. The disease also may appear in suckling pigs or adult swine. In such cases, the disease usually is 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. Annual cost of swine dysentery to U.S. pork producers has been estimated to be $100 million.

Cause
An anaerobic (killed by exposure to air) bacterium, Serpu-lina hyodysenXeriae (S. hyodyserUeriae), (previously called Treponema hyodyserUeriae) 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 various bacteria which look like S. hyodyserUeriae but are nonpathogenic. One of these, Serpulina innocens, has been studied and does not cause swine dysentery in pigs. The two types of bacteria can be identified by laboratory tests and oral inoculation into experimental pigs.
Recent advances in molecular biology have produced new approaches for identifying S. hyodyserUeriae. All of these are based on detecting unique DNA sequences in the S. hyodysenteriae genome. These new techniques are proving useful for diagnosing swine dysentery and for studying the epidemiology of the disease. A definitive diagnosis of swine dysentery should only be based on the isolation and identification of S. hyodyserUeriae in a qualified laboratory.
Transmission
The most common mode of transmission of swine dysentery from farm to farm is the asymptomatic carrier pig. Serpulina hyodyserUeriae is present in the feces of pigs that are either affected with, or have recovered from, swine dysentery. After susceptible pigs ingest the organisms, symptoms of swine dysentery usually occur in 2 to 21 days; however, longer incubation times have been reported. The incubation period is usually shortened by the ingestion of larger numbers of S. hyodyserUeriae.

Sows may harbor S. hyodyserUeriae 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 disease while nursing the sow but are affected after weaning.

Although S. hyodyserUeriae is an anaerobe, it will survive in feces for 1 to 2 months. Exact survival time is not predictable because of the influence of variable environmental factors such as temperature and moisture. The organism has been found in lagoon water collected from an infected premise (Table 1). Pigs that have recovered from swine dysentery may
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. We adhere to the policy that all persons shall have equal opportunity and access to our programs and facilities.