The following topics are a summary of current perception about the status of information regarding swine dysentery and its control.

There are very few herds remaining in the United States in which the ownership or the attending veterinarian are unaware of infection with Serpulina hyodysenteriae, the cause of swine dysentery. Exceptions are usually herds with particularly poor management and production, or in which there is no veterinary supervision.

Most herds will demonstrate clinical signs that can lead to a specific diagnosis if they are left free of specific anti-dysentery medication. Other observations such as history, gross necropsies, and histopathology can contribute to a more specific diagnosis. Sentinel animals have been used to enhance this observation. Culture techniques provide definitive identification of Serpulina hyodysenteriae in nearly all instances. There are also very specific probes based on genetic make-up that can easily identify relatively small numbers of organisms. These can be accessed through special requests but are not widely available pending some method of making them commercially viable.

Therefore, herds that have swine dysentery are almost always identifiable with modest effort.

Ability to identify and eliminate infected herds is greatly enhanced by recent advances regarding diagnosis of conditions such as porcine colonic spirochetosis (PCS) and porcine proliferative enteritis (PPE). Authors such as Andrews et al. (1982) and Taylor et al. (1980) have discussed the presence of a milder enteritis related to spirochetal infection of the large intestine. More recently, Duhamel (1994) reported on a better differential regarding this disease. This eliminates potential confusion between swine dysentery and PCS.

After all the concerns have settled regarding the etiology of PPE, the fact remains that it is currently easily differentiated from swine dysentery with histopathology and anaerobic culture techniques. Better methods for identifying agents involved in PPE are soon likely to become available but are not necessary for differentiation from swine dysentery.

Diagnostic techniques described above can be used for the definitive identification of herds affected with Serpulina hyodysenteriae, the agent responsible for swine dysentery.

Numerous publications over the years have indicated that there has been a decline in the incidence of swine dysentery. A credible study in 1982 indicated a 40 percent incidence in herds in Iowa (Egan et al.). Efforts in the early 1900s suggest that the incidence may have declined to levels such as 11 percent (Mapother, 1990) or 18 percent of herds at risk (Schultz, 1992). These specific numbers have been questioned, but there is little reason to argue with the decline in incidence of swine dysentery.

Further support of a declining incidence is the frequently quoted practitioner observation that there is simply less swine dysentery observed in herds that are well-managed. There is also less volume of vaccine sales. Many herds have been freed of swine dysentery through stimulus from better management of economics supplemented by better methodology in swine dysentery elimination. Information on elimination has been disseminated through efforts of LCI and AASP. Practicing veterinarians and producers simply have more confidence in their ability to manage this disease.

The National Committee on the Control and/or Eradication of Swine Dysentery (NCCESD) has decided to reduce efforts based on the belief that the swine industry does not want another highly organized control program and swine dysentery is a disease that can be managed on the local level.

The interested producer can easily avoid contamination with swine dysentery simply by practicing good biosecurity. Animals should be purchased only from herds that are willing to communicate observations of the ownership and the veterinarian with regard to herd health status. Examples are SPF animals, minimal disease animals, and other designations. Further biosecurity mandates the use of appropriately clean transportation vehicles and isolation of newly arrived animals. Additional insurance is provided by judicious medication of new arrivals after a period of initial observation.

Prevention of dissemination through people, vehicles, and herd proximity are also very applicable. Judicious management can almost invariably avoid introduction of swine dysentery into a herd with reasonable communication between producer and veterinarian.

Currently marketed vaccines appear to have some short-term benefits but have not received wide acclaim as a major player in the ultimate elimination of infection from herds. This does not preclude the possibility of better vaccines appearing on the market in the future, but this is not an essential to ultimate control of swine dysentery.

The methodology for elimination from individual herds has been published in various media, including LCI publications. There is no need to repeat the methodology. Very simply, the technology is available to eliminate swine dysentery from any herd. This may involve application of sanitation and medication or other techniques that are widely understood.

Elimination from infected herds can also involve procedures such as surgical derivation of animals, offspring segregation, multiple site methodology, or modified medicated early weaning (MMEW). These techniques have been described and are readily applicable. Some information indicates that early weaning procedures and offspring segregation are applicable even in animals weaned as late as 21-days.

If the industry so desires, swine dysentery can be eliminated from individual herds and ultimately from the swine population of the United States. There was once a great concern about detection of carrier animals. Carrier tests may be useful in the late stages of an eradication program. In the meantime, there are very few herds that cannot be identified using current methodology and there are very few herds in which the disease cannot be eliminated using current methodology. This precludes the need for a large-scale federal program because the motivation for individual herd clean-up is clearly economic in nature. The swine industry is probably not ready for a large official program at this time. Perhaps sometime in the distant future, there may be need for a more coordinated program if the number of infected herds becomes very low and some help is needed in identification of those herds. This would seem to be a few years in the future.

Suitable cooperation between producers and practicing veterinarians with some help from diagnostic laboratories can easily result in the identification of nearly every herd infected with swine dysentery. There is profound economic motivation to control this disease and to prevent movement of the disease to other herds. Elimination of the disease from selected herds is not necessarily easy but is certainly achievable and in most cases will have obvious economic motivation.

It would seem that it is time to urge the swine industry to look at the costs of swine dysentery on an individual herd basis and to ascend above the inertia that prevents elimination of the disease from individual herds at the cost of reduced productivity and profitability. Therefore, it seems appropriate to defer a national program at this time in favor of continuing education of the swine industry with regard to the options currently available to reduce swine dysentery to a condition of minimal significance.

1. Andrews et al: A Porcine Colitis Caused by a Weakly beta-hemolytic Treponeme. Proceedings AAVLD, 1982, p. 395.

2. Duhamel: Porcine Colonic Spirochetosis: A Diarrheal Disease Associated with a Newly Recognized Species of Intestinal Spirochetes. Proceedings AASP, 1994, p. 267.

3. Egan et al: Prevalence of Swine Dysentery, Transmissible Gastroenteritis, and Pseudorabies in Iowa, Illinois, and Missouri Swine. Proceedings USAGA, 1982.

4. Mapother et al: An Estimate of the Prevalence of Swine Dysentery in US Swine Herds During 1989-91. Proceedings LCI, 1993.

5. Schultz: Is It Time To Wipe Out Swine Dysentery? National Hog Farmer, Jan 15, 1993, p. 14.

6. Taylor et al: Production of Diarrhea and Dysentery in Pigs by Feeding Pure Cultures of a Spirochaete Differing from Treponema hyodysenteriae. Vet Rec 106:326, 1980.