Steps for Treatment, Control and Elimination of Swine Dysentery
Swine dysentery (SD or bloody scours), once one of the most expensive swine diseases, largely disappeared in North America in the 1990’s with three site production and improved hygiene, among other changes in swine industry structure. However, since the early 2000s, SD has re-emerged in swine operations in portions of the U.S. and several Canadian provinces. SD is an intestinal bacterial disease that is very expensive to treat and control medically. It is very difficult to completely eliminate once pigs and facilities are contaminated. SD can be spread by infected swine, rodents and other animals in contact with infected swine as well as any fecal material on equipment or clothing. Biosecurity practices are effective at reducing the exposure risks and, when properly implemented, will prevent or slow the spread of this disease (and other diseases) between farms. Your swine veterinarian can assist you in creating a biosecurity plan to prevent introduction to your herd as well as accurate diagnosis should clinical signs of SD be suspected. For more information on how to recognize SD, see the Pork Information Gateway’s Factsheet, “ Swine Dysentery (Bloody Scours); Recognition and Awareness, Diagnosis, Transmission and Clinical Signs”.
- Discuss the challenges of SD treatment
- Review the importance of SD prevention
- Discuss SD elimination mechanisms
- Discuss steps to for successful elimination and control
Treatment and control measures
- Treatment and control relies on use of effective medications
- Elimination by partial depopulation, medicate-clean-move protocols, or depopulation-repopulation can be successful if thoroughly executed
- As site population size increases, elimination becomes more difficult with coordination of medication, animal movement and environmental clean-up necessary to eliminate SD
- Your veterinarian can be a valuable resource in developing an appropriate control or eradication plan
Once a diagnosis of SD is confirmed, treatment becomes necessary and relies heavily on use of specific antimicrobials. Brachyspira spp. have become resistant to many of the antimicrobials used in the past, particularly in countries outside of the U.S. Selection of an appropriate antibiotic, as well as the route and duration of administration, can be provided by your swine veterinarian. Continuous or repeated pulse doses of antimicrobials are often necessary to treat and provide ongoing control of SD, which is why prevention is strongly preferred. No effective commercial vaccination products are currently available. Relying on medications for control is a costly activity, which can and will lead to resistance over time, thus failure of the control program. Also, public concern with antimicrobial resistance affects use and availability of the limited number of effective antimicrobials. Producers attempting antibiotic free production simply cannot have SD in their herds.
Elimination: early years
Depopulation of an entire herd followed by repopulation (“depop/repop”) with SPF (specific pathogen free) stock, coupled with extensive facility cleaning was successful in eliminating infections in the 1960-70s, but was/ is a very costly option. The identification of the causative bacteria in 1971 offered opportunities for the development of alternative control/elimination methods through better understanding of pathogen spread and antibiotic use. Several economical antibiotics effectively eliminated Brachyspira from pigs while being fed. This allowed a partial depopulation protocol, with repeated cycles of prolonged medication, cleaning, disinfection and moving groups of pigs to a clean environment. Properly implemented, this strategy was often successful. The limited number of available antibiotics useful for treatment and control of SD symptoms are often unable to eliminate Brachyspira from the pig or the environment. Denagard (tiamulin hydrogen fumurate) is still used and effective, but antibiotic sensitivity is required and may limit effectiveness as the United States therapeutic levels are restricted by label instructions. Antibiotic continued use adds considerable cost to production because of the prolonged and high levels needed for feed use. Of over 20 antimicrobials used for treatment and control of SD over the last 60 years, most are no longer available in the U.S. and those that remain have lost some effectiveness. The cost of SD treatment is high, and likely to be economically unsustainable long term. Due to the cost and limited treatment options available, the best approach is prevention based on a properly formulated biosecurity plan to prevent introduction of Brachyspira spp.
Elimination: have a written plan and follow it!
Medication costs and decreased performance in infected herds can result in a loss of approximately $9-15 per pig produced. Thus, the disease is too expensive to “live with” and most producers will choose to eliminate the disease from their pigs and facilities. Elimination can be by total herd depopulation and clean up, or using a modified approach of medicate, move, clean with a rolling line of separation between “clean and dirty” groups or facilities. The economics of a “rolling medicate-clean up-eliminate” method of elimination is not as expensive as total herd depopulation, even with a decrease of 1 to 2 weeks of production. Most producers will regain the cost of elimination from their sow herds or finishing facilities within a year (Wood and Lysons, 1988).
Since SD is expensive to treat and control, and is currently at low incidence levels, it is extremely important to focus on disease prevention, in which your veterinarian can serve as a vital resource. Your veterinarian can assist you in diagnosis, proper medication selection, and methods of treatment, control, or elimination of SD that are best suited for your operation. Any attempt to eliminate SD from a site or herd will require dedicated commitment of the entire production staff. A comprehensive, site-specific, written plan of action must be developed and followed. Key components include:
- Attempt elimination only during the warm months when organism is less hardy
- Certain medications properly dosed and administered may eliminate Brachyspira shedding, hence the sequence of medicate-move-medicate-move has been useful on some farms
- Essentially, pigs are medicated while aggressively removing feces from their environment
- Pigs are moved to clean, segregated premises while continuing medication
- These two steps are often repeated, with thorough biosecurity between groups and stages
- Removal of all feces and organic matter is essential for elimination; soap and disinfectants are used to clean facilities to remove the bacteria from the environment
- Aggressively control mice, rodents, birds, and wildlife and limit access to swine and swine facilities:
- Feces from infected mice are a source of Brachyspira indefinitely
- Eliminate mouse populations and mouse feces
- Mice eating medicated pig feed will shed less Brachyspira; assure any remaining mouse populations eat only SD-effective medicated feed
- Medication and early weaning (MEW) to an off-site nursery can be used to help break the cycle of infection from sows to piglets, but requires proper drug selection, timing, and dosages to be effective
- “Flush” manure systems should plan to use only fresh water indefinitely rather than lagoon water
- Manure storage areas and transport vehicles are potential sources of infection
- Diminish manure storage and consult your veterinarian for specific recommendations based on your particular farm exposure
Prevention – if you don’t have SD, don’t get it!
Keeping infective materials or pigs out requires implementation of effective biosecurity procedures. Key components include:
- Biosecurity protocols that should be developed with your swine veterinarian
- Health history of new sources should be investigated prior to placement of feeder or breeding stock to prevent facility contamination
- Breeding stock should be quarantined without exposure to antibiotics for at least 30 days, before entering the herd and no observance of diarrhea
- Examine daily for any signs of diarrhea
- Removal of antibiotics allows disease signs to be expressed as the early as 2-4 weeks if a group is infected
- Antibiotics in the feed or water can suppress symptoms of disease, but will not by themselves eliminate the infection and may mask clinical signs or detection
- In some situations, testing feces may be warranted prior to entry to a breeding herd. There is no antibody (blood) test available.
- Biosecurity protocols should be implemented for all personnel in potential contact with infected pigs or pigs’ environment, including service personnel
- Isolate your production facility from visitors and off-farm vehicles
- Feed trucks, rendering trucks and service vehicles should be kept away from swine areas on site
- All visitors must follow strict established biosecurity protocols
- All vehicles hauling pigs are cleaned, disinfected and dried prior to use, including vehicles transporting pigs to market
- All footwear and clothing exposed to off-site swine or manure should be changed before entry (boots or footwear worn in other swine locations should be changed before entry)
- Decontaminate all possible fomites such as boots, clothing, and pig handling equipment
- Clean and disinfect load-out area immediately after use. Prevent reentry of wash water to pig areas.
- Bird-proof facilities to keep out birds, wildlife, and other animals to reduce farm-to-farm exposure
- Aggressively suppress rodents and insects in the facilities to reduce exposure
Accurate diagnosis of intestinal disease in growing and finishing swine is very important because the clinical signs of several important infectious diseases are similar. Swine dysentery (bloody scours) can be difficult to differentiate from ileitis (Lawsonia), salmonellosis, whipworms, gastric ulcers or other intestinal disturbances without laboratory assistance. Yet, if SD is in your herd, it often will cost more than any of these other enteric pathogens. Hence, SD is a disease to avoid because of the high costs of treatment, control and production losses, and hardiness of the causative bacteria, Brachyspira, within the environment. Preventing strongly beta-hemolytic colonies of Brachyspira spp. from entering your herds and contaminating your facilities is by far the preferred strategy. Prevention can be accomplished by slight modifications to and thorough execution of principles of biosecurity routinely applied for many other diseases, such as porcine epidemic diarrhea (PED) or and porcine reproductive and respiratory syndrome (PRRS). Your swine veterinarian is a key information source for development of prevention and biosecurity plans, and essential for accurate diagnosis, treatment, control and elimination should this disease enter you herd.
References and Citations
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Burrough, E. R. 2017. Swine dysentery: etiopathogenesis and diagnosis of a reemerging disease. Vet Pathol 54(1):22-31. doi: 10.1177/0300985816653795.
Hampson, D. J., and E. R. Burrough. 2019. Swine Dysentery and Brachyspiral Colitis. In: J. J. Zimmerman, L. A. Karriker, A. Ramirez, K. J. Schwartz, G. W. Stevenson and J. Zhang, editors, Diseases of Swine. Wiley-Blackwell, Hoboken, NJ. p. 951-970.
Harris, D. L. 1984. The epidemiology of swine dysentery as it relates to the eradication of the disease. Compendium on Continuing Education for the Practicing Veterinarian 6(2):S83-S88.
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Martínez-Lobo, F. J., Á. Hidalgo, M. García, H. Argüello, G. Naharro, A. Carvajal, and P. Rubio. 2013. First identification of “Brachyspira hampsonii” in wild European waterfowl. PLoS One 8(12):e82626. (Research Support, Non-U.S. Gov’t) doi: 10.1371/journal.pone.0082626.
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Mirajkar, N. S., N. D. Phillips, T. La, D. J. Hampson, and C. J. Gebhart. 2016b. Characterization and recognition of Brachyspira hampsonii sp. nov., a novel intestinal spirochete that is pathogenic to pigs. J Clin Microbiol 54(12):2942-2949. doi: 10.1128/JCM.01717-16.
Mushtaq, M., S. Zubair, T. Råsbäck, E. Bongcam-Rudloff, and D. S. Jansson. 2015. Brachyspira suanatina sp. nov., an enteropathogenic intestinal spirochaete isolated from pigs and mallards: genomic and phenotypic characteristics. BMC microbiology 15:208. doi: 10.1186/s12866-015-0537-y.
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