Swine Dysentery in Pigs: Bloody Diarrhea, Weight Loss, and Brachyspira Infection

Quick Answer
  • Swine dysentery is a contagious large-intestinal disease of pigs that causes soft stool that can progress to mucus-heavy, bloody diarrhea.
  • It is most often linked to Brachyspira hyodysenteriae, but Brachyspira hampsonii and Brachyspira suanatina can also cause the same syndrome.
  • Common warning signs include reduced appetite, dehydration, hollow flanks, weight loss, and diarrhea moving through a group of pigs.
  • Your vet usually confirms the diagnosis with fecal or colon samples for PCR and anaerobic culture, often alongside postmortem or histopathology findings.
  • Early veterinary care matters because affected pigs can decline quickly, spread infection through feces, and need herd-level treatment and biosecurity planning.
Estimated cost: $150–$2,500

What Is Swine Dysentery in Pigs?

Swine dysentery is a contagious disease of the large intestine in pigs. It causes inflammation in the cecum, colon, and rectum, leading to diarrhea that often becomes thick with mucus and may contain visible blood. In many herds, the disease is most noticeable in growing and finishing pigs, where it can slow growth and increase losses.

The condition has long been associated with Brachyspira hyodysenteriae, a spiral-shaped bacterium. More recent veterinary references also recognize Brachyspira hampsonii and Brachyspira suanatina as causes of the same clinical syndrome. These bacteria spread mainly by the fecal-oral route, so contaminated manure, water, boots, trailers, and equipment can all play a role.

For pet pigs and small hobby herds, swine dysentery can be especially frustrating because the first signs may look like a routine stomach upset. But when stool becomes mucoid, dark, or bloody, and a pig starts losing condition, it is time to involve your vet. Fast action helps protect the sick pig and lowers the risk of spread to other pigs on the property.

Symptoms of Swine Dysentery in Pigs

  • Soft stool or loose manure early in the course
  • Mucus-heavy diarrhea
  • Bloody or dark red-brown diarrhea
  • Reduced appetite or not eating normally
  • Dehydration, including dry appearance and sunken eyes
  • Hollow flanks and rapid weight loss
  • Poor growth or falling behind pen mates
  • Weakness or increased death loss in untreated groups

See your vet immediately if your pig has bloody diarrhea, repeated mucus-filled stool, weakness, or signs of dehydration. Swine dysentery can move through a group and may look similar to other serious intestinal diseases, including salmonellosis, proliferative enteropathy, intestinal spirochetosis, or heavy whipworm infection. Mild cases may start with soft feces and reduced appetite, but worsening stool, weight loss, or multiple pigs becoming sick should raise concern quickly.

What Causes Swine Dysentery in Pigs?

Swine dysentery is caused by infection with certain strongly beta-hemolytic Brachyspira bacteria. The classic cause is Brachyspira hyodysenteriae, but veterinary sources also identify B. hampsonii and B. suanatina as true causes of swine dysentery. After a pig swallows the organism, the bacteria colonize the large intestine and damage the surface lining, which leads to excess mucus, bleeding, and poor fluid reabsorption.

Spread happens mainly through contact with infected feces. That means manure-contaminated pens, boots, feeders, water sources, trailers, and transport vehicles can all help move the infection. Carrier pigs may also shed bacteria without looking severely ill, which makes herd control harder.

Other factors can make outbreaks more likely or more severe. These include crowding, poor sanitation, movement of pigs without quarantine, rodent exposure, and mixing pigs from different sources. In real-world cases, pigs may also have more than one intestinal problem at the same time, so your vet may look for additional pathogens or parasites when diarrhea is severe or not responding as expected.

How Is Swine Dysentery in Pigs Diagnosed?

Your vet usually starts with the history, age group affected, and the appearance of the diarrhea. Mucohemorrhagic diarrhea in growing pigs is strongly suspicious, especially if several pigs are affected and weight loss is developing. A physical exam, manure evaluation, and sometimes necropsy findings help guide the next steps.

To confirm the diagnosis, your vet may submit feces, fecal swabs, colon contents, or colon tissue for PCR and selective anaerobic culture. PCR can provide rapid detection of important swine dysentery organisms, while culture helps identify strongly beta-hemolytic Brachyspira and may support antimicrobial susceptibility testing. Histopathology of the large intestine can also show the typical inflammatory changes seen with this disease.

Because several pig diseases can cause diarrhea, your vet may also test for Lawsonia intracellularis, Salmonella, intestinal spirochetes, parasites such as whipworms, or mixed infections. This matters because treatment and herd management can change depending on what else is present. In the U.S., diagnostic lab fees for Brachyspira testing can be relatively modest per sample, but the full cost range rises once farm calls, multiple pigs, shipping, necropsy, and herd-level planning are included.

Treatment Options for Swine Dysentery in Pigs

Spectrum of Care means you have options. Here are treatment tiers at different price points.

Budget-Conscious Care

$150–$600
Best for: Stable pigs that are still drinking, small hobby herds, or pet parents who need evidence-based care with careful cost control
  • Exam with your vet or herd-health consultation
  • Targeted fecal testing such as PCR on selected sick pigs
  • Early antimicrobial plan chosen by your vet based on likely organisms and local resistance concerns
  • Oral fluids, electrolyte support, and close monitoring of hydration and manure output
  • Strict manure cleanup, isolation of affected pigs, and basic boot-and-equipment disinfection
Expected outcome: Fair to good when started early, but relapse or continued spread can happen if infected pigs remain in contact with the group or if resistance is present.
Consider: Lower upfront cost, but less testing may make it harder to confirm the exact organism, detect mixed infections, or choose the most effective medication plan.
Most Common

Recommended Standard Treatment

$600–$1,500
Best for: Most pigs and small herds where the goal is to confirm the diagnosis, treat early, and reduce spread
  • Full veterinary exam and herd history review
  • PCR plus selective anaerobic culture on feces or colon samples
  • Medication plan directed by your vet, with consideration of susceptibility or MIC data when available
  • Supportive care for dehydration, appetite loss, and weight loss
  • Pen-level or herd-level sanitation, isolation, traffic control, and rodent control recommendations
  • Follow-up testing or reassessment if diarrhea persists
Expected outcome: Good in many cases when treatment starts promptly and biosecurity steps are followed, though growth setbacks can continue for a period after recovery.
Consider: Higher cost range than conservative care, and culture or susceptibility testing can take longer than PCR, but the extra information can improve decision-making.

Advanced / Critical Care

$1,500–$2,500
Best for: Severe dehydration, bloody diarrhea with rapid decline, repeated outbreaks, or situations where pet parents want every available diagnostic and management option
  • Urgent veterinary assessment for weak, dehydrated, or rapidly declining pigs
  • Expanded diagnostics including necropsy, histopathology, culture, PCR panels, and susceptibility testing
  • Intensive fluid support and individualized nursing care for severely affected pigs
  • Detailed herd outbreak investigation with quarantine, movement control, environmental review, and deeper sanitation planning
  • Retesting, monitoring of response, and longer-term control strategy for recurrent or multi-pen disease
Expected outcome: Variable. Some pigs recover well with aggressive care, while others have lasting weight loss, poor performance, or death if disease is advanced or multiple pathogens are involved.
Consider: Most comprehensive approach, but it requires more time, more samples, and a higher cost range. It may also reveal herd-level problems that need ongoing management.

Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.

Questions to Ask Your Vet About Swine Dysentery in Pigs

Bring these questions to your vet appointment to get the most out of your visit.

  1. You can ask your vet which diseases are highest on the list besides swine dysentery, such as Salmonella, Lawsonia, or whipworms.
  2. You can ask your vet which samples will give the best answer right now: feces, fecal swabs, colon tissue, or necropsy samples.
  3. You can ask your vet whether PCR, culture, or both are the best fit for your pig or herd.
  4. You can ask your vet if antimicrobial susceptibility or MIC testing is recommended before choosing treatment.
  5. You can ask your vet how to isolate sick pigs and what cleaning steps matter most for boots, pens, feeders, and trailers.
  6. You can ask your vet what signs mean dehydration is becoming dangerous and when recheck care is needed the same day.
  7. You can ask your vet whether other pigs in contact need monitoring, testing, or preventive management changes.
  8. You can ask your vet what realistic recovery timeline to expect for stool quality, appetite, and weight gain.

How to Prevent Swine Dysentery in Pigs

Prevention focuses on biosecurity and manure control. Because swine dysentery spreads through infected feces, the most helpful steps are keeping pens clean, removing manure promptly, preventing fecal contamination of feed and water, and cleaning boots, tools, and transport surfaces between groups. If you bring in new pigs, quarantine them and discuss screening plans with your vet before they mix with resident pigs.

Rodent control also matters. Veterinary references specifically include rodent control and biosecurity as part of swine dysentery control, since pests and contaminated environments can help maintain or move infection. Limiting unnecessary traffic between pens and avoiding shared dirty equipment can reduce spread.

If your pig has had diarrhea before, or if you keep more than one pig, work with your vet on a herd-health plan rather than waiting for another outbreak. That plan may include when to test, which pigs to sample first, how to handle manure safely, and what to do after transport or new arrivals. Prevention is rarely one step. It is a combination of sanitation, quarantine, monitoring, and fast response when stool changes appear.

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