Swine Dysentery: Diagnosis, Treatment, and Prevention

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-25

Key Takeaways

• Swine dysentery is caused by Brachyspira hyodysenteriae, manifesting as mucohemorrhagic diarrhea, particularly in growing-finishing pigs, leading to significant economic losses.
• Diagnosis relies on clinical signs like watery yellow diarrhea progressing to mucoid, bloody feces, and is confirmed via fecal PCR or culture for B. hyodysenteriae, differentiating it from conditions like PPE or Salmonellosis.
• First-line antimicrobial treatments include tiamulin (10-15 mg/kg IM) or valnemulin (3-4 mg/kg in water), with regional antibiogram data crucial for effective strategic rotation due to varying resistance patterns.
• Supportive care involves electrolyte solutions for hydration, dietary adjustments (reduced crude protein, increased soluble fiber), and pain management with meloxicam.
• Rigorous biosecurity measures are paramount for prevention, including strict quarantine protocols for new stock, thorough equipment disinfection (e.g., formaldehyde fogging), and effective rodent control.
• While no commercial vaccines exist, autogenous bacterins have shown limited efficacy, underscoring the importance of proactive biosecurity and prompt, evidence-based treatment to mitigate mortality, which can reach 30% in untreated cases.

Immediate Summary: Swine dysentery is a severe infectious diarrheal disease caused by Brachyspira hyodysenteriae that primarily affects growing-finishing pigs. Characterized by mucohemorrhagic diarrhea and significant economic losses, it requires prompt antibiotic treatment (e.g., tiamulin, valnemulin) combined with rigorous biosecurity measures to control spread.

graph TD
    A[Watery Diarrhea] --> B{Mucoid or Bloody?}
    B -->|Yes| C[Check for Fever >40°C]
    B -->|No| D[Consider other diarrheas]
    C --> E[+ Anorexia? + Weight Loss?]
    E -->|Yes| F[Probable Swine Dysentery]
    E -->|No| G[Salmonellosis? Lawsonia?]
    F --> H[Collect fecal samples for PCR/culture]

Clinical Presentation and Differential Diagnosis

Swine dysentery presents with:

• Early stage: Watery yellow diarrhea (days 1-2)
• Progressive stage: Mucoid feces with blood streaks (days 3-5)
• Chronic cases: Intermittent diarrhea with weight loss

Evidence-Based Treatment Protocols

Antimicrobial Therapy

1. First-line:
2. Tiamulin (10-15 mg/kg IM q24h for 3-5 days)
3. Valnemulin (3-4 mg/kg in water for 5 days)

1. Alternatives:
2. Lincomycin (11 mg/kg IM q24h)
3. Carbadox (55 ppm in feed)

Clinical Note: Resistance patterns vary regionally - always conduct antibiograms during outbreaks (Hampson et al., 2019).

Supportive Care

• Hydration: Electrolyte solutions (NaCl 3.5g + KCl 1.5g/L water)
• Diet: Reduce crude protein to 16%, increase soluble fiber
• Pain management: Meloxicam (0.4 mg/kg q24h)

Biosecurity Prevention Matrix

FAQ Section

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  "@type": "FAQPage",
  "mainEntity": [
    {
      "@type": "Question",
      "name": "Can swine dysentery spread to humans?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "No direct zoonotic risk exists, but Brachyspira species can survive in water sources, requiring proper farm hygiene."
      }
    },
    {
      "@type": "Question",
      "name": "How long does immunity last after infection?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "Pigs develop partial immunity for 8-12 weeks post-infection, but reinfection with different strains is possible."
      }
    },
    {
      "@type": "Question",
      "name": "What's the minimum effective disinfectant?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "2% sodium hydroxide or 1:200 iodophor solutions for 30 minutes contact time effectively kill Brachyspira."
      }
    },
    {
      "@type": "Question",
      "name": "Are there vaccine options available?",
      "acceptedAnswer": {
        "@type": "Answer",
        "text": "No commercial vaccines exist yet, though autogenous bacterins show 40-60% efficacy in challenge studies."
      }
    }
  ]
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Key Research Citations

1. Burrough ER (2020). Swine Dysentery: Clinical Perspectives. Vet Clin North Am Food Anim Pract. 36(1):41-54.
2. Mahu M, et al. (2021). Brachyspira hyodysenteriae virulence factors. Vet Res. 52:45.
3. Rubin JE, et al. (2022). Antimicrobial resistance patterns in North American isolates. J Vet Diagn Invest. 34(2):210-218.

Practical Action Steps

1. Immediate isolation of affected pigs with dedicated equipment
2. Fecal PCR testing of 10% of pens to determine prevalence
3. Water line sanitation with hydrogen peroxide at 50 ppm
4. Strategic antimicrobial rotation based on local resistance data

Note: Mortality can reach 30% in untreated cases - early intervention is critical for herd recovery.