Pigeon fever (caused by Corynebacterium pseudotuberculosis) remains a significant equine infectious disease with expanding geographic distribution. The organism can persist in soil and contaminated environments for extended time periods, and the disease can present with variable clinical signs leading to diagnostic and management challenges for practitioners.
Disease expression can depend on host immunity and environmental conditions. Horses with internal infections have a higher fatality rate and require intensive, prolonged therapy. Current epidemiologic trends, appropriate diagnostics, and evidence‑based treatment protocols are essential for effective management and biosecurity planning in equine populations.
Hosts
Primary hosts:
- Horses and donkeys are infected by a biotype of Corynebactyerium pseudotuberculosis called biovar equi.
- Cattle are also susceptible to biovar equi, as well as biovar ovis (the biotype of Corynebacterium pseudotuberculosis that causes a disease called caseous lymphadenitis in sheep and goats)
- Water buffaloes
Potential hosts:
- Camelids are more commonely infected with biovar ovis, but can contract biovar equi
- Rare human infections have been reported
Clinical Signs
The incubation period for pigeon fever is typically 3-4 weeks.
Presentations:
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External abscesses:
- Commonly in pectoral or ventral abdominal regions; may also appear in limbs, axilla, triceps, prepuce, mammary areas, and head
- Abscesses usually are well-encapsulated and contain tan, odorless purulent exudate
- Seldom signs of systemic illness if internal involvement also is suspected.
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Internal abscesses:
- Affects approximately 8% of cases; can have fatality rate up to 30-40%
- Organ involvement may include liver, kidneys, spleen, and lungs; septic arthritis and osteomyelitis are also possible
- Concurrent external abscesses possible
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Ulcerative lymphangitis:
- Rare manifestation involving severe, painful distal limb swelling and cellulitis, draining lymphatic tracts
- Significant lameness with secondary laminitis a risk
- Systemic signs may include fever, lethargy, and anorexia
Healthy adult horses usually recover from external abscess form within 2-6 weeks; recovery may take many months in severely affected animals.
Report Pigeon Fever
Pigeon fever is an immediately reportable disease. If you suspect pigeon fever, please contact the State Veterinarian at
503-986-4711. ODA can assist in getting samples properly submitted and with potential biosecurity needs.
Diagnosis & Treatment
Definitive diagnosis is made via culture or PCR of purulent material. Internal involvement may require ultrasound, bloodwork, imaging, and repeated evaluations.
Treatment usually involves:
- External abscess management: lance, drain, flush; monitor systemic parameters
- Antibiotics used selectively depending on systemic involvement and location
- Internal abscesses often require prolonged antimicrobial therapy and supportive care
- Strict biosecurity, hygiene, and quarantine procedures required
Prevention
The bacteria can survive in soil for up to eight months and for a couple of months in hay and shavings.
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Vector control:
- Implement vector control strategies on premises
- Educate clients on environmental management and fly control
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Biosecurity:
- Reinforce equipment hygiene and avoid cross‑contamination
- Clean fomites and use appropriate disinfectants
- Establish quarantine protocols for new and sick horses
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Monitor:
- Monitor at‑risk herds during peak seasons; consider environmental factors such as dry weather, dust, and fly populations
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