What is Pigeon Fever? 

Pigeon Fever caused by Corynebacterium pseudotuberculosis is a bacteria most often found in the Southwestern United States but reported throughout North America. Outbreaks in areas in which the bacteria had previously not been or only rarely reported have occurred during times of drought.

Clinical Signs: There are three forms of Pigeon Fever: external abscesses, internal infection and ulcerative lymphangitis/limb infection. 

External Abscesses:

• Most common form of infection; can be single or multiple abscesses. 
• Abscesses can occur anywhere on the body but are commonly located in the pectoral area (on the front of the chest thus the name “pigeon fever” or “pigeon breast”). 
• Abscesses are well encapsulated and contain tan, non malodorous exudate (pus). 
• Horses with external abscesses are normally not ill. However, affected horses may develop a fever. 
• Horses with external abscesses may also have internal infection, and systemic antimicrobial treatment may be necessary. 

Internal Infection: 

• Occurs in approximately 8% of affected horses, and is associated with a high case fatality rate (30 to 40%). 

Ulcerative Lymphangitis: 

• Involves severe limb swelling with infection and abscessation of the lymphatics (vessels responsible for transporting fluid from the limbs back to circulation) 
• Can affect one or more legs
• Severe lameness, fever, lethargy and anorexia can occur 
• Chronic and recurrent infection can occur

Diagnosis: Bacterial culture of aspirate or exudate from the wounds/abscesses is used to identify the bacteria. Serologic testing can help diagnose internal abscesses. Ultrasound examination is helpful to identify and aspirate external and internal abscesses.

Treatment: External abscesses can generally be treated with drainage and flushing. Ulcerative lymphangitis and internal infection must be treated more aggressively with antimicrobial therapy, sometimes for extended treatment periods. 

Prevention: Currently there is no licensed vaccine for Corynebacterium pseudotuberculosis available in the United States.