Fowl Cholera in Chickens: Symptoms, Causes and Treatment

Pasteurella multocida is a gram-negative coccobacillus with multiple capsular types (A, B, D, E, F) and somatic types that vary in virulence. Type A is the most common cause of fowl cholera.

• Carrier wildlife: Wild birds (especially waterfowl, crows, and sparrows), rodents, and cats are natural reservoirs. A single infected wild bird near a poultry facility can introduce the organism.
• Carrier chickens: Recovered birds can carry Pasteurella in their nasal passages for months. Introducing recovered birds or birds from farms with a history of cholera is a primary introduction route.
• Contaminated water and feed: Pasteurella survives in moist soil and contaminated water for days to weeks. Shared water sources are an efficient flock spread mechanism.
• Stress triggers: Heat stress, poor nutrition, concurrent infection, and transport dramatically increase susceptibility to cholera. Peracute outbreaks often follow a stressful event in an endemically exposed flock.

The combination of sudden deaths with purple combs and swollen wattles is highly suggestive of fowl cholera.

• Necropsy findings: Classic findings include petechial hemorrhages throughout the heart and liver surfaces, congested and enlarged liver with pinpoint necrotic foci (a pathognomonic finding for P. multocida), and excess fluid in the pericardium and body cavity.
• Bacteriology: Blood smears or impression smears from liver stained with Wright's or Giemsa stain often show bipolar-staining coccobacilli. Culture on blood agar confirms P. multocida within 24-48 hours.
• Differentials: Newcastle disease (neurological signs, no swollen wattles), erysipelas (diamond-skin lesions, peracute death in turkeys), blackhead (yellow diarrhea, liver lesions in cecae).

Fowl cholera responds well to antibiotic treatment if started early. Treatment reduces mortality but does not eliminate the carrier state in recovered birds.

Penicillin (first choice): Procaine penicillin G at 3,000 IU/kg body weight IM once daily, or penicillin V in water. Highly effective against most P. multocida strains.

Oxytetracycline: 5-10 mg/kg in drinking water for 5-7 days. Broad availability and effectiveness make this a practical choice for flock-wide treatment.

Sulfonamides: Sulfadimethoxine or sulfamethazine in water (0.05% for 6 days) provides good coverage. Often combined with enhanced supportive care.

Fluoroquinolones: Enrofloxacin under veterinary prescription for resistant strains. Culture and sensitivity testing guides selection when first-line drugs fail.

Depopulation and disinfection: In severe outbreaks, complete depopulation followed by thorough disinfection and a minimum 3-week downtime before restocking may be the only way to break the cycle in endemic operations.

• Vaccinate in endemic areas using a killed bacterin specific to the capsular type present in your region. Two doses 3-4 weeks apart are needed. Annual revaccination maintains protection.
• Control wild bird and rodent access to poultry housing. Sparrows, crows, and waterfowl are primary Pasteurella reservoirs. Screen all openings and remove feed spills that attract wildlife.
• Never introduce birds with an unknown health history. Purchase from P. multocida-free flocks with documented health records.
• All-in, all-out management prevents recovered carrier birds from serving as a reservoir for new, susceptible arrivals.
• Maintain litter quality and avoid heat stress during summer months. Peracute outbreaks frequently follow heat stress events in flocks with endemic Pasteurella exposure.