Fowl cholera (FC) is a highly contagious bacterial disease affecting both domestic and wild birds. It is caused by
Pasteurella multocida, a gram-negative, non–spore-forming, rod-shaped bacterium. There are at least 16 somatic serotypes of
P. multocida, each varying in virulence and pathogenicity.
Fowl cholera occurs in two forms: acute and chronic. Birds that survive the acute stage, or those infected with less virulent strains, often go on to develop localized, chronic infections.
Clinical Signs of Fowl Cholera
Clinical signs vary depending on whether the disease presents in its acute or chronic form.
Acute Form
Affected birds may show:
- Fever
- Loss of appetite
- Lethargy
- Ruffled feathers
- Mucous discharge from beak
- Increased respiratory rate
- Cyanosis (darkening of the face, comb or wattles)
- Difficulty breathing
- Diarrhea that begins yellow-gray and progresses to watery green with mucus
- Coughing
- Retraction of the head (opisthotonos)
- Swelling of the face, comb, or wattles
Chronic Form
Following the acute phase, the infection may become localized and chronic. Signs depend on the tissues involved and may include:
- Respiratory tract: Tracheal rales, coughing, and nasal or oral discharge
- Ear infection: Wry neck (torticollis)
- Joints or feet: Lameness, swelling, inflammation, and abscess formation
- Sinuses: Facial swelling and discharge
- Comb and wattles: Swelling, inflammation, and abscesses
The chronic form may last 3–4 weeks, but in some cases can persist for months or even years, despite treatment.
Transmission
Fowl cholera spreads through horizontal transmission via direct or indirect contact with infected birds. It is commonly introduced into a flock through wild birds, rodents, predator exposure, newly introduced carrier birds, or contaminated objects (fomites).
P. multocida enters the body through mucous membranes (oral, nasal, or conjunctival) or through breaks in the skin.
Common routes of transmission include:
- Direct contact: Close contact with infected birds and their secretions.
- Ingestion: The most common route, via contaminated feed, water, or environment.
- Predators: Non-fatal attacks from animals such as dogs, cats, or raccoons, which can carry high bacterial loads in their mouths and claws.
- Fomites: Contaminated equipment, clothing, cages, or feeders.
The bacterium can persist in the environment for extended periods—up to 3–4 weeks in water and as long as 4 months in soil. Chronically infected birds are a major source of transmission and may remain carriers for life. However, many strains are susceptible to sunlight, heat, drying, and common disinfectants.
