Fowl cholera :

       It is a contagious, bacterial disease that affects domestic and wild birds worldwide ( turkey and waterfowl are more susceptible than chicken ).

• It usually occurs as a septicaemia of sudden onset with high mortality and morbidity , but chronic and asymptomatic infection also occur .
• Older chicks are more susceptible .

 Etiology :

  Pasteurella multocida type A

( small, gram negative , non-motile with a capsule that exhibit pleomorphism after repeated subculture ; give bipolar appearance when stained with Wright’s stain )

Transmission :

a. Direct contact with infected birds

• Secretions made from infected birds ( mouth, nose , conjunctiva, ete )
• Close contact with one another

b. Ingestion

• Through contamination of the environment , feed or water with faces from the infected host.

c. Predator attacks

• Non fatal predator attack from wild or domestic animals ( dog/cat – carrier of bacteria in oral cavity )

d. Fomites : contamination of equipment , clothing , cages, feeders

e. Aerosol form

• multocida can persist in env. For weeks after the outbreak.

Pathogenesis :

Entrance through URT mucosal membrane , conjunctiva , cutaneous wound

1. Start of acute septicaemia with coagulopathies.
2. Production of endotoxin ; endothelial damage ; edema , haemorrhages , shock, sudden death
3. Bacteremia ; spreading to lung

        Clinical signs:

a. Acute form :

• Sudden changes in mortality without previous signs
• Fever
• Loss of appetite
• Ruffled feathers
• Mucous discharge from mouth
• Green watery diarrhoea
• difficulty
• blue/purple colouration of skin and swelling of comb / wattle
• Pneumonia is particularly common in turkey

Fig: green feces in fowl cholera

b. Chronic form :

• Signs are related to localized infection of wattles, joints, tendon sheath , foot pads; which often are swollen because of accumulated fibrinosuppurative exudate .
• Exudative conjunctivitis and pharyngitis
• Torticollis
• Failure of growth and development
• Drop in egg production
• Dermal necrosis in turkey

fig: lesions in fowl cholera

Postmortem finding :

1. Peracute and acute forms :

1. Disease shows primarily vascular disturbances

• General passive hyperemia and congestion throughout the carcass
• Petechial and ecchymotic haemorrhages in subepicardial and subserosal locations.

1. Enlargement of liver and spleen
2. Increased amount of peritoneal and pericardial fluids.

2. Subacute form :

   Multiple , small , necrotic foci may be disseminated throughout liver and spleen.

3. Chronic forms :

• Suppurative lesions may be widely distributed, often involving resp. Tract , conjunctiva and adjacent tissue of head .
• Caseous arthritis and productive inflammation of peritoneal cavity and oviduct
• Fibronectin dermatitis
• Sequestered necrotic lung lesion
• Osteomyelitis

Diagnosis :

• History
• Clinical signs and lesions
• Isolation and identification of bacteria
• PCR testing
• Serological test : AGID , ELISA , whole blood agglutination , agar diffusion test
• Immunofluorescence microscopy

  DDx :

• Erysipelas
• Septicaemic viral
• Infectious coryza
• Fowl typhoid
• Fowl plague ( avian flu )
• Duck plague