Fowl Cholera (Pasteurellosis)

Fowl cholera (FC) is a highly contagious bacterial disease caused by Pasteurella multocida. There are many serotypes of P. multocida with differing pathogenicity. FC is seen in both wild and domestic birds, including mammals. Young, growing birds are most susceptible.

The disease most frequently presents in birds as an acute septicaemia, where death may be the first sign observed. However, a more chronic and asymptomatic form of the disease can also occur. When clinical signs do develop, the most frequent include diarrhea, ruffled feathers increased respiratory rate, depression, and bluish to purplish color comb (cyanosis) immediately prior to death.

Sometimes chickens may recover or develop a chronic infection. Chronic FC occurs generally as a localized infection of a particular region of the body--specifically in the hock or wing joints, footpad, tendon sheath, ear, sinuses, wattles, or sternal bursae. When chronic infections involve the ear, it is usually relating to the middle ear and cranial bones, resulting in torticollis.

Transmission

FC is spread a number of different ways:

• Direct contact with infected birds: Secretions made from infected birds, requiring close contact with one another.
• Ingestion: Most common route, involving contamination of the environment, feed, or water with feces from infected birds. Chronically infected birds may shed the virus in their droppings even following recovery.
• Predator attacks: Non-fatal predator attacks from wild or domestic animals (dogs, cats, and raccoons are known to be carriers of high amounts of the bacterium in their oral cavities). Any chicken that has been in a predator's mouth or mouthed by a predator should be treated immediately with appropriate antibiotics.
• Fomites: Contamination of equipment, clothing, cages, feeders, etc.
• Aerosol form

P. multocida can persist in the environment for weeks after an outbreak. Chronically infected carriers play a major role in the spread of this disease, and infected birds can remain carriers for life.

Confirmed Cases of Fowl Cholera

Affected	History	Diagnostic Findings	Tests used	Ref
18-week old turkeys	History of difficulty walking, recumbency, and increased mortality, with no respiratory signs.	Severe keel bursitis and synovitis of the hock joints, where P. multocida was isolated.	Necropsy; bacterial culture	CAHFS Connection, October 2016
Eight adult Rhode Island Red laying hens from a small commercial free range flock	History of listlessness and death	Fbrinous coelomitis, perioophoritis, multifocal hepatitis and splenitis. Isolation of P. multocida.	Necropsy; bacterial culture	CAHFS Connection, August 2015
Multiple 10-week-old turkeys		Presence of airsacculitis, pneumonia, splenitis, and arthritis. P. multocida was isolated from multiple tissues.	Necropsy; bacterial culture	CAHFS Connection, January 2017
18-week-old chukar partridge flock	5-7% mortality for 3 consective days.	Mild splenomegaly with multiple pale foci and subtle hepatitis. Large numbers of P. multocida isolated from the liver, kidney, and spleen.	Necropsy; histopathology; bacterial culture	CAHFS Connection, October 2013
10-week-old pheasants	Clinical signs of swollen legs and hocks. History of increased mortality in the flock.	Septicemia; swollen and mottled spleen, dark red and mottled liver, dark red lungs, caseous exudate in the bursa of Fabricius, and dark red and edematous testes were seen in some birds. P. multocida was isolated from the hock, spleen, and liver.	Necropsy; histopathology; bacterial culture	CAHFS Connection, February 2013
Flock of 12-week-old crossbred commerical laying hens	Increased mortality	Necropsy revealed marked pericarditis and oophoritis, with mild enlargement of the spleen. P. multocida was cultured from the ova, pericardium, and liver. Enrichment culture for Salmonella was negative.	Necropsy; bacterial culture	New Zealand Veterinary Journal, Quarterly review of diagnostic cases, January to March 2016
Adult laying hens on a free-range farm	History of recent flooding of the paddock. Clinical signs consisted of sudden death, and increased mortality rate.	All hens were laying but the developing ovules were large and flaccid with empty oviducts. The lungs were normal in the majority of the birds but in one they were slightly larger, very congested and haemorrhagic. Cultures of the lung from this bird and from the bone marrow and liver in the other birds revealed the presence of P. multocida.	Necropsy; bacterial culture	New Zealand Veterinary Journal, Quarterly review of diagnostic cases, January to March 2016
44-week-old brown laying hens from a commerical flock	Increased mortality over a one-week period and decreased egg production.	Necropsy revealed evidence of coalescing regions of splenic necrosis, multifocal to coalescing hepatic necrosis, and bacterial endocarditis. Culture of the spleen revealed the presence of P. multocida.	Necropsy; bacterial culture	New Zealand Veterinary Journal, Quarterly review of diagnostic cases, July to Sept 2016