Fowl Cholera (Avian Pasteurellosis)

Fowl Cholera (Avian Pasteurellosis) is a peracute, most virulent and highly contagious diseases of poultry. It has got world wide distribution and many countries considered this disease as notifiable disease.

Etiology

Fowl Cholera (Avian Pasteurellosis) is caused by Pasteurella multocida is highly pathogenic for poultry.

It is a gram negative, non motile, non-spore forming and rod shaped organism. There are different categories of strains that may be extremely virulent, virulent, highly invasive and avirulent type.

About 16 serotypes have been demonstrated based on precipitation tests but the cross reactions occurs between the serotypes are found to have good diagnostic value.

The organism is highly susceptible to drying, coal tar and other disinfectants. Again P. multocida is subdivided into P. m. multocida, P. m. septica and P. m. gallicida.

P. m. gallicida causing disease in web-footed birds.

Epidemiology

Prevalence of infection

Fowl Cholera (Avian Pasteurellosis) is seen worldwide and was one of the first infectious diseases to be recognised, by Louis Pasteur in 1880.

Predisposing factors

Predisposing factors include high density and concurrent infections such as respiratory viruses.

Source of infection

• Carrier birds, excretions, carcasses of the infected birds, feeds, water are acting as important source of infection.
• Rats, cats, and possibly pigs acts as reservoirs.
• Infection usually spread through conjunctival, oral, nasal exudates, faeces, contaminated soil, equipment and people.

Transmission

• Ingestion of contaminated feed and water.
• By contact with infected materials.

Host affected

• All avian species are susceptible.
• Ducks, geese, water fowl and turkeys are more susceptible than chicken.
• Mostly growers and adult birds are being affected than young ones.
• Caged chickens are less affected by P. multocida.

Pathogenesis

• The disease can range from acute septicaemia to chronic and localised infections and the morbidity and mortality may be up to 100%.
• Many of the lesions are related to vascular disturbances.
• Hyperemia is especially evident in the vessels of the abdominal viscera.
• Petechial and ecchymotic hemorrhages are common, particularly in subepicardial and subserosal locations.
• Increased amounts of peritoneal and pericardial fluids are frequently seen.
• The liver may be swollen and often develops multiple, small, necrotic foci.

Clinical signs

• Fowl Cholera (Avian Pasteurellosis) has been divided into peracute, acute, chronic and localized infection.

Peracute

• No clinical signs noticed and dead birds are found dead with good with bodily condition.

Acute

• The incubation period is usually 5-8 days.
• Affected birds are dull, depressed, and anorectic.
• Mucous discharge from orifices.
• Cyanosis of mucous membrane.
• Foetid diarrhea.

Chronic

• Birds survived from acute form of disease are due to low virulent infection manifests depression, conjunctivitis, dyspnoea, lameness, toriticolis (twisting of the neck) and swollen wattles.

Necropsy Findings

• Per acute and acute form: These forms show marked congestion of carcass, multiple petechiation in all visceral organs, multiple pin-point necrotic foci in the liver.
• Free yolk found in the body cavity in layer birds .
• Sub acute: Edema of lungs in turkeys, pneumonia and focal perihepatitis and yolk peritonitis. Purulent pneumonia (especially in turkeys).
• Cellulitis of face and wattles.
• Purulent arthritis.
• Lungs with a consolidated pink ‘cooked’ appearance in turkeys.
• Fowl cholera -Liver – Necrotic foci Chronic Caseous arthritis of hock and foot joints.
• Swelling and induration of both wattles.
• Caseous exudate in the middle ears.

Diagnosis

• History, clinical signs and lesions are useful for diagnosis of the disease.
• In peracute cases stained impression smear made from liver, heart show the bipolar organism.
• Pneumonic cases, smears from lung prepared, stained and examine for organism.
• Isolation and identification of the organism done by using the cultural and biochemical test.
• Isolation can be done in pasteurella free mice or rabbits with an inoculum of opened tissue collected from affected animal.
• P. mutocida inoculated lab animal will die in 24-48 hours.

Sample collection

• Impression smear from liver, heart, lung.
• P. mutocida inoculated lab animal will die in 24-48 hours.

Differential diagnosis

• Salmonellosis
• Pullorum disease
• Fowl typhoid

Treatment

• There is no response for the antibiotic treatment in birds infected with peracute form of disease.
• Administration of sulphaquinoxaline in food / water for turkeys and tetracycline for all avian species are effective.
• Combination of streptomycin, dihydro streptomycin offers a very good response.
• Use of sodium salicylate in drinking water for 3 days may provide a good recovery from infection.
• Sulphonamides, tetracyclines, erythromycin, streptomycin and penicillin are effective.
• Long-term or periodic use of antibiotic is essential to control the recurrence of infection.

Prevention

• Aminisitration of bacterins at 8 and 12 weeks Live oral vaccine at 6 weeks of age.

Control

• The bacterium is easily destroyed by environmental factors and disinfectants, but may persist for prolonged periods in soil.
• Strict biosecurity measures, good rodent control and hygiene must be adhered.
• Depopulation, cleaning, disinfection of the buildings, equipments must be done to eradicate infection.