Synonyms
Avian cholera, avian pasteurellosis and Avian haemorrhagic septicaemia
Aetiology
Pasteurella multocida is the causative agent of fowl cholera. It is a gram negative non motile, non spore forming rod occurring singly or in pairs in chains or in filaments with leishman stain. There is bipolar staining of the rods.
Age/host range
The disease affects birds of all ages, older birds are more susceptible than younger birds. Chickens, turkeys and water fowls,(increasing order of susceptibility), game birds(especially pheasants and ducks), feral birds and birds in zoological collections and aviaries are susceptible. Turkeys are more susceptible than chickens.
Transmission
Carrier birds, clinically diseased poultry and carcasses of birds which have died of the infection are sources of infection while mode of transmission may be orally by ingestion of polluted feed and water.
Rodents and formites are means of transmission.
Cannibalism is also a means of transmission.
The Clinical signs
The incubation period is usually 5-8 days. The morbidity and mortality may be up to 100%.
Fowl cholera occurs in several forms
i-peracute
ii-acute
iii-chronic
In the peracute form, there may be no premonitoring signs and large number of birds in the flock are found dead but in good body condition.
In acute outbreaks, there may be marked depression, fever, reduced feed consumption, stringy mucoid discharge from the nasal and oral passages; diarrhea which is initially watery and whitish in colour but later becomes greenish and mucoid. Labored breathing may be seen. Cyanosis of unfeathered part such as comb and wattle.
In the chronic form, there may be weight loss, conjunctivitis, dyspnea and rattling noises develop from exudates in air passages; lameness as a result of joint infections; chickens develop abscessed wattles and swollen joints and foot pads; Caseous exudates may form in the sinuses around the eyes and pharynx; torticolis/turkeys may have twisted necks.
Post-mortem lesions
In acute infection
Sometimes none or limited lesions are seen, they are mainly vascular disturbances.
Petechial and ecchymotic haemorrhages in lungs, abdominal fats and intestinal mucosa.
Subpericardial haemorrhage is a characteristic finding in fowl cholera.
Livers are swollen with multiple military or submilitary necrosis.
Matured follicles appear flaccid and there is yolk peritonitis.
In chronic infection
Purulent pneumonia(especially turkeys)
Cellulitis of face, combs and wattles
Putrid arthritis
Lungs with a consolidated pink cooked appearance in turkeys.
Diagnosis
Tentative diagnosis is based on characteristic clinical signs and post-mortem lesions. Positive diagnosis is by isolation and recognition of the organism. Impression smears of the liver and heart blood will show bipolar organisms.
Differential diagnosis
Acute and chronic salmonellosis
Treatment
Sulphonamides, tetracyclines, erythromycin, penicillin are effective in treatment of the infection.
Prevention
Ensure strict biosecurity practices.
Vaccination: dead vaccine of P. multocida is prepared at Nigeria veterinary research institute vom and administered intramuscularly or subcutaneously to birds immunity lasts for 3-6 months. Vaccination is advisable on fowl cholera endemic farms.
Do not vaccinate for fowl cholera except that you have a problem on the farm.
Formites and Rodent control is essential to prevent future outbreaks.