Fowl cholera is a septicaemic disease (blood infection) of chickens. In its severest form. fowl cholera is one of the most harmful and highly contagious diseases. inflicting heavy mortality. but less severe (chronic) and harmless conditions also occur. Losses from fowl cholera usually occur in laying flocks. Chickens less than 16 weeks of age are usually quite resistant. Mortality ranges from 0 to 2%. but greater losses have been reported. Reduced egg production and persistent localized infection usually occur.
Cause
A bacterium called Pasteurella multocida . Strains of P. multocida vary in their disease-producing power
(virulence). Some are most harmful, others moderately so, and a certain number harmless.
Spread
I. Spread of P. multocida within a flock is mainly by excretions from mouth, nose, and conjunctiva of diseased
birds. These excretions contaminate their environment, particularly feed and water. Thus. spread is through
contaminated feed and water. Birds are infected through mouth, nose and eye, and through wounds.
2. Spread can be also by people, clothing, or their footwear.
3. Spread through the air does occur between pens. However, spread through water and feed is more
common.
4. The disease is not egg-transmitted.
Symptoms
I. The disease occurs in several forms. In the severest form, there are no preceding symptoms and a
large number of birds in a flock are found dead, in good bodily condition. 50% or more may die. Birds
between I 2 and 18 weeks of age are most susceptible.
2. In the less severe form, marked depression, loss of appetite, mucus discharges from the openings, ruffled
feathers, bluish discoloration of comb and wattles, and foul-smelling greenish coloured diarrhoea may be
seen.
3. The chronic form is seen in birds which survive the severe disease. Symptoms are usually due to localized
infection. Symptoms include depression, difficult breathing, and later lameness, twisting of the neck to
one side, and swelling of the wattles . One or both the wattles may be swollen containing
cheesy, hard deposit. Chronically infected birds may die, remain infected for long periods, or recover.
Postmortem Findings
I. Postmortem findings in the severe form include marked congestion of the carcass, pinpoint haemorrhages
throughout the internal organs, and multiple necrotic areas (areas of dead tissue) in the liver .
The liver may be enlarged and also show very small haemorrhages on the surface.
2. In the laying hens free yolk may be present in the abdominal cavity.
3. In the less severe disease, oedema of the lungs (i.e., accumulation of fluid) and pneumonia (inflammation
of lungs) are seen.
4. In chronic cases, changes include arthritis (inflammation) of the hock and foot joints, and swelling of one
or both wattles (Fig. 79).
Diagnosis
The history of the disease, symptoms and postmortem findings are helpful, but all forms of the disease can be
confused with other infections. Demonstration of P. multocida confirms the diagnosis.
Treatment
I . The severest form of fowl cholera is so rapid that t reatment is rarely of value.
2. In the less severe form, a number of drugs have proved effective. They include sulphonamides and antibiotics.
In antibiotics, penicillin, streptomycin, oxytetracycline, chlortetracycline, and erythromycin have been
used successfully.
Control
I. Dispose of all birds and clean and disinfect the buildings thoroughly. Good management practices with
emphasis on sanitation are the best means of preventing fowl cholera.
2. The main source of infection is the sick bird, or those that have recovered but still carry the organism.
Only young birds should be introduced as new stock. They should be raised in a clean environment
completely isolated from other birds.
3. Vaccination should be considered in areas where fowl cholera is prevalent, but it should not be substituted
for good sanitary practice.
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