Fowl cholera

Introduction

Fowl cholera is a highly contagious and potentially deadly bacterial disease affecting poultry, particularly chickens. Caused by Pasteurella multocida, this disease can result in significant economic losses due to high mortality rates, reduced egg production, and persistent infections in poultry farms. Understanding the causes, symptoms, and control measures is crucial for effective management.

What is Fowl Cholera?

Fowl cholera is a septicemic disease (a severe blood infection) that primarily affects chickens older than 16 weeks. It manifests in acute, subacute, and chronic forms, each with varying severity. While some cases lead to sudden death without prior symptoms, others present as ongoing infections with more manageable effects.

Cause of Fowl cholera

Fowl cholera is caused by the bacterium Pasteurella multocida. Different strains of this bacterium vary in virulence, with some being highly lethal while others cause milder infections. The bacteria thrive in contaminated environments and spread rapidly among poultry.

Modes of Transmission

Mode	Description
Direct Contact	Infected birds excrete bacteria through the mouth, nose, and eyes, contaminating shared food, water, and surroundings.
Indirect Contact	Humans, contaminated equipment, clothing, and footwear can introduce bacteria into a flock.
Airborne Spread	The disease can spread between pens through respiratory secretions.
Wound Infections	Open wounds provide an entry point for bacteria, increasing susceptibility.
Non-Egg Transmission	Unlike some poultry diseases, fowl cholera is not transmitted through eggs.

Symptoms of Fowl Cholera

Fowl cholera, triggered by Pasteurella multocida, manifests in poultry and wild birds with diverse symptoms, ranging from acute to chronic. In acute cases, birds exhibit sudden, severe signs, including:

• Abrupt death, often within hours, with few prior clues
• High fever, causing listlessness and reduced movement
• Refusal to eat, leading to rapid weight loss
• Disheveled feathers and a crouched stance
• Watery, green, or yellow diarrhea
• Mucus or blood-tinged discharge from the beak or nostrils
• Breathing difficulties, such as gasping or rattling sounds
• Swollen combs, wattles, or legs, sometimes with a purplish hue
• Sharp decline in egg output in layers

Chronic cases show subtler, lingering symptoms, such as:

• Persistent respiratory issues, like sneezing or a nasal drip
• Stunted growth or ongoing weight loss
• Reduced or irregular egg production
• Occasional limping or localized infections

Form	Symptoms
Acute	Sudden death without warning symptoms, high mortality rates (up to 50%), birds appear healthy but are found dead.
Subacute	Depression, loss of appetite, mucous discharges, ruffled feathers, bluish discoloration of comb and wattles, foul-smelling green diarrhea.
Chronic	Localized infections, swollen wattles with cheesy deposits, lameness, twisted neck, prolonged infections leading to persistent disease or recovery.

Postmortem Findings

Postmortem findings in birds with fowl cholera, caused by Pasteurella multocida, vary depending on whether the disease is acute or chronic. Below are the key observations:

Acute Fowl Cholera:

• Generalized congestion: Blood vessels appear engorged, especially in internal organs.
• Liver abnormalities: Enlarged, friable liver with a mottled appearance or small, grayish-white necrotic spots.
• Spleen changes: Enlarged, dark, and congested spleen, sometimes with necrotic foci.
• Lungs: Congested, edematous, or showing frothy exudate; occasionally, pneumonic lesions.
• Heart: Pericarditis with fluid or fibrin around the heart; epicardial hemorrhages.
• Kidneys: Swollen, congested, or with a mottled appearance.
• Mucous membranes: Nasal, oral, or tracheal cavities may contain mucus or blood-tinged exudate.
• Septicemia signs: Widespread bacterial dissemination, with organs appearing dark and congested.
• Egg yolk peritonitis: In laying hens, yolk material in the abdominal cavity with inflammation.

Chronic Fowl Cholera:

• Localized abscesses: Caseous (cheesy) or purulent lesions in wattles, joints, footpads, or sternal bursae.
• Respiratory lesions: Thickened air sacs, fibrinous exudate, or cheesy material in nasal passages or sinuses.
• Joint involvement: Swollen joints with yellowish, purulent material (arthritis).
• Liver and spleen: Chronic cases may show adhesions or small, firm necrotic nodules.
• Ocular lesions: Exudate or cloudiness in the eyes, sometimes with corneal opacity.
• Reproductive tract: In hens, ovarian atrophy or inflamed oviducts with retained yolk material.

Additional Notes:

• Carcasses may appear well-fleshed in acute cases due to rapid death, but emaciation is common in chronic cases.
• The presence of Pasteurella multocida can be confirmed through bacterial culture or PCR from affected tissues (liver, spleen, or lungs).
• Lesions may mimic other diseases like avian influenza or Newcastle disease, necessitating laboratory confirmation.

Finding	Description
Hemorrhages	Small pinpoint hemorrhages are found throughout internal organs.
Liver Necrosis	Dead tissue patches in the liver, often with multiple lesions also called cornmeal liver.
Enlarged Liver	The liver may show small hemorrhages on the surface.
Lung Issues	Fluid accumulation (edema) and pneumonia in subacute cases.
Joint Inflammation	Arthritis in hock and foot joints, swelling of one or both wattles.

Diagnosis of Fowl Cholera

Diagnosis of Fowl Cholera (Plagiarism-Free): Diagnosing fowl cholera involves a combination of clinical signs, postmortem findings, and laboratory tests to confirm Pasteurella multocida infection.

1. Clinical History and Signs:
   • Acute cases: Sudden deaths, fever, lethargy, diarrhea, respiratory distress, or swollen wattles.
   • Chronic cases: Lameness, swollen joints, nasal discharge, or reduced egg production.
   • History of stressors (e.g., crowding, wet conditions) or exposure to carriers (e.g., wild birds).
2. Postmortem Examination:
   • Acute: Hemorrhages, congested organs, enlarged liver/spleen, and septicemic signs.
   • Chronic: Abscesses, joint swelling, or cheesy exudate in respiratory or ocular tissues.
   • Findings guide initial suspicion but are not specific, as lesions may mimic other poultry diseases.
3. Laboratory Confirmation:
   • Bacterial Culture: Swabs from liver, spleen, lungs, or heart blood plated on selective media (e.g., blood agar) to isolate P. multocida. Bipolar-staining, gram-negative rods are characteristic.
   • Polymerase Chain Reaction (PCR): Detects P. multocida DNA in tissue samples for rapid, specific results.
   • Histopathology: Tissue sections may show bacterial infiltration, necrosis, or inflammatory changes.
   • Serology: Tests like ELISA can detect antibodies in chronic or recovered birds, indicating exposure.
4. Differential Diagnosis:
   • Rule out diseases with similar signs, such as avian influenza, Newcastle disease, E. coli septicemia, or erysipelas, using specific lab tests (e.g., viral PCR, bacterial cultures).
   • Chronic cases may resemble mycoplasmosis or infectious coryza, requiring careful differentiation.
5. Epidemiological Clues:
   • Outbreaks linked to contaminated water, rodent vectors, or carrier birds (e.g., turkeys, waterfowl).
   • Seasonal patterns (worse in cold, damp conditions) or flock management issues (e.g., poor sanitation).

Diagnostic Notes:

• Rapid diagnosis is critical in acute outbreaks to limit flock losses.
• Samples must be fresh, as P. multocida is fragile outside the host.
• Biosecurity assessment (e.g., vector control, equipment sanitation) supports diagnosis and control planning.

Treatment Options

1. Acute Cases – The rapid onset of acute fowl cholera makes treatment ineffective.
2. Subacute and Chronic Cases—Antibiotics such as penicillin, streptomycin, oxytetracycline, chlortetracycline, and erythromycin can effectively reduce bacterial load.

Control and Prevention Strategies

1. Biosecurity Measures:

• Dispose of infected birds immediately to prevent the spread.
• Clean and disinfect poultry houses thoroughly.
• Avoid introducing recovered but still infectious birds into healthy flocks.
• Implement strict biosecurity measures, including restricted access to poultry areas and disinfection of footwear and equipment.

2. Management Practices:

• Keep birds in a clean and dry environment.
• Ensure proper ventilation and reduce overcrowding.
• Daily clean and disinfect feeding and drinking sites.

3. Vaccination:

• Vaccination is an effective preventive measure in areas where fowl cholera is common.
• Vaccines should complement, not replace, good management and biosecurity practices.

New Insights and Emerging Concerns

• Antibiotic Resistance: Overuse of antibiotics can lead to resistance, making treatment difficult. Alternative therapies such as probiotics and herbal extracts are being explored.
• Climate Change Impact: Rising temperatures and environmental changes can influence bacterial survival and disease outbreaks, necessitating adaptive control strategies.
• Genetic Resistance: Research is ongoing to develop chicken breeds with natural resistance to P. multocida.
• FAQ’s

1. Can fowl cholera spread to humans?

While Pasteurella multocida can infect humans, it is rare. Direct contact with infected birds should be minimized, and hygiene practices should be followed.

2. How long can P. multocida survive in the environment?

The bacterium can survive in soil, water, and contaminated surfaces for weeks to months, emphasizing the need for thorough cleaning and disinfection.

3. What is the best way to prevent fowl cholera?

Strict biosecurity, good sanitation, vaccination, and immediate removal of infected birds are the most effective preventive measures.

4. Can recovered birds be reintroduced into the flock?

No, as they may still carry and spread the bacteria, even if they appear healthy.

5. Is fowl cholera seasonal?

Outbreaks are more common in wet and cold seasons due to increased bacterial survival in moist environments.

Conclusion

Fowl cholera is a serious disease with devastating effects on poultry farming. Preventive measures, including strict biosecurity, good farm management, and vaccination, are the most effective strategies to control its spread. Farmers should remain vigilant, adopt emerging solutions, and ensure timely intervention to safeguard their poultry against this deadly disease.