Symptoms and Lesions of Chronic Respiratory Disease (CRD) in Chickens

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Chronic Respiratory Disease (CRD) is a pervasive health issue in poultry, particularly chickens. According to recent studies, CRD affects up to 30% of poultry flocks globally, leading to significant economic losses due to reduced productivity, increased mortality, and the cost of treatments and preventive measures. It is caused by Mycoplasma gallisepticum and has significant repercussions on poultry health and farm productivity.

CRD impacts the respiratory system, leading to breathing difficulties and systemic health issues.
Visible lesions often accompany the disease, such as inflamed respiratory tissues and organ damage.
Early diagnosis and effective prevention methods are crucial to controlling its spread.
A thorough understanding of symptoms can significantly enhance poultry management.

Causes of Chronic Respiratory Disease (CRD) in Chickens

Chronic Respiratory Disease (CRD) in poultry is caused by multiple factors, with the most common being:

Mycoplasma gallisepticum: This bacterium is the primary causative agent of CRD. It infects the upper respiratory system, causing inflammation and impaired lung function.
- Reference: Kleven, S. H. (2008). “Mycoplasma gallisepticum infection in poultry.” Avian Disease.
Environmental Factors: Poor ventilation, high ammonia levels, inadequate humidity, and overcrowding can stress birds and make them more susceptible to respiratory infections.
- Reference: De Jong, I. C., et al. (2012). “Air quality and respiratory disease in poultry.” Avian Pathology.
Secondary Bacterial Infections: CRD often occurs alongside other bacterial pathogens such as Escherichia coli or Pasteurella multocida, which exacerbate the symptoms of the disease.
- Reference: Abdallah, M. F., & Alhaj Ali, S. (2019). “Bacterial pathogens associated with Mycoplasma gallisepticum infection in chickens.” Journal of Applied Poultry Research.
Viral Infections: Viruses like Infectious Bronchitis Virus (IBV) or Newcastle Disease Virus (NDV) can predispose birds to secondary infections, contributing to CRD.
- Reference: Cavanagh, D., & Naqi, S. A. (2003). “Infectious bronchitis.” In: Diseases of Poultry.
Improper Nutrition: Poor diet can weaken the immune system of poultry, making them more prone to respiratory diseases like CRD.
- Reference: Bercovier, H., et al. (1994). “The effect of nutrition on immune function in poultry.” Poultry Science.

These factors combined contribute to the development and severity of CRD in poultry.

Common Symptoms of

Chronic Respiratory Disease (CRD) in Chickens

Respiratory Distress

Labored Breathing: Chickens exhibit open-mouth breathing or gasping.
Wheezing and Rattling Sounds: Audible respiratory noises, especially noticeable during quiet hours.
Coughing: Persistent wet or dry coughs.

Nasal Discharge

Sticky or clear mucus emanating from the nostrils.
Nasal blockages exacerbate respiratory difficulties, often resulting in sneezing.

Swollen Facial Features

Sinus Swelling: Noticeable puffiness around the eyes and nasal area.
Eye Discharge: Watery or sticky secretions that may crust over.
Conjunctivitis: Inflammation of the membrane surrounding the eyes.

Reduced Appetite and Weight Loss

Affected birds lose interest in feed, resulting in poor nutrition.
Weight Loss: Rapid decline in body mass and vigor.

Decline in Egg Production

Lower egg output and compromised shell quality.
Eggs may display irregular shapes or thin shells.

Lethargy and Isolation

Affected chickens exhibit reduced energy levels.
Tend to isolate themselves from the flock.

Feather Dullness

Feathers appear ruffled or lack their natural sheen.

Ocular and Auricular Symptoms

Inflammation or discharge around the eyes and ears.
Frequent head shaking as chickens attempt to alleviate discomfort.

Pathological Lesions Associated with CRD

Air Sacculitis: Cloudy, inflamed air sacs filled with exudates.
Tracheitis: Mucus-lined trachea with inflamed walls.
Lung Lesions: Congested and discolored lung tissues.
Perihepatitis and Pericarditis: Advanced inflammation extending to the liver and heart.
Sinus Exudate: Thick yellowish material obstructing the sinuses.

Table: Quick Reference to CRD Symptoms and Lesions

Symptom/Lesion	Description	Severity Level
Labored Breathing	Open-mouth breathing, gasping	High
Nasal Discharge	Sticky or clear mucus	Medium
Swollen Sinuses	Puffiness around eyes and nasal area	High
Air Sacculitis	Cloudy and inflamed air sacs	High
Reduced Appetite	Decreased interest in food	Medium
Drop in Egg Production	Fewer and lower-quality eggs	High
Lethargy	Low energy and isolation	Medium
Feather Dullness	Ruffled, dull feathers	Low

Why Early Detection is Crucial

“An ounce of prevention is worth a pound of cure.” — Benjamin Franklin

This wisdom is particularly relevant in managing Chronic Respiratory Disease (CRD) in chickens. Proactive measures, such as vaccination and biosecurity, significantly reduce mortality rates and the economic burden caused by treatment costs and productivity losses.

Early identification of CRD symptoms can:

Prevent outbreaks within the flock.
Reduce mortality and improve recovery prospects.
Minimize economic losses through timely intervention.

Prevention Tips

What is the primary cause of CRD in chickens?

Enforce Strict Biosecurity

Limit visitor access to poultry areas.
Disinfect equipment, housing, and feed supplies regularly.
Prevent contact between domestic and wild birds.

Implement Vaccination Programs

Administer vaccines against Mycoplasma gallisepticum, such as the MG-Bacterin or live attenuated vaccines like F-Vax MG. For more information on vaccine protocols and schedules, consult resources from reputable veterinary organizations or your local poultry health advisor.
Follow an established vaccination schedule tailored for your flock.

Isolate and Monitor Sick Birds

Immediately quarantine symptomatic chickens.
Monitor their health closely to track disease progression.

Ensure Proper Nutrition

Provide a diet rich in vitamins (e.g., Vitamin A, Vitamin D3) and minerals (e.g., Selenium).
Supplement with probiotics to boost gut health and immunity.

Optimize Environmental Conditions

Maintain clean, dry, and ventilated living spaces.
Avoid overcrowding to minimize stress and pathogen exposure.

Conduct Routine Health Surveillance

Perform regular flock health checks. Use specific health indicators such as respiratory rate, body condition score, and egg production levels. Tools like automated monitoring systems or health scorecards can aid in identifying early signs of CRD.
Engage veterinarians for comprehensive health assessments.

Control Parasites and Other Stressors

Treat for external parasites such as mites and lice.
Avoid unnecessary disturbances that stress the flock.

Encouragement for Poultry Farmers

Managing CRD requires vigilance, knowledge, and consistent effort. By implementing preventive measures, recognizing symptoms early, and adopting best practices, you can ensure your flock’s health and productivity. Stay proactive and consult experts when needed to safeguard your investment.

FAQs

What is the primary cause of CRD in chickens?

CRD is caused by Mycoplasma gallisepticum, a bacterial pathogen that affects the respiratory system.

Can CRD spread between chickens?

Yes, CRD spreads through direct contact, airborne droplets, and contaminated tools or feed.

How does CRD affect egg production?

Infected chickens often exhibit reduced egg output and poor shell quality.

Are there treatments available for CRD?

Yes, antibiotics can help manage symptoms, but early detection and supportive care are critical.

What are the most effective preventive measures for CRD?

Strict biosecurity, vaccination, proper nutrition, and regular health monitoring are key to preventing CRD.

Dr. Farhana Afroz

Dr.Farhana Afroz Lovely ,DVM Sylhet Government Veterinary College, Shahjalal University of Science and Technology (SUST), ex service holder " VIP Shahadat poultry and Hatchery", ex Instructor Baily Bridge Diploma College.