Mycoplasma, commonly known as Chronic Respiratory Disease (CRD) in poultry, is a contagious bacterial infection caused by Mycoplasma gallisepticum. This disease primarily affects the respiratory system of chickens and other poultry, leading to severe economic losses due to reduced growth rates, decreased egg production, and increased mortality.
Understanding CRD's causes, symptoms, prevention, and management is crucial for poultry farmers to maintain healthy flocks and prevent financial losses.
What is Mycoplasma (CRD)?
Mycoplasma gallisepticum (MG) is a bacterium lacking a cell wall, making it resistant to some antibiotics. It spreads through direct bird-to-bird contact, airborne droplets, contaminated feed, water, and equipment. The infection is chronic and persistent, affecting both broilers and layers, causing respiratory distress, reduced feed conversion efficiency, and secondary infections.
Causes of Mycoplasma (CRD) in Poultry
The main cause of CRD in poultry is the bacterium Mycoplasma gallisepticum (MG). Several factors contribute to the spread and severity of this disease:
- Direct Contact with Infected Birds – Mycoplasma spreads when healthy birds interact with infected birds.
- Contaminated Environment – Feed, water, litter, and equipment can harbor bacteria.
- Airborne Transmission – CRD spreads through airborne droplets from coughing and sneezing birds.
- Vertical Transmission (Eggs) – Infected breeder hens can pass Mycoplasma to chicks through eggs.
- Environmental Stress – Overcrowding, poor ventilation, and fluctuating temperatures increase susceptibility.
- Weakened Immunity – Birds with compromised immunity due to nutritional deficiencies or other infections are more prone to CRD.
Symptoms of Mycoplasma (CRD) in Poultry
CRD symptoms vary from mild to severe, depending on the bird's immune status and environmental factors. Common symptoms include:
- Sneezing and coughing
- Nasal discharge (clear or foamy mucus)
- Swollen sinuses and watery eyes
- Labored breathing (gasping and wheezing sounds)
- Depression, reduced activity, and ruffled feathers
- Reduced feed intake and weight loss
- Drop in egg production and poor eggshell quality
- Secondary bacterial infections (E. coli, Pasteurella)
Severe cases may lead to high mortality rates, particularly in young chicks and stressed birds.
Diagnosis of CRD in Poultry
Proper diagnosis is essential for effective control. The following methods help identify Mycoplasma gallisepticum (CRD):
- Clinical Observation – Based on symptoms such as respiratory distress and nasal discharge.
- Serological Tests (ELISA, PCR) – Detects Mycoplasma antibodies in blood samples.
- Culture Tests – Isolates Mycoplasma from respiratory secretions.
- Post-Mortem Examination – Reveals swollen air sacs and excessive mucus in the lungs.
Prevention of Mycoplasma (CRD) in Poultry
Prevention is the best strategy for controlling Mycoplasma in poultry farms. Implementing strict biosecurity measures, vaccination, and proper farm management significantly reduces disease outbreaks.
1. Biosecurity Measures
- Quarantine new birds for at least 2-3 weeks before introducing them to the flock.
- Restrict farm access to unauthorized personnel and vehicles.
- Regularly disinfect poultry houses, feeders, and equipment.
- Control rodents, wild birds, and insects that can carry Mycoplasma.
- Maintain proper ventilation to reduce airborne bacterial spread.
2. Vaccination Programs
- Live and inactivated vaccines are available to prevent Mycoplasma infections.
- Vaccinate breeder flocks to prevent vertical transmission to chicks.
- Follow the recommended vaccine schedule for broilers and layers.
3. Environmental Control & Stress Reduction
- Avoid overcrowding to reduce bird-to-bird transmission.
- Provide balanced nutrition to boost immunity.
- Keep litter clean and dry to minimize bacterial growth.
- Minimize temperature fluctuations and humidity to reduce stress.
4. Use of Antibiotics for Prevention
- Prophylactic use of antibiotics like Tylosin, Tiamulin, and Doxycycline helps prevent Mycoplasma infections.
- Avoid excessive antibiotic use to prevent resistance development.
Management & Treatment of Mycoplasma (CRD)
Once Mycoplasma infects a flock, eradication is difficult, but proper management can reduce its impact.
1. Antibiotic Treatment
Although Mycoplasma has no cell wall, some antibiotics effectively control the infection:
- Tylosin, Tiamulin, Erythromycin – Reduce bacterial load in mild cases.
- Doxycycline, Oxytetracycline – Treat secondary infections.
- Lincomycin-Spectinomycin combinations – Effective against severe CRD outbreaks.
- Antibiotics should always be used under veterinary supervision.
2. Supportive Care & Nutrition
- Provide electrolytes and vitamin supplements (A, C, and E) to boost immunity.
- Keep birds in a warm, stress-free environment to aid recovery.
- Improve feed quality with probiotics and prebiotics to enhance gut health.
3. Culling Chronically Infected Birds
- Severely infected birds should be culled and disposed of properly.
- Prevent further disease spread by maintaining strict biosecurity.
Economic Impact of Mycoplasma (CRD) in Poultry Farming
Mycoplasma infections result in significant economic losses due to:
High morbidity and mortality in young chicks.- Reduced feed conversion efficiency, leading to slow growth.
- Drop in egg production and poor-quality eggs.
- Increased costs of medication and disease control.
- Trade restrictions due to contaminated flocks.
Conclusion
Mycoplasma (CRD) is a serious respiratory disease in poultry that requires strict preventive measures and effective management strategies. Biosecurity, vaccination, and proper antibiotic use are the key approaches to controlling CRD.
Poultry farmers must focus on early detection, good farm management, and stress reduction to prevent Mycoplasma infections and ensure profitable poultry production.