CRD disease in chickens is a chronic respiratory disorder that can silently spread through a flock and is very difficult to treat. The disease causes chickens to wheeze, lose weight, eat less, lay fewer eggs, and can cause serious losses to the entire flock if not detected early and handled promptly. Let’s explore in depth with Vemedim the infection mechanism, recognizable signs, and practical prevention and treatment strategies to help farmers take a more proactive approach to flock management.
Causes of CRD in chickens
CRD (Chronic Respiratory Disease), also known as chicken asthma, is one of the most common and hardest-to-treat chronic respiratory diseases in chickens today. CRD is caused by the bacterium Mycoplasma gallisepticum.
This bacterium attacks the upper respiratory tract of chickens, causing sinusitis, airsacculitis, bronchitis, and persistent inflammation, making the disease chronic. CRD is commonly seen in chicks from 3 weeks of age and older, and is especially severe between 3 weeks and 3 months of age. Adult chickens can also become infected and remain lifelong carriers, transmitting the pathogen to the next generation through eggs.
>> See also:
- Causes, prevention, and effective treatment of Newcastle disease
- Gumboro disease: Causes, prevention, and effective treatment
Transmission routes of CRD
CRD can spread rapidly through a flock via many different routes. Understanding the transmission mechanism helps farmers proactively break the chain of infection. Common transmission routes include:
- Vertical transmission: Mycoplasma bacteria can be passed from hen to chick through eggs, causing newly hatched chicks to already carry the pathogen.
- Horizontal transmission: The bacteria spread from sick chickens to healthy ones through the air, drinking water, feed, feces, litter, or through farming equipment, clothing, and footwear of workers.
- A damp housing environment with high levels of toxic gases (NH₃, H₂S, CO₂), dust, and poor ventilation creates favorable conditions for the disease to spread more quickly.
- Sudden weather changes, poor nutrition, or stress can also weaken chickens and make them more susceptible to disease.
CRD often appears together with other diseases such as infectious bronchitis (IB), infectious laryngotracheitis (ILT), Gumboro, E. coli, etc., making symptoms more severe and treatment more difficult.
Symptoms of CRD in chickens
When chickens are infected with Mycoplasma, symptoms usually appear gradually but persist for a long time, greatly affecting production performance. Below are the characteristic signs that farmers should pay attention to:
- Reduced appetite or loss of appetite: This is the earliest and most common sign; chickens become lethargic, sluggish, and less active.
- Wheezing and whistling sounds during breathing: Due to bronchitis and airsacculitis, chickens often breathe with their beaks open, especially at night.
- Sinusitis and nasal discharge: Nasal secretions may be clear or cloudy, and may stick around the nostrils, causing nasal congestion and difficulty breathing.
- Swelling around the eyes, conjunctivitis, and tearing: This is a characteristic symptom that helps distinguish CRD from other respiratory diseases.
- Swollen face, mild head edema, ruffled feathers, lethargy, stunted growth, and a clear drop in egg production in laying hens.
- In breeding and laying hens, poor hatchability, small eggs, and thin shells are also typical signs when the disease persists.
If not detected and treated promptly, CRD can last for weeks, increasing mortality due to weakness or secondary infections.
How to prevent CRD in chickens
Prevention is always the most effective and economical measure for chicken asthma because once the disease occurs, treatment is usually prolonged, costly, and difficult to fully resolve. Measures to apply include:
Maintain hygiene in housing and the farming environment
This is the first and most important step to limit the emergence of pathogens.
- Clean and disinfect poultry houses, feeders, and drinkers regularly with the safe disinfectant solution Vemedim BKC (GSGC).
- Keep the coop dry and well-ventilated, avoiding drafts while still ensuring air circulation.
- Mix probiotics or lime powder into the litter with Vemedim Vime Yucca (KMPC) to reduce moisture, odor, and inhibit bacteria.
- Maintain a moderate stocking density to avoid overcrowding, stress, and increased risk of disease transmission.
- Isolate newly introduced chickens for at least 10 days to monitor their health before mixing them with the main flock.
Control and eliminate pathogens in breeding flocks
Farmers should conduct periodic blood testing to detect and remove Mycoplasma-positive birds from breeding flocks.
Boost flock immunity
A healthy flock with a strong immune system will resist disease more effectively. Therefore, essential nutrients and vitamins should be supplemented regularly, such as:
- Supplement Vitamins A, C, E, D3, and K with Vemedim Aminovit, Vemedim AD3E to enhance resistance and restore the respiratory mucosa.
- Supplement electrolytes and digestive enzymes with Vemedim Senarex, Vemedim Vime Tax T to help chickens reduce stress and recover quickly after illness or vaccination.
- Use Vemedim Canxiphos to supplement minerals and essential amino acids, helping chickens boost metabolism and develop healthily.
Vaccination and use of CRD preventive medications
Currently, some vaccines and CRD preventive products are used to reduce disease incidence. However, vaccination should only be carried out when the flock is completely healthy and not carrying latent infection.
Proper management of microclimate conditions and stress reduction
Chickens are very sensitive to changes in weather, temperature, humidity, or high stocking density. Therefore, it is necessary to:
- Maintain stable temperature and humidity in the coop.
- Provide good shelter when there is cold wind or heavy rain.
- Limit noise and strong disturbances to avoid frightening the chickens.
- Supplement vitamins and electrolytes during weather changes, transport, or after vaccination to reduce stress in chickens.
CRD disease is one of the chronic respiratory diseases that causes major losses in chicken farming, especially in broilers and laying hens. To control the disease effectively, farmers need to implement synchronized measures combined with a strict hygiene and disinfection program. When these measures are fully carried out and appropriate technical support is provided, the flock will be better protected, losses reduced, and production efficiency improved. Contact Vemedim for consultation if you need support!
