CRD stands for Chronic Respiratory Disease. It is one of the most common and economically damaging respiratory infections in poultry, primarily affecting chickens and turkeys.
The disease is caused by the bacterium Mycoplasma gallisepticum. While it can cause mild respiratory symptoms on its own, it frequently combines with other pathogens like E. coli or viruses (like Newcastle Disease or Infectious Bronchitis) to cause a much more severe condition known as Complicated CRD (CCRD).
Common Symptoms to Watch For
- Respiratory Distress: Coughing, sneezing, rales (gurgling/rattling sounds when breathing), and open-mouth breathing.
- Facial Signs: Nasal discharge, watery or foamy eyes, and swelling of the face or sinuses.
- Production Drop: A sharp decline in egg production in layers and poor weight gain in broilers.
Effective Prevention Solutions
Because Mycoplasma gallisepticum lacks a cell wall, it is highly fragile in the environment but exceptionally good at spreading vertically (from breeder hen to the egg) and horizontally (bird-to-bird via dust, droplets, or shared water). Prevention is always cheaper and more effective than treatment.
1. Source CRD-Free Chicks
Only buy day-old chicks from reputable, certified Mycoplasma-free hatcheries. If the parent stock has CRD, the chicks will often hatch with it.
2. Strict Biosecurity & Hygiene
- Footbaths and Sanitization: Restrict farm visitors. Use footbaths at the entrance of every pen.
- Flock Segregation: Implement an “all-in, all-out” management system. Never mix birds of different ages or sources in the same house.
- Water Sanitation: Clean and disinfect water lines regularly. Mycoplasma spreads rapidly through shared drinking water.
3. Optimize Ventilation and Litter Management
High ammonia levels from damp litter irritate the birds’ respiratory tracts, destroying the natural mucosal barriers and making it incredibly easy for CRD to take hold. Ensure the poultry house has excellent airflow to flush out ammonia and moisture without creating direct, cold drafts on the birds.
4. Vaccination
In high-risk areas or multi-age layer farms where eradication is difficult, vaccinating pullets before they go into production can prevent severe clinical drops in egg production. Consult a local veterinarian for the best vaccine strain (e.g., F-strain, TS-11, or 6/85) for your region.
Effective Treatment Solutions
If an outbreak occurs, quick action is required to minimize mortality and production loss. Because CRD is bacterial, it responds well to specific antibiotics—though it is vital to remember that antibiotics suppress the bacteria to allow the bird to recover, but they rarely eliminate the carrier status entirely.
1. Targeted Antibiotic Therapy
Standard antibiotics like penicillin do not work because Mycoplasma lacks a cell wall. You must use antibiotics that target protein synthesis inside the bacteria.
- First-line Mycoplasma Treatments: Tylosin, Tilmicosin, Tylvalosin, or Tiamulin are highly effective specifically against Mycoplasma.
- Broad-Spectrum Options (for Complicated CRD): If E. coli has joined the infection, broad-spectrum antibiotics like Enrofloxacin, Doxycycline, or Neomycin-Oxytetracycline combinations are often administered via drinking water for 3 to 5 days.
2. Supportive Care
- Mucolytics: Adding a mucolytic like Bromhexine to the water can help dissolve the thick mucus in their airways, allowing the birds to breathe easier and drink/eat their medication.
- Vitamins and Electrolytes: Stress formulas rich in Vitamin A, C, and E help repair the damaged respiratory lining and boost the immune system during treatment.
Important Warning: Always observe the specific withdrawal periods for any antibiotic used before marketing the meat or eating/selling the eggs.
Signs of CRD
The signs of CRD are weepy eyes, head shaking, gurgling.
Other diseases that have similar clinical signs are Infectious Coryza, Infectious bronchitis, Infectious laryngotracheitis and Fowl cholera.
Antibiotic Treatments of CRD
The Poultry vets will prescribe antibiotics that can help to control the disease. Most chicken antibiotics are not registered for egg laying hens – and are used off label!
Firstly Antibiotics – Pet Chicken vet
- Doxycycline – is a great antibiotic against Mycoplasma.
- Tylosin can also be used alone but is usually use it with Doxycycline.
- Lincomycin combined with Spectinomycin, is water antibiotic works well and has no withholding period for egg layers – a bonus.
- Chortetracycline – works okay not as good as Doxycycline but has no withholding period for egg layers – a bonus.
- Enrofloxacin – is a great antibiotic against Mycoplasma, and other secondary bacteria.
- Amoxicillin and Clavulonic acid is often used in conjunction to treat secondary bacterial infections.
- The poultry vets also use antibiotic eye drops and Antibiotic nose drops. This route of medication is brilliant as the drugs get right to the place of infection.
