CRD (Chronic Respiratory Disease): Causes, Symptoms, and Treatment
TL;DR: CRD is caused by Mycoplasma gallisepticum and shows up as gurgling or rattling breathing sounds and nasal discharge — but unlike coryza, it produces no foul smell. Treat with Premoxil (10g per gallon) daily for 5-7 days, then Vitmin Pro for Day 8-10. The bird can remain a silent carrier after treatment, so isolate it if new signs appear.
What Is CRD?
CRD, or Chronic Respiratory Disease, is caused by the Mycoplasma gallisepticum bacteria. It’s one of the most common poultry diseases in the Philippines — see our guide to common gamefowl diseases for how it stacks up against other threats — especially in hot, humid conditions or overcrowded coops. CRD is contagious: if one bird is infected, there’s a high chance it spreads to the entire flock.
What Are the Symptoms of CRD?
Gurgling or rattling sounds when breathing (tracheal rales) is the most obvious sign of CRD — hold the bird close to your ear, and if you hear gurgling or whistling as it breathes, it’s CRD.
- Gurgling or rattling sounds when breathing (tracheal rales) — this is the most obvious sign
- Nasal discharge, sneezing, coughing
- Watery or bubbly eyes, eye discharge
- Swollen face (in severe cases)
- Head shaking, gaping (mouth open to breathe)
How to tell CRD from coryza and coccidiosis: CRD does not cause the foul-smelling nasal discharge that marks infectious coryza — smell, not sound, is what separates the two. And unlike coccidiosis, CRD does not cause bloody droppings. Breathing sounds are the CRD-specific tell.
How Do You Treat CRD With Premoxil?
Treat CRD with Premoxil daily for 5-7 days, then move to a 3-day recovery phase. This amount is given per gallon of water, not scaled to a specific bird weight — this guide doesn’t state a weight basis, so follow the product label if you’re dosing a bird noticeably lighter or heavier than a gamefowl.
| Day | Medication |
|---|---|
| Day 1–7 | Premoxil — 10g (2 sachets) per gallon of water. Replace with a fresh mix daily. |
Premoxil works against CRD because it contains Amoxicillin + Tylosin — the Tylosin component specifically targets Mycoplasma.
Important: Even after treatment, the bird may still be a carrier of Mycoplasma. This means it can still spread the disease to other birds even without symptoms. Monitor the flock and isolate previously infected birds if new signs of CRD appear.
Recovery Phase
| Day | Medication |
|---|---|
| Day 8–10 | Vitmin Pro — 10g (2 tsp) per gallon of water, daily |
How Do You Prevent CRD?
Good coop ventilation is the single biggest prevention factor — CRD thrives in enclosed, dusty, overcrowded conditions.
- Good ventilation in the coop — do not keep it too enclosed
- Reduce dust inside the coop
- Isolate newly arrived birds for 2 weeks before introducing them to the flock
- Reduce stress — avoid overcrowding and extreme heat
What Are the Golden Rules for Treating CRD?
- Treatment doesn’t guarantee the bird is free of Mycoplasma. Even after a full course of Premoxil, the bird may still be a carrier and can spread CRD to other birds without showing symptoms — monitor the flock and isolate previously infected birds if new signs appear.
- Do not mix medication with Vitmin Pro on the same day during treatment. Give Vitmin Pro only during the recovery phase (after the treatment protocol).
- Always use freshly prepared medicated water each day. Do not reuse yesterday’s mix.
- Remove all other water sources during treatment to ensure the birds drink the medicated water.
- Isolate sick birds immediately from the healthy flock — do not wait.
- Complete the entire treatment course even if the bird looks fine by Day 2. Stopping early risks creating drug-resistant bacteria.
- Prevention is better than treatment. Keep the coop clean, sand dry, deworm regularly, and vaccinate properly.
Disclaimer: This guide is for reference purposes and is based on manufacturer product labels and published poultry health sources. Consult a veterinarian for severe or unusual cases. Observe the proper withdrawal period before consuming meat or eggs from treated birds.
Frequently Asked Questions
What causes CRD in chickens?
CRD (Chronic Respiratory Disease) is caused by Mycoplasma gallisepticum bacteria. It is common in the Philippines in hot, humid conditions or overcrowded coops, and is contagious across the flock.
What is the first sign of CRD?
Gurgling or rattling sounds when breathing (tracheal rales) is the most obvious sign. Hold the bird close to your ear — if you hear gurgling or whistling as it breathes, it is CRD.
How do you treat CRD?
Premoxil — 10g (2 sachets) per gallon of water, daily for 5-7 days with a fresh mix each day — then Vitmin Pro for the recovery phase on Day 8-10.
Why does Premoxil work against CRD?
Premoxil contains Amoxicillin plus Tylosin, and the Tylosin component specifically targets Mycoplasma, the bacteria that causes CRD.
Can a chicken still spread CRD after treatment?
Yes. Even after treatment the bird may still be a carrier of Mycoplasma and can spread it without showing symptoms. Monitor the flock and isolate previously infected birds if new signs appear.
How is CRD different from infectious coryza?
CRD does not produce the foul-smelling nasal discharge that marks infectious coryza. Gurgling or rattling breathing sounds, not a bad smell, are the giveaway for CRD.
How can you prevent CRD?
Keep good ventilation and reduce dust in the coop, isolate newly arrived birds for 2 weeks before introducing them to the flock, and reduce stress from overcrowding or extreme heat.