Mycoplasma Guide
Mycoplasma in Chickens
Why the rattle keeps coming back, what a carrier bird means for your flock, and how testing settles it.
This page is laboratory information, not veterinary treatment advice. Your vet decides on treatment. A PCR test tells you which organism you are dealing with first.
Mycoplasma is the reason so many backyard flocks have a respiratory problem that improves, then comes back every time the weather turns or a new bird arrives. Two species matter most: Mycoplasma gallisepticum, usually respiratory, and Mycoplasma synoviae, which can be respiratory but often shows up in the joints.
👀 What it looks like
| Sign | More typical of |
| Rattling or bubbling breathing, especially at night | M. gallisepticum |
| Foamy or bubbly eye, swollen sinuses, swollen face | M. gallisepticum |
| Clear nasal discharge and sneezing that lingers for weeks | M. gallisepticum |
| Swollen hocks and foot pads, limping, reluctance to move | M. synoviae |
| Drop in egg production, poor growth in young birds | Both |
The distinguishing feature is not how bad it looks, it is how long it lasts. A cold clears. Mycoplasma settles in.
⚠️ Why carriers are the real problem
Once a bird is infected it generally stays infected for life, even after the visible signs stop. Antibiotics can quiet the symptoms without clearing the organism, so the bird looks recovered and keeps shedding. It spreads bird to bird through droplets and shared water, and in Mycoplasma gallisepticum it can also pass from hen to chick through the egg, which means a hatch can start out infected.
That is why one apparently healthy new bird can restart the whole problem months later, and why “she seemed fine when I bought her” is something we hear constantly.
❌ What else it might be
- Infectious bronchitis or other viral respiratory disease, which usually moves through a flock faster.
- Ammonia burn from bedding that needs changing, which affects everyone in the coop at once and improves with ventilation.
- Gapeworm, which causes gasping and neck stretching rather than a wet rattle.
- Aspergillosis, a fungal problem from mouldy bedding or feed.
🧬 Testing for it
We run PCR on an oral or choanal swab, which looks for the organism’s genetic material directly. Swab collection instructions walk through it.
| Result | What it means |
| Detected | That species of Mycoplasma is present in that bird. This is the point to talk to your vet about management and about the rest of the flock |
| Not detected | It was not found in that sample from that bird on that day. Sample more than one bird if you are asking a flock level question, and include the birds that look fine, because carriers usually do |
Swabs mail back in a plain envelope with no kit to buy first. Turnaround is 2 to 3 business days from the day your samples arrive at the lab, results load into your Pullidex account, and samples are held for one week after testing. Disease screening is currently available for chickens.