Silkie guide
MG and MS in Chickens: How to Keep Mycoplasma Out of Your Flock
MG and MS are two of the most common diseases in backyard flocks, and two of the most frustrating, because once a flock has them, they don't go away. The good news is that they are very preventable. With strict biosecurity and healthy birds from a careful breeder, most keepers never have to deal with them at all.
This guide explains what they are, what to look for, and the exact habits we use on our farm to keep them out.
What are MG and MS?
Both are bacteria from the mycoplasma family that infect chickens, turkeys and other birds.
- MG (Mycoplasma gallisepticum) mainly affects the respiratory system: the eyes, sinuses, windpipe and air sacs. It's sometimes called chronic respiratory disease, or CRD.
- MS (Mycoplasma synoviae) is usually milder in the airways, but it can spread into the joints and cause lameness and swelling. This is called infectious synovitis.
Signs of MG
- Foamy or bubbly eyes. This is the classic sign. It often starts in one eye.
- Swelling around the eyes or face
- Sneezing, coughing, or a rattling, gurgling sound when breathing
- Nasal discharge
- Fewer eggs, and birds that aren't growing or eating well
Signs of MS
- Limping, or a bird that sits a lot and doesn't want to walk
- Swollen, warm hocks (ankle joints) or footpads
- Blisters on the breast
- Mild sneezing or rattly breathing, though often there are no breathing signs at all
- Thin or rough eggshells at the pointed end of the egg
Signs alone can't tell you for sure. Other illnesses, like infectious coryza, infectious bronchitis or a simple eye injury, can look similar. Limping can also come from an injury or bumblefoot. Only a lab test can confirm MG or MS.
Why it matters: infected birds stay infected for life
This is the most important thing to know. Antibiotics can calm the symptoms, but they don't clear the infection. A bird that has had MG or MS stays a carrier for life. It can look perfectly healthy for months, then flare up again with stress (moving, weather changes, molting, a new flock member) and spread it to every bird it meets.
That's why the best treatment is prevention.
How MG and MS spread
From bird to bird
Through sneezes, coughs and shared water. Once one bird has it, it usually spreads through the whole flock.
Through the egg
An infected hen can pass MG and MS into her eggs, so chicks can hatch already infected. This is why buying hatching eggs and chicks from a careful, tested flock matters so much.
On people, shoes and equipment
Between flocks, people are one of the most common ways mycoplasma travels. It hitches a ride on hands, shoes, clothing, feed scoops, carriers and egg cartons. Research has also found MG can survive for a while in a person's nose and on hair and feathers, so visiting someone else's chickens and then going straight to your own is a real risk.
From wild birds
Wild songbirds can carry MG. In North America, house finches are well known for it: an infected finch gets swollen, crusty eyes. Wild birds that drop droppings into your run, feeders or the ground your chickens forage on can bring it in.
From new birds
Adding a bird that looks healthy but is secretly a carrier is one of the easiest ways to bring MG or MS home.
Biosecurity: how to keep MG and MS out
Clean hands and shoes between every pen
- Wash and sanitize your hands before and after handling birds, and between pens and coops, not just at the end of the day.
- Use a boot dip or a disinfectant spray on your shoes between pens, or keep a separate pair of boots for each coop.
- Never go straight from another person's flock, a poultry swap or a feed store with live birds to your own chickens. Shower and change clothes and shoes first.
Keep wild birds away from food and water
- Keep feeders and waterers covered, or inside the coop, where wild birds can't land on them or poop in them.
- Don't hang wild bird feeders near your coop or run.
- If your chickens free-range, keep them away from places wild birds gather and poop: under trees where birds roost, around bird feeders and baths, and near spilled seed. A covered run is safest.
Quarantine new birds
Keep any new bird separate from your flock, ideally out of sharing distance and with its own feeder, waterer and shoes, for at least 30 days. Watch closely for any sign of illness before they meet your flock.
Buy from tested, NPIP-certified breeders
The National Poultry Improvement Plan (NPIP) is the program that certifies flocks as tested for diseases. Ask breeders what they test for, and how they handle a bird that shows signs.
Keep your flock strong
Stress lets mycoplasma flare up. Good ventilation, dry bedding, plenty of space and good feed all help.
How testing works
There are two main kinds of lab tests, and they answer different questions:
| Test | How it's done | What it tells you |
|---|---|---|
| PCR (swab) | A swab from the roof of the mouth, throat or eye | Whether the bacteria are there right now. It's most accurate while a bird is actively sick and shedding. |
| Blood test (antibodies) | A small blood sample | Whether the bird has ever been exposed. It takes time after infection for antibodies to show up, so a very recent infection can test negative. |
Timing matters. A swab taken from a bird that isn't actively shedding can come back negative even if the bird is a carrier, so test birds that are showing signs, and test more than one bird. MG and MS can also cross-react on some blood tests, so labs often run a second test to confirm. In Florida, your vet or an NPIP tester can send samples to the state lab, the Bronson Animal Disease Diagnostic Laboratory in Kissimmee.
What to do if you suspect MG or MS
- Separate the bird right away, and do its chores last, with separate shoes and gloves.
- Get it tested through a vet or your state lab. Ask about testing other birds in the flock too.
- Don't sell, trade, show or hatch eggs from the flock until you know what you're dealing with.
- Talk to a vet about your options. Antibiotics need a vet's prescription, and they won't cure a carrier, so many breeders choose to cull infected birds and start over clean.
Can people catch MG or MS?
No. MG and MS are bird diseases and aren't known to infect people. The concern is people carrying the bacteria from one flock to another on their hands, clothes and shoes.
How we handle it at FancyFlock. We take MG very seriously. We clean and sanitize our hands and shoes between every pen and coop. We keep our birds' food away from places wild birds can reach. And we don't take chances: if we ever see foamy, bubbly eyes, we cull that bird and test. As breeders, we've learned firsthand how easily mycoplasma can travel on people, so we treat every coop visit like it matters, because it does. Questions? Reach out anytime.