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Western Small Flocks Collaborative

Mycoplasma

Learn about the signs and symptoms of Mycoplasma gallisepticum (Mg) and Mycoplasma synoviae (Ms), how they spread, ways to prevent them, and what to do if you suspect infection in your flock.

Mycoplasma Factsheet
Silhouette shape of Mycoplasma

Quick Facts

Silhouette of dark brown bacteria Mycoplasma is a bacteria
Silhouette icon of a Infectious Laryngotracheitis virus infected chicken Infected birds may look healthy but can spread disease for life
Silhouette of dark brown pair of gloves The bacteria is hard to eliminate in a flock
Silhouette icon of a dark brown human figure Does not spread to or infect humans
Silhouette icon of a light brown turkey Affects chickens, turkeys, peafowl, and gamebirds. Rare in ducks and geese

What is Mycoplasma?

Mycoplasma gallisepticum (Mg) and Mycoplasma synoviae (Ms) are bacterial infections that affect chickens, turkeys, and other birds. Mycoplasma spreads through respiratory droplets, direct bird-to-bird contact, contaminated equipment, and even infected hatching eggs. These diseases are common in backyard flocks. Once infected, birds can carry the bacteria for life. Antibiotics may reduce clinical signs but will not eliminate infection. Biosecurity and flock management are the best ways to prevent and control disease.

Silhouette icon of a brown caution symbol with an exclamation point in the center There is no cure and infected birds can become life-long carriers and continue to shed the bacteria for life.
Chicken affected with Mg showing symptoms of infraorbital sinus swelling.
Turkey affected with both Mg and Ms showing symptoms of infraorbital sinus swelling and ocular and nasal discharge.

Signs of Mycoplasma

General signs (both Mg and Ms)

  • Watery eyes or conjunctivitis
  • Swelling around the face
  • Sneezing, coughing, rattling or gurgling sounds
  • Nasal discharge; dirty nostrils from feed sticking to mucus

Mycoplasma gallisepticum (Mg):

  • More severe respiratory disease
  • Swollen sinuses, especially in turkeys
  • Lower egg production and hatchability in laying hens
  • Embryos may pip but fail to hatch

Mycoplasma synoviae (Ms):

  • Often mild or unnoticed in the respiratory tract
  • Can spread to joints, causing swelling, uneven hocks, and lameness
  • Birds may limp or sit more if legs are painful

Other impacts:

  • More severe illness and higher death loss if birds also have other infections (like E. coli)
  • Mortality is usually low in uncomplicated cases, especially in mature birds, but younger flocks can be affected more seriously
Common signs of mycoplasma in poultry.
Common signs of mycoplasma in poultry.

How does Mycoplasma Spread?

Hen to egg and chick (vertical transmission):

  • Infected breeder hens can pass Mycoplasma to their eggs.
  • Chicks hatch already infected, even if they look healthy.
  • Infected chicks can spread Mycoplasma to other chicks.
  • Contaminated incubators or hatchers can infect many chicks at once.

Equipment, people, and pests (mechanical transmission):

  • Spread happens through equipment, clothing, shoes, or litter.
  • Droppings, mucus, and dust can contaminate feeders, waterers, and housing.
  • Wild birds, rodents, and insects like beetles can carry the bacteria between flocks.

Bird-to-bird (direct transmission):

  • Birds pick up the infection through the eyes or respiratory tract.
  • Sick or carrier birds spread it directly to flockmates.
  • The bacteria can move short distances in the air on droplets or dust.
  • Stress (like moving, mixing flocks, or starting to lay) can trigger signs in carriers.
Diagram of three different kinds of routes for spreading disease
Arrows show three routes of spread: from hen to egg and chick (vertical), by contaminated equipment, people, or pests like wild birds, rodents, and beetles (mechanical), and directly from bird-to-bird.

How Do You Treat Mycoplasma?

Antibiotics can help reduce signs of disease and lower the level of bacteria in the flock, but they cannot cure Mycoplasma. Because these bacteria do not have a cell wall, only certain antibiotics are effective. Check with your veterinarian to guide next steps.

How Do You Prevent Mycoplasma?

Practice Biosecurity

  • Limit contact with birds from other flocks.
  • Wear coop-dedicated shoes to keep out germs.
  • Keep the coop, equipment, and your hands clean.

Keep Wild Birds Out

  • Don’t let your birds commingle with wild birds
  • Use netting to keep wild birds out and your birds in
  • Cover feed and water.

Limit Visitors and Shared Tools

  • Require approved visitors to wear clean clothes and boot covers.
  • Minimize sharing tool or equipment.

Buy from Clean Sources

  • Choose hatcheries and breeders that test for Mycoplasma.
  • Do not buy birds from swaps, auctions, or unknown sources.

Don’t Hatch Mycoplasma

  • Mycoplasma can pass from hen to chick through the egg.
  • Selling or hatching eggs from infected flocks can spread the disease to new birds and new flocks.

What if Mycoplasma is Found in Your Flock?

Work with a Veterinarian

  • Mg may be reportable to your state animal health officials, depending on the state.
  • Your veterinarian can help confirm the disease and guide next steps.

Isolate Sick Birds

  • Separate sick birds from the flock.
  • This limits the chance of spreading the bacteria.

Don’t Spread Disease

  • Do not buy or sell birds during or after an outbreak.
  • Even healthy-looking birds can shed this bacteria.
  • Mixing age groups allows older carrier birds to infect younger birds. Keep age groups separate or practice all-in all-out management.

Manage a Flock Long-Term

  • Infected birds remain carriers, so some flocks may choose to depopulate their flock.
  • If Mycoplasma is reportable in your state, there may be additional management requirements.