Mycoplasma gallisepticum: Frequently Asked Questions

By Anne Lichtenwalner DVM Ph.D., University of Maine Cooperative Extension

MG (Mycoplasma gallisepticum) is considered to be the most problematic of the poultry mycoplasmal diseases. This FAQ aims to explain the mycoplasmas in general, this disease in particular, and why it matters to both small and large poultry producers.

  • MG is a slow spreading infection, and often infected birds remain healthy without showing any overt signs of disease. Once other complicating factors — such as environmental stressors (elevated heat, ammonia levels, dust, or cold drafts), nutritional deficiencies, other infections (such as infectious bronchitis or laryngotracheitis virus) — lower immunity of the flock, MG may flare up as overt disease.
  • MG adversely affects fertility, hatchability, and survival of baby chicks.
  • MG will spread easily to other flocks on the farm, to neighbor’s flocks, to birds of different species, and to wild birds.

What are mycoplasmas? These are very tiny bacteria-like organisms that have less of a cell wall than do other bacteria. There are many species of mycoplasma, and many of them infect only certain animals. For instance, some cause no problems; some are associated with mastitis in cattle, some with respiratory disease in pigs, and some cause mild respiratory infections in wild birds. Some are very host-species specific; for instance, M. bovis infects cattle but not pigs. In contrast, some — like MG — can infect a number of different avian hosts.

What types of birds get MG? MG can cause problems in chickens, turkeys, ducks, geese, game birds, and even wild birds, such as finches.

Is MG a problem in people? No, this disease has not been shown to cause disease in people. However, other respiratory diseases of poultry — like avian influenza — are definitely a problem for people, so contact with birds that show signs of a “cold” or sinusitis (coughing, sneezing, runny eyes, swollen faces) should be limited. If you have sudden deaths in a flock for any reason, seek help from a poultry vet (or the state vet) and MINIMIZE CONTACT. Because of dust, bacteria, fungi, molds, and viruses such as influenza, it’s good to wear a mask while working with the birds. Also, wash hands well after being around the birds and use biosecurity measures (outerwear for barn use only, footbaths, etc).

What does MG infection look like? MG infection can look like many respiratory diseases, and often occurs with several other respiratory diseases, such as Infectious Bronchitis, Newcastle Disease, and/or with E. coli infections. A cough, loud breathing, swelling of the sinuses, and watery eyes are common signs. Decreases in feed intake, egg production or weight gain will occur. Males and also younger birds tend to be more affected, and the disease is worse in the winter months. While it tends to be a more serious disease in turkeys, chickens also will show losses.

How does MG spread? Transmission directly from bird to bird via respiratory secretions, or indirectly from contaminated dust, droplets or feathers, is common. Also, it can be spread vertically: from infected parent birds via the eggs. It can live for days to weeks depending on what kind of material is present: longer in chicken manure or eggs, shorter on clean, dry surfaces. Therefore, removing infected birds and cleaning well, followed by a “down” time for the chicken areas of at least a few weeks, is suggested. In a chicken house, water from unsanitary “drinkers” is the most important source of spreading the infection from bird to bird.

How do I know if MG is present in my flock? Diagnosis can be done via necropsy and culture of ill or dead birds, along with using a blood test to see if your flock has antibodies to MG. Just having antibodies does not mean you have a current problem with MG, but once birds have been infected with it, they may be able to infect other birds, even if they don’t look sick (“carriers”). An infected flock remains infected for life. Contact your veterinarian, or your state department of agriculture, to find out more about MG testing.

How do I disinfect if MG was in my flock? Freezing does not reliably kill MG outside of the host bird, but heat and drying do. Removing the infected flock, thorough cleaning and drying out of the house, and then disinfection with bleach or any of the commercially available products, such as phenolic compounds, should be effective. Leave the premises open (bird-free) for several weeks (hot, dry weather is optimal) before restocking with new birds.

Why should I bother to prevent MG? Because it can be an underlying cause of production losses, can combine with other diseases to kill birds, and can become chronically present in a flock due to “carriers,” it’s worthwhile to prevent MG.

How can I prevent MG in my flock?

  1. Start with clean birds: The National Poultry Improvement Plan (NPIP) is one of the best resources to protect your poultry investment. Starting with MG-free birds, and keeping MG out of your flock with good biosecurity, is by far the best plan.
  2. Good sanitation: Keep drinking water/drinkers and feeders clean. Outside runs should be on well drained soil and water puddles should be removed.
  3. Simple is best: The more birds of different ages, breeds, and types are on the farm, the greater the risk of infection.
  4. Keep it clean: Don’t let wild birds, or new birds of unknown (untested) background, bring MG into your flock. Net the top of coops to keep wild birds out; keep feeders contained and think carefully before you chose to do “free range” for your flock.
  5. You may want to investigate MG vaccines, which can be given to young birds by spray or eyedrops, but which come in large-dose sizes (~1000 doses) and which may not be effective. These vaccines may not be allowed in Maine; check with the state department of agriculture.

Where can I buy MG-free chicks? There is at least one heritage hatchery and there are commercial hatcheries producing NPIP-certified MG-free chickens (this information may change; look at the NPIP website to be sure information is current). ASK YOUR SUPPLIER if the chicks are from an NPIP certified MG free hatchery.

Other Informational Sites:

FAQ about MG from Washington State, which gives a nice summary of biosecurity practices for the small poultry producer: Mycoplasma galliscepticum (MG): Frequently Asked Questions ~ What is Mycoplasma galliscepticum (MG)? (PDF).

Information in this publication is provided purely for educational purposes. No responsibility is assumed for any problems associated with the use of the products or services mentioned. No endorsement of products or companies is intended, nor is a criticism of unnamed products or companies implied.

© 2012

Published and distributed in furtherance of Acts of Congress of May 8 and June 30, 1914, by the University of Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture cooperating. Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.

Call 800.287.0274 or TDD 800.287.8957 (in Maine), or 207.581.3188, for information on publications and program offerings from University of Maine Cooperative Extension, or visit

In complying with the letter and spirit of applicable laws and pursuing its own goals of diversity, the University of Maine shall not discriminate on the grounds of race, color, religion, sex, sexual orientation, including transgender status or gender expression, national origin, citizenship status, age, disability, genetic information or veteran’s status in employment, education, and all other areas of the University of Maine. The University provides reasonable accommodations to qualified individuals with disabilities upon request.

Questions and complaints about discrimination in any area of the University should be directed to Karen Kemble, Esq., Director of Equal Opportunity, ADA Coordinator, Title IX Coordinator, Rehabilitation Act Section 504 Coordinator, The University of Maine, 5754 North Stevens Hall, Room 101, Orono, ME 04469-5754, telephone 207.581.1226, TTY 207.581.9484.