Marek’s Disease Important Tips For Backyard Chicken Keepers

*Disclaimer. I’m not professional veterinarian. I’m a content creator. This is not veterinary or medical advice. My content is not a substitute for professional services of any kind. For further information please contact your local livestock veterinarian and/or agricultural extension office. Your decisions for the care of your livestock are solely your responsibility.

My backyard flock has never experienced a Marek’s outbreak or a disease outbreak of any kind. My flock has never experienced illness, mites, or lice. I found resources online and in my personal poultry library to share this information with you about Marek’s disease as a content request from a viewer. The beginner poultry care guides listed in the resources helped me as a new backyard chicken owner establish effective care, maintenance, and biosecurity for my backyard flock. With some forethought, intention, and a little work you too can raise healthy, disease-free backyard chickens. Keep in mind, no prevention measures are 100% effective every time and in every case. For best results stack prevention measures and adjust according to your flock’s breed, purpose, your region, and the disease and pest pressure specific to your region.

Marek’s was discovered in 1907 by the Hungarian veterinarian Joseph Marek. Marek’s is a form of herpes virus that can survive for a long time dormant within the environment. It is spread by dander (naturally occurring dead skin dust) on the feathers of the chicken. The virus replicates with in the feather the follicles. The virus is spread by contact with infected chickens or dander. People can transmit the virus between flocks accidentally if they come into contact with infected chickens or dander and then come into contact with their own flock. There is no known cure for Marek’s and it is almost always fatal sometimes causing 100% mortality within an infected flock. While Marek’s was formally discovered in 1907, the virus is thought to have existed for many years before that as part of the viral and bacterial landscape of the world.

Marek’s typically presents in young and developing chickens with symptoms of Marek’s disease becoming apparent before 5 months of age. Symptoms include paralysis, one leg stretched forward and the other backward, droopy wings, enlarged follicles especially on their legs, change in eye color or blindness, rapid weight loss, loss of appetite, paleness, nervous ticks or lack of coordination. Marek’s can also cause body-wide tumors in various organs.

Marek’s can be triggered within a flock for a variety of reasons, the most common are exposure due to poor biosecurity and/or as a result of a stress trigger which lowers their immunity, making them more susceptible to the virus. This be caused by something totally normal like the seasonal hormonal fluctuation of going back on lay after winter dormancy or by other common stress causing conditions. Frequently changing the flock dynamic too often (adding or taking away members too often throughout the year), inadequate space, excessive droppings, unsanitary conditions, excessive predator pressure, improper or inadequate nutrition can all contribute to stress in chickens. Poor biosecurity can include things like visiting other chicken environments and then wearing those same clothing items around your own flock especially footwear, or adding chickens to your flock either baby chicks or adult chickens without observing an isolation period of at minimum two but preferably 4 weeks to ensure the new chickens are free from illnesses, pests, and diseases.

Certain breeds of chicken are more susceptible to the virus than others, specifically, Marek’s is especially devastating to Leghorn chickens and Silkies. There is no cure for Marek’s. Vaccination is thought to be the best way to prevent the virus from presenting in your flock. Unvaccinated chickens that are raised by a mother hen receive some natural immunity and general disease resistance from the mother hen. This natural immunity is shared through maternal antibodies many of which are present in the egg before it is hatched. Mother hens also naturally regulate a baby chicks body temperature and reduce their stress levels as well as imparting important skills like foraging for food. An interesting note, the chicken breed the Egyptian Fayoumi has proven to be resistant to many common chicken diseases including Bird flu, Marek’s and New Castle’s disease. This breed’s natural disease resistance is not currently fully understood and is being actively studied by the scientists.

Chickens that have had Marek’s but recovered and no longer have symptoms will continue to shed the virus throughout their lives and in their environment. Vaccination to be effective has to be done at the hatch, after 24 hours the chicken has likely already been exposed and the vaccination will not be as effective. The vaccination can be administered by a professional veterinarian typically at the hatchery.  Marek’s vaccine is available for purchase to backyard chicken owners but unfortunately is only sold in sizes that would accommodate 1000s of chickens. The vaccine is temperature sensitive and cannot be reused once it’s been opened making it impractical for most backyard chicken owners to administer themselves. If you were to attempt this, you could collaborate with other chicken owners to share the cost of vaccination. If you were to attempt this follow the administration instructions on the vaccination packaging. The easiest way I have found to have chickens vaccinated for Marek’s is to choose that option when purchasing chickens from the hatchery. No vaccination is 100% effective in every case, every time, it is an optional precaution. To know what vaccinations may or may not be appropriate for your flock, you can explore what poultry diseases and viruses are most common in your area and adjust your veterinary care, treatment, and prevention plan accordingly. Your local livestock veterinarian may be able to answer additional questions.

You can increase your chances of never experiencing Marek’s in your flock with the following tips. No prevention strategy or precaution works 100% of the time in every case. Disease and virus pressure varies based on things like your region, your care methods, your chosen breed of chicken, and the size of your flock. For best results I have found it is good to stack all the prevention methods and measures that are practical.

Practice good biosecurity. Have dedicated clothing you only wear when working with your chickens and at no other time, especially footwear. Change clothing after being in other environments or residents where chickens are present (i.e. a trip the farm box store or a friend’s house who also keeps chickens). Wash your hands with soap before and after handling your chickens and especially after handling someone else’s chickens. Don’t allow visitors to walk with their outside footwear in your chicken or disinfect their shoes prior to allow them to walk around your flock. You can ask visitors to also wash their hands with soap before and after interacting with your flock. Isolate any new members to your flock for 2-4 weeks prior to introducing them to your current flock to ensure the new flock members don’t have any pests or diseases before incorporating them into your existing flock. Sanitize any used poultry equipment you choose to use with your flock thoroughly before using it with your own flock. Have an isolation plan ready to enact if you notice Marek’s symptoms or any concerning symptoms develop within your flock and remove any impacted chickens from the flock while you determine your treatment path choices.

Reduce your flock’s stress levels to naturally bolster their immunity. Ensure your flock has adequate space for the number of chickens you have in their coop and run. Provide your chickens with adequate poultry feed that is appropriate for their purpose and breed. Ferment your chicken feed to increase its nutritional benefits and make it easier to consume and digest for your flock. Make flock changes intentionally and try to reduce the number of times you disrupt your flock’s pecking order. Some common practices include only adding new flock members in the spring season and processing or culling flock members (if necessary) in the fall season to reduce the number of changes your flock endures each year. Do not attempt to cull or process a chicken at home without first doing research and obtaining the proper equipment. This can result in unusable meat and the needless suffering of you and the animal. The American Pastured Poultry Association (I’m not affiliated with them) offers many free online resources about processing poultry at home. Allow mother hens to raise chicks naturally to share their natural immunity, teach skills, and reduce the stress level of young chicks.

Develop effective cleaning and maintenance routine for your chicken area. Perform regular daily and seasonal deep cleaning maintenance of your chicken area. Replace nesting materials as needed and ensure whatever bedding method you’re using whether it is deep bedding method or spot clean and scoop method replace your chosen ground cover litter in entirety annually or more frequently depending on the specific kind of chicken housing, you’re using to keep pests and disease from spreading in used decaying litter. The frequency and intensity of your cleaning routines is heavily influenced by the size of your flock, your regional weather extremes, and the kind of chicken housing you’re utilizing. Use livestock cleaning supplies when working in your chicken area like an all-natural castile soap. Harsh, heavily scented chemical cleaning solutions intended for indoor use are not livestock safe and could harm your chicken’s skin, feathers, and respiratory system.

Utilize vaccination services offered by your hatchery or your poultry breeder. Vaccination from the hatchery is both convenient and affordable. While no vaccination is effective 100% of the time and in every case, vaccination is thought to be most effective way to prevent Marek’s in your backyard flock. In addition, you can practice sound biosecurity, reduce your flock’s stress levels through responsible animal husbandry, and regularly clean and maintain your chicken area. If possible, allowing mother hens to raise chicks naturally offers many potential benefits including reduced stress and improved natural immunity. Resources which informed this post are listed below.

I hope you enjoyed this post about Marek’s and what you can do to protect your backyard flock. If you enjoyed this post be sure to check out Chuck’s other social media for more backyard chicken and homesteading tips and content.

The following resources were used to inform this blog post.

Resources

Department of Animal Science, MAREK’S DISEASE IN BACKYARD POULTRY FLOCKS November 2022, Tom Tabler, Department of Animal Science Maria Prado, Department of Animal Science,  University of Tennessee Pramir Maharjan, Department of Agricultural and Environmental Sciences, Tennessee State University Jessica Wells, Department of Poultry Science, Mississippi State University. Retrieved April 26, 2026 from: chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://utia.tennessee.edu/publications/wp-content/uploads/sites/269/2023/10/D185.pdf

Two of my personal favorite beginner chicken care guide books are listed below. I’m not affiliated with these books, authors, or publishers in any way. I consider them wonderful beginner poultry care books.

Storey’s Guide to Raising Chickens, 4th Edition: Breed Selection, Facilities, Feeding, Health Care, Managing Layers & Meat Birds Hardcover, December 27, 2017, by Gail Damerow (Author)

The Beginner’s Guide to Raising Chickens: How to Raise a Happy Backyard Flock (Raising Chickens Guide), Jun 4, 2019, by Anne Kuo (Author)