Marek’s Disease: Frequently Asked Questions (FAQ)

Marek’s Disease can be a daunting challenge for poultry owners, but understanding the disease and how to manage it can make all the difference. Below are answers to some of the most common questions flock owners ask about Marek’s, presented in an easy-to-read format.

Read here for FAQ format.

What is Marek’s Disease?

Marek’s Disease is a highly contagious viral infection caused by a herpesvirus. It primarily affects chickens but can also infect other birds (though not turkeys or ducks). The disease spreads through feather dander, dust, and contaminated environments and causes symptoms such as paralysis, weight loss, tumors, and sudden death. Marek’s is one of the most common poultry diseases worldwide.

Can humans catch Marek’s Disease?

No, humans cannot catch Marek’s Disease. The virus only infects birds and poses no threat to human health. Eggs and meat from infected chickens are safe to eat, as long as the bird is otherwise healthy and not on medications with withdrawal times.

How does Marek’s Disease spread?

Marek’s spreads through feather dander, dust, and respiratory droplets from infected birds. The virus is incredibly resilient and can survive in the environment for months, contaminating coops, bedding, and equipment. Chickens typically inhale or ingest the virus particles, which then infect their bodies.

What are the symptoms of Marek’s Disease?

Symptoms vary depending on the strain of the virus and the bird’s immune response. Common symptoms include:

• Paralysis: One leg stretched forward and one backward, or drooping wings.

• Weight Loss: Birds appear thin, with a protruding keel bone.

• Tumors: Lumps under the skin or in internal organs.

• Gray Eyes (Ocular Marek’s): Cloudy or grayish eyes, leading to blindness.

• Sudden Death: Birds may die unexpectedly without showing any signs of illness.

Can Marek’s Disease be cured?

No, there is no cure for Marek’s Disease. Once a bird is infected, the virus remains in its body for life. However, vaccination can help prevent symptoms and reduce losses in the flock. Supportive care can also improve the quality of life for symptomatic birds.

How can I tell if my flock has Marek’s Disease?

The only way to confirm Marek’s Disease is through a post-mortem necropsy performed by a veterinarian or poultry diagnostic lab. However, common signs like paralysis, weight loss, or tumors may strongly indicate Marek’s. If you suspect Marek’s, contact your local veterinary diagnostic lab for guidance.

What should I do if I suspect Marek’s in my flock?

• Isolate Sick Birds: Remove symptomatic birds from the flock immediately to reduce viral shedding.

• Strengthen Biosecurity: Clean and disinfect the coop, feeders, and waterers.

• Consult a Vet: Reach out to a veterinarian or poultry diagnostic lab for confirmation and advice.

• Vaccinate New Birds: Start vaccinating chicks to help protect future generations.

How can I prevent Marek’s Disease?

• Vaccinate Chicks: Vaccinate all new chicks within 24 hours of hatching for the best protection.

• Quarantine New Birds: Keep new or returning birds separate from your flock for at least 30 days.

• Practice Good Biosecurity: Clean coops regularly, control dust, and prevent visitors or wild birds from entering your flock’s space.

• Breed for Resistance: Select birds that show natural resistance and remain healthy despite exposure.

If I vaccinate my chicks, can they still get Marek’s Disease?

Yes, vaccinated birds can still become infected with the Marek’s virus, but the vaccine helps prevent symptoms like paralysis, tumors, and death. Vaccinated birds may still carry and shed the virus, so biosecurity measures are still important.

Does Marek’s Disease spread through hatching eggs?

Marek’s Disease does not pass directly from parent birds to eggs (no vertical transmission). However, eggshells can become contaminated with feather dander or dust carrying the virus. It’s important to sanitize hatching eggs from a Marek’s-positive flock before incubating them.

Can other poultry species get Marek’s Disease?

Marek’s Disease primarily affects chickens. Other birds like turkeys, ducks, and quail are generally not affected by the virus, though turkeys have their own strain of a herpesvirus that is unrelated to Marek’s. If you raise chickens with other poultry, the chickens can still spread Marek’s within their group, but they won't infect other species.

What should I do with birds that show symptoms of Marek’s Disease?

• Isolate the Bird: Move the bird to a quarantine area to reduce exposure to the flock.

• Provide Supportive Care: Offer high-protein foods, vitamins, and electrolytes to support the bird’s health.

• Consider Euthanasia: If the bird is suffering or severely symptomatic (e.g., paralysis, inability to eat or drink), humane euthanasia may be the kindest option.

• Dispose of the Body Safely: Bury or incinerate the body to prevent further contamination.

How long does the Marek’s virus survive in the environment?

Marek’s virus can survive for several months in the environment, especially in dust and feather dander. It can even persist for years in some cases, making regular cleaning and disinfection critical in Marek’s-positive flocks.

What disinfectants kill Marek’s virus?

Effective disinfectants include:

• Virkon S: A broad-spectrum disinfectant that kills viruses, bacteria, and fungi.

• Bleach Solution: Use a 1:10 dilution of household bleach and water.

• Oxine AH (Activated): Effective against viruses when used with an activator.

Always clean surfaces thoroughly before applying disinfectant, as organic matter like droppings can reduce effectiveness.

Can I sell birds or eggs from a Marek’s-positive flock?

Yes, but ethical guidelines require full disclosure to buyers about the health status of your flock. Be transparent about Marek’s exposure and recommend that buyers vaccinate chicks and quarantine new birds. Eggs should be sanitized before shipping to minimize the risk of contamination.

What is the best way to manage a Marek’s-positive flock long-term?

• Vaccinate New Birds: Vaccinate all chicks within 24 hours of hatch to reduce symptoms and losses.

• Practice Strong Biosecurity: Keep coops clean, control feather dander, and quarantine new additions.

• Breed for Resistance: Focus on breeding birds that remain healthy despite exposure to Marek’s.

• Monitor Symptoms: Regularly check your flock for signs of illness and isolate symptomatic birds promptly.

• Accept the Challenges: Marek’s Disease will remain in your environment long-term, but with proper management, you can maintain a healthy and productive flock.

Have More Questions?

If you have additional questions about Marek’s Disease or need help managing your flock, don’t hesitate to reach out to a veterinarian or poultry expert. With proper care and informed decision-making, it’s possible to manage Marek’s-positive flocks successfully.