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What Is Marek’s Disease In Chickens?

What Is Marek’s Disease In Chickens?

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Of all the viral diseases, Marek’s disease is probably the scariest. It attacks quickly and takes chickens so young. But what is Marek’s disease in chickens? What are the signs, and how do we prevent it? Let’s take a look together. 

What Is Marek’s Disease In Chickens? 

Marek Disease is a viral infection related to the herpes virus. Marek’s is the most common virus to afflict flocks today, and it is arguably the most contagious. Your chickens could get infected as early as 3-4 weeks old. But they learn to cope with the disease this early. In older chickens, it is more apparent and spreads quickly. 

This disease is famous for its ability to cause tumors, blindness, and early death. And once one chicken has it, it spreads like wildfire. But we are getting a little ahead of ourselves here.

Marek’s Disease In Chickens Symptoms

If you know anything about chickens, you know that they hide illness well. As an animal that tastes delicious to every predator out there, they hide as self-preservation. So it’s apart of our daily job to check for the slightest signs of a sick chicken. Because once the symptoms become apparent, your chicken has been ill for a while. 

Some of the most common Marek’s disease symptoms are:

  • Lack of appetite
  • Weightloss
  • Greying iris
  • Irregular pupil shape
  • Poor vision
  • Raised feather follicles
  • Tumors inside and outside the body
  • Stop laying eggs
  • Paralysis of the neck, wings, and legs

We have ordered the Mareks Disease symptoms from minimal concern to the most severe. But it’s also important to remember that not every chicken shows these signs. Some chickens are asymptomatic and can live their whole lives as carriers of the disease. 

Causes Of Marek Disease

What is Marek’s disease in chickens? An awful disease that no one should have to suffer through. Now that we know what it is, we can talk about what causes it. Marek’s is the Alphaherpesvirinae herpes virus. An infected chicken or wild bird spreads this virus through feather dander. And in some cases, mice and rats can carry the dander into the coop with them. When your chickens inhale or eat the dander, they contract the virus for life. 

The tricky thing about dander is that it hides everywhere. It gets in the coop’s floorboards, in the food dishes, on you, and travels by air. Even if the original chicken with Marek’s has passed, they could infect your flock years later by hidden dander in the coop.

There are even cases of dander floating in from a neighbors coop that infects a flock. It’s also possible that the previous owners of your home had infected chickens. And the virus can live in the dry ground for years, possibly infecting your current flock. 

Treatment Options

The most challenging part of Marek’s disease is that there is no treatment for it. There are no medications you can give your chickens or ways to cure Marek’s. Once your chicken gets Marek’s disease, they will have it for life, and therefore spread it to your other chickens as well. 

Depending on how severe the symptoms are, you can accommodate your hens. These accommodations aren’t the easiest, and your entire flock will likely get the disease. But they will still give you the fresh eggs and meat you crave. 


The first step if you suspect Marek’s disease is to isolate your chicken. Though in most cases, your flock has already contracted the disease. But on the off chance that your chicken hasn’t shed the virus yet, this could save your flock. 

Clean, Clean, Clean

Now that your sick chicken is isolated, you should remove the rest of the flock from the area. Then deep clean every nook and cranny of the coop, run, food dishes, and waterers. Remember that dander is microscopic and likely to get caught in the smallest places. 

In dry environments, Marek Disease can live a year and a half without a host. And some research suggests it can live up to seven! Cleaning with bleach is the best way to kill the virus. However, you shouldn’t get your hopes up of irradicating the virus with washing alone. 

Mild Case Treatments

There is no Marek’s disease treatment that will cure the virus. But you can help our flock build up immunities to fight the disease instead. Feeding a healthy diet along with probiotics and vitamins will boost your hen’s immunities. 

Daily checks will also help you keep an eye on your chicken’s symptoms. Marek’s disease chicken regression is a real thing. Your chickens could live years without any issues. Then suddenly, their health degrades for the worse. 

Test The Ground

If you don’t have chickens already, you can have the ground tested to prevent Marek’s disease. We’ve mentioned above that Mareks disease could live in the land for years. Depending on your location, the average is anywhere between 3-7 years. So if you are new to the house and not too late, you should have the soil tested. 

Marek’s Disease Prevention

So, how does someone prevent Marek disease, to begin with? The best way to prevent Marek’s is to buy vaccinated chickens. The Mareks disease vaccine is given to most hatchlings on the day they are born. And it has a very high success rate in preventing this illness. 

If you buy chickens from a local breeder, you should double-check that they give the Marek’s disease vaccine. If they don’t vaccinate, you should keep those new chickens isolated for 30 days while the vaccine takes effect. After you are sure that your new chickens don’t have any illnesses, you can add them to your flock. 

During this isolation period, you should also take extra precautions not to cross-contaminate. Always tend to your existing flock first to not spread disease. Then when you finish caring for the isolated birds, change your clothes, and wash your hands thoroughly. Some illnesses, such as Marek’s Disease, can spread by you cross-contaminating with dander on your clothes. 

And the last method of prevention is to keep rodents out of the chicken area. Rats and mice are notorious for bringing dander and illness in from nearby farms. You can prevent rodents by putting away all food every night and proofing the coop. It’s not possible to keep all rodents away, but you can try! 

Other than giving the Marek’s disease vaccine, there isn’t much you can do. You can keep the coop area clean, but it is hard to irradicate it with cleaning alone. The only fool-proof method of preventing Marek’s disease is to vaccinate all your birds. 

How Long Can Chickens Live With Marek’s? 

Some chickens will live a long and healthy life with Mareks disease. And since some chickens never show any symptoms of Mareks, you might never know they have it. These hens can live eight or more years with no issues. 

But there is no Marek’s disease recovery for chickens that have permanent vision loss or paralysis. These chickens can’t live healthy lives and will need constant attention for basic needs. Once your chicken develops these symptoms, the humane thing to do is to euthanize them. It is hard for our beloved chickens, but it is more humane than letting them suffer.

Can Humans Get Merek’s Disease From Chickens?

You have nothing to fear if your chickens develop Marek’s disease. It is not a zoonotic disease that spreads from animals to people. So you won’t need to take special precautions for yourself or your children. 

But it can spread to other poultry and specific pet bird species as well. So if you have other birds on the property, you will need to take precautions not to contaminate them. Changing your clothes after caring for the infected chickens and washing your hands is essential. And hopefully, you can keep the disease to a minimum. 

Can You Still Eat The Eggs And Meat? 

You might be wondering if it is safe to eat the eggs of a chicken who has tested positive for Marek’s. And the answer is yes; you can certainly eat the eggs. In the later stages of Marek’s disease, your chickens will develop tumors on the ovaries and oviducts. But if your hen is still laying eggs, then there is no reason not to eat the eggs.

And if you raise broilers, you don’t have anything to fear when eating the meat. It probably isn’t a great idea to butcher a chicken with too many tumors for food. But you can certainly eat a chicken that is asymptomatic or has minimal issues. You won’t get sick from eating any part of the chicken that has tested positive for Mareks Disease. 


What is Marek’s Disease in chickens? It is an awful disease that’s preventable with a simple vaccine. If you happen to get chickens already infected with the disease, it can be impossible to get rid of. But if you vaccinate your chicks from a young age or buy them vaccinated, you will have no worries. In either case, there’s a long road ahead of you if your chickens have Marek’s Disease. 

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What is Marek's Disease In Chickens?

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