Hey there, folks! Today, we will explore a topic vital for every backyard hobbyist to understand – Marek’s disease. This common yet preventable illness can be a real party pooper in the vibrant life of your backyard flock. So, let’s arm ourselves with knowledge and ensure our feathery friends lead happy and healthy lives, free from the clutches of Marek’s disease. What is Marek’s disease in chickens? Let’s find out.

Understanding Marek’s Disease

What is it?

Before battling Marek’s disease, let’s get to know our enemy better. Marek’s disease is caused by a chicken herpes virus, but breathe easy because it doesn’t affect us humans.

However, once a chicken catches it, it’s a lifelong deal. The silver lining here is that most infected birds won’t get sick.

Marek’s is so common that your chickens probably have it already. It’s just dormant, waiting for an opportunity to manifest itself in the form of tumors, respiratory diseases, or some other malady that a compromised immune system allows.

That’s right… Your chickens will probably not show signs of Marek’s disease unless they are over-stressed, ill from some other disease, injured, or otherwise weakened to the point that Marek’s has the OPPORTUNITY to wake up.

Who is at Risk?

Certain breeds, like Leghorns and light egg-type breeds, are more prone to Marek’s disease, with Silkies being the most susceptible. While it commonly affects birds between 6 and 30 weeks, older birds aren’t entirely safe.


The Silent Invader

Marek’s disease is like that silent invader that slips in unnoticed. It spreads through virus-laden dander that chickens inhale. The tricky part is that this virus can live for years in the dander, turning your coop into a long-term Marek’s disease residence.

The remedy for this is, of course, a complete clean-out and disinfection of the coop.


Nervous System

Marek’s disease doesn’t play nice, targeting the nerves, spinal column, and brain, leading to paralysis and head tremors in the affected birds.

Other Forms

But it doesn’t stop there; Marek’s disease can also cause tumors in internal organs, eyes, and even the skin, causing the birds to lose weight and become emaciated.

  • Eyes This occurs rarely, but when it does, it can show up as graying of the iris, unequal-sized pupils, blindness in one or both eyes, and, of course, death.
  • Skin Problems can be bloody legs and enlarged feather follicles, but not death.
  • Organs This shows up more commonly than the other two forms. It causes large tumors, diarrhea, weight loss, and death.



Identifying Marek’s disease involves observing symptoms, necropsy, and biopsy examination of tissues. Thankfully, many diagnostic animal labs can test for this disease, helping you to confirm your suspicions.


The Mighty Shield

Now, onto the good news! You can shield your flock from Marek’s disease through vaccination, a dependable way to prevent the clinical disease.

Chicks should be vaccinated right away after hatching. If a chick already has Marek’s disease, the vaccine won’t work, so it must be done immediately. Chicks should be kept away from older chickens for as long as practicable.

Most store-bought chicks come vaccinated. Otherwise, a vaccine can be purchased. Tractor Supply usually has it. You can find it online at several outlets.

Vaccine Handling

Handling the vaccine correctly is crucial. It involves following specific temperature controls and usage time frames to ensure its effectiveness against Marek’s disease.

Once opened, the vaccine efficacy drops quickly. Placing the vial in a bowl of ice will give you about an hour and a half to vaccinate your chicks. That is plenty of time for a small flock.

To vaccinate a chick, gently pinch the skin just behind the head and inject the vaccine into the skin. Be careful. If your eyes itch for a while after the vaccination process, you got some vaccine in your eye. Don’t worry. It will go away soon. I told you to be careful:)

Vaccinating a Chick  Chickenmethod.com

Common Misperceptions

Turkey and Chicken Coexistence

You might have heard that keeping turkeys and chickens together can prevent Marek’s disease. Well, that’s a myth. Turkeys carry a related virus that prevents Marek from causing tumors, but that doesn’t help the chickens because the turkeys aren’t sharing.

Natural Resistance

Another misconception is that not vaccinating birds will lead to natural resistance over time. Spoiler alert: It doesn’t work that way with Marek’s disease. You can help your chickens stay strong, though, by making sure they have a safe, clean, and healthy environment to live in.

Be the Guardian of Your Flock

As the guardian of your flock, it’s your duty to protect them from Marek’s disease. You can ensure your feathery friends a happy and healthy life with the right knowledge.

Got any Marek’s disease stories or tips to share? Drop them in the comments below! And don’t forget to share this post to help spread awareness and keep more flocks safe from Marek’s disease.



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