Concerned chicken owner observing their flock, illustrating the hidden threat of Marek's disease.

Unraveling Marek's Disease: What Every Chicken Owner Should Know

Soraya Malik in Health & Wellness December 2025 • 3 min read.

"Early detection, prevention, and management strategies to protect your flock from this common poultry threat."

Marek's disease is a widespread and highly contagious viral disease affecting chickens. As a chicken owner, understanding this disease is crucial for protecting your flock. Named after the Hungarian veterinarian József Marek, who first described it in 1907, Marek's disease can have devastating effects on poultry health and productivity.

The disease is caused by a type of herpesvirus known as Marek's Disease Virus (MDV). MDV is highly contagious and spreads through direct or indirect contact, primarily via feather dander and saliva. Once a chicken is infected, the virus remains with them for life, and they can shed it into the environment, posing a continuous risk to other birds. It is key to know that even vaccinated birds can become infected and shed the virus, although vaccination typically reduces the severity of symptoms and the amount of virus shed.

While Marek's disease has historically been known to affect younger birds, especially those under one year old, it can occur in older chickens as well. This makes continuous monitoring and preventive care essential, regardless of your chickens' age. This comprehensive guide delves into the symptoms, diagnosis, and management of Marek's disease, offering practical strategies to help you protect your flock.

Decoding the Symptoms: How to Spot Early Signs of Marek's Disease

Concerned chicken owner observing their flock, illustrating the hidden threat of Marek's disease.

Recognizing the early signs of Marek's disease is crucial for timely intervention. The symptoms can vary widely, making diagnosis challenging, but here's what to watch out for:

Neurological Issues: Marek's disease often affects the nervous system. Keep an eye out for symptoms such as:

Paresis or paralysis: Weakness or inability to move limbs.
Uncoordinated movements: Difficulty walking or maintaining balance.
Head tilting or tremors: Unusual head positions or shaking.

Other common symptoms:

Empowering Chicken Owners: Taking Control of Marek's Disease

While Marek's disease poses a significant challenge to chicken owners, understanding the disease and implementing effective prevention and management strategies can significantly reduce its impact. Early detection, proper vaccination, and diligent biosecurity practices are your best defenses. By staying informed and proactive, you can protect your flock and ensure a healthy, productive life for your chickens.

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Everything You Need To Know

What is Marek's disease and why is it a major concern for chicken owners?

Marek's disease is a highly contagious viral infection affecting chickens worldwide. First described by József Marek, the disease can have devastating effects on poultry health and productivity, making it a major concern for chicken owners. Because the virus, Marek's Disease Virus (MDV), is highly contagious and can spread through feather dander and saliva, outbreaks can quickly impact an entire flock. Even vaccinated birds can still be infected and shed the virus, which is why continuous monitoring and preventive care are essential for all chickens, regardless of age.

How does Marek's Disease Virus (MDV) spread among chickens?

Marek's Disease Virus (MDV) spreads primarily through direct or indirect contact, often via feather dander and saliva. Once a chicken is infected, the virus remains with them for life, and they can shed it into the environment, posing a continuous risk to other birds. This means that even if a chicken recovers from the initial symptoms, they can still spread the virus, highlighting the importance of biosecurity measures and preventative strategies.

What are the key neurological symptoms of Marek's disease in chickens?

Marek's disease often affects the nervous system, and key neurological symptoms include paresis or paralysis (weakness or inability to move limbs), uncoordinated movements (difficulty walking or maintaining balance), and head tilting or tremors (unusual head positions or shaking). Recognizing these early signs is crucial for timely intervention and can help in managing the disease's impact on the flock's health and productivity.

Can vaccinated chickens still get Marek's disease and spread the virus?

Yes, even vaccinated birds can become infected and shed Marek's Disease Virus (MDV). Vaccination typically reduces the severity of symptoms and the amount of virus shed, but it does not guarantee complete protection. This is why implementing diligent biosecurity practices is essential, along with early detection and management strategies. These measures are key to protect your flock from the disease.

What are the best strategies for chicken owners to protect their flock from Marek's disease?

The best strategies for chicken owners include early detection, proper vaccination, and diligent biosecurity practices. Early detection of symptoms, especially neurological signs, allows for timely intervention. Proper vaccination reduces the severity of symptoms and the amount of virus shed. Diligent biosecurity practices, such as controlling the environment and the introduction of new birds, can help minimize the spread of Marek's Disease Virus (MDV). By staying informed and proactive, chicken owners can significantly reduce the impact of Marek's disease and ensure a healthy, productive life for their chickens.