14/05/2026
*What is Marek’s Disease in Poultry?*
Marek’s disease is a very dangerous viral disease that affects chickens, especially young birds. It is caused by a virus called herpes virus. This disease attacks the bird’s nerves, eyes, skin, and internal organs. It can cause paralysis, weight loss, blindness, low egg production, and death.
Marek’s disease is one of the most common diseases in poultry farming worldwide and can cause heavy losses to farmers if not controlled properly.
How Marek’s Disease Spreads
The disease spreads mainly through:
Dust and feathers from infected birds
Air inside the poultry house
Dirty equipment
Workers’ clothes and shoes
Contaminated cages, feeders, and drinkers
An infected bird can spread the virus for a very long time, even if it does not look sick.
The virus can stay in poultry houses for many months because it survives in dust and feathers.
Birds Mostly Affected
Marek’s disease mostly affects:
Chicks and young birds
Birds between 6 weeks to 30 weeks old
Layers, broilers, and local chickens
It is more serious in birds that were not vaccinated properly.
Symptoms of Marek’s Disease
The signs can be different depending on the part of the body affected.
1. Paralysis of Legs and Wings
This is the most common sign.
You may see:
One leg stretched forward and the other backward
Birds unable to stand
Drooping wings
Difficulty walking
2. Weight Loss
Affected birds become thin even when feed is available.
3. Pale Comb and Weakness
Birds may look weak and dull.
4. Blindness
The eyes may change color to grey or whitish.
The bird may become blind and unable to find feed or water.
5. Sudden Death
Some birds may die suddenly without showing signs for long.
7. Swollen Skin or Feather Follicles
Sometimes the skin becomes rough with swollen feather areas.
What Happens Inside the Bird
The virus causes tumors inside the body.
It can damage:
Liver
Heart
Lungs
Spleen
Kidneys
Nerves
This is why birds become weak and paralyzed.
How Farmers Can Recognize Marek’s Disease
A farmer may suspect Marek’s disease when:
Young birds start becoming paralyzed
Birds die gradually
Antibiotics do not work
Birds lose weight continuously
Is There Treatment for Marek’s Disease?
NO complete treatment exists.
Because it is caused by a virus, antibiotics cannot cure it.
Antibiotics may only help control secondary bacterial infections.
Once a bird shows serious paralysis, recovery is very difficult.
What Farmers Should Do When They See Marek’s Disease
1. Separate Sick Birds
Remove weak or paralyzed birds immediately.
2. Improve Hygiene
Clean poultry house properly
Remove dust and feathers
Disinfect equipment
3. Reduce Stress
Stress makes the disease worse.
Avoid:
Overcrowding
Excessive heat
Poor feeding
4. Burn or Bury Dead Birds Properly
Do not throw dead birds around.
The Best Prevention for Marek’s Disease
Vaccination is the main protection.
Chicks are usually vaccinated:
At the hatchery
On the first day of life
Without vaccination, the risk becomes very high.
Important Things Farmers Should Know About Marek’s Vaccine
The vaccine helps protect birds from sickness
Vaccinated birds can still carry the virus
Vaccination must be done early before exposure
Poor vaccine handling can make it fail
The vaccine must stay cold and be used correctly.
