POULTRY · OWNER EDUCATION
Marek's Disease in Chickens
Marek's disease is a contagious viral disease that can cause nerve paralysis, tumors and immune suppression, especially in young chickens.
THE SHORT VERSION
Understanding supports better veterinary conversations.
Marek's disease is a contagious viral disease that can cause nerve paralysis, tumors and immune suppression, especially in young chickens. The same outward signs can occur with several diseases, so an examination and appropriately selected testing are important.
What is this condition?
Marek's disease is a contagious viral disease that can cause nerve paralysis, tumors and immune suppression, especially in young chickens. The same outward signs can occur with several diseases, so an examination and appropriately selected testing are important.
Which animals can be affected?
Risk factors, examination findings and management can differ between species and individual patients.
Why can it happen?
- Inhalation of virus shed in feather dust from infected chickens.
- The virus persists in poultry environments, and infected birds may shed it long-term.
What might an owner notice?
- Progressive leg or wing weakness, paralysis or abnormal posture.
- Weight loss, unequal pupils, vision change or unexpected deaths.
How is the problem investigated?
- Flock history and examination with necropsy and tissue testing.
- Other causes of paralysis and poor growth must be considered.
What might treatment involve?
- There is no curative treatment; supportive or humane end-of-life decisions may be needed.
- Flock biosecurity and vaccination planning protect future birds.
This is an overview, not a prescription or a recommendation for a specific individual animal.
What can owners do at home?
- Write down when the problem began and track appetite, drinking, waste, activity, breathing and medication use.
- Bring clear photos or short videos when they can be taken without stressing the animal.
- Follow the veterinary team's instructions for medication, feeding, isolation, environmental changes and rechecks.
Avoid actions that could make care less safe.
- Do not use human medication, leftover antibiotics or another animal's treatment without veterinary direction.
- Do not force food or water into an animal that cannot swallow normally, is struggling to breathe or may have an obstruction.
- Do not delay veterinary care when pain, breathing, appetite, urination, movement or responsiveness changes quickly.
What can the longer-term outlook involve?
The outlook depends on the underlying cause, severity, species and how quickly effective care begins.
Can risk be reduced?
- Provide species-appropriate nutrition, housing, sanitation and routine veterinary care.
- Learn the animal's normal behavior, appetite, body condition and waste pattern so meaningful changes are noticed early.
When should you arrange care?
- Contact a veterinarian promptly for progressive leg or wing weakness, paralysis or abnormal posture. or weight loss, unequal pupils, vision change or unexpected deaths..
- Arrange reassessment if signs return, worsen or do not improve as expected.
Seek emergency veterinary care if you notice:
SEEK EMERGENCY VETERINARY CARE- A bird unable to reach food or water, severe distress, breathing difficulty or rapidly increasing flock losses.
Sources behind this guide
VeterinaryPartner — client education from the Veterinary Information NetworkPrimary veterinary or veterinary-university guidance ↗Merck Veterinary Manual: poultryPrimary veterinary or veterinary-university guidance ↗Content last reviewed: September 17, 2026. Review status: veterinary-informed; independent veterinarian review not yet completed.