MAREK’S DISEASE

1. What is Marek’s Disease (MD)?

MD is a herpesvirus that causes nerve inflammation leading to paralysis. It is also associated with immunosuppression and tumours, particularly of the eyes and skin.

2. How is the virus transmitted from bird to bird?

MD is spread by a bird eating or breathing in an infected bird’s droppings or feather dust. The virus can survive in the environment for several months.

3. What species are affected by MD?

Chickens, and on rare occasions pheasants and turkeys, are affected. It most commonly affects chickens aged between 3 to18 months but can affect birds of any age.

4. What are the clinical signs of MD in a live bird?

• swollen crop
• swollen skin at base of feather
• blindness
• short-term or long-term paralysis of a wing or especially a leg

Birds may show some or all of these signs depending on the severity and strain of the virus.

5. How is MD identified?

There is no readily available test to identify MD in a live bird.

Diagnosis is made by tests to investigate and exclude other causes of the clinical signs. These may include blood tests, radiographs and screening of crop and faecal samples for parasites, fungal and bacterial infections.

A post-mortem with histopathology in most cases will identify MD.

6. What is the treatment for MD?

There is no specific treatment for MD. Secondary infections need to be treated. This may involve antibiotics, anti-fungal and antiparasitic drugs. In cases of severe illness your bird will need to stay in hospital for several days while it is stabilised, and fluids and nutritional supplements administered.

7. What preventative measures can be taken?

• Prevention is generally in the form of vaccination, which is considered to provide approximately 90% protection.
• Infected chickens can pass the virus before any clinical signs are seen so health check and quarantine all new birds before adding to the flock.
• Frequent cleaning and disinfection of the areas in which the chickens are housed.

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