Marek’s disease is widespread throughout the world and has viral origins. It’s caused by a highly contagious herpes virus that affects young chickens between 8 and 20 weeks old; nonetheless, there are good chances that the disease may affect adult chickens too.


Infection occurs either by direct contact with sick animals or by indirect contact such as the ingestion of infected food or water. Incubation and course of the disease is slow, it may take 40-50 days before it appears.

The mature virus is formed in the epithelium of the feather follicles, hence it is released throughout the environment. The pathogen can survive for months or years in the chickens’ bedding.


The infection can appear in different forms:

  • visceral
  • ocular
  • cutaneous
  • nervous

Nervous infection is the most classic form that usually affects young subjects: it leads to progressive paralysis of wings and legs.
The first symptom that appears in young chickens is a staggering and uncoordinated gait with a tendency to lower the wings. Afterwards, the animal takes on two classic positions which are:

  1. position to split
  2. position penguin


There is no prophylaxis for Marek’s disease and its control is based on the environmental prophylaxis: it’s essential to avoid that the chicks keep in touch with the infected areas and to try and select the most resistant genetic strains.
Vaccination is therefore the most effective prophylaxis mean against Marek’s disease, but also an hygienically correct breeding becomes fundamental, due to the resistance of the virus in the environment.
At the age of 1 day of life, therefore, it is essential, for the chicks, the vaccination (in the muscle or neck). The good breeder will make sure to buy chicks that have been vaccinated.

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