The Marek Effect

Marek’s disease is caused by an alphaherpesvirus that infects poultry. Birds shed the virus (MDV) from the skin cells of their feather follicles, and other birds contract it by inhaling these cells. MDV can remain viable in poultry-farm dust for very long periods of time. It attacks the chicken’s memory T-cells, which go on to form visceral tumours and infiltrate nerves in the wings and legs, causing paralysis.

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