Marek's Disease

This is a viral disease, caused by a herpes virus. There are several different forms of Marek's some cause a sort of paralysis on one side. Chickens can become lame in one leg and a wing drags on the floor. The classic Marek's pose often shown in the books is for a bird to be paralysed on the floor with one leg forward and one leg back although as the virus itself changes, vets say this is becoming less common to see and often it presents itself as weak, thin adult birds that have severe weight loss. Infection in the older, vaccinated bird is also becoming more frequent.

In very rare cases, a chicken will become lame and then make a full recovery but usually, the problem becomes worse and there is nothing that can be done for a sick bird. It is usually kinder to dispatch a bird if it appears to be suffering or if has lost mobility or quality of life.

Marek's lies dormant and doesn't show up in birds most of the time. It is usually triggered by stress. A high parasite load or a change in housing, bullying, feeding or management methods can trigger the disease. Point Of Lay birds seem to be particularly vulnerable.

Preventative measures

It is possible to vaccinate against Marek's Disease when birds are young, however unless you are buying commercial vaccinated stock or are purchasing your birds from a breeder who has sufficient quantities of birds to be able to vaccinate their stock, the vials of vaccine are usually only available in 500 or 1000 bird doses which makes it impractical to vaccinate small quantities of birds. Some strains of the virus are also changing which can make successful prevention through vaccination difficult.