Mareks disease is a highly contagious viral disease of poultry characterized bt T cell Lymphomas and peripheral nerve enlargement. standard criteria used for diagnosis include history, clinical signs, gross necropsy, and histopathology. 

Transmission 

Being highly contagious mareks are readily transmitted among chickens when fully developed it may be transmitted through feather follicles from which is released into the environment. It may survive for several months in the poultry house litter or dust. infected birds remain carriers for a long time and act as a source of infections for the virus.

manifestation 

Neurological  acute infiltration  of CNS and nerves which result in paralysis of legs, wings and neck

Visceral - Cause tumours in heart, ovary, tests muscles and even lungs 

Cutaneous - tumours of feather follicles 

signs

Paralysis of legs , wings and neck

Loss of weight

Grey iris or irregular pupil

Vision impairment

the skin around feather follicles become raised and roughened

Control and treatment

Buying chicken from a licenced hatchery that vaccinates their chicks against mareks

There is no effective treatment for Marek's disease

Vaccination is the central strategy for the prevention and control of mareks disease with strict sanitation and biosecurity to reduce or delay exposure