MAREK’S DISEASE: 6 SYMPTOMS
THE CLINICAL SIGNS OF MAREK’S during an acute outbreak will be signs of depression, with birds standing around looking ‘off colour’. This could be followed by lame or paralysed birds. Mortality may occur with no symptoms at all or there may be paleness, loss of appetite, diarrhoea and dehydration, gasping, or blindness. Note: many of these are also symptoms of other diseases.
SPECIFIC SYMPTOMS OF MAREK’S INCLUDES:
• Immune suppression and susceptibility to diseases like coccidiosis and blackhead. • Paralysis, notably where a bird will have one leg forward and one leg back, but it may also drag one leg or wing as if it is broken. This may occur between 6-12 weeks old but it’s also seen up until sexual maturity (20-25 weeks). • The nerves to the brain and neck may cause the head to bend under or twist to one side. The virus affects the major nerves to the legs or wings and the bird is unable to flex the muscles. • A condition previously known as range or transient paralysis may also be due to the Marek’s virus. • When the optic nerve is involved the iris may appear to be grey and the pupil becomes distorted and/ or blindness is apparent. This can develop much later in life, especially if the bird has been under stress. • The visceral form which causes tumours, notably the ovary, liver, kidneys or lungs is most usually seen in weeks 10-15. Tumours present in young birds suggest Marek’s disease but in older mature birds are more likely to be caused by another disease called lymphoid leucosis. Tumours on the skin which may appear as bleeding feather follicles that won’t heal may occur in young birds as well.