Ok here is the info on Mareks:
Marek’s Disease is a common, highly contagious disease of gallinaceous birds. It most commonly causes disease in chickens, but disease can occasionally occur in other species of birds such as turkeys, pheasants, quail, and even some species of ducks and geese. Infected birds often become chronic carriers, shedding the virus for long periods of time. Clinical disease usually occurs in birds less than 30 weeks of age, but can occasionally occur in older birds. The disease most frequently causes paralysis due to peripheral neuropathy and/or lymphoid cell tumors (lymphoma/lymphosarcoma). The disease is transmitted by direct contact with infected birds and through the feathers and dander from infected birds. The virus can persist in the environment for several months. Vaccines are effective when administered to embryos and very young chicks. Administration of vaccine to chicks more than a few days old is not recommended. Vaccinated birds, although protected from the clinical signs of the disease, can still carry the field strains of the virus and spread the disease to susceptible birds.
Marek’s Disease is a common, highly contagious disease of gallinaceous birds. It most commonly causes disease in chickens, but disease can occasionally occur in other species of birds such as turkeys, pheasants, quail, and even some species of ducks and geese. Infected birds often become chronic carriers, shedding the virus for long periods of time. Clinical disease usually occurs in birds less than 30 weeks of age, but can occasionally occur in older birds. The disease most frequently causes paralysis due to peripheral neuropathy and/or lymphoid cell tumors (lymphoma/lymphosarcoma). The disease is transmitted by direct contact with infected birds and through the feathers and dander from infected birds. The virus can persist in the environment for several months. Vaccines are effective when administered to embryos and very young chicks. Administration of vaccine to chicks more than a few days old is not recommended. Vaccinated birds, although protected from the clinical signs of the disease, can still carry the field strains of the virus and spread the disease to susceptible birds.
The internet is a much scarier place now than it was when I was your age. 
you lol
