There have recently been a few cases (confirmed and suspected) of Marek’s disease. The infected chickens have came from WI, and were in McHenry County and Evanston. One flock was made up of Orloffs.
Marek’s is very contagious and will affect an entire flock. There are neurological, ocular, and visceral forms of Marek’s. Symptoms of the neurological form of Marek’s include split-leg posture (one back, one forward, twisted neck, wings drooping). For more info on Marek’s: http://www.merckmanuals.com/vet/poultry/neoplasms/mareks_disease_in_poultry.html. Here, too, is a good post that includes lots of FAQs.
The virus is shed in feather dander and can be transmitted by humans from flock to flock. If you have a Marek’s bird, it’s best to destroy it, if not your whole flock. You should not get new birds until the old ones are gone, and the virus may remain in the environment. There is no cure for Marek’s.
Just a reminder:
— Always get birds from a reputable source.
— Buy only birds that look healthy.
— Quarantine the new birds for a few weeks to be sure they are healthy (however, they may be carriers of a disease without showing symptoms).
If you have a suspected Marek’s death, it would be good to get a necropsy and pathology report from a certified avian vet to protect your flock and others’ birds. Also, please let the chicken-keeping community know and notify the sources of your birds, as well as chicken owners who have visited your coop recently.