i have some things that might help!
https://www.knowyourchickens.com/mareks-disease-in-chickens/
https://www.thehappychickencoop.com/mareks-disease/
https://www.backyardchickens.com/articles/the-great-big-giant-mareks-disease-faq.66077/
https://extension.psu.edu/mareks-disease-in-chickens...