Reticuloendotheliosis is a mouthful of a medical term that refers to a rare viral disease that affects chickens. Some possible synonyms for this condition include avian leucosis, chicken lymphoma, Marek's disease, and lymphoproliferative disease. While these terms may be easier to pronounce, they all refer to the same serious health issue that can cause weight loss, paralysis, and even death in birds. Reticuloendotheliosis can be difficult to diagnose and treat, so it's important for poultry farmers and veterinarians to be aware of this disease and take preventative measures to minimize its impact.