Avian Leukosis is a viral disease that affects birds, particularly poultry like chickens. It is caused by the Avian Leukosis Virus (ALV), which can lead to tumors and other health issues in infected birds. The virus is primarily spread through direct contact or contaminated environments, making it a concern for poultry farmers. Symptoms of Avian Leukosis can include weight loss, lethargy, and swelling in various body parts. Infected birds may also show signs of respiratory distress or have difficulty laying eggs. Prevention strategies include good biosecurity practices and vaccination against the virus to protect flocks.