Avian immunosuppressive diseases are conditions that weaken the immune system of birds, making them more susceptible to infections and diseases. Common causes include viral infections, such as Avian Leukosis Virus and Marek's Disease Virus, which can lead to significant health issues in poultry and wild birds. These diseases can result in poor growth, increased mortality, and reduced egg production in affected birds. Early detection and management are crucial to minimize the impact on bird populations and ensure their overall health and productivity. Vaccination and biosecurity measures are often employed to prevent the spread of these diseases.