Crayfish Plague is a disease caused by the pathogen Aphanomyces astaci, which primarily affects freshwater crayfish. This disease is particularly harmful to native crayfish species, such as the European crayfish, leading to significant population declines. Infected crayfish often show symptoms like lethargy, loss of appetite, and a characteristic discoloration of their shells. The spread of Crayfish Plague is often linked to the introduction of non-native crayfish species, such as the North American signal crayfish, which can carry the disease without showing symptoms. Efforts to manage and control the spread of this disease are crucial for the conservation of native crayfish populations and aquatic ecosystems.