Bacterial and parasitic diseases of Anseriformes.

Several bacterial diseases are known to be major mortality factors of waterfowl (ducks, geese, and swans of the family Anatidae). Parasitic diseases of waterfowl are quite common but generally are not major mortality factors. However, parasites, if present during other disease outbreaks, can contribute to mortality. From a disease standpoint, the tendency of waterfowl to aggregate in large numbers during postbreeding molt, fall migration, and winter and spring migration can lead to the ready transfer of disease-causing organisms and can lead to high mortality from certain bacterial diseases.