Selecting any thumbnail image will display a full-sized version of the graphic. Avian botulism, or Western duck sickness, is one of the three most important disease problems of wild migratory birds. Each year, many birds are paralyzed or die after exposure to a toxin produced by the botulinum bacterium.
Losses vary from year to year and from species to species.
A few hundred birds may die one year at a specific location, with tens of thousands dying the following year at the same site. More than a million deaths from avian botulism have been reported in localized outbreaks in a single year. Outbreaks causing losses of 50,000 or more birds are fairly common. A Montana marsh experiences an outbreak of type C avian botulism. Avian botulism has been reported from every continent except Antarctica.