Duck viral hepatitis (type I) is caused by an avihepatovirus of the family Picornaviridae (duck hepatitis virus, DHV-1). It is a highly contagious disease of domestic ducks that causes mass mortality. Muscovy ducks and mallards can also be affected. Rats are the reservoir for the virus.
Clinical signs include listlessness, weakness, ducklings lying on their breast or side, uncoordinated limb movements called swimming movements, opisthotonus, followed by rapid death. Adult ducks are asymptomatic.