Duck Viral Hepatitis (DVH)

Duck viral hepatitis (DVH) is an acute, highly contagious, often fatal disease of young ducklings (less than 4 weeks old). DVH is caused by duck hepatitis virus type 1 (DHV-1), belonging to the Picornaviridae family and Avihepatovirus genus. The onset of DVH is rapid and the virus spreads quickly through susceptible flock members. It rarely occurs in ducks over 4 weeks old. If ducklings older than 4 weeks old are infected, they have a greater chance of survival and are not as severely affected. Ducklings that recover may shed the virus in their feces for up to 8 weeks.

In Asia, DHV type 1 A (DHAV) strains are prevalent, and these are further categorized into three different serotypes, which include: the traditional serotype 1 (DHAV-1), DHAV-2 (reported in Taiwan) and DHAV-3 (a novel serotype isolated in China and South Korea). In these regions, many ducks have been reported to be co-infected with multiple serotypes, usually involving DHAV-1 and DHAV-3.

Clinical signs
Early clinical signs include weakness, depression or reluctance to move. Close to death, affected ducklings will often develop spasmodic contractions in their legs, causing them to fall to their sides and kick out, like they are paddling their legs (this clinical sign is often referred to as 'leg paddling'). Soon after this clinical sign is observed, ducklings will usually die with their head and neck drawn backwards (known as 'opisthotonos').

Transmission
DHV is transmitted to ducklings through direct and indirect oral routes, and through inhalation. Brown rats are thought to act as a reservoir host of the virus.

Incubation Period
The incubation period for DVH is 24 hours and most ducklings die within 3-4 days.