Duck Hepatitis Virus

DHV-II
Order	RNA viruses
Family	Astroviridae
Genus	Astrovirus
Species	DHV-II

DHV-1 and DHV-III
Order	RNA Viruses
Family	Picornaviridae
Genus	Enterovirus
Species	Duck Hepatitis Virus I and III

Also Known As – Duck Viral Hepatitis – DVH – DH

Caused By – Duck Hepatitis Virus 1 and 3 – DHV-I – DHV-III

Introduction

Duck hepatitis is caused by the enteroviruses DHV-I and DHV-III.

It is a highly fatal disease of ducklings causing very high mortality, opisthotonus and hepatitis.

The disease is notifiable to the World Organisation for Animal Health (OIE)

Signalment

Ducks are the only species naturally affected.

DHV-I occurs only in young ducklings, usually <6 weeks of age and spreads rapidly within a flock. It is the most virulent of the three.

DHV-II is only reported in outdoor ducks on open fields.

Duck Hepatitis is not considered zoonotic.

Distribution

DHV-I is present worldwide.

DHV-II has only been reported in Norfolk, England and no outbreaks have been recorded since the 1980’s.

DHV-III has only occurred in the USA.

The rat acts as a vector for Duck Hepatitis.

Clinical Signs

Sudden deaths, Opisthotonus, Paresis, Paralysis, Enopthalmos.

DHV-I infection is most virulent. Death usually occurs within 1-2 hours of clinical signs.

Mortality rates are lower in DHV-II infections, reaching only 20%.

Diagnosis

On post-mortem examination, the liver is enlarged, appears greenish and displays distinct ecchymotic haemorrhages.

Splenic and kidney swelling may also be evident. Cutaneous haemorrhage is often noted.

On histopathology, necrosis and inflammatory infiltrate are visible within hepatic cells.

Innoculation from liver suspensions an be used for confirmation of all DHVs.

Direct immunofluorescence can also confirm presence of DHV-I.

Virus Neutralisation (VN) serological tests can be used to monitor vaccination response and epidemiology.

Treatment

No treatment is effective once infected.

Control

Vaccination is only commercially available against DHV-I. Immunisation involves two or three innoculations. Live, live attenuated and inactivated forms are available.

DHV-I can be prevented by strict isolation in the first 4-5 weeks of life.

The viruses are resistant to inactivation by heat, acid and some disinfectants. Only 5% phenol and formaldehyde are successful in inactivating the viruses.

Duck Hepatitis is a Class B disease listed by the Office des International Epizooties and thus any ducks exported require an international veterinary certificate that they are from a DVH free establishment and are not exhibiting clinical signs of DH. Vaccination status must also be disclosed.

References

Animal Health & Production Compendium, Duck Hepatitis Virus datasheet, accessed 05/06/2011 @ http://www.cabi.org/ahpc/