The
Picornavirus
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Child level |
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Same level |
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Genera |
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Duck Virus Hepatitis. Duck virus hepatitis (DVH) is a highly fatal contagious disease of young ducklings, 1-28 days of age. Ducklings are most susceptible at the younger ages and gradually become more resistant as they grow older. The disease is rarely seen in ducklings over 4 weeks of age. The onset of the disease is very rapid, it spreads quickly through the flock and may cause up to 90% mortality. Sick ducklings develop spasmodic contractions of their legs and die within an hour in a typical "arched-backward" position. The liver is enlarged and shows hemorrhagic spots. To prevent this disease, keep age groups isolated and vaccinate breeder ducks with an attenuated live virus duck hepatitis vaccine (to produce maternally immune ducklings). |
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Nature of the disease |
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DVH is caused by three different viruses. The most severe and widely distributed virus, duck hepatitis A virus (DHAV) 1 (formerly called DHV-1), belongs to the Picornaviridae, and causes disease in ducklings before 6 weeks old. The other two viruses are duck astrovirus (formerly known as DHV-2), which causes disease in ducklings between 6 and 10 weeks old and DHV-3 caused by another virus unrelated to DHV-1 and DHV-2 which causes milder disease. |
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Classification |
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DVH is an OIE notifiable disease. |
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Susceptible species |
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Ducks and geese (young animals). |
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Distribution |
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DHAV (formerly DHV-1) is present in Northern America, Europe and Asia, DHV-2 has only been found in the United Kingdom and DHV-3 has only been found in the United States of America. |
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Clinical signs |
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DHV-1 causes the most severe disease. The incubation period lasts 1 to 2 days and clinical signs include lethargy, anorexia and sudden death with opisthotonos within a few days. Morbidity is often 100% and mortality reaches 80%. Disease is less severe in ducks older than 7 weeks. |
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Post-mortem findings |
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The liver is enlarged with haemorrhagic lesions (petechia, ecchymosis) and decolouration. The spleen and kidneys can be augmented. |
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Differential diagnosis |
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Specimens required for diagnosis |
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Liver specimen can be collected at post mortem for virus identification. Serological test is possible using serum neutralisation, however due to the short course of the disease serological test is not used for diagnosis on live animals. |
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Transmission |
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The disease is very contagious and the virus excreted by faeces is transmitted by direct contact between birds or through fomites such as brooders, water, feed, equipment. Recovered animals can shed the virus for up to 8 weeks. |
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Risk of introduction |
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DHV could be introduced by the importation of live ducks from an infected country. Introduction by duck meat or duck product is possible but at low risk according to the instability of the agents. Rats have been described as a reservoir and control of this pest on arrival should be systematic. |
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Control / vaccines |
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If accidentally introduced, strict isolation and control of rats are necessary measures to control DHV. Vaccination against DHAV-1 and DHV-3 is possible using live attenuated vaccines. A killed vaccine is also available against DHAV-1. |
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References |
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