Submitted to: International Symposium on Avian Influenza
Publication Type: Abstract Only
Publication Acceptance Date: January 9, 2006
Publication Date: April 3, 2006
Citation: Pantin Jackwood, M.J., Swayne, D.E., Suarez, D.L. 2006. Pathogenicity of h5n1 avian influenza viruses in ducks [abstract] International Symposium on Avian Influenza. p.20. Technical Abstract: Ducks and other wild aquatic birds are the natural reservoir of influenza type A viruses which normally are nonpathogenic in these birds. However, since 2002, outbreaks of Asian H5N1viruses have resulted in mortality among waterfowl in domestic flocks, parks, and wild migratory birds. In order to assess the pathogenicity and transmission potential in ducks of these viruses, we have studied the clinical disease, gross and histologic lesions, and distribution of viral antigen in 5-week-old white Pekin ducks inoculated with either A/Vietnan/1203/04 or A/Prachinburi/6231/04. The results were compared with those obtained when young ducks were infected with these same viruses. Two out of eight 5-week-old ducks inoculated with A/Vietnam/1203/04 developed acute disease, including severe neurological dysfunction and death. This virus killed seven out of eight 2-week-old ducks. The brain, heart, and pancreas were the organs most consistently affected and viral antigen, as demonstrated by immunohistochemistry, was most often detected in the parenchyma of these organs. The second virus, A/Prachinburi/6231/04, did not produce clinical signs in any of the older ducks but did infect them. However, this virus killed three out of eight 2-week-old ducks, producing mild depression but no neurological signs. Lesions and viral replication were found primarily in the heart. Both viruses studied were excreted in large quantities from the respiratory tract. These results confirm that some of the circulating H5N1 isolates are capable of causing disease and death in ducks, however lethality is age dependent. Additional characterization of each isolate included genetic analysis of all 8 gene segments.