Submitted to: United States Animal Health Association Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: November 22, 2005
Publication Date: September 15, 2006
Citation: Pantin-Jackwood, M.J. 2006. Pathogenicity of avian influenza in ducks. In: Proceedings of the 109th Annual Meeting of the United States Animal Health Association, Hershey, Pennsylvania. p. 653-654. Technical Abstract: Ducks and other wild aquatic birds are the natural reservoir of influenza type A viruses, which usually are nonpathogenic in these birds. However, since late 2002, H5N1 outbreaks in Asia, and recently in Mongolia, Russia, Kazakhstan, the Urals, Romania, and Croatia, have resulted in mortality among waterfowl in recreational parks, domestic flocks, and wild migratory birds. We studied the pathogenicity and transmission potential in ducks of these new viruses by inoculating 2-week-old and 5-week-old white Pekin ducks with one of four Asian origin H5N1 highly pathogenic AI viruses. Young ducks inoculated with A/Vietnam/1203/04, A/Crow/Thailand/04 and A/Egret/HK/757.2/02 developed acute disease, including severe neurological dysfunction and death. These viruses killed 7 out of 8 two-week-old ducks but only 2 out of 8 of the five-week-old ducks. The brain, heart, pancreas, skeletal muscle, and adrenal glands were the most consistently affected organs and viral antigen was most often detected in the parenchyma of these organs. A fourth virus, A/Prachinburi/6231/04, killed 3 out of 8 two-week-old ducks, producing mild depression but not inducing neurological signs. In older ducks, this virus did not produce clinical signs but did affect weight gain. All four viruses studied were excreted in large quantities from respiratory, and to lesser extent, intestinal tracts. These results confirm that some of the circulating H5N1 isolates are capable of causing disease in ducks, with three of the four isolates studied inducing severe neurological signs and death, mainly in young birds. Subclinical infection or mild disease in adult ducks would not preclude the potential for carrying these viruses over long distances. This, and the increase of virus excretion found with these viruses, may suggest a more significant role of waterfowl in spreading these highly pathogenic AI viruses.