Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 2001
Publication Date: November 12, 2001
Technical Abstract: The normal host reservoir for type A influenza viruses are in wild waterfowl and shorebirds, but the virus frequently crosses species and has become endemic in several mammalian and poultry populations. The virus is thought to be asymptomatic in its natural host, but it often causes disease, sometimes severe, in other host species. For chickens and turkeys, a highly virulent form of the virus, highly pathogenic avian influenza, has been described on numerous occasions. In all these outbreaks, multiple basic amino acids are present at the hemagglutinin cleavage site that allows the virus to replicate systemically. Occasionally the presence of basic amino acids at the cleavage are not enough for a virus to be highly pathogenic, and a second factor of a loss of a glycosylation site at the cleavage site is also required. In serial chicken inoculations with the CK/PA/13609/93 virus, which has three basic amino acids at the cleavage site and is usually considered to be a low pathogenic virus, the virulence was increased to an intermediate pathogenic and a highly pathogenic form of the virus. The highly pathogenic virus had an additional glycosylation site near the receptor binding site that is thought to be critical in the virus becoming highly pathogenic. This represents a new way for a virus to become highly pathogenic, and the proposed mechanism will be presented.