Age at infection affects the pathogenicity of Asian highly pathogenic avian influenza H5N1 viruses in ducks

[Sally Furniss]

Age at infection affects the pathogenicity of Asian highly pathogenic avian influenza H5N1 viruses in ducks

M.J. Pantin-Jackwood^,^a^,^,, D.L. Suarez^a, E. Spackman^a and D.E. Swayne^a
^aSoutheast Poultry Research Laboratory, Agricultural Research Service, U.S. Department of Agriculture, 934 College Station Road, Athens, GA 30605, United States
Received 22 February 2007; revised 24 May 2007; accepted 11 June 2007. Available online 20 July 2007.


Abstract

The Asian highly pathogenic avian influenza (HPAI) H5N1 viruses have changed from producing no disease or mild respiratory infections in ducks to some strains causing systemic disease and death. Differences in pathogenicity between four of these viruses as well as the effect of host age on the outcome of infection were studied in ducks. Three of the viruses were highly lethal in 2-week-old ducks and induced severe neurological dysfunction. Neurological signs were also observed in 5-week-old ducks inoculated with one of these viruses; however mortality was low. The fourth virus studied did not induce neurological signs in 2-week-old ducks, but did produce moderate mortality. This virus caused no clinical signs or death in 5-week-old ducks. All viruses studied were isolated from oropharyngeal and cloacal swabs, and also from brain, heart, lung and muscle tissues, demonstrating systemic infection. All viruses evaluated transmitted efficiently to contact ducks. Phylogenetic analysis of the viruses studied and other Asian H5N1 HPAI viruses with diverse pathogenicity in ducks, showed changes in several genes, but none clearly associated with pathogenicity. In conclusion, the pathogenicity of circulating H5N1 HPAI viruses in ducks varies depending on the virus strain and the age of the duck and correlates with the level of viral replication in tissues. High titers of virus in organs, high viral shedding, and variable mortality enable ducks to circulate H5N1 HPAI viruses.

http://www.sciencedirect.com/scienc...serid=10&md5=6d1f8bff55cdc51116e89454888471a9

 

[Coleman]

Re: Age at infection affects the pathogenicity of Asian highly pathogenic avian influenza H5N1 viruses in ducks

Why did they take 2 and 5 week old ducklings?
That represents just the age of mast birds (they get slaughtered with 50 till 80 days - muscovy ducks get more time), but not of wild birds, which fly far distances.