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Title: Different routes of inoculation impact infectivity and pathogenesis of H5N1 high pathogenicity avian influenza virus infection in chickens and domestic ducks

Author
item KWON, YON-KUK - Foreign Agricultural Service (FAS, USDA)
item Swayne, David

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/3/2010
Publication Date: 9/3/2010
Citation: Kwon, Y., Swayne, D.E. 2010. Different routes of inoculation impact infectivity and pathogenesis of H5N1 high pathogenicity avian influenza virus infection in chickens and domestic ducks. Avian Diseases. 54:1260-1269.

Interpretive Summary: H5N1 high pathogenicity avian influenza (HPAI) viruses are believed to produce infection in poultry by being breathed into the respiratory tract. The objective of this study was to determine if H5N1 HPAI viruses can infect poultry by digestive and if so, by which mechanism this can occur. Both chickens and ducks were more susceptible to the H5N1 HPAI virus when exposed in the nose as compared to exposure to digestive tract. The upper alimentary was initial site affected upon consumption of infected meat or placement in stomach directly. However, digestive tract infection does require more virus to produce infection than respiratory tract exposure. These data suggest that respiratory exposure to H5N1 HPAI virus in birds is more likely to result in virus transmission than consumption of infected meat unless the latter contain high doses of virus such as in cannibalized infected carcasses.

Technical Abstract: The H5N1 type A influenza viruses classified as Qinghai-like virus (clade 2.2) are a unique lineage of type A influenza viruses with the capacity to produce significant disease and mortality in gallinaceous birds and water fowl including ducks. The objective of this study was to determine the susceptibility and pathogenesis of chickens and domestic ducks to A/Whooper Swan/224/05 (H5N1) highly pathogenic avian influenza (HPAI) virus when administered through respiratory or alimentary routes of exposure. The chickens and ducks were more susceptible to the H5N1 HPAI virus, as evidenced by low infectious and lethal viral doses, when exposed by intranasal as compared to alimentary routes of inoculation (intragastric or oral fed). In the alimentary exposure pathogenesis study, pathological changes included hemorrhage, necrosis and inflammation in association with virus detection were generally observed in most visceral organs of chickens between 2 and 4 DPI, which is similar to lesions and virus localization in birds exposed by natural or experimental intranasal routes. Similarly, the virus caused systemic infection in the ducks characterized by moderate lymphocytic encephalitis, necrotized hepatitis and pancreatitis with corresponded demonstration of virus. However, with alimentary exposure, lesions and/or virus was first demonstrated in upper alimentary tract on 1 DPI suggesting alimentary tract was initial site affected upon consumption of infected meat or gavage of virus in liquid medium. Alimentary infection does require higher exposure doses to produce infection when compared to intranasal exposure in chickens. These data suggest that respiratory exposure to H5N1 HPAI virus in birds is more likely to result in virus transmission than consumption of infected meat unless the latter contain high doses of virus such as in cannibalized infected carcasses.