Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/30/2002
Publication Date: 8/1/2002
Interpretive Summary: The purpose of this study was to determine and compare the susceptibility of laughing gulls to infection with the Hong Kong H5N1 bird flu virus, which caused illness and death in both chickens and humans during 1997, and a H5N3 bird flu virus that caused illness and death in both chickens and terns. In this study, neither virus caused illness or death in gulls. However, the latter H5N3 virus demonstrated a slightly greater ability to infect gulls as compared with the H5N1 Hong Kong virus. This suggests that the 1997 Hong Kong H5N1 viruses were not transmitted by gulls to poultry or humans.
Technical Abstract: Juvenile laughing gulls (Larus atricilla) were intranasally inoculated with either the A/tern/South Africa/61 (H5N3) (tern/SA) influenza virus or the A/chicken/Hong Kong/220/97 (H5N1) (chicken/HK) influenza virus, both of which are highly pathogenic viruses for chickens. Gulls inoculated with either virus did not demonstrate clinical disease or mortality within 14 days of inoculation. Gross lesions were minimal to mild, with only the ai sac (chicken/HK) or air sac and pancreas (tern/SA) containing lesions. Histological lesions in the tern/SA-inoculated gulls included mild to moderate air sacculitis and interstitial pneumonia and moderate necrotizing pancreatitis and hepatitis, with viral antigen being demonstrated only in the liver and pancreas. In contrast, viral antigen was not demonstrated in any tissues from the chicken/HK-inoculated gulls, and mild inflammatory lesions were confined to the air sac and lungs of a minority of gulls. Both viruses were reisolated at low titers from oropharyngeal and cloacal swabs up to 7 DPI. The tern/SA virus was reisolated from the lung and kidney of one gull at 14 DPI, and the chicken/HK virus was reisolated from the lung of one gull at 7 DPI. Only the two tern/SA-inoculated gulls sampled at 14 DPI had antibodies against AI viruses. The result of this investigation support the principle that influenza A virus infections in pelagic birds are largely asymptomatic but may not be entirely innocuous.