The First Finding of Tiger Influenza by Virus Isolation and Specific Gene Amplification

An influenza virus-like virus isolate was obtained from the specimen of a tiger died of high fever,anorexia,and twitch.This virus was confirmed to be influenza virus by characteristics of its morphology,physiochemistry,biology and serology.Further analysis was performed by amplification of the specific nucleic acid of influenza virus nucleoprotein gene.A 464 bp cDNA fragment,being amplified from both the virus cell culture and the suspension of specimens,was compared with the published sequences of influenza virus type A,B,C with the homology of 84.9%,35.0%,24.8%,respectively,indicating that the virus is an influenza virus type A isolate.This virus has been designated as A/tiger/Harbin/01/2002.Three 3-month-old domestic cats were infected with the virus by intravenous inoculation.One of the infected cats survived the infection and the other two were seriously sick and eventually died of the infection.The ill cats presented similar clinical signs and pathological changes,characterized by pneumonia,to that of tigers.The inoculated virus could be reisolated from the lung.Specific antibodies against the virus were measured by hemaglutination inhibition test.The antibody titers of survived tigers and cats were over 4 times higher than that of the sick and uninfected ones,respectively,demonstrating that the virus is pathogenic and sometimes even fatal for tigers and cats.This is the first report that influenza virus types A exists in tigers.