A direct immunofluorescence test for the rapid detection of avian influenza virus antigen in tissue impression smears

A direct immunofluorescent test on tissue impression smears for the simple, rapid, cheap and sensitive detection of avian influenza virus antigen is described. Cross immunofluorescence tests carried out on four avian influenza conjugates demonstrated that a conjugated anti-serum prepared against one influenza virus subtype would stain heterologous subtypes. Direct immunofluorescence on tissue impression smears from broilers infected with either avirulent or highly pathogenic avian influenza viruses was compared with virus isolation in embryonated hens' eggs, chick embryo liver and chick embryo fibroblast cell cultures. Immunofluorescence was as sensitive as virus isolation in eggs. In some cases antigen was detected by immunofluorescence where virus isolation failed due to the presence of antibody or the onset of autolysis. Virus isolation in chick embryo liver was more successful than chick embryo fibroblasts but not as sensitive as embryonated eggs.