The use of FTA® filter papers for diagnosis of avian influenza virus

Avian influenza viruses (AIVs) infect a wide range of host species including domestic poultry and wild birds; also, AIVs may infect humans in whom some highly pathogenic viruses (HPAIV) may cause acute fatal disease. Accurate laboratory diagnosis of AIV infections requires time-consuming and logistically complex precautionary measures for shipment of specimens or viruses to avoid biohazard exposure. The feasibility was investigated of the Flinders Technology Associates filter paper (FTA® card) for infectivity of AIVs and to preserve viral RNA for detection by RT-qPCR, sequencing and by DNA microarray assay. The infectivity of AIV subtype H6N2 and HPAIV subtype H5N1 was inactivated completely within one hour after adsorption to the FTA card at room temperature. FTA-adsorbed viral RNA remained stable for five months. Swab samples obtained from chickens infected experimentally with H5N1 virus and spotted directly onto the FTA® cards allowed a sensitive and straightforward diagnosis by RT-qPCR. FTA® cards were also suitable for examination of field samples, although AIV RNA was detected with reduced sensitivity in comparison to direct examination of swab fluids. The use of FTA® cards will facilitate safe transport of samples for molecular diagnosis of AIV avoiding the need for an uninterrupted cold storage.