Development of a reverse transcription loop-mediated isothermal amplification assay for H7N7 equine influenza virus.

We have developed a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay for detecting H7N7 equine influenza virus (EIV). The detection limit of the RT-LAMP assay was a virus dilution of 10(-4), which was 10 times more sensitive than that of Espline Influenza A&B-N and the same as that of reverse transcription polymerase chain reaction. The RT-LAMP assay specifically amplified H7N7 EIV strains but did not amplify several pathogens related to equine respiratory disease including H3N8 EIV strains. Because it provides ease of manipulation, the RT-LAMP assay is suitable for large-scale surveillance for H7N7 EIV. In addition, the combination of the H3N8 RT-LAMP assay, which was developed previously, with the H7N7 RT-LAMP assay should be useful to discriminate between H3N8 and H7N7 EIVs in clinical laboratories.