Development of a recombinase polymerase amplification assay for rapid detection of Haemophilus parasuis in tissue...

Haemophilus parasuis is the etiological agent of Glässer's disease in swine, which associates with severe economic losses in the swine industry worldwide. A real-time recombinase polymerase amplification assay (real-time RPA) was developed for direct and rapid detection of H. parasuis basing on the translation-initiation factor IF2 (infB) gene. The assay was performed successfully at 39°C for 20 min in Genie III, which is portable and chargeable by battery. The developed assay was highly specific for H. parasuis, and the limit of detection of the assay was 6.0 × 10³  fg of H. parasuis genomic DNA, which was the same as that of a real-time PCR developed previously. The assay was further evaluated on 68 pig tissue samples, and 18 (26.5%), 20 (29.4%), and 8 (11.8%) samples were positive for H. parasuis by the real-time RPA, real-time PCR and bacterial isolation, respectively. With the bacteria isolation as the reference method, the real-time RPA showed a diagnostic specificity of 83.33% and a diagnostic sensitivity of 100%. The above data demonstrated the well-potentiality and usefulness of the developed real-time RPA assay in reliable diagnosis of swine Glässer's disease, especially in resource limited settings.