Rapid and sensitive detection of PRRSV by a reverse transcription-loop-mediated isothermal amplification assay.

A real-time monitoring reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay was developed for the sensitive and specific detection of prototypic, prevalent North American porcine reproductive and respiratory syndrome virus (PRRSV) strains. As a higher sensitivity and specificity method than reverse transcription polymerase chain reaction (RT-PCR), the RT-LAMP method only used a turbidimeter, exhibited a detection limit corresponding to a 10(-4) dilution of template RNA extracted from 250 μL of 10(5) of the 50% tissue culture infective dose (TCID(50)) of PRRSV-containing cells, and no cross-reactivity was observed with other related viruses including porcine circovirus type 2, swine influenza virus, porcine rotavirus and classical swine fever virus. From forty-two field samples, 33 samples in the RT-LAMP assay was detected positive, whereas three of which were not detected by RT-PCR. Furthermore, in 33 strains of PRRSV, an identical detection rate was observed with the RT-LAMP assay to what were isolated using porcine alveolar macrophages. These findings demonstrated that the RT-LAMP assay has potential clinical applications for the detection of highly pathogenic PRRSV isolates, especially in developing countries.