Development of a rapid cyprinid herpesvirus 2 detection method by loop-mediated isothermal amplification.

Cyprinid herpesvirus 2 (CyHV2) is a pathogen that causes severe disease and high mortality in goldfish and Prussian carp. We developed a six primer loop-mediated isothermal amplification (LAMP) assay targeting the intercapsomeric triplex protein gene. CyHV-2 DNA was 10-fold serially diluted (10(8)-10(0) copies μl(-1)) and was used as the template to determine primer sensitivity. LAMP assays were performed with DNA templates from other pathogens to determine specificity. The LAMP assay had an unequivocal detection limit of 10 copies μl(-1), which was 100 times lower than that of the polymerase chain reaction. Other pathogen strains were not amplified by the LAMP primers, indicating good specificity. SYBR Green I was added to visually detect the amplification products. Assay applicability was evaluated in 120 samples of Carassius auratus gibelio, and a positive rate of 92·5% was obtained. In conclusion, a conventional LAMP assay has high convenience, rapidity, sensitivity and specificity for detecting CyHV-2 in infected aquatic organisms. Significance and impact of the study: Herpesviral haematopoietic necrosis, caused by cyprinid herpesvirus 2 (CyHV-2), is a severe disease of goldfish and Prussian carp associated with high mortality. We developed a loop-mediated isothermal amplification (LAMP) assay to detect CyHV-2 at relatively low plasmid DNA copy levels. The results show that the LAMP assay has a number of advantages (simple, sensitive, rapid and specific) over the conventional polymerase chain reaction and can be applied in the laboratory and field. Particularly, the method is highly applicable to facilitate surveillance and early diagnosis of CyHV-2.