A loop-mediated isothermal amplification method for the detection of members of the genus Ranavirus

Rapid diagnosis of largemouth bass ranavirus in fish samples using the loop-mediated isothermal amplification method

Largemouth bass ranavirus (LMBV) has been recognized as the causative pathogen responsible for infectious skin ulcerative syndrome in cultured largemouth bass in China. A fast and simple LMBV detection method is urgently needed. Here, a loop-mediated isothermal amplification (LAMP) assay was established for the detection of this virus using primers targeting the major capsid protein gene of LMBV. The amplification conditions were optimized; the assay was specific for the diagnosis of LMBV, as there was no cross-reactivity with other four Iridoviridae viruses (large yellow croaker iridovirus, Singapore grouper iridovirus, tiger frog virus, and soft-shelled turtle iridovirus), grass carp reovirus, white spot syndrome virus, or healthy largemouth bass. The sensitivity of the LAMP assay was found to be 8.55 × 10¹ copies/μL of LMBV DNA, which was 10-fold higher than that of the conventional PCR. Application of the LAMP assay was evaluated using 10 clinical samples, and the results indicated the reliability of the test as a rapid, field diagnostic tool for LMBV detection. Thus, the simplicity and nearly instrument-free LAMP method provides an alternative for rapid and sensitive detection of LMBV and has great potential for early diagnosis of LMBV infection in the farm.

Rapid and Sensitive Detection of Lymphocystis Disease Virus Genotype VII by Loop-Mediated Isothermal Amplification

Lymphocystis disease virus (LCDV) infections have been described in gilthead seabream (Sparus aurata L.) and Senegalese sole (Solea senegalensis, Kaup), two of the most important marine fish species in the Mediterranean aquaculture. In this study, a rapid, specific, and sensitive detection method for LCDV genotype VII based on loop-mediated isothermal amplification (LAMP) was developed. The LAMP assay, performed using an apparatus with real-time amplification monitoring, was able to specifically detect LCDV genotype VII from clinically positive samples in less than 12 min. In addition, the assay allowed the detection of LCDV in all asymptomatic carrier fish analysed, identified by qPCR, showing an analytical sensitivity of ten copies of viral DNA per reaction. The LCDV LAMP assay has proven to be a promising diagnostic method that can be used easily in fish farms to detect the presence and spread of this iridovirus.

Development of a rapid assay to detect the jellyfish Cyanea nozakii using a loop-mediated isothermal amplification method

Blooms of the harmful jellyfish Cyanea nozakii, which are a severe nuisance to fisheries and tourisms, frequently occur in the northern East China Sea, Yellow Sea, and Bohai Sea. To provide early warning of this species, a simple and effective molecular method for identifying C. nozakii was developed using the loop-mediated isothermal amplification method (LAMP). The LAMP assay is highly specific and uses a set of four primers that target six different regions on the mitochondrial cytochrome c oxidase subunit I (COI) gene of C. nozakii. The amplification conditions, including the dNTP and betaine concentrations, the inner primer to outer primer concentration ratio, reaction time and temperature, were optimized. The LAMP assay amplified DNA extracted from tissue samples of C. nozakii but did not amplify DNA from other common scyphozoans and hydrozoans collected in the same region. In addition, the LAMP assay was more sensitive than conventional PCR. Therefore, the established LAMP assay is a sensitive, specific, fast, and easily performed method for detection of C. nozakii at different stages in their life cycle.