Rapid detection of a fish iridovirus using loop-mediated isothermal amplification (LAMP)

A loop-mediated isothermal amplification (LAMP) procedure is described to detect the genomic DNA molecule of red seabream iridovirus (RSIV), a fish iridovirus belonging to the Iridoviridae family. The RSIV DNA was amplified using DNA extracts obtained from spleen of infected red seabream, Pagrus major and from various RSIV isolates. The method was at least 10 times more sensitive than conventional PCR in detecting for the presence of RSIV. A striking feature of the LAMP reaction is its ability to synthesize a large amount of DNA leading to the production of a white precipitate, magnesium pyrophosphate, as a by-product. The presence or absence of this white precipitate facilitates easy detection of the RSIV genomic DNA without the use of gel electrophoresis. A strong correlation exists between the amount of input viral DNA copy and the corresponding turbidity reading at the end of the reaction; hence, the LAMP reaction may be used potentially to quantify RSIV particles in the infected fish.