Development of a loop-mediated isothermal amplification with lateral flow dipstick (LAMP-LFD) assay for the detection of Dactylogyrus monogeneans in goldfish (Carassius auratus)

The monogenetic trematode, genus Dactylogyrus, is an important group of ectoparasites that causes disease in fish, which can result in economic losses, particularly in the ornamental fish market. Dactylogyrus monogeneans attach to the host's gills, causing respiratory disorders and potentially leading to fish morbidity and mortality. In this study, we developed a detection method for Dactylogyrus spp. infection in goldfish (Carassius auratus) using a loop-mediated isothermal amplification (LAMP) assay coupled with a lateral flow dipstick (LFD). The LAMP-LFD assay, which targets the 28S rDNA gene, could be completed in 75 min (60 min for LAMP and 15 min for LFD) under isothermal conditions at 65 °C. It showed high specificity with no cross-amplification with related parasites or the definitive host's DNA. The sensitivity of the LAMP-LFD assay was 3 pg/µL for the 3 identified Dactylogyrus species: D. vastator, D. formosus, and D. baueri. Clinical sample examination (n = 30) showed that the LAMP-LFD results were consistent with those of microscopy, indicating 100% agreement in this sample set. In summary, the LAMP-LFD assay we developed could be used as a rapid and convenient method for detecting Dactylogyrus spp. in goldfish. This could further aid parasite detection, support outbreak surveillance, and reduce veterinary health issues in ornamental fish aquaculture.