DNA detection of Paragonimus westermani: Diagnostic validity of a new assay based on loop-mediated isothermal amplification (LAMP) combined with a lateral flow dipstick.

Paragonimus westermani (P. westermani) is widely spread in Asian countries and is one of the most important causative agents for lung fluke diseases. The prevention and control of Paragonimiaisis mainly depends on the accurate diagnosis and effective treatment. In this study, we developed a loop-mediated isothermal amplification (LAMP) assay targeted to a portion of the Ty3/gypsy-like LTR retrotransposon (Rn1) sequence coupled with a lateral flow dipstick (LFD) for the rapid detection of P. westermani-specific amplicons. The positive LAMP products were biotin-labeled and hybridized with a fluorescein isothiocyanate-labeled probe which could be visually detected by LFD. No cross-reaction were observed with other parasitic pathogens including Trichinella spiralis, Anisakis simplex, Schistosoma japonicum and Gnathostoma spinigerum, but this LAMP assay could not distinguish P. westermani with Paragonimus skrjabini and Paragonimus heterotremus. The detection limit of the LAMP assay for P. westermani was 2.7 fg/µL, while that of PCR method was 27 fg/µL. LAMP method was applied to detect P. westermani genomic DNA in blood samples form experimental infected dogs, and results showed the parasite was detectable as early as week 2. LAMP-LFD assay applicability was successfully tested in dog blood samples collected from five cities (Wenzhou, Hangzhou, Huzhou, Jiaxing and Shaoxing) in Zhejiang province. In summary, the established LAMP-LFD assay targeted to the Rn1 sequence is a rapid and convenient method for specific detection of P. westermani.