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.

Paragonimiasis in Yongjia County, Zhejiang Province, China: clinical, parasitological and karyotypic studies on Paragonimus westermani.

Paragonimiasis in Yongjia County, Zhejiang Province, China, has been of such public health concern that a specialized Institute for Paragonimiasis Control has been established there. The study reported here involved both parasitological research on Paragonimus westermani in the endemic areas and a clinical analysis of 94 cases of paragonimiasis. Eggs were found in sputum, feces and brain tissue in 45 cases. Twenty patients, 19 of whom where children under 10 years of age, showed hepatic injury. Treatment with praziquantel or bithionol had satisfactory results in all cases. Dimensions of the parasite eggs, metacercariae from freshwater crabs and adult flukes suggested that the form of P. westermani in Yongjia is the 'small type': a suggestion supported by karyotypic studies on gonad cells from adult flukes collected from experimentally infected animals as all were found to be diploid. In conclusion, the 'small type' or diploid form of P. westermani is the cause of paragonimiasis pulmonary symptoms in Yongjia.

Evolutionary relationships between trematodes and snails emphasizing schistosomes and paragonimids.

Snails and digeneans have been associated for at least 200 million years. Their inter-relationships over such a time-span must have been complex and varied. Few studies have attempted to explore these relationships in the light of knowledge of the phylogeny of both host and parasite groups. Here we focus on two important families of digeneans, the Schistosomatidae and the Paragonimidae, for which molecular phylogenies are available. We investigate the types of evolutionary relationships between host and parasite, operating at different phylogenetic depths, that might explain current host specificity and distributions of both associates. Both families of parasites utilise a number of highly diverged gastropod families, indicating that host extensions have featured in their histories. However, schistosomatids and paragonimids show different patterns of association with their snail hosts. As befits the apparently more ancient group, schistosomatids utilise snails from across a wide phylogenetic range within the Gastropoda. The genus Schistosoma itself has experienced one long-range host switch between pulmonates and caenogastropods. By contrast, paragonimids are restricted to two superfamilies of caenogastropods. Despite these differences, modern schistosomatid species appear to be more host specific than are paragonimids and host additions, at the level of host family, are far less common among species of schistosomatids than among paragonimids. Some species of Paragonimus exhibit remarkably low levels of host specificity, with different populations utilising snails of different families. Existing knowledge relating to the phenomenon will be presented in the context of phylogenies of schistosomatids, paragonimids, and their snail hosts. Discussion focuses on the usefulness of current theories of snail-digenean coevolution for interpreting these findings. In the past, much emphasis has been placed on the idea that digeneans engage in a one-to-one arms race with their snail host. We consider that phylogenetic tracking rather than an arms-race relationship might be a common alternative. Not being bound by the restrictions imposed by an arms race, some digeneans might be able to extend to new host species more easily than the literature suggests. Switches into related host taxa are most likely. However, ecologically equivalent but unrelated gastropod hosts may also be exploited. Given the right ecological setting, digeneans are able to switch across considerable phylogenetic distances. Examples from the Paragonimidae and Schistosomatidae are given.