Abstract
PurposeTo perform environmental sampling and molecular identification of Paragonimus in endemic regions, which may help in minimizing transmission among humans.MethodsMountain crabs from the genus Potamiscus were collected and the encysted metacercariae were extracted and subjected to morphological identification, followed by animal inoculation in Sprague–Dawley (SD) rats. After 112 days of infection, animals were killed and adult worms were extracted from lungs and muscles. The morphology of adult worms was characterized by microscopy and molecular identification was done by polymerase chain reaction, followed by sequencing of cox1 and ITS2 genes. Phylogenetic analysis was done by maximum parsimony method.ResultsA total of 447 crabs were captured from the streams of Tongchang Town, Jinping County, Yunnan Province, China. The infection rate was found to be 41% (186 out of 447 crabs). The metacercariae of Paragonimus skrjabini was identified by the characteristics round or spherical encysted form measuring 410 to 460 × 400 to 460 µm. After animal infection in SD rats, adults were presumptively confirmed to be P. skrjabini, which was also confirmed by gene amplification and sequence analysis of cox1 and ITS2 regions. Paragonimus skrjabini clustered with previously reported P. skrjabini from Yunnan and Vietnam. The confidence values of their branches were > 95%. Phylogenetic analysis of the ITS2 region revealed two distinct clusters with distinct geographical grouping. Phylogenetic analysis with the combined data sets reiterated the geographical grouping with P. skrjabini from Yunnan clustering with strains from Vietnam.ConclusionMetacercariae of P. skrjabini was discovered in freshwater crabs in Yunnan province, China, and the strains were phylogenetically related to P. skrjabini from Vietnam.
Highlights
Paragonimiasis is an important food-borne zoonosis, especially in Asian countries
The oral and ventral suckers were 80–120 μm and 120–60 μm, in diameter, respectively. These features roughly correlated with P. skrjabini and the metacercariae were subjected to animal inoculation
The other characteristic features observed were in the left (660 to 2000 × 320 to 1120) and right testis (1600 to 1650 μm × 885 to 1175 μm) and an ovary (1575 to 1800 μm × 1325 to 1500 μm). Based on these morphologic features, worms that were presumptively identified as P. skrjabini were subjected to molecular identification
Summary
Paragonimiasis is an important food-borne zoonosis, especially in Asian countries. This parasitic infection manifests as acute or chronic lung infection caused by the trematodes of the genus Paragonimus. The genus Paragonimus consists of varied species such as Paragonimus skrjabini complex and the Paragonimus ohirai complex, overlapping the geographical ranges of the Paragonimus westermani complex [1]. The morphological features of large metacercariae found for the first time in Vietnam resembled that of Paragonimus skrjabini [2]. In Asia, P. skrjabini is an important pathogen, along with P. westermani, causing infections in humans throughout Asia. Among the different species complexes, P. skrjabini has been previously reported mainly in East Asia and China [3].
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