[Prevalence of Paragonimus infection and molecular characterization of Paragonimus in freshwater crabs from selected areas of Yunnan Province].

Authors

J Zhang, Y Xiang, Y Zeng, X Lu, D Hu, M Yang, X Mei, Y Chen

Published in

Zhongguo xue xi chong bing fang zhi za zhi = Chinese journal of schistosomiasis control. Volume 38. Issue 4. Pages 399-406. Aug 11, 2026.

Abstract

To investigate the prevalence of Paragonimus infection in freshwater crabs from selected areas of Yunnan Province, and to perform molecular characterization and phylogenetic analysis of the isolated parasites based on the internal transcribed spacer 2 (ITS2) and cytochrome c oxidase subunit I (COI) gene sequences.
Freshwater crabs were collected from both local markets and natural streams in Zhaotong City, Pu'er City, Dehong Dai and Jingpo Autonomous Prefecture, Baoshan City, Honghe Hani and Yi Autonomous Prefecture and Lincang City of Yunnan Province from May to August 2025. Paragonimus metacercariae were isolated using a sieve and sedimentation method. After morphological identification of the metacercariae, the infection rate and infection intensity of Paragonimus in freshwater crabs were calculated. Then genomic DNA was extracted from an individual metacercaria, and ITS2 and COI gene fragments were amplified using a PCR assay and sequenced. The obtained sequences were aligned with those available in the GenBank database. Genetic distances were calculated with the software MEGA 11.0 based on the Kimura 2-parameter model, and phylogenetic trees were built using the neighbour-joining method.
A total of 600 freshwater crabs were collected, with 18 positive for Paragonimus metacercariae. The prevalence of Paragonimus infection was 12.00% (18/150) in freshwater crabs from Zhaotong City, while no Paragonimus infection was detected in crabs from other five prefectures (cities). Twenty metacercariae were recovered, with an overall infection intensity of 1.11 metacercariae per crab. Morphological observation revealed two types of Paragonimus metacercariae, including 19 resembling P. skrjabini, and 1 resembling P. paishuihoensis. Ten metacercariae of distinct morphotypes were randomly selected for molecular identification, and sequence alignment and phylogenetic analysis of ITS2 and COI genes identified 9 as P. skrjabini and 1 as P. paishuihoensis. The nine ITS2 gene sequences shared 98.34% to 100.00% homology with the reference sequence of P. skrjabini (GenBank accession number: KX129924.1), and the single ITS2 gene sequence showed 100.00% homology with the reference sequence of P. paishuihoensis (GenBank accession number: OM401939.1), while its COI sequence showed 98.80% homology with the reference sequence of P. paishuihoensis (GenBank accession number: AB679288.1). Phylogenetic analysis further confirmed that the 10 sequences were clustered separately into the clades of P. skrjabini and P. paishuihoensis.
This study reports the first detection of P. paishuihoensis in freshwater crabs from Zhaotong City, Yunnan Province, and confirms P. skrjabini as the dominant Paragonimus species in this region. Molecular identification and phylogenetic analysis based on ITS2 and COI genes are effective to distinguish Paragonimus species, which provides the scientific evidence for precise control of paragonimiasis in Yunan Province.

PMID:
42779241
Bibliographic data and abstract were imported from PubMed on 24 Sep 2026.

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