Investigation on freshwater crab populations and Paragonimus infections in the Minjiang River basin along the middle section of Wuyi Mountain / 中国血吸虫病防治杂志

ABSTRACT

Objective To investigate the populations of freshwater crabs, the intermediate host of Paragonimus and Paragonimus infections in freshwater crabs in the Minjiang River basin along the middle section of Wuyi Mountain, so as to provide baseline data for parasitic disease control and research and expansion of the parasite resource bank. Methods From November 2020 to April 2021, freshwater crabs were sampled from streams and ditches neighboring residential areas in Jianning County and its neighboring Ninghua, Shaowu, Jiangle and Shunchang counties. The crab species was identified based on the morphological features of the terminal segment of the first abdominal appendage of male crabs, and Paragonimus infections were detected in freshwater crabs. The Paragonimus metacercariae were isolated, and the types of metacercariae were identified based on the metacercaria size, cystic wall thickness, and the excretory bladder and intestinal tract morphology. In addition, the prevalence, intensity and index of metacercaria infections were calculated in freshwater crabs. Results There were seven crab species found in Jianning County and six neighboring water systems along the Minjiang River basin, including Sinopotamon jianglense, S. fukinense, Huananpotamon lichuanense, H. lini, H. shenni, H. planopodum, Bottapotamon engelhardti, and there were metacercariae of three Paragonimus species detected in these crabs, including P. westermani, P. skrjabini and P. sanpingensis, with a prevalence rate of 43.6% (125/287). The infection rates of P. westermani, P. sanpingensis and P. skrjabini were 57.1% (48/84), 26.2% (22/84) and 61.8% (21/34) in S. jianglense, and the infection rates of P. westermani and P. sanpingensis were 52.6% (51/97) and 30.9% (30/97) in S. fukinense, while the rate of P. westermani infection was 6.9% (5/72) in H. lichuanense, which is the first record of P. westermani infections in H. lichuanense. Mixed P. westermani and P. sanpingensis infections were predominantly found in freshwater crabs sampled from Jianning County, where the rate of Paragonimus infections was 70.4% (76/108), with 15.3 metacercariae identified in each crab with Paragonimus infections and 1.9 metacercariae found in each gram of crabs with Paragonimus infections, and the index of metacercariae infections was 20.5. In addition, P. westermani, P. skrjabini and P. sanpingensi metacercariae were found in freshwater crabs sampled from Jianning-neighboring counties, where the rate of Paragonimus infections was 52.3% (56/107), with 9.8 metacercariae identified in each crab with Paragonimus infections and 0.9 metacercariae found in each gram of crabs with Paragonimus infections, and the index of metacercariae infections was 4.6. Conclusion There are multiple freshwater crab species and Paragonimus infection is high in freshwater crabs in Jianning County and its neighboring Minjiang River basin, which is a high-risk natural focus for Paragonimus infections.