Survival and infectivity of Paragonimus westermani Metacercariae in soy sauce–marinated crayfish

Paragonimus westermani, a zoonotic lung fluke, causes respiratory symptoms resembling tuberculosis. In Asia, human infections typically occur through the consumption of raw or marinated freshwater crabs or crayfish containing P. westermani metacercariae. With increasing global food trade and occasional exposure during international travel, cases have been reported in non-endemic regions, raising significant food safety concerns. In this study, naturally infected freshwater crayfish (Cambaroides similis) were collected from Haenam, South Korea. Crayfish were marinated in soy sauce containing either 10 % or 20 % sodium chloride (NaCl) and stored at 4 °C for 1–60 days. P. westermani metacercariae were recovered at each time point and morphologically classified as viable, borderline (uncertain viability), or dead. To assess infectivity, 100 P. westermani metacercariae from each group were orally inoculated into beagle dogs (n = 3 per group), and worm recovery was assessed after 12 weeks. After 14 days of marination, the survival rates of P. westermani metacercariae were 83.3 % in 10 % NaCl and 2.0 % in 20 % NaCl soy sauce. Complete inactivation occurred after 60 days in 10 % NaCl and 30 days in 20 % NaCl. Infectivity tests showed worm recovery rates of 82.5 % (viable), 33.7 % (borderline), and 0 % (dead). These findings indicate that even high-salt, cold-storage marination does not guarantee parasite inactivation. Viable P. westermani metacercariae can persist in marinated crayfish under commonly used culinary conditions. These results underscore the risk of foodborne lung fluke infections and emphasize the need for clearer public health guidance regarding the consumption of undercooked or inadequately processed freshwater crustaceans.