Investigation of parasitic infection in food on market in Qingpu District of Shanghai during 2015‒2023

ObjectiveTo understand the status of parasitic infection in the food sold on market in Qingpu District of Shanghai, and to provide an evidence for the development of prevention and control strategies for parasitic infection applicable to Qingpu District.MethodsAquatic products, meat products and other foodstuffs sold on online shops, at farm product markets, supermarkets/foodstores and restaurants were sampled in Qingpu District, Shanghai, during 2015‒2023, based on the administrative division of Qingpu District. The parasitic infection in the food samples were examined using pressing method and digestion for detecting metacercariae in freshwater products and pickled products, using dissection microscopy for Anisakis larvae in seawater products, Taenia cysticercus and Trichinella encysted larvae in meat products.ResultsA total of 1 079 samples of food products were examined during 2015‒2023, with a total parasite infection rate of 13.44%. The total parasite infection rate of freshwater fish products was 3.40% (16/471), and the difference of parasite infection rates between different freshwater fish species was statistically significant (χ2=229.609, P=0.001). The total infection rate of Clonorchis sinensis was 3.18% (15/471), which had been detected in Pseudorasbora parva, Cyprinidae rhodeus, and Carassius auratus, with a positive rate of 77.78% (7/9), 50.00% (5/10) and 3.90% (3/77), respectively. Metorchis orientalis was detected in in Pseudorasbora parva, with a positive rate of 33.33% (3/9). The positive rate of Gnathostoma spinigerum (third-stage larvae) was 0.81%. Paragonimus metacercariae were not detected in the freshwater shrimps and crabs. The infection rate of seawater fish products was 26.46%. The difference of parasite infection rate in seawater fishes was statistically significant (χ2=109.181, P=0.001). A total of 53 pork and beef samples were tested, none was detected with Trichinella larva cysts, Taenia solium metacercariae, and Taenia saginata metacercariae. The total infection rate of pickled yellow mud snail products was 58.11% (43/74). Paragonimus metacercariae was not detected in any of the pickled aquatic product samples.ConclusionThere are different degrees of parasitic infection in freshwater products, seawater products and pickled aquatic products in Qingpu District of Shanghai. The risk of parasite infection from raw or undercooked foods is high. Health education on healthy dietary practices such as throughly cooked food should be strengthened for local residents.