In the natural environment, there are many parasites that use freshwater fish, snails, shrimps, crabs, etc. as intermediate hosts, and humans as intermediate hosts or end hosts. The common fish parasites in China are C. sinensis and Pneumocystis. The cysts of C. sinensis are parasitized in freshwater fish, and the cysts of Pneumocystis parasites are often parasitized in crabs. When the temperature and time of raw food or cooking processing does not reach the conditions for killing infective larvae, it is very easy to infect people. Parasitic disease.
Spoilage
Live fresh fish is sterile, but the body, gills, and intestines contain approximately the same types of bacteria as the waters. In addition, fish from fishing to cooking and processing often come in contact with containers, packaging materials, and transportation vehicles, causing fish to become contaminated. Bacteria that are commonly found in marine fish and can cause spoilage and deterioration of the fish are: Pseudomonas, Achromobacter, Flavobacterium, Mortierella, etc. In general, bacteria in freshwater fish, in addition to marine fish bacteria, there are often Alcaligenes, Aeromonas and Brevibacterium. These bacteria, which live in a nutrient-rich environment of the fish, multiply quickly under suitable temperature conditions (20-30 ° C), and are very likely to cause fish spoilage.