Fish and parasites

Fish are infected with 283 times more parasitic worms than they were 40 years ago. Anisakis worms can infect a variety of marine fish and squid, as well as whales and dolphins, and can be present in fish used raw for sushi.

Scientists analysed the abundance of Anisakis, or herring worm, between 1978 and 2015, gathering  data on the average number of parasites per fish from 123 studies – which included 56,778 fish across 215 species. They found a 283-fold increase over nearly 40 years.

Anasakis starts its life cycle in the intestines of marine mammals, is excreted into their faeces and then infects fish, small crustaceans or krill in the larval stage.If eaten by fish they go on to form a cyst in the muscle tissue of that fish. When the fish gets eaten by the marine mammal, the life cycle recommences.

Humans can also contract these parasitic worms by consuming smoked or improperly frozen fish The worm can’t survive inside us, and are unable to complete their life cycle there. But the presence of this parasite can still initiate an immune response in people that can cause nausea, vomiting and diarrhoea.  The good news is that the seafood processing industry and sushi chefs are skilled at spotting and removing these worms.

The reason for the increased abundance of the parasites may be linked to the rise in marine mammal numbers from the 1970s onwards after the introduction of protections against hunting. Warming seas could also increase the rate of Anasakis reproduction.  Minimizing the number of worms that people are encountering in their sushi dinner is going to become more challenging into the future as we get these increasing abundances. (New Scientist.  Donna Lu, Global Change Biology, DOI: 10.1111/gcb.15048).

My take: depressing  isn’t it?  Challenges everywhere you look, and still no toilet paper!  (I don’t mean to be flippant, but it seems that there is no end to the ways we are messing up our planet.  And we vote in people who don’t care).


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