Experts from the University of Washington point to a dramatic increase in fish parasitic worms. When fish are consumed, the worms transmit to marine mammals and humans.

According to a study published in the Global Change Biology journal, the number of worm parasites has increased 283-fold since the 1970s.

Image by Anilocra from en.wikipedia

The parasitic worm Anisakis simplex lives in the marine mammals digestive tract. The study is the first serious research to show evidence that this parasitic worm is potentially dangerous to humans.

Potentially Low Human Risk

If people consume unboiled fish, the parasite can attack their intestinal wall. It causes symptoms similar to food poisoning – especially nausea, vomiting and diarrhea.

Anisakis simplex in food chain. Autor: CDC/Alexander J. da Silva from Wikimedia

The health risks of these parasites are relatively low for humans. In most cases, the worm dies after a few days and the symptoms disappear. Worms cannot reproduce or live in the human gut for more than a few days.

This disease is called anisakiosis or anisakidosis. Doctors rarely diagnose it because most people assume they have just experienced a more severe food poisoning case.

Risk to Marine Mammals

Researchers believe that worms can have a major impact on marine mammals such as dolphins, whales and seals. Worms multiply in the  animals’ intestines and enter the ocean in the feces. Through the food chain the parasites get through crustaceans and fish back into mammals.

Image by Claudia Beer from Pixabay

Co-author of the study, Chelsea Wood, said: “It is seldom thought that parasites could be the reason why some marine mammal populations are unable to recover as expected.”

Although scientists do not yet know the physiological effects of these parasites on marine mammals. “The parasites can live in their bodies for years, which, of course, could have harmful effects”, Wood said.