The amount of Anisakis worms, which humans and marine mammals can ingest by eating raw fish, has increased 283 times in recent decades, according to an American study.
- Parasitic worms infect small crustaceans, then the entire food chain.
- The manifestations are comparable to those of food poisoning.
You will probably never look at your sushi the same way again. On the basis of thousands of works carried out during the last decades, researchers from the university of washington (United States) studied the evolution of Anisakis populations between 1978 and 2015.
The worms measure up to two centimeters in length, and can infect humans and marine mammals such as dolphins, whales and seals, by ingesting raw or undercooked seafood or fish.
The population of Anisakis multiplied by 283 in 37 years
In study published in 2020 in the scientific journal Global Change Biologyresearchers reported that the population of Anisakis had increased 283 times in 37 years.
“It’s interesting because it shows how the risks to humans and marine mammals change over time. This is important to know, first from a public health point of view, but also to understand what is happening to populations of marine mammals that are not doing well.”according to Chelsea Wood, one of the study’s authors and assistant professor at University of Washington School of Aquatic and Fisheries Sciences.
Symptoms similar to those of food poisoning
After hatching in the ocean, the worms begin by infecting small crustaceans, such as copepods, which form the basis of plankton. When small fish eat these infected crustaceans, the worms change hosts, and thus move up to larger fish.
When humans consume infected fish, the parasites can invade their intestinal walls and cause symptoms similar to food poisoning, such as nausea, vomiting and diarrhea. In general, the worms die after a few days and the symptoms disappear. As a result, the disease, called anisakiasis, is rarely diagnosed.
Ability to reproduce in the body of marine mammals
While the health risks posed by Anisakis to humans are relatively low, researchers believe they could have a major impact on the marine mammals that harbor them.
In fact, worms can live for several years and reproduce in the body of marine mammals, without scientists knowing what physiological effects their hosts can suffer. They are then released into the ocean via the excrement of marine mammals.
“A massive and growing risk to the health of marine mammals”
“One of the major takeaways from this study is that we now know there is a massive and growing risk to the health of marine mammals.says Chelsea Wood. The presence of parasites is not often thought to be the reason why marine mammal populations fail to recover.”
The authors of the study do not have a certain explanation for the reason for such an increase in the population of Anisakis in recent decades. Nevertheless, they suggest that climate change, increased nutrients from fertilizers, and the simultaneous increase in the population of marine mammals could be possible factors.
