New parasite discovered: turns popular fish meat into jelly-like mucus

Kudoa is found in both mackerel and cod

The Kudoa parasite can turn fish into a jelly-like substance, but it is not dangerous to humans. For a long time, researchers only found it in mackerel, but in the fall of 2023, scientists from the Institute of Marine Research (IMR) also discovered the parasite in cod. The discovery was made as a result of taking a repeat sample in the spring of 2024.

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The parasite Kudoa thyrsites has several microscopic spores that settle in the muscle tissue of the fish. When the fish is dead, the spores begin to produce an enzyme that turns the fish meat into a jelly-like and liquid mass.

Earlier, Norwegian scientists discovered kudoa in coastal cod in different areas from the Skagerrak to the Lofoten Islands.

“We analyzed 30 cod samples and found kudoa in one of them. According to marine scientist Lucilla Giulietti, the species of cod in question was caught in the Westfjord near the Lofoten Islands.” Giulietti says it's important to highlight that only 30 fish have been studied so far. Therefore, the results are not as convincing as for coastal cod.

The fact that marine scientists have now found kudoa in coastal cod marks a scary idea: «this means the parasite is present in Norwegian waters.»

Marine scientists have been monitoring kudoa in fish for 20 years: “Previously, we only found the parasite in mackerel that migrated from the south or from the British Isles. For a long time we thought it originated with anadromous fish.

Scientists are now finding it in coastal fish, meaning the parasite spends its entire life cycle in Norwegian waters.

“If the parasite is present along the coast, it could potentially infect farmed fish as well,” — warns Giulietti.

Until now, the life cycle of the parasite remains a mystery to scientists. But now that they know which areas of the coast have infected cod species, the researchers will take various environmental samples from there.

«The goal of this work — learn more about the parasite's life cycle. Then we can learn more about how it infects fish. In addition, in the future we will continue research on cod,” — concludes Giulietti.