Friday, December 2, 2016

Anisakis simplex in fish

Anisakis simplex, known as ‘herring worm’ and ‘whale-worm’, is  only one larval type among several, occurring in marine fish. Fresh fish is the principle vehicle for Anisakis simplex infection in humans, especially if it is eaten raw or undercooked. The nematodes can invade the wall of the human digestive tract, causing inflammation, ulceration, and granuloma formation.

The larvae die quite quickly in fish that is frozen and do not survive effective cooking, and so processed fish and seafoods present a negligible risk of infection.

However, the larvae may survive in some fermented, lightly salted, or cold-smoked and marinated fish products such as pickled herrings and gravadlax.

The Dutch experience with anisakidosis forced the authorities it impose regulations regarding salt, temperature and storage time to kill larvae in herring. Larvae are killed by proper heating, 60-70 °C and deep freezing at -20 °C or below for some days.

The growing trend for consumption of raw and lightly cooked fish, such as sushi and sashimi, in the West is thought to be increasing the likelihood of human infection with anisakid worms.

Wild fish are considered to carry a much higher risk of infection than farmed fish. Researchers found no anisakid larvae in farmed salmon. The first confirmed human case of anisakiasis in the United States was reported in 1972.

Anisakiasis has however, emerged in the past 35 years as a serious public health problem in Japan, where raw fish are commonly eaten.
Anisakis simplex in fish

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