Survival of Anisakis simplex (s.s.) L3 exposed to different combinations of acetic acid and sodium chloride: In vitro observations

Parasitic nematode larvae within the family Anisakidae are important food-borne parasites with importance for consumer health and international trade. Apart from inactivation of larvae in fish products by heating and/or freezing, marination of herring fillets is widely used. The preferred marination process applies a solution with high contents of sodium chloride and acetic acid. We here describe the direct lethal effect on Anisakis simplex (sensu stricto) of different combinations of sodium chloride and acetic acid. We incubated a total of 1440 isolated worm larvae in 36 different combinations of sodium chloride and acetic acid over 8 weeks (w) at 5 °C. Worm mortality was correlated to incubation time, but acetic acid showed the strongest effect when compared to sodium chloride. Full worm mortality was induced by acetic acid (10 %) within 2 w and by 6 % acetic acid after 8 w. Sodium chloride was less effective as worms were alive in 10 % sodium chloride until 4 w and in 8 % until 8 w. A synergistic effect was noted as a combination of 4 % acetic acid and at least 2 % sodium chloride was effective within 6 w. At 8 w 2 % acetic acid combined with 6 % sodium chloride was found lethal for larvae. It cannot be excluded that worm larvae in host tissues will exhibit different mortality rates due to the protective effect of host cells.