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 <i>Anisakis simplex</i> (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.