Cultivation as an Estimate for Infectivity of Larval Anisakis simplex from Processed Herring.

In vitro cultivation was used to estimate viability and potential infectivity of anisakine nematodes in edible fish. Salted and spiced Baltic herring were examined by dissection for the presence of larval Anisakis simplex . Stage-3 larvae, dissected from herring, were incubated for 4 d at 37°C in a medium containing liver extract and fresh bovine blood to enable dormant larvae to display spontaneous motion. In some instances movement became apparent only on days 2 or 3 in vitro. Larvae able to develop in vitro through one molt in these cultures were considered to have greater potential for causing disease in consumers than those that moved but did not molt. Mortality of larvae in fish increased as fish brining increased from week 1 to week 4, when it reached 100%. Salt concentration in the fish flesh also increased with time: 1 week, 5.6-8.2%; 2 weeks, 9.6-12.9%, 3 weeks, 11.6-14.0%; 4 weeks, 12.2-14.6%.