Behavioral and physiological changes of Anisakis simplex complex third stage larvae upon heating

There is increasing information on the time-temperature conditions that can be lethal for Anisakis larvae, but little is known about the infective potential of larvae that survive heat treatments. To characterize the risks associated with accidentally undercooked fish, in this paper, more than 5000 Anisakis larvae in the third stage (L3) were individually treated, at quasi-isothermal conditions, in a thermal cycler at 50 °C for different exposure times (0–320 s). After heat exposition, surviving larvae were collected and their locomotor activity, resistance to simulated gastric juice (SGJ), agar penetrative ability, and respiration capacity were evaluated. Results show that, even after relatively short treatments that rendered survival ratios (St50°C) close to 1 (i.e. all alive), some behavioral and physiological characteristics can be considerably impacted. Thus, L3 locomotor activity and agar penetrative ability significantly decreased after 60 s at 50 °C (S60s = 1), while heat expositions for 90 s (S90s ≈ 0.98) also reduced the resistance to SGJ and the respiration capacity. Our study reveals that the behavior of heat-treated Anisakis larvae depends on the intensity of the treatment and the longer the exposure time at 50 °C, the greater the changes observed in all the tested indicators. Further research is needed to elucidate the implications of the decline of these indicators on infectivity. •Survival ratio (S) of Anisakis larvae (L3) treated at 50 °C for 0–320 s ranges 1-0.•Mafart model properly describes lifespan of surviving L3 incubated in gastric juice.•Larvae are not able to penetrate into agar after >120 s at 50 °C (i.e. S ≤ 0.88).•Locomotor activity and respiration capacity are modified even at S close to 1.•Results provide data to characterize the risk when-in-doubt thermal situations.