Effects of temperature on Anisakis simplex sensu stricto L3 larvae experimentally challenged in rainbow trout (Oncorhynchus mykiss) and Mozambique tilapia (Oreochromis mossambicus).

Human anisakiasis is a foodborne disease that has been increasingly reported worldwide and is caused by the consumption of raw or undercooked seafood infected with zoonotic nematodes of the genus Anisakis Dujardin, 1845. One of the most frequently reported species, both in fish paratenic hosts as well as in human patients, is Anisakis simplex sensu stricto (s.s.), which is distributed within some of the globe's main fishing grounds in the North Pacific and Atlantic oceans. In order to clarify the influence of temperature on this parasite in vivo, third-stage larvae of A. simplex s.s. were surgically challenged in the body cavities of rainbow trouts (Oncorhynchus mykiss) and Mozambique tilapias (Oreochromis mossambicus). Larval survival and tissue migration were then analyzed after 6 and 12 weeks. The results showed that survival rates of larvae were lower at 27 and 33 °C than at 3, 9, 15 and 21 °C. Also, migration to the body muscle was observed to be highest at 9 °C. These results suggest that third-stage larvae of A. simplex s.s. are more adapted to lower temperatures in experimentally challenged fish, which may justify its distribution in cold northern waters.