The Natural History of Anisakiasis in Animals1,2

Abstract

Adult anisakid nematodes are known to be parasites in the alimentary tracts of amphibians, reptiles, birds, and mammals. The known life cycle patterns among the anisakids are reviewed and from what is known, it is not possible to predict whether those hosts in which larval forms occur are true intermediate hosts or paratenic hosts. This is especially true of marine fishes in which third- and fourth-stage larvae are common. Among physical parameters known to influence the survival, development, and distribution of anisakids, temperature apparently is an important one. Similarly, a series of experiments has revealed that two unidentified species of Contracaecum from marine fish are not infective to laboratory mammals primarily because of their inability to survive mammalian body temperatures. It has also been demonstrated that Contracaecum larvae normally present in the digestive tracts of marine fishes will migrate out of dead hosts or into their mesenteries and musculature. Thus, in considering the potential public health importance of larval anisakids in marine fish, those in the digestive tract should not be considered as unimportant since they will migrate into muscles.