The Public Health Implications of Larval Thynnascaris Nematodes from Shellfish1,2

Abstract

Nematodes of the genus Thynnascaris, which as adults parasitize fishes and as larvae occur in fishes and invertebrates, are reviewed with emphasis on their possible public health implications. Reported invertebrate hosts include a variety of species in seven phyla; eight new host records are reported here. At least three types of larval Thynnascaris occur in shrimp of North and Central America and may infect as many as 80% of some size-groups of commercial penaeid shrimp. Reviewed and presented information indicate that larvae of Thynnascaris, like those of anisakine ascaridoids, are killed by usual methods of food processing and preparation. Unlike anisakine larvae, most types of larval Thynnascaris tested fail to infect experimentally inoculated laboratory mammals. However, larvae of Thynnascaris aduncum have been implicated, but not confirmed, as agents of human gastrointestinal eospinophilic granulomata in France, and data are presented showing that a type of larval Thynnascaris from the cutlassfish, Trichiuris lepturus, possibly identical to a type from the brown shrimp, infects and produces gastrointestinal lesions in the mouse.