Fish Acanthocephalans as Potential Human Pathogens

Abstract

Abstract Purpose of Review Acanthocephalans attach to the gastro-intestinal mucosa of the host (mammals, birds, reptiles, amphibians, fish) by use of a proboscis equipped with a series of hooks. Teleosts serve as definitive hosts to some acanthocephalans, which can affect the nutritive status of the fish, due to absorption of nutrients in the gut, but they are not infective to humans. Other acanthocephalans, residing as larvae/juveniles in other compartments of the fish, apply mammals (whales, seals) as definitive hosts. They are as shown in this review potentially zoonotic, as consumption of live larvae in infected fish may lead to human infection associated with severe abdominal symptoms. Recent Findings Acanthocephalans, belonging to the genera Bolbosoma and Corynosoma, occur in their larval/juvenile stage in various body compartments of fish (paratenic hosts). They use marine mammals (cetaceans and pinnipeds) as definitive hosts, in which the adult parasite attaches to the gastro-intestinal mucosa. Eggs from the female acanthocephalan leave the host with faeces, and in the marine environment, they are ingested by small crustaceans (amphipods, isopods, copepods, krill), serving as intermediate hosts. When fish ingest the infected crustacean, the larva will infect the fish (then serving as paratenic host) awaiting predation by a marine mammal. Human consumption of raw or semi-raw fish dishes may lead to infection, development of symptoms, hospitalization and in some cases surgery. Summary Increases of marine mammal populations (seals and whales) in marine waters with exploitable fish stocks may increase the general infection pressure and thereby increase occurrence (prevalence and intensity) of the larval stages in fish. This may increase the risk of human infection. Preventive measures (prior freezing or heat treatment) are recommended before consumption of fishery products.