Heterophysiasis, an intestinal fluke infection of man and vertebrates transmitted by euryhaline gastropods and fish

Abstract

Heterophyes heterophyes, agent of human heterophyiasis in the Near East, is transmitted in marine lagoons and saline inland waters, where the euryhaline intermediate hosts are abundant. In Egypt, mullets, the predominant second intermediate hosts, are customarily consumed raw; thus man becomes infected easily. Symptoms of human infections are usually considered mild. Mullets do not seem to be affected by the metacercariae encysted in the muscles, whereas the growth of the snail host Pirenella conica was found to be enhanced due to the infestation by the trematodes. In laboratory experiments, the flukes were found to be well developed in dogs, foxes and cats, but failed to reach sexual maturity in several other potentially piscivorous mammals and birds. In nature, dogs probably serve as the major reservoir hosts. Heterophyiasis is most prevalent in the Nile Delta, a huge brackish water area which is densely populated by humans and, consequently, also by dogs and cats. In the Far East, besides Heterophyes nocens, several other heterophysids with marine or fresh-water life-cycles are known to infect humans. © 1984 Biologische Anstalt Helgoland.