Chapter 12: Digeneans: Snail-Borne Parasites of Concern to Aquaculture
Digeneans or flukes (formerly called digenetic trematodes) form a class of flatworm parasites, associated with fishes, that require a molluscan intermediate host (Hoffman and Schubert 1984). In most cases, snails and fishes serve as first and second intermediate hosts, respectively, for digenean species; fish-eating birds commonly serve as final or definitive hosts for these same parasites (although fishes also may serve as final hosts). The U.S. aquaculture industry is most concerned with several digenean species known to occasionally cause serious infections in captive fishes. Of particular concern are yellow grub Clinostomum complanatum (previously known as C. marginatum), white grub Posthodiplostomum minimum, eye fluke Diplostomum spathaceum, and more recently, one or more species of the digenean genus Bolbophorus (Moore et al. 1984; Hoffman 1999; Venable et al. 2000). Interest and justification for using black carp Mylopharyngodon piceus has centered around the potential of black carp to disrupt the parasite’s life cycle by having the black carp reduce the numbers of snails that carry C. complanatum and Bolbophorus, primarily on fish farms that raise channel catfish Ictalurus punctatus. Clinostomus complanatum and Bolbophorus are covered in more detail in the following accounts.