Gyrodactylus anguillae, a gill trematode parasite of eels, was described from Denmark in 1959, on Anguilla anguilla, the European Eel, and subsequently from wild and cultured populations from Spain, France, the British Isles, Italy, Croatia, Ukraine, and Israel. The occurrence of this parasite in Europe, before the start of the global eel trade, suggests a European origin (Hayward et al. 2001b). Morphologically identical Gyrodactylus sp. have been collected in North America, Japan, China, and Australia. Genetic studies indicate that the European, North American, and Australian populations are genetically identical (Asian samples were not available for DNA analysis). The widespread occurrence of an identical parasite among 5 species of long-separated Anguilla spp. is indicative of recent introduction. the global trade in eels has resulted in the culture of European A. anguilla in Asia, and in shipments of live A. anguilla to North America The transport of eels, especially juveniles (elvers) in ballast water, is probable (Hayward et al. 2001b).
Gyrodactylus anguillae was first collected in North America in the Cooper River,(South Carolina) Choptank and Wicomico Rivers, on the eastern shore of Maryland. Prevalence was moderate (18-30% of eels examined). Since this parasite prefers brackish and marine waters, this parasite is suspected to be widespread along the coast of Eastern North America.