The introduction and dispersal of Centrocestus formosanus (Nishigori, 1924) (Digenea : Heterophyidae) in Mexico: A review

The taxonomy, distributional history, present occurrence, life-cycle, morph ology of developmental stages and epizootiology of the heterophyid trematod e Centrocestus formosanus (Nishigori, 1924) in Mexico are reviewed. This pa rasite was most likely introduced to Mexico with the importation of the fir st intermediate host, the thiarid snail Melanoides tuberculata, from Asia i n 1979. Centrocestus formosanus was first recorded in 1985 as metacercariae in fry of the first generation of black carp Mylopharyngodon piceus import ed from China and subsequently in other fish from a farm in central Mexico. Since that time the trematode has spread rapidly over a wide area which in cludes central Mexico and both the Atlantic and Pacific coasts. This rapid spread has apparently been enabled by previous propagation of M. tuberculat a in Mexico. Metacercariae of C. formosanus occur encysted on the gills of fish. They have been found in 39 species of fish of the families Atherinida e, Characidae, Cichlidae, Cyprinidae, Eleotridae, Gobiidae, Goodeidae, Icta luridae, Mugilidae and Poeciliidae from 11 Mexican states (Colima, Guanajua to, Hidalgo,Jalisco, Michoacan, Morelos, San Luis Potosi, Sonora, Tabasco, Tamaulipas and Veracruz). The heron Butorides striatus is the only known na tural definitive host in Mexico. Further research towards better understand ing of all aspects of the life cycle, transmission, host-parasite relations hips and the effective control of C. formosanus in Mexico is necessary. It should also include monitoring of the present distribution of hi. tubercula ta and its infection with larval stages of C. formosanus. Much more emphasi s should be given to histopathological studies to assess actual impact of t he parasite on fish of differ-ent species and age classes. Thr spectrum of natural definitive hosts and their epizootiological importance in the trans mission and maintenance of the parasite in Mexico should also be better doc umented. Adequate preventive and control measures should be applied in aqua culture, with emphasis given to prevention of movement of infected fish sto cks.