{'fraction_non_alphanumeric': 0.025514771709937333, 'fraction_numerical': 0.008952551477170993, 'mean_word_length': 5.55425219941349, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
The Introduction and Dispersal of Centrocestus formosanus (Nishigori, 1924) (Digenea: Heterophyidae) in Mexico: A Review

Abstract The taxonomy, distributional history, present occurrence, life cycle, morphology of developmental stages and epizootiology of the heterophyid trematode Centrocestus formosanus (Nishigori, 1924) in Mexico are reviewed. This parasite was most likely introduced to Mexico with the importation of the first intermediate host, the thiarid snail Melanoides tuberculata, from Asia in 1979. Centrocestus formosanus was first recorded in 1985 as metacercariae in fry of the first generation of black carp Mylopharyngodon piceus imported 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 includes central Mexico and both the Atlantic and Pacific coasts. This rapid spread has apparently been enabled by previous propagation of M. tuberculata 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 Atherinidae, Characidae, Cichlidae, Cyprinidae, Eleotridae, Gobiidae, Goodeidae, Ictaluridae, Mugilidae and Poeciliidae from 11 Mexican states (Colima, Guanajuato, Hidalgo, Jalisco, Michoacán, Morelos, San Luis Potosí, Sonora, Tabasco, Tamaulipas and Veracruz). The heron Butorides striatus is the only known natural definitive host in Mexico. Further research towards better understanding of all aspects of the life cycle, transmission, host-parasite relationships and the effective control of C. formosanus in Mexico is necessary. It should also include monitoring of the present distribution of M. tuberculata and its infection with larval stages of C. formosanus. Much more emphasis should be given to histopathological studies to assess actual impact of the parasite on fish of different species and age classes. The spectrum of natural definitive hosts and their epizootiological importance in the transmission and maintenance of the parasite in Mexico should also be better documented. Adequate preventive and control measures should be applied in aquaculture, with emphasis given to prevention of movement of infected fish stocks.