Metacercariae of Centrocestus formosanus (Trematoda: Heterophyidae) in Australoheros facetus (Pisces: Cichlidae) in Brazil

Abstract

Heterophyid metacercariae were found in the gills of Australoheros facetus (Jenyns, 1842) collected from the Pampulha reservoir, Belo Horizonte, Minas Gerais, Brazil, between February and April 2010. The cysts were counted and used to perform experimental studies (artificial excystment and infection of mice). Fifty specimens of A. facetus were analyzed and it was found that the prevalence of infection was 100% and mean infection intensity was 134 metacercariae/fish (range: 4-2,510). Significant positive correlations were seen between total fish length and intensity of infection; between fish weight and intensity of infection, and between parasite density and fish length. Morphological analyses on metacercariae and adult parasites obtained from experimentally infected mice made it possible to identify Centrocestus formosanus (Nishigori, 1924). This is the first report of C. formosanus in A. facetus in Brazil.

Molecular Phylogenetics of Centrocestus formosanus (Digenea: Heterophyidae) Originated from Freshwater Fish from Chiang Mai Province, Thailand

“…The number of circumoral spines of C. formosanus is 32 spines in most cases [1,18]. It is also similar to a previous study that reported 32 circumoral spines of C. formosanus [3–5]. This species differed from the related species; C. caninus which has 26–30 spines [6].…”

“…The worm was reported to be infected in humans in Taiwan, Japan, and Lao PDR [2,3]. It is distributed in many countries, i.e., Taiwan (China), Japan, the Philippines, India, Lao PDR, Mexico, and Brazil [3–5]. Centrocestus caninus is a closely related species to C. formosanus.…”

“…It has been reported to infect humans in Thailand and Lao PDR [6,7]. Various species of freshwater fish act as the second intermediate host of C. formosanus, including Puntius brevis , Cyclocheilichthys repasson, Osteochilus hasseltii , and Australoheros facetus [2,5]. In northern Thailand, Centrocestus metacercariae have been highly infected in freshwater fish, including P. brevis , Esomus metallicus , and Anabas testudineus [8–10].…”

Metacercarial Infection of Wild Nile Tilapia (Oreochromis niloticus) from Brazil

“…The formation of metacercariae in gills is related to the occurrence of asphyxia and mortality as well as delayed development, which cause damage to fish farming [ 30 ]. In Brazil, C. formosanus was recorded firstly in its molluscan intermediary host, the invader thiarid Melanoides tuberculata (Müller, 1774) [ 31 , 32 ], and recently reported in fish ( Australoheros facetus (Jenyns, 1842) and Poecilia reticulata Peters, 1859) and bird ( Butorides striata (Linnaeus, 1758)) from the Pampulha reservoir [ 19 , 33 , 34 ]. This heterophyid was previously reported in O. niloticus from Egypt [ 35 , 36 ], Vietnam [ 37 – 39 ], and Saudi Arabia [ 40 ] but had not yet been reported in this cichlid in South America.…”

“…In fact, the prevalence and intensity of infection by C. formosanus observed in O. niloticus in the Pampulha reservoir are smaller than those previously verified for A. facetus , a native cichlid, from the same area of study (100%, 134 metacercariae/fish resp.) [ 19 ]. On the other hand, low intensities of infection for C. formosanus and A. compactum were also reported in O. niloticus by different authors from other countries [ 35 – 40 ], which may suggest a relative resistance of this fish to these parasites.…”