Clinostomum Complanatum (Trematoda, Digenea): a Parasite of Birds and Fishes with Zoonotic Potential in Southern Brazil
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Revista Brasileira de Higiene e Sanidade Animal Print version ISSN 1981 – 2965 Revista Brasileira de Higiene e Sanidade Animal, v. 08, n. 1, p. 99 - 114, jan-mar, 2014 http://dx.doi.org/10.5935/1981-2965.20140007 Artigo Cientifico Medicina Veterinária Clinostomum complanatum (Trematoda, Digenea): a parasite of birds and fishes with zoonotic potential in southern Brazil. A Revieuw Fernando Jonas Sutili 1, Luciane Tourem Gressler 1, Luis Fernando Vilani de Pelegrini 2* _________________________________________________________________________________________________________________ ABSTRACT: Clinostomum complanatum is a digenean trematoda belonging to the Clinostomidae family with a complex life cycle, usually taking molluscs and fishes as intermediate hosts and birds as final hosts. Man may become the final host by eating raw or undercooked fish meat carrying the metacercarial stage of the parasite. Therefore, this trematode deserves great attention not only for the losses in production and discards of fish carcasses, but also for its zoonotic potential. Parasitic diseases transmitted to man through fish consumption have been especially reported in Eastern countries, where the habit of eating dishes based on raw fish meat is common. Nonetheless, C. complanatum has been reported in free-living fishes and specimens in fish farms in southern Brazil, thus representing a risk to the health of fish consumers. Strict regulations should be implemented in Brazil in order to control the quality of the fish destined for human consumption, and public awareness of the dangers of eating raw fish should be raised. Key words: Fish parasite, public health, digenean, metacercariae, raw meat Clinostomum complanatum (Trematoda, Digenea): um parasita de aves e peixes com potencial zoonótico no sul do Brasil. Uma Revisão RESUMO: Clinostomum complanatum é um trematoda digenético pertencente à família Clinostomidae com um ciclo de vida complexo, tendo normalmente moluscos e peixes como hospedeiros intermediários e aves como hospedeiros finais. O homem pode tornar-se o hospedeiro final através do consumo de carne de peixe crua ou mal cozida portando as 99 metacercárias. Assim, este parasita merece atenção não só pelas perdas na produção e no descarte de carcaças de peixes que acarreta, mas também pelo seu potencial zoonótico. Parasitoses transmitidas através do consumo de peixes têm sido relatadas especialmente em países do oriente, onde o hábito de consumir pratos que utilizam carne de peixe crua é comum. Entretanto, a presença de C. complanatum em peixes de vida livre e de criações já foi reportada no sul do Brasil, o que representa um risco à saúde dos consumidores de carne de peixe. Regulamentações efetivas devem ser implementadas no Brasil a fim controlar a qualidade do peixe destinado ao consumo humano e os riscos da ingestão de carne de peixe crua devem ser amplamente esclarecidos perante a comunidade. Palavras-chave: Parasita de peixe, saúde pública, digenético, metacercária, carne crua _____________________________ 1 Programa de Pós Graduação em Farmacologia, Departamento de Fisiologia e Farmacologia, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil 2 Departamento de Medicina Veterinária Preventiva, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil *Author for correspondence: E-mail: [email protected] Introduction health, such as the idea of not baking food Public health issues caused by too much to preserve its nutrients, may parasitic diseases transmitted through the prompt the acquisition of parasites consumption of raw or insufficiently (OKUMURA et al., 1999). In Brazil there cooked fish meat has called the attention of is a great demand for dishes prepared with researchers and authorities in the recent raw fish, like sushi and sashimi, due to the years. The increasing concern about the wide acceptance of oriental cuisine. Other importance of food quality to people’s influences such as the Peruvian with the 100 ceviche, the Spanish with the marinated belongs to the Clinostomidae family. It has and the Dutch with the green herring also been described as a parasite of fish-eating constitute a risk to consumer’s health for birds (KAGEI et al., 1988; DIAS et al., they similarly make use of raw fish meat 2003b; PESENTI et al., 2007; (BARROS et al., 2006). PAPAZAHARIADOU et al., 2008) and There are dozens of helminth fresh and brackish water fish (DIAS et al., parasites of fish that cause diseases in 2003b; AGUILAR-AGUILAR et al., 2010; humans. Some examples are the nematodes GHOLAMI et al., 2011; VIOLANTE- of the family Anisakidae and Eustrongylus GONZALEZ et al., 2009) in many sp., the cestode Diphyllobothrium spp. and countries. Amphibians such as salamanders the trematode Ascocotyle (Phagicola) and frogs have been reported as hosts of C. longa (OKUMURA et al., 1999). Several complanatum and other clinostomes trematodes which parasitize fish and may (MCALLISTER et al., 2007, 2010; cause human infection are allocated in the LEMKE et al., 2008). Members of this suborder Digenea. Such infections may be family have already been registered in rare and occasional, as is the case of areas with an average temperature of 10°C, clinostomiasis, which is caused by demonstrating its widespread distribution Clinostomum complanatum (EIRAS, (GRABDA-KAZUBSKA, 1974). 1994). Besides its zoonotic potential, this Most digenetic trematodes have a trematode also deserves great attention for complex life cycle. Molluscs are almost the losses in production and discards of always the obligatory intermediate hosts, fish carcasses. and at least two hosts are involved, the Life Cycle definitive one being a fish or a piscivorous Clinostomum complanatum is a bird in most of the cases (Figure 1). Fish digenetic endoparasite of vertebrates which present the unique potential of acting both 101 as intermediate (harboring metacercariae) mucosa (DIAS et al., 2003a), oral cavity or definitive host (PAVANELLI et al., and lung (PESENTI et al., 2007) of 2002). While studying the life cycle of C. piscivorous birds. DIAS et al. (2003a) Complanatum on the floodplain of high observed an intense liquefactive necrosis in Paraná river (Brazil), DIAS et al. (2003b) the attachment sites of C. complanatum in observed the mollusc species the oesophagus of A. cocoi. SHAMSI et al. Biomphalaria peregrina as the first (2013) reported that this digenea may intermediate host, several fish species as inflict great pathological effect on the oral the second, and various aquatic avian and oesophageal epithelium, as acute species as definitive hosts. The highest inflammation in mucosal and submucosal prevalence among the fishes was found in layers and occasionally in muscular layer. Loricariichthys platymetopon (60.8%), and The bird reacts to the infection through among the birds in Ardea cocoi (95%). encapsulation of the larvae in fibrous Fish species belonging to families such as tissue. Gymnotidae, Cichlidae (SILVA-SOUZA The histopathological evaluation of & LUDWIG, 2005), Characidae a bird (Nycticorax nycticorax) presenting (ABDALLAH et al., 2004), Callichthydae heavy C. complanatum infestation showed (DIAS et al., 2003b; ABDALLAH et al., severe necrosis and acute inflammation of 2006), Loricariidae (DIAS et al., 2003a) the oral epithelial tissue and submucosa, and Heptapteridae (VIANNA et al., 2005; with mononuclear cells being the dominant MORAIS, 1980) have been found hosting inflammatory cells around the attachment C. complanatum in Brazilian rivers. site. Sections of immature C. complanatum Patogenicity were also present in the muscular layer, in The adult form of C. complanatum which the parasites were surrounded by a is usually seen attached to the esophageal thin zone of necrotic cells and a capsule of 102 fibrous tissue (SHAMSI et al., 2013). The are embedded in the muscle, and accidental authors suggested that the damaged tissues human infection would most likely occur. may interfere with the bird’s ability to Fish Culture swallow and lead to malnutrition. As a The presence of encysted result, the immune system is weakened and metacercariae of C. complanatum in fish the animal is thus prone to more serious characterizes the yellow spot disease pathogens. (Figure 2). The unpleasant appearance of In fish C. complanatum larvae are the fish is unappealing to the consumer, found encysted in various regions of the (SILVA-SOUZA & LUDWIG, 2005) body, such as muscle, oral cavity, eyes, resulting in discard of carcasses during gills, subcutaneous tissue, gonads, inspection and economic losses intestines, liver and other organs (BRANDÃO, 2004). In addition, the (PAVANELLI et al., 2002; VIANNA et infection affects the fish’s feeding habit, al., 2005; SILVA et al., 2008). According acquisition of body weight and fecundity, to MALEK & MOBEDI (2001), an and may culminate in death. inflammatory reaction usually occurs in the Drugs containing praziquantel tissue surrounding the metacercariae, thus represent an alternative for the treatment of facilitating visualization of the parasite and the yellow spot disease. However, the preventing its ingestion. Nonetheless, the toxin released by the parasite upon death authors mentioned that some fish may and the secondary infections that may become resistant to the presence of the install in the damaged tissue are likely to metacercariae, in which case the cause fish death (MITCHELL, 1995; inflammatory reaction is not triggered. SILVA et al., 2009). Control of the That would make observation of the parasite