Metagonimus yokogawai (Trematoda: Heterophyidae): From Discovery to Designation of a Neotype

Metagonimus yokogawai (Katsurada, 1912) Katsurada, 1912 (Trematoda: Heterophyidae) is parasitic in the small intestine of mammals including man and birds in Far Eastern Russia, Korea, Japan, China, and Taiwan. In the present study, the metacercariae and adults of M. yokogawai were redescribed to designate a neotype of this fluke together with reviews of previous studies including study histories from the first discovery to now. We particularly, attempted to review the study histories and morphological descriptions of M. yokogawai for the species validity, and compared with the morphological characteristics and life cycles of the closely related species, Metagonimus takahashii and Metagonimus miyatai. Finally, we proposed a differential key for the 8 known Metagonimus species distributed in East Asia. Metacercariae were obtained from the body muscles of sweetfish (Plecoglossus altivelis) collected in the Asahi River at Takebe-cho, Kita-ku, Okayama City, Okayama Prefecture, Japan. Adults were recovered from the small intestine of Syrian golden hamsters, to which the metacercariae had been fed 14 days before. A neotype was selected out of the present adult specimens. The Asahi River at Takebo-cho became the type locality of M. yokogawai. In conclusion, the present review shows that M. yokogawai, M. takahashii, and M. miyatai are valid and discriminated by means of morphological characteristics.

Centrocestus formosanus (Opisthorchiida: Heterophyidae) como causa de muerte de alevines de tilapia gris Oreochromis niloticus (Perciforme: Cichlidae) en el Pacífico seco de Costa Rica

Centrocestus formosanus (Opisthorchiida: Heterophyidae) as a cause of death in gray tilapia fry Oreochromis niloticus (Perciforme: Cichlidae) in the dry Pacific of Costa Rica. Centrocestus formosanus is a zoonotic trematode from Asia and has been mainly associated as cause of death of cultured fish. To identify pathogen trematode species in tilapia fry (Oreochromis niloticus) and to determine mollusks hosting these parasites, freshwater mollusks were collected from tilapia cultured ponds and experimental infections were carried out with tilapia fries and different mollusk species. A total of 907 freshwater mollusks were obtained from tilapia ponds and were identified to species level, four gastropods and one bivalve were determined: Melania tuberculata, Melanoides turricula, Pomacea flagellata, Haitia cubensis and Anodontiles luteola. For the first time, the presence of M. turricula and H. cubensis are reported in Costa Rica. Seven morphotypes of cercariae (Xifiodiocercaria, Equinostoma, Oftalmocercaria, Parapleurolofocercus, Cistocerca, Furcocercaria and Leptocercaria) parasitizing all five species of mollusks were found, all of distome type. Experimental exposure of tilapia fry to M. tuberculata demonstrated that the parapleurolofocercus morphotype found in the mollusk is in accordance with the finding of C. formosanus in tilapia fry. An abundance and mean intensity of 1018-1027 digeneans per gill in each exposed fish was determined. Centrocestus formosanus is reported for the first time in Costa Rica, for which the primary and secondary intermediate hosts were also determined. Rev. Biol. Trop. 58 (4): 1453-1465. Epub 2010 December 01.

Centrocestus formosanus es un parásito trematodo zoonótico originario de Asia asociado con muertes de peces principalmente de cultivo. 907 moluscos provenientes de estanques sembrados con tilapias, seleccionados uno por provincia fueron identificados al nivel taxonómico especifico. Se identificaron cuatro gastrópodos y un bivalvo: M. tuberculata, M. turricula, P. flagellata, H. cubensis y A. luteola. Se reporta, por primera vez, la presencia de dos especies de moluscos en Costa Rica. Se identificaron siete morfotipos de cercarias parasitando las cinco especies de moluscos encontradas. En la segunda exposición experimental se demostró que el morfotipo parapleurolofocercus encontrado en M. tuberculata concuerda con el hallazgo de C. formosanus en alevines de tilapia, después del examen clínico, anatomopatológico y parasitológico realizado a los alevines expuestos. Las metacercarias fueron extraídas del quiste utilizando microagujas y micropinzas lavadas en solución salina fisiológica (0.65%), fijadas en formol caliente al 4% y después esquematizadas con una cámara clara adaptada a un microscopio fotónico, estimándose una abundancia e intensidad media de 1018-1027 digeneos por branquia en cada pez parasitado, determinándose así el hospedador intermediario primario y secundario del parásito. En el presente trabajo se reporta por primera vez Centrocestus formosanus en Costa Rica.

Molecular Markers for Identification of Stellantchasmus falcatus and a Phylogenic Study using the HAT-RAPD Method

Stellantchasmus falcatus is a minute intestinal fluke in the family Heterophyidae. Metacercariae, the infective stage, were reported in a marine fish, mullet Liza subviridis, and a fresh water fish, Dermogenus pusillus, in Thailand. Adults were found in chicks, rats, cats, and humans. Morphological studies were done for comparing Stellantchasmus sp. worms found in 2 different fish hosts; their shapes and organ arrangements were very similar except for the prepharynx length. Therefore, the present study aimed to compare their DNA fingerprints using the HAT-RAPD method for both types of Stellantchasmus and several other related species. Ten arbitrarily selected primers (OPA-04, OPA-09, OPN-02, OPN-03, OPN-09, OPN-12, OPP-11, OPR-15, OPX-13, and OPAD-01) were used. It was found that OPA-09, OPN-03, and OPAD-01 were able to generate S. falcatus specific fragments in mullets which consisted of 200, 760, and 280 bp, respectively. In addition, the results of morphologic, DNA fingerprinting, and phylogenetic analyses strongly suggest that the fresh water and marine specimens of Stellantchamus may be different species.

Prevalence of the Intestinal Flukes Haplorchis taichui and H. yokogawai in a Mountainous Area of Phongsaly Province, Lao PDR

Phongsaly Province, located in the northernmost area of Lao PDR, was previously suggested to be endemic for the liver fluke Opisthorchis viverrini infection. To confirm, or rule out, this suggestion, the Phonxay village in the Khoua District, Phongsaly Province, was selected for a survey. Ten volunteers (8 men and 2 women aged 31-57 years) who consumed raw freshwater fish and had gastrointestinal troubles were treated with a single dose of praziquantel (40 mg/kg) and pyrantel pamoate (10 mg/kg) and purged with magnesium sulfate to recover any worm parasites. Eight of the 10 volunteers expelled 1 or more species of trematodes, nematodes, or cestodes (worm positive rate; 80%). The worms were morphologically identified as H. taichui (861 worms from 8 people), H. yokogawai (59 from 6 people), Phaneropsolus bonnei (1 from 1 person), Trichostrongylus sp. (2 from 2 people), Ascaris lumbricoides (2 from 1 person), Enterobius vermicularis (11 from 3 people), and Taenia saginata (1 strobila with scolex from 1 person). The results indicate that the mountainous area of Phongsaly Province, Lao PDR, is not endemic for the liver fluke but endemic for intestinal flukes, in particular, Haplorchis taichui and H. yokogawai.

Heterophyid metacercarial infections in brackish water fishes from Jinju-man (Bay), Kyongsangnam-do, Korea

Heterophyid metacercarial infections in brackish water fishes, i.e., perch, shad, mullet, redlip mullet, and goby, of Jinju-man (Bay), Kyongsangnam-do, Korea, were investigated using a digestion technique. Among 45 perch (Lateolabrax japonicus), the metacercariae of Heterophyopsis continua were found in 55.6% (18.5 metacercariae per fish), Stictodora spp. in 28.9% (3.6), and Metagonimus takahashii in 6.7% (17.0). The metacercariae of H. continua were detected in 23 (65.7%) of 35 shad (Konosirus punctatus). Among 15 mullet (Mugil cephalus), the metacercariae of Pygidiopsis summa were found in 100% (105.9 metacercariae per fish), Heterophyes nocens in 40.0% (8.5), H. continua in 13.3%, and Stictodora spp. in 6.7%. Among 12 redlip mullet (Chelon haematocheilus), the metacercariae of P. summa were detected in 91.7% (1,299 metacercariae per fish), H. nocens in 16.7%, and Stictodora spp. in 16.7%. Among 35 gobies (Acanthogobius flavimanus), the metacercariae of Stictodora spp. were found in 82.9% (44.5 metacercariae per fish), and H. continua in 25.7% (2.8). The adult flukes recovered from a cat experimentally infected with metacercariae from perches were compatible with M. takahashii. The results confirm that the estuarine fish in Jinju-man (Bay) are heavily infected with heterophyid metacercariae. Furthermore, it was found for the first time that the perch acts as a second intermediate host for M. takahashii.

Melanoides tuberculatus (Gastropoda: Thiaridae) as intermediate host of Heterophyidae (Trematoda: Digenea) in Rio de Janeiro metropolitan area, Brazil

No final da década de 60, caramujos da espécie Melanoides tuberculatus, originários do nordeste africano e sudeste asiático, foram introduzidos no Brasil. Os primeiros registros de espécimes infectados com cercárias foram feitos no Estado do Rio de Janeiro em 2001. O presente estudo relata a ocorrência de M. tuberculatus infectados com larvas de trematódeos na cidade do Rio de Janeiro. O sedimento dos criadouros foi coletado e peneirado através de malhas de 0,25 polegadas. Os caramujos foram transportados em recipientes com água dos criadouros, sendo medidos e posteriormente individualizados. Eles foram expostos à luz e temperatura artificiais para induzir a emergência cercariana. As cercárias mais ativas foram processadas pelos métodos de coloração diferencial e de impregnação por nitrato de prata. Os caramujos negativos foram subsequentemente dissecados. Aproximadamente 700 caramujos foram coletados. Seu comprimento variou de 1,2 a 3,3 cm. A taxa de prevalência foi de 15,76% apesar de 53,76% dos caramujos estarem infectados em uma das áreas. Os caramujos estavam infectados com rédias e cercárias do tipo pleurolofocerca. A morfologia e a quetotaxia cercarianas foram compatíveis com as da família Heterophyidae principalmente devido à presença de nadadeiras medianas dorsais e ventrais e à ausência de receptores sensoriais CI dorsais.

Human infection of Centrocestus caninus in Thailand.

Examination of fecal samples, collected after treatment with praziquantel, of the persons positive with opisthorchioid eggs residing in the northern provinces of Thailand, was carried out. Five adults Centrocestus were recovered in one sample from Doi Saket, Chiang Mai and one adult was found in another fecal sample from Wiang Pa Pao, Chiang Rai. The worms had 26-30 spines arranging in two rows around the oral sucker which agreed with the character of C. caninus. This is the first record of natural human infection with Centrocestus in Thailand.

Study of the body surface of Haplorchis yokogawai (Katsuta, 1932) and H. taichui (Nishigori, 1924) (Trematoda:Heterophyidae).

The morphology of the surface of two heterophyid flukes, Haplorchis yokogawai and H. taichui, that can infect humans eating raw fish flesh, has been studied using scanning and transmission electron microscopy. The body surface of both species is covered with scale-like, serrated spines with the exception of areas around the oral sucker, ventrogenital opening and excretory pore. The species slightly differ by the dentation pattern of tegumental spines: H. yokogawai has finer and more numerous spine teeth (maximum tooth number 14-16) while H. taichui has more serrated spines, mostly with a lower number (up to 10-12) of somewhat more robust teeth. However, because of the variability, the shape and dentation of spines do not seem to be reliable diagnostic features enabling mutual differentiation of both species.

Two species of heterophyid larval digeneans from a thiarid gastropod thiara tuberculata (Muller) from India

Dos especies de cercarias heterofídeas, cercaria de Haplorchis taichi y de Haplorchis pumilio fueron obtenidas de Thiara tuberculata de Visakhpatnam, India. Este es el primer registro de ambos parásitos en India. Las características de la cercaria H. Kaichiu están constituídas por la presencia de dos series de finos pliegues, uno lateral y otro dorsoventral, 15 espinas puntiagudas distribuidas en tres filas alternadas y siete pares de glándulas lobuladas de penetración dispuestas en dos líneas longitudinales. La cercaria de H. pumilio se caracteriza por la presencia de dos series de finos pliegues caudales, 15 espinas puntiagudas en tres filas alternadas y siete pares de voluminosas glándulas unicelulares de penetración

Haplorchis pumilio (Looss) infection in man in northeastern Thailand.

During a clinical trial of praziquantel for human opisthorchiasis, Haplorchis pumilio Looss were recovered from the stools of 12 patients. This is the third species of Haplorchis spp. reported from man in Thailand.

The sensory receptors of two cercariae from Malaysia: Trichobilharzia brevis (Schistosomatidae) and Haplorchis Pumilio (Heterophyidae).

A description of sensory receptors of Trichobilharzia brevis is given. They are compared with the five Schistosomatidae described by Richard (1971), namely, Trichobilharzia ocellata, schistosoma mansoni, S. bovis, S; haematobium and S. rodhaini. All these species display very similar chaetotaxic characters. In the study of the cercaria of Haplorchis pumilio, comparison with the few Opisthorchioidea cercarial sensory organs already known has enabled the authors to characterise the chaetotaxy for this superfamily.