Stellantchasmus falcatus (Digenea: Heterophyidae) in Cambodia: Discovery of Metacercariae in Mullets and Recovery of Adult Flukes in an Experimental Hamster

Abstract

Stellantchasmus falcatus (Digenea: Heterophyidae) is first reported from Cambodia through recovery of the metacercariae from mullet fish and adult flukes from an experimentally infected hamster. We purchased 7 mullets, Chelon macrolepis, in a local market of Phnom Penh, Cambodia, and each of them was examined by the artificial digestion method on May 2010. The metacercariae of S. falcatus were detected in all mullets (100%) examined, and their average density was 177 per fish. They were elliptical, 220×168 μm in average size. They were orally infected to an hamster to obtain adult flukes. Adults recovered at day 10 post infection were observed with a light microscope and a scanning electron microscope (SEM). They were small, 450×237 μm in average size, had a small oral sucker (41×50 μm), subglobular pharynx (29×21 μm), slender esophagus (57 μm), long and thick-walled expulsor (119×32 μm), spherical ovary (58×69 μm), and 2 ovoid testes (right: 117×74 μm; left: 114×63 μm). Eggs were small, yellow, and 23×12 μm in average size. In SEM observations, tegumental spines were densely distributed on the whole tegument, and single small type I sensory papillae were distributed around the lip of oral sucker. The small ventral sucker was dextrally located and had 8 type I sensory papillae on the left margin. It has been first confirmed in the present study that the mullet, C. macrolepis, is playing the role of a second intermediate host of S. falcatus in Cambodia.

Infections of Digenetic Trematode Metacercariae in Wrestling Halfbeak, Dermogenys pusilla from Bangkok Metropolitan Region in Thailand

“…In addition, S. falcatus metacercariae were similar in size to S. fal-catus metacercariae (220 × 168 µm in average size) in mullet from Cambodia. Their prevalence and average intensity were 100% and 177 metacercariae per fish infected, respectively [17]. In contrast, they were somewhat smaller than those from the mullet in Vietnam.…”

“…The metacercariae were 297× 232 µm in size and had a V-shaped excretory bladder [18]. Many species of fish, including the wrestling halfbeak, garfish (Xenentodon canciloides), mullet (Mugil cephalus), mullet (C. macrolepis), common carp (Cyprinus carpio), and grass carp (Ctenopharyngodon idella) have been reported to be the second intermediate hosts for S. falcatus metacercariae in Thailand, Myanmar, Laos, Cambodia, Korea, and Vietnam [10,17,19,20]. Recently, Wongsawad et al [7] reported that the metacercariae found in the wrestling halfbeak in Chiang Mai province was S. dermogenysi n.…”

Zoonotic Trematode Metacercariae in Fish from Yangon, Myanmar and Their Adults Recovered from Experimental Animals

“…The metacercariae of S. falcatus were detected only in the mullet, Chelon macrolepis , like in Cambodia [ 37 ]. They were also found in several species of fish, i.e., mullet ( M. cephalus and L. haematocheila ), goby ( A. flavimanus ), wrestling halfbeak ( D. pusilla ), X. canciloides , giant gouramy ( O. gourami ), common carp ( C. carpio ), and grass carp ( C. idella ), in Japan, Hawaii, China, Korea, Thailand, Vietnam, and Lao PDR [ 38 – 45 ].…”

“…They were also found in several species of fish, i.e., mullet ( M. cephalus and L. haematocheila ), goby ( A. flavimanus ), wrestling halfbeak ( D. pusilla ), X. canciloides , giant gouramy ( O. gourami ), common carp ( C. carpio ), and grass carp ( C. idella ), in Japan, Hawaii, China, Korea, Thailand, Vietnam, and Lao PDR [ 38 – 45 ]. Among these fish intermediate hosts, the mullet is the most frequently reported in various regions [ 25 , 37 – 41 ]. The size of S. falcatus metacercariae in this study (225×165) were nearly the same with those in Cambodia (220×168), but somewhat smaller than those in Vietnam (297×232) [ 25 , 37 ].…”

“…Among these fish intermediate hosts, the mullet is the most frequently reported in various regions [ 25 , 37 – 41 ]. The size of S. falcatus metacercariae in this study (225×165) were nearly the same with those in Cambodia (220×168), but somewhat smaller than those in Vietnam (297×232) [ 25 , 37 ]. The adult worms (447×233) were nearly the same in size with those of Chai et al (450×237: 10-day-old in a hamster), but they were slightly smaller than those of Dung et al (468×298: from residents of Vietnam) and Chai et al (481×239: 8-day-old in a hamster) [ 8 , 25 ].…”