Echinostoma sp. Classification. Phylum Platyhelminthes (flatworms). Class: Trematoda (Flukes). Order Echinostomatiformes. Family Echinostomatidae. J Travel Med. Sep 1;24(5). doi: /jtm/tax Infection with Echinostoma sp. in a group of travellers to Lake Tanganyika, Tanzania, in January Delineation of the European Echinostoma spp. was carried out based on molecular, morphological and ecological data. The large-scale.

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We detected metacercariae of Echinostoma revolutum in Filopaludina sp. Adult flukes were harvested from experimentally infected hamsters at days 14 and 17 post-infection.


A total of 37 collar spines were arranged around the head collar, and large excretory granules were seen in 2 canals of the excretory bladder. The day old adult flukes were elongated, ventrally curved, and 5.

The head collar had a total of 37 collar spines arranged in 2 alternating rows, including 5 corner spines on each side. The cirrus sac contained a saccular seminal vesicle, a prostatic gland, and an unarmed cirrus.

Two tandem testes were smooth or slightly lobed. These morphological characters were similar to those of E. We tentatively identified it as E. The taxonomic relationship of E. In heavy infections, they can cause mucosal ulceration, bleeding, and severe inflammation in human patients. To date, 20 species of zoonotic echinostomes belonging to 9 genera have been discovered worldwide EchinostomaEchinochasmusAcanthoparyphiumArtyfechinostomumEchinoparyphiumEpisthmiumHimasthlaHypoderaeumand Isthmiophora [ 1 ].

Among them, Echinostoma is the most important and 7 zoonotic species of Echinostoma are known; Echinostoma revolutumE. It was first discovered as an intestinal fluke of ducks but is now known to infect a variety of avian and mammalian species, including geese, muskrats, and humans [ 1 – 3 ].

Vietnam was among the list of countries where E. However, it was based upon a suggestion on the presence of the larval stage, Cercaria spinifera [ 7 ]. No other detailed zp about this echinostome in Vietnam is available.

In the present study, we purchased Filopaludina sp. We detected metacercariae and identified them as E. A total of metacercariae from 30 snails 15 per snail were collected in the digested material using a stereomicroscope.

Metacercariae were examined echimostoma and measured using a light microscope. Three ducks were orally infected with metacercariae each and 2 hamsters were orally infected with 50 metacercariae each.

No worms were recovered from cehinostoma the ducks. To observe the surface ultrastructure, some of the adult worms were washed several times with 0. They had characteristically large, round excretory granules in 2 descending canals of the main excretory bladder.

Collar spines, 37 in total, were clearly visible around echinoatoma head collar, with 5 corner spines on each side and 27 ventral, lateral, and dorsal spines, in 2 alternating s Fig.

Echinostomiasis – Microscopy Findings

The metacercariae were detected mainly in the pericardial sac of the snail. The adult flukes were elongated, ventrally curved, and 5. The head collar of the adult was distinct, bearing 37 collar spines arranged in 2 alternating rows, including 5 corner spines on each side. The oral sucker was subterminal. The prepharynx was very short, and the pharynx was well developed. The esophagus was somewhat long.


The cirrus sac was well developed, containing a saccular seminal vesicle and an unarmed cirrus. The ventral sucker was round and moderately large. The ovary was transversely elliptical and located on the median line of the body. Testes were tandom, smooth or slightly lobed. The tegument of the anterior region of the body was densely covered with scale-like spines Figs. The tegumental spines became sparse toward the posterior part of the body. There were numerous ciliated or aciliated sensory papillae distributed around the oral sucker and head collar Fig.

The arrangement of the collar spines, including the 5 corner spines, was clearly visible. The corner spines were characteristically arranged in 2 rows, 3 oral and 2 aboral, on each side Fig. Small, scale-like tegumental spines were distributed on the surface around the ventral sucker Fig. On the lip of the ventral sucker, many sensory papillae were distributed. The cirrus was seen to have protruded out of the cirrus sac. Scanning electron microscopic SEM views of E. Ventral view of a whole worm showing its elongated and leaf-like appearance, with a distinct head collar, and oral and ventral suckers.

The tegument around the oral sucker and head collar showing its smooth surface and numerous sensory papillae and the characteristic arrangement of the collar spines, including the 5 corner spines.

The tegument posterior to the head collar is covered with scale-like spines. The lip of the ventral sucker covered by many sensory papillae. An unarmed cirrus is seen protruded from the cirrus sac. The results of this study indicated that the life cycle of E. Eating raw or improperly cooked snails may cause human echinostomiasis which should be verified through epidemiological surveys and clinical interventions in Vietnam.

There was a taxonomic problem in identifying our specimens because of the complexity in the systematics of collar-spined echinostomes, the so-called ‘ revolutum ‘ group [ 89 ]. Within this group, more than 30 species have been described. However, at present, only 12 species, E. Their differential features, in terms of the life cycle, morphology, and geographical distribution, are reviewed in Table 1. Characteristic features of the collar-spined Echinostoma belonging to the ‘ revolutum ‘ group.

It is of note that the morphology of the adult flukes is almost indistinguishable between E. In our study, the attempt to infect ducks failed and adult flukes were successfully recovered only from hamsters. The second intermediate host was Filopaludina snails, a viviparid molluscan species. The first intermediate host for our flukes may be the same or different species of viviparid snails, although this was not confirmed in our study. These results are compatible with E. However, this needs to be clarified through molecular and genetic studies, and the taxonomic significance of E.


We herein tentatively designated our specimens as E. Another point that needs to be discussed is the size of the metacercariae. With regard to E. The size of metacercariae may vary depending on the amount of pressure placed on the cover slip.

However, it should be further determined whether all metacercariae within these size range belong to a single taxon of E. Few studies of echinostome flukes have been performed in Vietnam.

Kanev [ 6 ] studied Cercaria spinifera presumed to be E. Recently, metacercariae of Echinochasmus japonicus were reported from a species of freshwater fish, Labeo rohita in Vietnam [ 24 ]. In addition, 2 echinostomq of echinostome cercariae species undetermined were detected from several species of freshwater snails in Nam Dinh Province, Vietnam [ 25 ].

The Type 2 cercariae [ 25 ] detected from Gyraulus convexiusculus snails may be those of Echinostoma sp. However, this identification needs to be clarified.

Regarding the surface topography of E. There is one report which focused on echniostoma collar region [ 26 ]. Although several ultrastructural studies were performed on echinostpma was thought to be E. The surface ultrastructure of the collar region of E. In particular, the end group and lateral group collar spines were almost identical. However, our adult flukes were obtained from experimental hamsters mammal whereas those in Kanev et al. Therefore, the taxonomic issue needs to be further clarified on our observed worms.

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Author information Article notes Copyright and License information Disclaimer. This article has been cited by other articles in PMC. Abstract We detected metacercariae of Echinostoma revolutum in Filopaludina sp. Echinostoma revolutumEchinostoma juriniechinostome, metacercaria, Filopaludina snail, Vietnam. Open in a separate window.

Table 1 Characteristic features of the collar-spined Echinostoma belonging to the ‘ revolutum ‘ group. Fried B, Toledo R, editors. The Biology of Echinostomes.

Fried B, Graczyk TK. Recent advances in the biology of Echinostoma species in the ‘revolutum’ group. Foodborne intestinal flukes in Southeast Asia.