Surface Ultrastructure of Heterophyes heterophyes. (Trematoda: Heterophyidae) Collected from a Man. S. UGA,1’5 M. MORIMOTO,2 T. SAITO,3 AND S. K. RAI4. Accacoelium contortum (Trematoda: Accacoeliidae) a trematode living as a monogenean: morphological and pathological implications. Zoonotic trematode infections are an area of the neglected tropical diseases that have become of major interest to global and public health due to their.

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Fish Diseases Diagnostic Service. Accacoelium contortum Rudolphi, Monticelli, is a frequent but poorly known trematode found on gills, pharynx and digestive tract of the ocean sunfish Mola mola L. Although the morphology of A. The main objective of this paper is to explore this peculiar host-parasite relationship. A total of ocean sunfish were examined for the presence of A. The oropharyngeal chamber gills and pharynx and the digestive tract were analysed. As the previous descriptions of this species seem to be based on contracted specimens, for the morphological study the parasites were killed using two methods: New information on the morphology of A.

New diagnostic traits for some structures are provided: The length of the ventral sucker peduncle and the position of the vitellarium were found to be associated with the contraction degree of the specimen. Immature individuals of this species are described for the first time. An intense proliferative inflammatory response of host gill and pharynx epithelium at the host-parasite interface was detected and parasites became partially covered by overgrowths of host tissues.

The induction of prominent histological alterations associated with A. The ocean sunfish, Mola mola L. Tetraodontiformes, Molidaeis the largest bony fish of the world [ 12 ].

Its unique size and morphology has increased the interest of large public aquariums in keeping this species in their facilities. However, husbandry of ocean sunfish is very complicated due to the fact that this species is very sensitive to stress [ 3 ], together with the high prevalence and abundance of parasites on fish [ 4 — 8 ]. Surprisingly, information about the effect of the parasites on the ocean sunfish is very scarce. One of the most frequent parasites is the trematode Accacoelium contortum Rudolphi, Monticelli Accacoeliidae Odhner, a poorly known parasite mainly located within the oropharyngeal chamber on gills, oral cavity and pharynx provoking important alterations of the host tissues.

The Accacoeliidae includes parasitic hemiuroids mostly reported in M. Accacoelium contortum is the type-species of the family and the only known species of the genus Accacoelium Monticelli, This trematode has been reported in ocean sunfish from the Mediterranean, North East Atlantic and South Pacific [ 49 — 11 ], with a single record in blotched picarel, Spicara maena L.

Centracanthidae [ 12 ].

Fascioliasis: An Ongoing Zoonotic Trematode Infection

Accacoelium contortum is mostly an ectoparasite, although it has also been reported within the oesophagus and digestive tract [ 46891113 — 17 ]. The general external morphology and attachment organs of A. In this regard, the ectoparasitic behaviour of this species is an exception among the Accacoeliidae, and very infrequent within the class Trematoda mostly endoparasites [ 9 ]. Despite being unique in its kind, little is known about the biology of A.

During an extensive parasitological survey on M. This provided us with the opportunity to obtain detailed morphological data for A. In the present work we also describe the biology of this trematode and the special relationship between the host and the parasite.

Fascioliasis: An Ongoing Zoonotic Trematode Infection

In the same way, the pathological effects of the parasites on its host are described, also discussing how the parasite adapts to the external environment. Confidence intervals of prevalence Rrematoda were calculated using Quantitative Parasitology 3. For morphological descriptions, some of the parasites collected from fresh fish were fixed and mounted to be examined under light microscopy and scanning electron microscopy SEM. It is widely recognised that the descriptions of helminths must not be based on contracted specimens [ 21 ]; however, previous descriptions of Accacoelium contortum seem to be based on contracted specimens.


In order to compare contracted and relaxed specimens morphologically, parasites were killed and fixed at different temperatures, resulting in different degrees of contraction [ 22 ]. Morphological description is based on relaxed specimens only.

Sucker dimensions length, width, and depth were taken from unmounted specimens, as the specimens were mounted laterally because of the protuberant ventral sucker, preventing measurement of the width of the acetabulum. Measurements were tdematoda using Image Jurnao 3. Some sections were stained with Giemsa to detect the presence of secondary bacterial infections.

The 18S was amplified in three fragments with the primer pairs: The 28S was jurnao in two fragments with the primer pairs: And the ITS-2 was amplified with the primer pairs: Consensus sequences were assembled using Bioedit 7.

Four immature specimens were also found in the stomach of one fish. A significant difference in trrematoda abundance of A.

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

Infection sites of Accacoelium contortum in the ocean sunfish Mola mola L. Detail of b showing little swellings arrows on gill tissue caused by A. The morphology of the newly collected parasite specimens from the Western Mediterranean ocean sunfish is in accordance with previous descriptions of A. However, our examination of the newly collected specimens enabled us to add further morphological detail in order to help to identify the species.

A description of the immature specimens, unreported up to date, is included. Specimens of Accacoelium contortum in the ocean sunfish Mola mola L. General morphology as in Bray and Gibson [ 9 ]; additional morphological comments follow. Forebody with a ventral depression with transverse folds, extending from oral sucker to base ventral sucker peduncle Fig.

Tegument of forebody including trdmatoda sucker peduncle bearing conical to dome-shaped papillae [ A single crown of circum-oral papillae present Fig. Oral sucker ventro-subterminal, with soft pre-oral lobe Fig. Ventral sucker on a long peduncle in relaxed specimens 0.

Trematofa very short in contracted specimens 0.

Posterior extremity of vitellarium always extending beyond the ovary, up to posterior extremity of body. Morphometric data for relaxed and contracted specimens of Accacoelium contortum from the ocean sunfish Mola mola L. In histological sections, the nucleate and anucleate external layers of the tegument are covered with a thick outer dense homogenous layer, particularly thicker over the parasite papillae see detail in Fig.

Histology of infections by Accacoelium contortum in gills of the ocean sunfish Mola mola L. Stained in H-E, except for b and d. Tegumental papillae not observed. Forebody with strongly folded ventral depression. Oral sucker ventro-subterminal, 0. Genital primordium observed in some specimens. Both 18S pb and 28S pb sequences for isolates of A. Parasites located on gills and pharynx were always clustered in groups Fig.

Suckers attached them to the host tissues and to other parasites, while the hindbodies of several parasites were rolled around other individuals. When parasites were removed, the round swellings caused by the vacuum action of the suckers were visible on fish tissues and on parasite surfaces Fig.

In the areas surrounding parasite clusters, different types of macroscopic alterations such as tissue proliferations, swellings or malformations were observed Fig. On the gills, parasites were often located in pits between deformed and bent gill filaments and surrounded by gill tissue proliferations Fig.


In the histological sections, the surrounding areas where A. Parasites were surrounded by large papillary folds associated with intense epithelial hyperplasia and infiltration with inflammatory cells of the subepithelial connective tissue Fig.

Epithelial hyperplasia was characterised by an intense proliferation of the epithelial layers and also by mucous cells, mainly in the papillary folds.

In the areas of the host-parasite interface, an external thick pale-pink layer and pyknotic necrotic epithelial cells were observed Fig. Clusters of bacterial colonies jurna, revealed, in preparations stained with Giemsa, in the external layer closely associated to the necrotic debris surrounding the infected tissues Fig. In the pharynx, parasites were also enclosed in pits within large tissue proliferations displaying similar characteristics as described before Fig.

Affected pharyngeal epithelium also displayed intense hyperplasia jurrnal sometimes necrotic external layers. In some cases, pharyngeal epithelium displayed a specific eosinophilic compact outer layer termatoda contact with the parasite forebody see detail in Fig.

The compact outer layer was not observed on pharyngeal epithelium in contact with the parasite hindbody Fig. Preparations stained with Giemsa revealed a secondary bacterial infection Fig.

Histology of infections by Accacoelium contortum in pharynx of the ocean sunfish Mola mola L. The parasites trrmatoda in the stomach were always scattered, grematoda were neither clustered nor related to apparent changes in the nearby epithelium. Most of the mature specimens of Accacoelium contortum occurred in the oropharyngeal chamber gills, oral cavity and pharynxand only a few disperse mature and immature parasites were found within the stomach.

Interestingly, parasite abundance was significantly higher in the right gills than in the left gills. This asymmetry is not common in gill parasites, and only some authors have reported differences in parasite abundance between left and right gills, e.

It is very difficult to find anatomical reasons to explain this because fish are bilaterally symmetrical. A possible explanation in ocean sunfish could ttematoda related to fish behaviour, as this species tends to incline the body laterally when resting on the surface [ 34 — 36 ] or when swimming in the water column [ 3436 — 39 ].

These studies indicated that ocean sunfish tend to incline the bodies mainly to the right when they are ascending, implying that they mostly expose the left side to the air when they have arrived at the surface to rest.

Parasites in the left side would be in these moments submitted to partial desiccation, heating or UV exposure that could somehow compromise their survival. The molecular analysis confirms that all morphotypes, relaxed and contracted, belong to the same species, A.

This study includes several new diagnostic morphological features. The different morphology of the tegumental papillae on the forebody is described in detail and the circum-oral papillae are described for the trenatoda time.

Moreover, the peduncle of the ventral sucker of A. However, the absolute and relative values of the length of the ventral sucker peduncle in the relaxed specimens are the highest values among the accacoeliids reported to date: Rhynchopharynx paradoxa Odhner, is the only accacoeliid with a markedly developed peduncle of the ventral sucker marked: According to our observations, the ventral sucker peduncle of A.