Trichobilharzia Mergi Sp. Nov. (Trematoda: Digenea: Schistosomatidae), a Visceral Schistosome of Mergus Serrator (L.) (Aves: Anatidae)
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Parasitology International 62 (2013) 300–308 Contents lists available at SciVerse ScienceDirect Parasitology International journal homepage: www.elsevier.com/locate/parint Trichobilharzia mergi sp. nov. (Trematoda: Digenea: Schistosomatidae), a visceral schistosome of Mergus serrator (L.) (Aves: Anatidae) Libuše Kolářová a,b,⁎, Karl Skírnisson c, Hubert Ferté d, Damien Jouet d a Institute of Immunology and Microbiology, First Faculty of Medicine, Charles University in Prague, Czech Republic b General Hospital in Prague, Czech Republic c Institute for Experimental Pathology, University of Iceland, Keldur, Reykjavík, Iceland d EA 4688, USC-VECPAR, UFR de Pharmacie, Université de Reims Champagne-Ardenne, France article info abstract Article history: Parasitological investigations on red-breasted mergansers (Mergus serrator L.) in Iceland revealed digenean Received 16 September 2012 flukes of the family Schistosomatidae. Adult worms were detected in blood vessels of the large intestine and Received in revised form 6 February 2013 eggs were deposited in the mucosa and surrounded by granulomatous reactions. Traditional morphological Accepted 4 March 2013 methods showed that the flukes have very slender filiform bodies, males are equipped with a short Available online 13 March 2013 gynaecophoric canal and both suckers and spatulate ends are present on each sex. Among characteristics of the flukes which render them morphologically distinct from other Trichobilharzia species are: i) males—well Keywords: fi Trichobilharzia mergi sp. n. developed vesicula seminalis (v.s.) consisting of a short v.s. externa and a signi cantly longer (approx. 3 Description times) v.s. interna, unusually well developed genital papilla and localization of the first testis a relatively long Morphology distance posterior to the gynaecophoric canal; ii) eggs—small and elongated with slightly rounded poles and Sequence a short terminal spine. DNA taxonomic techniques confirmed that a new species had been identified, Phylogenetic analysis Trichobilharzia mergi sp. n. The sequence data were deposited in GenBank under the accession numbers Life-cycle JX456151 to JX456172. Comparison of the results with our previously published data on characterization of Mergus serrator DNA of cercariae isolated from freshwater lymnaeid snails showed that larval development of T. mergi is Iceland associated with Radix balthica L. (=Radix peregra Müller, 1774; = Radix ovata Draparnaud, 1805). Crown Copyright © 2013 Published by Elsevier Ireland Ltd. All rights reserved. 1. Introduction 50%, but usually no more than 5% of examined snails are found to be infected by Trichobilharzia larvae [4]. Avian schistosome flukes are characterized by a two-host life cycle. Cercariae of Trichobilharzia spp.arealsoabletopenetratetheskinof The larval stadia (cercariae) develop in aquatic snails (intermediate non-compatible hosts (mammals), but their further development is in- hosts) from which they are released into surrounding water. Free swim- complete and the parasites die early after the infection. In humans skin in- ming cercariae actively seek vertebrate hosts and soon after penetration fection by bird schistosomes manifests as an allergic skin reaction known into the skin of specificdefinitive (compatible) hosts they transform to as cercarial dermatitis or swimmer's itch. The causative agents of the dis- schistosomula which migrate throughout the hosts' organs and develop ease are reputed to be mostly cercariae of Trichobilharzia spp. [5]. to adult flukes producing eggs. Depending on the species, adults localize Identification of Trichobilharzia adults and larvae is difficult. Tradi- either in the visceral organs or in the tissue of nasal area [1]. tional methods do not always allow adults and eggs from birds and The most commonly reported avian schistosomes are flukes of the cercariae from snails to be easily differentiated; the species-specific genus Trichobilharzia which represent the largest genus of the family morphological features are minute and their recognition is frequently Schistosomatidae. The adult flukes have been found all over the influenced by personal experiences of the examiner [6].Taxonomic world and waterfowl have been described as the most common definition of Trichobilharzia adult flukes is based mainly on the relative definitive hosts [1,2].However,theywerealsodetectedinpasserine positions of internal organs, surface structures of the tegument and the birds and in birds of the orders Ciconiiformes and Coraciiformes [1,3]. location of the parasites in their definitive hosts [1];onthemorphology Pulmonate snails of the families Lymnaeidae and Physidae were most of eggs [7]; on the distribution of sensory papillae on cercariae [8];or often reported as Trichobilharzia intermediate hosts [4]. The prevalence on the character of parasite life cycle, including information on the rates of adult schistosomes in birds was frequently found to exceed species of intermediate host [2]. Molecular techniques have become eminently suitable tools for identification of adult and larval stages of ⁎ Corresponding author. Tel.: +420 271 019 254; fax.: +420 272 140 458. Trichobilharzia species. Among these are sequences of gene regions E-mail address: [email protected] (L. Kolářová). such as the 28S and the internal transcribed spacers (ITS) of ribosomal 1383-5769/$ – see front matter. Crown Copyright © 2013 Published by Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.parint.2013.03.002 L. Kolářová et al. / Parasitology International 62 (2013) 300–308 301 DNA and the mitochondrial cox1. These have suggested great diversity 2. Material and methods in avian schistosomes and enabled new causative agents of cercarial dermatitis to be discovered [9–15]. Genetic techniques have also sug- 2.1. Examination of birds gested novel explanations of details of parasite life cycles, and thereby help our understanding the epizootology and epidemiology of bird Eighteen ducklings of three species—14 M. serrator, three Anas schistosomes [12,16,17]. Although these techniques are very specific platyrhynchos and one Anas penelope, obtained from Lake Botnsvatn and sensitive methods for identification of particular schistosomes, in early September 2005, 2006 and 2009, and one adult Gavia immer DNA sequencing alone is not sufficient for discrimination between found dead in July 2005—were examined for the presence of visceral species and need supplementing by traditional methods [18]. and nasal schistosomes according to Kolářová et al. [6]. Birds collected We have in the past examined Icelandic snails and birds for the in 2005 (3 specimens) and 2006 (9) were kept frozen at −20 °C until presence of larval and adult schistosomes and our results revealed examination; birds from 2009 (6) were examined fresh. that several taxonomically undefined schistosome species are present Scrapings from intestinal mucosa of the large intestine, rectum in that country [7,10,19]. In the present study we applied both tradi- and posterior part of the small intestine were compressed between tional and molecular techniques in an examination of the taxonomic two slides and examined under a microscope for the presence of status of adult flukes isolated from the red-breasted merganser schistosome eggs. For each bird the shape and size of several dozen (Mergus serrator L.) originating from Lake Botnsvatn. eggs (Fig. 1a,b) were examined morphologically and their dimensions Lake Botnsvatn is an oligotrophic body of water of area approxi- measured. mately 1 km2 in the northern part of Iceland. In both late July 2004 Adult schistosomes were excised from blood vessels of the colon and August 2005 dozens of people acquired swimmer's itch after and small intestine as described by Kolářová et al. [6]. The parasite wading in the lake [20]. Investigations on Radix balthica L. (=Radix fragments and eggs so obtained were examined under a stereomicro- peregra Müller, 1774; = Radix ovata Draparnaud, 1805) collected in scope. Slender fragments of the smaller flukes were separated from a the lake in August 2004 and 2005 confirmed an unusually high considerably larger Trichobilharzia species, the latter being flukes that number of snails that shed ocellate furcocercariae (10% out of 100 the authors aim to deal with in a separate paper. and 19.5% out of 133 snails on the two occasions, respectively). Sequencing data from a part of this material confirmed the presence 2.2. Description of schistosomes of three different species of Trichobilharzia cercariae in the lake: the haplotype Trichobilharzia sp. “haplotype peregra” [19]; Trichobilharzia Measurements of eggs and adults were performed on native fresh regenti [10] and the species that we describe in the present article—a mounts prior to fixation in 95% ethanol and subsequent freezing for mo- species designated as Trichobilharzia sp. V by Skírnisson and Kolářová lecular investigation. The morphological description of the adults was [7] and Trichobilharzia sp. 2 by Aldhoun et al. [10]. made on fresh, separately mounted fragments of 15 males and 11 fe- Only few duck species breed and raise ducklings at Lake Botnsvatn males, including 6 males and 1 female that were fixed (4% formalde- during summer. In order to find out which of them might act as final hyde) and stained by borax carmine (Tables 1, 2). Morphological hosts for Trichobilharzia spp. in the ecosystem, individuals of the most details were photographed frequently using a digital camera (Leica DC commonly breeding duck species—M. serrator were shot