Browsing by Author "Georg von Samson-Himmelstjerna"

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    High genetic diversity in the Dirofilaria repens species complex revealed by mitochondrial genomes of feline microfilaria samples from Narathiwat, Thailand
    (2019-01-01) Esra Yilmaz; Sirichit Wongkamchai; Sabrina Ramünke; Georgios D Koutsovoulos; Mark L. Blaxter; Sven Poppert; Roland Schaper; Georg von Samson-Himmelstjerna; Jürgen Krücken; Institut Sophia Agrobiotech - (ISA); Freie Universität Berlin; University of Edinburgh; Universitat Basel; Swiss Tropical and Public Health Institute (Swiss TPH); Faculty of Medicine, Siriraj Hospital, Mahidol University; Bayer AG
    © 2018 Blackwell Verlag GmbH Dirofilaria repens is a zoonotic, mosquito-borne filaria infecting carnivores, particularly dogs. It is expanding its range in Europe but epidemiological information is sparse for other Eurasian regions. In Hong Kong and India, the closely related species Candidatus Dirofilaria hongkongensis was proposed. Previous analysis of 2.5 kb partial mitochondrial genome sequences containing the particularly variable non-coding control region revealed low diversity in European D. repens while Asian nematodes showed high diversity. Sequences derived from feline blood samples from Narathiwat (Thailand) led to the proposal of a third potential species, Dirofilaria sp. “Thailand II”. To avoid bias from rapidly evolving non-coding regions, this study aimed to compare Dirofilaria sp. “Thailand II” with D. repens and C. D. hongkongensis based on complete mitochondrial genomes. Using PCRs and Sanger sequencing, three complete mitochondrial genomes (13,651 bp) were assembled from DNA obtained from different feline blood samples. Mitochondrial genome organization was identical to other onchocercids with eleven protein-coding, two rRNA and 22 tRNA genes and no atp-8 gene. All genes were on the same strand showing an extremely high thymidine content (56.7%). Maximum-likelihood phylogenetic analysis using protein and rRNA sequences confirmed closer relationship of Dirofilaria sp. “Thailand II” to C. D. hongkongensis than to D. repens. All distances between these three putative species were considerably larger than the distance between the valid sibling species Onchocerca volvulus and Onchocerca ochengi. Sequencing of a 2.5 kb fragment containing the control region from microfilarial DNA from additional feline blood samples from Narathiwat 3–4 years later revealed that these also fell into the C. D. hongkongensis clade but were remarkably different from C. D. hongkongensis and Dirofilaria sp. “Thailand II”. Since D. repens-like filaria are absent from dogs in Narathiwat, further field studies are required to confirm if these genotypes represent locally circulating cat-specific Dirofilaria genotypes or species.
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    The Mitochondrial Genomes of the Zoonotic Canine Filarial Parasites Dirofilaria (Nochtiella) repens and Candidatus Dirofilaria (Nochtiella) Honkongensis Provide Evidence for Presence of Cryptic Species
    (2016-10-11) Esra Yilmaz; Moritz Fritzenwanker; Nikola Pantchev; Mathias Lendner; Sirichit Wongkamchai; Domenico Otranto; Inge Kroidl; Martin Dennebaum; Thanh Hoa Le; Tran Anh Le; Sabrina Ramünke; Roland Schaper; Georg von Samson-Himmelstjerna; Sven Poppert; Jürgen Krücken; Freie Universität Berlin; Justus Liebig University Giessen; IDEXX Laboratories; Universitat Leipzig; Mahidol University; Università degli Studi di Bari; Ludwig-Maximilians-Universität München; Universitätsklinikum Heidelberg; Vietnamese Academy of Science and Technology Institute of Biotechnology; Department of Parasitology Veterinary Medical University; Bayer Animal Health GmbH; Universitatsklinikum Hamburg-Eppendorf und Medizinische Fakultat; German Center for Infection Research (DZIF), Partner site Giessen-Marburg-Langen; German Center for Infection Research (DZIF), Partner Sites Hamburg
    © 2016 Yilmaz et al. Background: Cutaneous dirofilariosis is a canine mosquito-borne zoonosis that can cause larva migrans disease in humans. Dirofilaria repens is considered an emerging pathogen occurring with high prevalence in Mediterranean areas and many parts of tropical Asia. In Hong Kong, a second species, Candidatus Dirofilaria hongkongensis, has been reported. The present study aimed to compare mitochondrial genomes from these parasites and to obtain population genetic information. Methods and Findings: Complete mitochondrial genomes were obtained by PCR and Sanger sequencing or ILLUMINA sequencing for four worms. Cytochrome oxidase subunit 1 sequences identified three as D. repens (all from Europe) and one as C. D. hongkongensis (from India). Mitochondrial genomes have the same organization as in other spirurid nematodes but a higher preference for thymine in the coding strand. Phylogenetic analysis was in contradiction to current taxonomy of the Onchocercidae but in agreement with a recent multi-locus phylogenetic analysis using both mitochondrial and nuclear markers. D. repens and C. D. hongkongensis sequences clustered together and were the common sister group to Dirofilaria immitis. Analysis of a 2.5 kb mitochondrial genome fragment from macrofilaria or canine blood samples from Europe (42), Thailand (2), India (1) and Vietnam (1) revealed only small genetic differences in the D. repens samples including all European and the Vietnam sample. The Indian C. D. hongkongensis and the two Thai samples formed separate clusters and differences were comparatively large. Conclusion: Genetic differences between Dirofilaria spp. causing cutaneous disease can be considerable whereas D. repens itself was genetically quite homogenous. C. D. hongkongensis was identified for the first time from the Indian subcontinent. The full mitochondrial genome sequence strengthens the hypothesis that it represents an independent species and the Thai samples might represent another cryptic species, Candidatus Dirofilaria sp. ‘Thailand II’, or a quite divergent population of C. D. hongkongensis.