Veterinary Biosciences - Research Publications

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    Phylogenetic Relationships of the Strongyloid Nematodes of Australasian Marsupials Based on Mitochondrial Protein Sequences
    Sukee, T ; Beveridge, I ; Koehler, AV ; Hall, RS ; Gasser, RB ; Jabbar, A (MDPI, 2022-11)
    Australasian marsupials harbour a diverse group of gastrointestinal strongyloid nematodes. These nematodes are currently grouped into two subfamilies, namely the Cloacininae and Phascolostrongylinae. Based on morphological criteria, the Cloacininae and Phascolostrongylinae were defined as monophyletic and placed in the family Cloacinidae, but this has not been supported by molecular data and they are currently placed in the Chabertiidae. Although molecular data (internal transcribed spacers of the nuclear ribosomal RNA genes or mitochondrial protein-coding genes) have been used to verify morphological classifications within the Cloacininae and Phascolostrongylinae, the phylogenetic relationships between the subfamilies have not been rigorously tested. This study determined the phylogenetic relationships of the subfamilies Cloacininae and Phascolostrongylinae using amino acid sequences conceptually translated from the twelve concatenated mitochondrial protein-coding genes. The findings demonstrated that the Cloacininae and Phascolostrongylinae formed a well-supported monophyletic assemblage, consistent with their morphological classification as an independent family, Cloacinidae. Unexpectedly, however, the subfamily Phascolostrongylinae was split into two groups comprising the genera from macropodid hosts (kangaroos and wallabies) and those from vombatid hosts (wombats). Genera of the Cloacininae and Phascolostrongylinae occurring in macropodid hosts were more closely related compared to genera of the Phascolostrongylinae occurring in wombats that formed a sister relationship with the remaining genera from macropods. These findings provide molecular evidence supporting the monophyly of the family Cloacinidae and an alternative hypothesis for the origin of marsupial strongyloid nematodes in vombatid hosts that requires further exploration using molecular approaches and additional samples.
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    Speciation in the genus Cloacina (Nematoda: Strongylida): species flocks and intra-host speciation
    Chilton, NB ; Shuttleworth, MA ; Huby-Chilton, F ; Koehler, AV ; Jabbar, A ; Gasser, RB ; Beveridge, I (CAMBRIDGE UNIV PRESS, 2017-11)
    Sequences of the first and second internal transcribed spacers (ITS1 + ITS2) of nuclear ribosomal DNA were employed to determine whether the congeneric assemblages of species of the strongyloid nematode genus Cloacina, found in the forestomachs of individual species of kangaroos and wallabies (Marsupialia: Macropodidae), considered to represent species flocks, were monophyletic. Nematode assemblages examined in the black-striped wallaby, Macropus (Notamacropus) dorsalis, the wallaroos, Macropus (Osphranter) antilopinus/robustus, rock wallabies, Petrogale spp., the quokka, Setonix brachyurus, and the swamp wallaby, Wallabia bicolor, were not monophyletic and appeared to have arisen by host colonization. However, a number of instances of within-host speciation were detected, suggesting that a variety of methods of speciation have contributed to the evolution of the complex assemblages of species present in this genus.
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    Phylogenetic relationships of the nematode subfamily Phascolostrongylinae from macropodid and vombatid marsupials inferred using mitochondrial protein sequence data
    Sukee, T ; Beveridge, I ; Koehler, A ; Hall, R ; Gasser, RB ; Jabbar, A (BMC, 2021-10-09)
    BACKGROUND: The subfamily Phascolostrongylinae (Superfamily Strongyloidea) comprises nematodes that are parasitic in the gastrointestinal tracts of macropodid (Family Macropodidae) and vombatid (Family Vombatidae) marsupials. Currently, nine genera and 20 species have been attributed to the subfamily Phascolostrongylinae. Previous studies using sequence data sets for the internal transcribed spacers (ITS) of nuclear ribosomal DNA showed conflicting topologies between the Phascolostrongylinae and related subfamilies. Therefore, the aim of this study was to validate the phylogenetic relationships within the Phascolostrongylinae and its relationship with the families Chabertiidae and Strongylidae using mitochondrial amino acid sequences. METHODS: The sequences of all 12 mitochondrial protein-coding genes were obtained by next-generation sequencing of individual adult nematodes (n = 8) representing members of the Phascolostrongylinae. These sequences were conceptually translated and the phylogenetic relationships within the Phascolostrongylinae and its relationship with the families Chabertiidae and Strongylidae were inferred from aligned, concatenated amino acid sequence data sets. RESULTS: Within the Phascolostrongylinae, the wombat-specific genera grouped separately from the genera occurring in macropods. Two of the phascolostrongyline tribes were monophyletic, including Phascolostrongylinea and Hypodontinea, whereas the tribe Macropostrongyloidinea was paraphyletic. The tribe Phascolostrongylinea occurring in wombats was closely related to Oesophagostomum spp., also from the family Chabertiidae, which formed a sister relationship with the Phascolostrongylinae. CONCLUSION: The current phylogenetic relationship within the subfamily Phascolostrongylinae supports findings from a previous study based on ITS sequence data. This study contributes also to the understanding of the phylogenetic position of the subfamily Phascolostrongylinae within the Chabertiidae. Future studies investigating the relationships between the Phascolostrongylinae and Cloacininae from macropodid marsupials may advance our knowledge of the phylogeny of strongyloid nematodes in marsupials.
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    Ocular Filariasis in Human Caused by Breinlia (Johnstonema) annulipapillata Nematode, Australia
    Koehler, A ; Robson, JMB ; Spratt, DM ; Hann, J ; Beveridge, I ; Walsh, M ; McDougall, R ; Bromley, M ; Hume, A ; Sheorey, H ; Gasser, RB (CENTERS DISEASE CONTROL & PREVENTION, 2021-01)
    We report a human case of ocular filariasis, caused by a species of Breinlia nematode, from Queensland, Australia. Morphological and molecular evidence indicated that the nematode Breinlia (Johnstonema) annulipapillata, or a closely related taxon, likely transmitted from a macropodid marsupial host was involved, which might represent an accidental finding or an emerging zoonosis.
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    The mitochondrial genomes of Ancylostoma caninum and Bunostomum phlebotomum - two hookworms of animal health and zoonotic importance
    Jex, AR ; Waeschenbach, A ; Hu, M ; Van Wyk, JA ; Beveridge, I ; Littlewood, DTJ ; Gasser, RB (BMC, 2009-02-11)
    BACKGROUND: Hookworms are blood-feeding nematodes that parasitize the small intestines of many mammals, including humans and cattle. These nematodes are of major socioeconomic importance and cause disease, mainly as a consequence of anaemia (particularly in children or young animals), resulting in impaired development and sometimes deaths. Studying genetic variability within and among hookworm populations is central to addressing epidemiological and ecological questions, thus assisting in the control of hookworm disease. Mitochondrial (mt) genes are known to provide useful population markers for hookworms, but mt genome sequence data are scant. RESULTS: The present study characterizes the complete mt genomes of two species of hookworm, Ancylostoma caninum (from dogs) and Bunostomum phlebotomum (from cattle), each sequenced (by 454 technology or primer-walking), following long-PCR amplification from genomic DNA (approximately 20-40 ng) isolated from individual adult worms. These mt genomes were 13717 bp and 13790 bp in size, respectively, and each contained 12 protein coding, 22 transfer RNA and 2 ribosomal RNA genes, typical for other secernentean nematodes. In addition, phylogenetic analysis (by Bayesian inference and maximum likelihood) of concatenated mt protein sequence data sets for 12 nematodes (including Ancylostoma caninum and Bunostomum phlebotomum), representing the Ascaridida, Spirurida and Strongylida, was conducted. The analysis yielded maximum statistical support for the formation of monophyletic clades for each recognized nematode order assessed, except for the Rhabditida. CONCLUSION: The mt genomes characterized herein represent a rich source of population genetic markers for epidemiological and ecological studies. The strong statistical support for the construction of phylogenetic clades and consistency between the two different tree-building methods employed indicate the value of using whole mt genome data sets for systematic studies of nematodes. The grouping of the Spirurida and Ascaridida to the exclusion of the Strongylida was not supported in the present analysis, a finding which conflicts with the current evolutionary hypothesis for the Nematoda based on nuclear ribosomal gene data.
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    Analyses of mitochondrial amino acid sequence datasets support the proposal that specimens of Hypodontus macropi from three species of macropodid hosts represent distinct species
    Jabbar, A ; Beveridge, I ; Mohandas, N ; Chilton, NB ; Littlewood, DTJ ; Jex, AR ; Gasser, RB (BMC, 2013-11-21)
    BACKGROUND: Hypodontus macropi is a common intestinal nematode of a range of kangaroos and wallabies (macropodid marsupials). Based on previous multilocus enzyme electrophoresis (MEE) and nuclear ribosomal DNA sequence data sets, H. macropi has been proposed to be complex of species. To test this proposal using independent molecular data, we sequenced the whole mitochondrial (mt) genomes of individuals of H. macropi from three different species of hosts (Macropus robustus robustus, Thylogale billardierii and Macropus [Wallabia] bicolor) as well as that of Macropicola ocydromi (a related nematode), and undertook a comparative analysis of the amino acid sequence datasets derived from these genomes. RESULTS: The mt genomes sequenced by next-generation (454) technology from H. macropi from the three host species varied from 13,634 bp to 13,699 bp in size. Pairwise comparisons of the amino acid sequences predicted from these three mt genomes revealed differences of 5.8% to 18%. Phylogenetic analysis of the amino acid sequence data sets using Bayesian Inference (BI) showed that H. macropi from the three different host species formed distinct, well-supported clades. In addition, sliding window analysis of the mt genomes defined variable regions for future population genetic studies of H. macropi in different macropodid hosts and geographical regions around Australia. CONCLUSIONS: The present analyses of inferred mt protein sequence datasets clearly supported the hypothesis that H. macropi from M. robustus robustus, M. bicolor and T. billardierii represent distinct species.
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    Phylogenetic Analysis of Mitogenomic Data Sets Resolves the Relationship of Seven Macropostrongyloides Species from Australian Macropodid and Vombatid Marsupials
    Sukee, T ; Koehler, A ; Hall, R ; Beveridge, I ; Gasser, RB ; Jabbar, A (MDPI, 2020-12)
    Nematodes of the genus Macropostrongyloides inhabit the large intestines or stomachs of macropodid (kangaroos and wallabies) and vombatid (wombats) marsupials. This study established the relationships of seven species of Macropostrongyloides using mitochondrial (mt) protein amino acid sequence data sets. Phylogenetic analyses revealed that species of Macropostrongyloides (M. lasiorhini, M. baylisi, M. yamagutii, M. spearei, M. mawsonae and M. woodi) from the large intestines of their hosts formed a monophyletic assemblage with strong nodal support to the exclusion of M. dissimilis from the stomach of the swamp wallaby. Furthermore, the mitochondrial protein-coding genes provided greater insights into the diversity and phylogeny of the genus Macropostrongyloides; such data sets could potentially be used to elucidate the relationships among other parasitic nematodes of Australian marsupials.
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    Phylogenetic analysis of the Australasian paralysis ticks and their relatives (Ixodidae: Ixodes: Sternalixodes)
    Kwak, ML ; Beveridge, I ; Koehler, AV ; Malipatil, M ; Gasser, RB ; Jabbar, A (BMC, 2017-03-02)
    BACKGROUND: The Australasian paralysis ticks and their relatives, Ixodes Latrielle, subgenus Sternalixodes Schulze, are some of the most important ticks in the region. However, very little is known about their phylogenetic relationships. The aim of this study was to elucidate the evolutionary relationships of members of the subgenus Sternalixodes by undertaking phylogenetic analyses of morphological and molecular datasets. METHODS: Adult females (n = 64) of Sternalixodes, including Ixodes anatis Chilton, 1904, Ixodes confusus Roberts, 1960, Ixodes cornuatus Roberts, 1960, Ixodes cordifer Neumann, 1908, Ixodes dendrolagi Wilson, 1967, Ixodes hirsti Hassall, 1931, Ixodes holocyclus Neumann, 1899, Ixodes myrmecobii Roberts, 1962 and Ixodes trichosuri Roberts, 1960, were examined morphologically. Subsequently, these Ixodes spp. were genetically characterised using cytochrome c oxidase subunit 1 (cox1) gene and the internal transcribed spacer 2 (ITS-2) of the rRNA. Both morphological and molecular datasets were analysed using various phylogenetic methods to assess the evolutionary relationship of various members of the subgenus Sternalixodes. RESULTS: Phylogenetic analyses of the cox1 sequences and morphological characters datasets revealed that the Australian and Papuan Sternalixodes formed a distinct clade with the New Zealand member of the group I. anatis positioned basally, in a separate clade. Ixodes holocyclus, I. cornuatus and I. myrmecobii formed a distinctive clade in both the cox1 and morphological phylogenies. However, based on phylogenetic analysis of the ITS-2 data, I. holocyclus formed a separate clade whereas I. cornuatus and I. myrmecobii grouped in a different clade. CONCLUSIONS: The cox1 and morphological data suggest that the subgenus Sternalixodes is paraphyletic, and I. anatis is not a sternalixodid tick; hence, it should not be included in the subgenus. Based on the phylogenetic analyses of cox1 and ITS-2 sequences, it appears that I. myrmecobii and I. cornuatus are not subspecies of I. holocyclus. Although this study provided better insights into the taxonomic status of the subgenus Sternalixodes, a complete morphological and molecular (using multiple markers) phylogenetic analysis including all members of the subgenus would be required to more accurately elucidate the evolutionary relationships within the subgenus.
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    Description of Cloacina atthis sp. nov. from the stomach of the euro (Macropus robustus) (Marsupialia: Macropodidae) from Western Australia based on morphological and molecular criteria
    Beveridge, I ; Hanh, N ; Nyein, S ; Cheng, C ; Koehler, A ; Shuttleworth, ME ; Gasser, RB ; Jabbar, A (SPRINGER, 2014-09)
    A new species of strongyloid nematode from the genus Cloacina (Chabertiidae: Cloacininae) is described from the stomach of the hill kangaroo or euro (Macropus robustus) (Marsupialia: Macropodidae) from Western Australia. Cloacina atthis sp. nov. was found only in euros from the Pilbara region in the northwest of Western Australia, in spite of extensive collecting of the same host species from around the Australian continent. C. atthis is most closely related to Cloacina clymene, a species found in the same host species but only in the eastern half of the continent; the two species differ in minor morphological features (the shape of the wall of the buccal capsule, spicule lengths, the degree of sclerotisation of the gubernaculum and the shape of the vagina) as well as in differences in the internal transcribed spacers of ribosomal DNA. This study highlights the importance of using molecular methods when investigating the apparently disjunct distributions of strongyloid nematodes.
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    Pharyngostrongylus thylogale n. sp (Nematoda: Strongylida) from the stomachs of macropodid marsupials defined by morphological and molecular criteria
    Chilton, NB ; Huby-Chilton, F ; Gasser, RB ; Koehler, AV ; Beveridge, I (SPRINGER, 2016-10)
    Pharyngostrongylus thylogale n. sp. (Nematoda: Strongylida) is described from the stomach of the red-legged pademelon, Thylogale stigmatica (Gould) (Marsupialia: Macropodidae) from north-eastern Queensland and Papua New Guinea, having formerly been confused with P. iota Johnston & Mawson, 1939. Pharyngostrongylus thylogale n. sp. differs from all congeners in having 12 labial crown elements rather than eight or 16. Pharyngostrongylus iota was found in T. stigmatica, but only in southern Queensland and northern New South Wales, in the subspecies T. s. wilcoxi, compared with P. thylogale n. sp. which was found in T. s. stigmatica in northern Queensland and T. s. oriomo in Papua New Guinea. Differences in the sequences of the first and second internal transcribed spacers (ITS-1 and ITS-2) of the nuclear ribosomal DNA of P. thylogale n. sp. and ten congeners support the erection of the new species, and the validity of the morphospecies examined. However, results of the phylogenetic analyses of the molecular data also provide evidence for the existence of cryptic species within P. kappa Mawson, 1965. No obvious co-evolutionary relationships were observed between parasite species and their macropodid marsupial hosts.