The Experts below are selected from a list of 201 Experts worldwide ranked by ideXlab platform
S. C. Bishop - One of the best experts on this subject based on the ideXlab platform.
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Genome-wide association and regional heritability mapping to identify loci underlying variation in nematode resistance and body weight in Scottish Blackface lambs
Heredity, 2013Co-Authors: V Riggio, M.j. Stear, O Matika, R Pong-wong, S. C. BishopAbstract:The genetic architecture underlying nematode resistance and body weight in Blackface lambs was evaluated comparing genome-wide association (GWA) and regional heritability mapping (RHM) approaches. The traits analysed were faecal egg count (FEC) and immunoglobulin A activity against third-stage larvae from Teladorsagia circumcincta , as indicators of nematode resistance, and body weight in a population of 752 Scottish Blackface lambs, genotyped with the 50k single-nucleotide polymorphism (SNP) chip. FEC for both Nematodirus and Strongyles nematodes (excluding Nematodirus ), as well as body weight were collected at approximately 16, 20 and 24 weeks of age. In addition, a weighted average animal effect was estimated for both FEC and body weight traits. After quality control, 44 388 SNPs were available for the GWA analysis and 42 841 for the RHM, which utilises only mapped SNPs. The same fixed effects were used in both analyses: sex, year, management group, litter size and age of dam, with day of birth as covariate. Some genomic regions of interest for both nematode resistance and body weight traits were identified, using both GWA and RHM approaches. For both methods, strong evidence for association was found on chromosome 14 for Nematodirus average animal effect, chromosome 6 for Strongyles FEC at 16 weeks and chromosome 6 for body weight at 16 weeks. Across the entire data set, RHM identified more regions reaching the suggestive level than GWA, suggesting that RHM is capable of capturing some of the variation not detected by GWA analyses.
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Quantitative trait loci associated with parasitic infection in Scottish blackface sheep
Heredity, 2006Co-Authors: G Davies, Mohamed Ahmed Ezzeddin Benothman, A. Kerr, S. Mitchell, M.j. Stear, O Abuagob, S. C. BishopAbstract:This study aimed to identify quantitative trait loci associated with endoparasitic infection in Scottish Blackface sheep. Data were collected from 789 animals over a 3-year period. All of the animals were continually exposed to a mixed nematode infection by grazing. Faecal samples were collected in August, September and October each year at ca. 16, 20 and 24 weeks of age; Nematodirus spp. eggs were counted separately from the other species of nematodes. Blood samples were collected in October from which immunoglobulin A (IgA) activity was measured and DNA was extracted for genotyping. In total, 139 Microsatellite markers were genotyped across eight chromosomal regions (chromosomes 1, 2, 3, 5, 14, 18, 20 and 21) in the sires and progeny were genotyped for the markers that were polymorphic in their sire. Evidence was found for quantitative trait loci (QTL) on chromosomes 2, 3, 14 and 20. QTL associated with specific IgA activity were identified in chromosomes 3 and 20, in regions close to IFNG (chromosome 3) and the MHC (chromosome 20). QTL associated with Nematodirus FEC were identified on chromosomes 2, 3 and 14. Lastly, QTL associated with non-Nematodirus Strongyle FEC were identified on chromosomes 3 and 20. This study has shown that some aspects of host resistance to gastrointestinal parasites are under strong genetic control, therefore these QTL could be utilised in a marker-assisted selection scheme to increase host resistance to gastrointestinal parasites.
Neil B Chilton - One of the best experts on this subject based on the ideXlab platform.
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Internal transcribed spacer rDNA can be used to infer the phylogenetic relationships of species within the genus Nematodirus (Nematoda: molineoidea).
International Journal for Parasitology, 2000Co-Authors: Fabienne Audebert, Marie-claude Durette-desset, Neil B ChiltonAbstract:Abstract Sequences of the first internal transcribed spacer rDNA were characterised for four veterinary important species of gastrointestinal nematodes from the genus Nematodirus . The sequence data were combined with previously published data of the second internal transcribed spacer to determine whether these rDNA regions provided a suitable number of informative characters to determine the phylogenetic relationships of species within the genus. A total of 32 alignment positions of the first internal transcribed spacer data set and 33 characters from the second internal transcribed spacer data set were informative in phylogenetic analyses. Irrespective of whether the data from each spacer were analysed separately or combined, only one most parsimonious tree was produced, with the relationships of the four species fully resolved. In addition, several regions of conservatism in the first internal transcribed spacer sequence among the four Nematodirus species suggests that this rDNA region may also provide phylogenetic information for higher taxonomic levels within the Molineoidea.
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Differences in the second internal transcribed spacer of four species of Nematodirus (Nematoda: Molineidae)☆
International Journal for Parasitology, 1998Co-Authors: Lisa A. Newton, Neil B Chilton, Ian Beveridge, Robin B. GasserAbstract:Abstract Genetic differences among Nematodirus spathiger, Nematodirus filicollis, Nematodirus helvetianus and Nematodirus battus in the nucleotide sequence of the second internal transcribed spacer (ITS-2) of ribosomal DNA ranged from 3.9 to 24.7%. Pairwise comparisons of their ITS-2 sequences indicated that the most genetically similar species were N. spathiger and N. helvetianus. N. battus was the most genetically distinct species, with differences ranging from 22.8 to 24.7% with respect to the other three species. Some of the nucleotide differences among species provided different endonuclease restriction sites that could be used in restriction fragment length polymorphism studies. The ITS-2 sequence data may prove useful in studies of the systematics of molineid nematodes.
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differences in the second internal transcribed spacer of four species of Nematodirus nematoda molineidae
International Journal for Parasitology, 1998Co-Authors: Lisa A. Newton, Neil B Chilton, Ian Beveridge, Robin B. GasserAbstract:Genetic differences among Nematodirus spathiger, Nematodirus filicollis, Nematodirus helvetianus and Nematodirus battus in the nucleotide sequence of the second internal transcribed spacer (ITS-2) of ribosomal DNA ranged from 3.9 to 24.7%. Pairwise comparisons of their ITS-2 sequences indicated that the most genetically similar species were N. spathiger and N. helvetianus. N. battus was the most genetically distinct species, with differences ranging from 22.8 to 24.7% with respect to the other three species. Some of the nucleotide differences among species provided different endonuclease restriction sites that could be used in restriction fragment length polymorphism studies. The ITS-2 sequence data may prove useful in studies of the systematics of molineid nematodes.
Robin B. Gasser - One of the best experts on this subject based on the ideXlab platform.
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Identification of Nematodirus species (Nematoda: Molineidae) from wild ruminants in Italy using ribosomal DNA markers.
International Journal for Parasitology, 1999Co-Authors: Robin B. Gasser, Luca Rossi, Xing-quan ZhuAbstract:Abstract The sequence of the second internal transcribed spacer of ribosomal DNA was determined for four species of Nematodirus ( Nematodirus rupicaprae , Nematodirus oiratianus , Nematodirus davtiani alpinus and Nematodirus europaeus ) from roe deer or alpine chamois. The second internal transcribed spacer of the four species varied in length from 228 to 236 bp, and the G+C contents ranged from 41 to 44%. While no intraspecific sequence variation was detected among multiple samples representing three of the taxa, sequence differences of 5.9–9.7% were detected among the four species. Nematodirus davtiani alpinus and N. rupicaprae were genetically most similar (94.1%), followed by N. oiratianus , N. europaeus and N. rupicaprae (91.1–91.5%), whereas N. oiratianus was genetically most different from N. davtiani alpinus . The interspecific sequence differences were exploited for the delineation of the four species by PCR-based restriction fragment length polymorphism (using two enzymes) and single-strand conformation polymorphism. The results have implications for diagnosis, epidemiology and for studying the systematics of the Nematodirinae.
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Differences in the second internal transcribed spacer of four species of Nematodirus (Nematoda: Molineidae)☆
International Journal for Parasitology, 1998Co-Authors: Lisa A. Newton, Neil B Chilton, Ian Beveridge, Robin B. GasserAbstract:Abstract Genetic differences among Nematodirus spathiger, Nematodirus filicollis, Nematodirus helvetianus and Nematodirus battus in the nucleotide sequence of the second internal transcribed spacer (ITS-2) of ribosomal DNA ranged from 3.9 to 24.7%. Pairwise comparisons of their ITS-2 sequences indicated that the most genetically similar species were N. spathiger and N. helvetianus. N. battus was the most genetically distinct species, with differences ranging from 22.8 to 24.7% with respect to the other three species. Some of the nucleotide differences among species provided different endonuclease restriction sites that could be used in restriction fragment length polymorphism studies. The ITS-2 sequence data may prove useful in studies of the systematics of molineid nematodes.
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differences in the second internal transcribed spacer of four species of Nematodirus nematoda molineidae
International Journal for Parasitology, 1998Co-Authors: Lisa A. Newton, Neil B Chilton, Ian Beveridge, Robin B. GasserAbstract:Genetic differences among Nematodirus spathiger, Nematodirus filicollis, Nematodirus helvetianus and Nematodirus battus in the nucleotide sequence of the second internal transcribed spacer (ITS-2) of ribosomal DNA ranged from 3.9 to 24.7%. Pairwise comparisons of their ITS-2 sequences indicated that the most genetically similar species were N. spathiger and N. helvetianus. N. battus was the most genetically distinct species, with differences ranging from 22.8 to 24.7% with respect to the other three species. Some of the nucleotide differences among species provided different endonuclease restriction sites that could be used in restriction fragment length polymorphism studies. The ITS-2 sequence data may prove useful in studies of the systematics of molineid nematodes.
Marie-claude Durette-desset - One of the best experts on this subject based on the ideXlab platform.
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Development of Nematodirus spathiger (Nematoda, Molineoidea) in the rabbit and comparison with other Nematodirus spp parasites of ruminants
Parasitology Research, 2004Co-Authors: Fabienne Audebert, J. Cassone, D. Kerboeuf, Marie-claude Durette-dessetAbstract:The morphogenesis and chronology of the life cycle of Nematodirus spathiger (Railliet, 1896), a parasite of ruminants, were studied in detail in an experimental host. Twenty-four worm-free rabbits were each infected per os with N. spathiger larvae and were killed at 12 h after infection (12 HAI) and every day from 1 DAI to 23 DAI. By 12 HAI , all the larvae were exsheathed and present in the small intestine. The third moult occurred between 4 DAI and 5 DAI. The last moult occurred between 13 DAI and 16 DAI. The prepatent period lasted 21–24 days. The distribution of N. spathiger along the small intestine of the rabbit was assessed. The chronology of the life cycles was compared for various Nematodirus spp from ruminants in their natural hosts and in the rabbit ( N. battus , N. spathiger ).
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Internal transcribed spacer rDNA can be used to infer the phylogenetic relationships of species within the genus Nematodirus (Nematoda: molineoidea).
International Journal for Parasitology, 2000Co-Authors: Fabienne Audebert, Marie-claude Durette-desset, Neil B ChiltonAbstract:Abstract Sequences of the first internal transcribed spacer rDNA were characterised for four veterinary important species of gastrointestinal nematodes from the genus Nematodirus . The sequence data were combined with previously published data of the second internal transcribed spacer to determine whether these rDNA regions provided a suitable number of informative characters to determine the phylogenetic relationships of species within the genus. A total of 32 alignment positions of the first internal transcribed spacer data set and 33 characters from the second internal transcribed spacer data set were informative in phylogenetic analyses. Irrespective of whether the data from each spacer were analysed separately or combined, only one most parsimonious tree was produced, with the relationships of the four species fully resolved. In addition, several regions of conservatism in the first internal transcribed spacer sequence among the four Nematodirus species suggests that this rDNA region may also provide phylogenetic information for higher taxonomic levels within the Molineoidea.
Fabienne Audebert - One of the best experts on this subject based on the ideXlab platform.
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Development of Nematodirus spathiger (Nematoda, Molineoidea) in the rabbit and comparison with other Nematodirus spp parasites of ruminants
Parasitology Research, 2004Co-Authors: Fabienne Audebert, J. Cassone, D. Kerboeuf, Marie-claude Durette-dessetAbstract:The morphogenesis and chronology of the life cycle of Nematodirus spathiger (Railliet, 1896), a parasite of ruminants, were studied in detail in an experimental host. Twenty-four worm-free rabbits were each infected per os with N. spathiger larvae and were killed at 12 h after infection (12 HAI) and every day from 1 DAI to 23 DAI. By 12 HAI , all the larvae were exsheathed and present in the small intestine. The third moult occurred between 4 DAI and 5 DAI. The last moult occurred between 13 DAI and 16 DAI. The prepatent period lasted 21–24 days. The distribution of N. spathiger along the small intestine of the rabbit was assessed. The chronology of the life cycles was compared for various Nematodirus spp from ruminants in their natural hosts and in the rabbit ( N. battus , N. spathiger ).
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Internal transcribed spacer rDNA can be used to infer the phylogenetic relationships of species within the genus Nematodirus (Nematoda: molineoidea).
International Journal for Parasitology, 2000Co-Authors: Fabienne Audebert, Marie-claude Durette-desset, Neil B ChiltonAbstract:Abstract Sequences of the first internal transcribed spacer rDNA were characterised for four veterinary important species of gastrointestinal nematodes from the genus Nematodirus . The sequence data were combined with previously published data of the second internal transcribed spacer to determine whether these rDNA regions provided a suitable number of informative characters to determine the phylogenetic relationships of species within the genus. A total of 32 alignment positions of the first internal transcribed spacer data set and 33 characters from the second internal transcribed spacer data set were informative in phylogenetic analyses. Irrespective of whether the data from each spacer were analysed separately or combined, only one most parsimonious tree was produced, with the relationships of the four species fully resolved. In addition, several regions of conservatism in the first internal transcribed spacer sequence among the four Nematodirus species suggests that this rDNA region may also provide phylogenetic information for higher taxonomic levels within the Molineoidea.
