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Mladen Vujosevic - One of the best experts on this subject based on the ideXlab platform.
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host b chromosomes as potential sex ratio distorters of intestinal nematode infrapopulations in the yellow necked mouse Apodemus flavicollis
Journal of Helminthology, 2019Co-Authors: Vladimir M Jovanovic, Jelena Blagojevic, Borislav Cabrilo, Olivera Bjeliccabrilo, Ivana Budinski, Tanja Adnađevic, Mladen VujosevicAbstract:The yellow-necked mouse, Apodemus flavicollis, can be considered as a model for genetic polymorphism produced by the frequent presence of supernumerary or B chromosomes (Bs). Host genetic background is rarely taken into account in studies of parasite sex ratio. The main aim of this study was to investigate the range of infrapopulation sex ratios for nematode parasites of the yellow-necked mouse and to determine which factors most influence variation in parasite sex ratios. Six nematode species found in the collected yellow-necked mice were analysed. We confirmed the predominant pattern of female-biased sex ratios in vertebrate parasite infrapopulations. The presence of B chromosomes in host genomes played an important role in infrapopulations of Heligmosomoides polygyrus, Syphacia stroma and Trichuris muris, as hosts with B chromosomes carried a higher proportion of males. The relative increase of males in infrapopulations could result from a shift in parasite life history strategy, induced by adaptation to the specific host genotypes (Bs present). In a meta-analysis with previously published data, the sex determination system was demonstrated to play a significant role in nematode sex ratio variation, as well as specific life history patterns, such as the place of egg hatching.
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the origin of b chromosomes in yellow necked mice Apodemus flavicollis break rules but keep playing the game
PLOS ONE, 2017Co-Authors: Marija Rajicic, Jelena Blagojevic, Ivana Budinski, Tanja Adnađevic, Svetlana A Romanenko, T V Karamysheva, A S Bogdanov, Vladimir A Trifonov, N B Rubtsov, Mladen VujosevicAbstract:B chromosomes (Bs) are known for more than hundred years but their origin, structure and pattern of evolution are not well understood. In the past few years new methodological approaches, involving isolation of Bs followed by whole DNA amplification, DNA probe generation, and fluorescent in situ hybridization (FISH) or the B chromosome DNA sequencing, has allowed detailed analysis of their origin and molecular structure in different species. In this study we explored the origin of Bs in the yellow-necked wood mouse, Apodemus flavicollis, using generation of microdissected DNA probes followed by FISH on metaphase chromosomes. Bs of A. flavicollis were successfully isolated and DNA was used as the template for B-specific probes for the first time. We revealed homology of DNA derived from the analyzed B chromosomes to the pericentromeric region (PR) of sex chromosomes and subtelomeric region of two pairs of small autosomes, but lower homology to the rest of the Y chromosome. Moreover, all analysed Bs had the same structure regardless of their number per individual or the great geographic distance between examined populations from the Balkan Peninsula (Serbia) and Eastern Europe (south region of Russia and central Belarus). Therefore, it was suggested that B chromosomes in A. flavicollis have a unique common origin from the PR of sex chromosomes, and/or similar evolutionary pattern.
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exploring supernumeraries a new marker for screening of b chromosomes presence in the yellow necked mouse Apodemus flavicollis
PLOS ONE, 2016Co-Authors: Vanja Bugarskistanojevic, Jelena Blagojevic, Marija Rajicic, Gorana Stamenkovic, Thomas Liehr, Nadezda Kosyakova, Mladen VujosevicAbstract:Since the density of simple sequence repeats (SSRs) may vary between different chromosomes of the same species in eukaryotic genomes, we screened SSRs of the whole genome of the yellow necked mouse, Apodemus flavicollis, in order to reveal SSR profiles specific for animals carrying B chromosomes. We found that the 2200 bp band was amplified by primer (CAG)4AC to a highly increased level in samples with B chromosomes. This quantitative difference (B-marker) between animals with (+B) and without (0B) B chromosomes was used to screen 20 populations (387 animals). The presence/absence of Bs was confirmed in 96.5% of 342 non mosaic individuals, which recommends this method for noninvasive B-presence detection. A group of 45 animals with mosaic and micro B (μB) karyotypes was considered separately and showed 55.6% of overall congruence between karyotyping and molecular screening results. Relative quantification by qPCR of two different targeted sequences from B-marker indicated that these B-specific fragments are multiplied on B chromosomes. It also confirms our assumption that different types of Bs with variable molecular composition may exist in the same individual and between individuals of this species. Our results substantiate the origin of Bs from the standard chromosomal complement. The B-marker showed 98% sequence identity with the serine/threonine protein kinase VRK1 gene, similarly to findings reported for Bs from phylogenetically highly distant mammalian species. Evolutionarily conserved protein-coding genes found in Bs, including this one in A. flavicollis, could suggest a common evolutionary pathway.
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diversity of nematodes in the yellow necked field mouse Apodemus flavicollis from the peripannonic region of serbia
Journal of Helminthology, 2016Co-Authors: Borislav Cabrilo, Jelena Blagojevic, Vladimir M Jovanovic, Olivera Bjeliccabrilo, Ivana Budinski, Mladen VujosevicAbstract:Up to six nematode species were identified from 86 specimens of the yellow-necked field mouse Apodemus flavicollis from three mountainous localities known as Avala, Cer and Liskovac in Serbia. The highest prevalence of infection of 97% was recorded from Mt. Avala. Only one nematode species, Syphacia frederici, occurred in all three localities. There was complete overlap in nematode species from Mts. Avala and Liskovac, whereas the taxonomic distinctness of Mt. Cer was seen in the presence of the insect-transmitted species Rictularia proni. Locality was a statistically significant factor in all the best-fitted generalized linear models of variation in abundances. The highest level of both species richness and parasite alpha diversity (Shannon's H= 1.47) was found in the easternmost Mt. Liskovac, whereas the diversity indices were lowest for the westernmost Mt. Cer (Shannon's H= 0.48). In view of this geographical difference, the beta diversity indices were calculated along a west to east longitudinal gradient.
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screening of b chromosomes for presence of two genes in yellow necked mice Apodemus flavicollis mammalia rodentia
Genetika, 2015Co-Authors: Marija Rajicic, Jelena Blagojevic, Tanja Adnadjevic, Gorana Stamenkovic, Mladen VujosevicAbstract:B chromosomes (Bs) are a very heterogeneous group of extra chromosomes. In various species Bs occur with different nucleotide sequences ranging from repetitive to protein coding. In yellow-necked field mice, Apodemus flavicollis Bs are small euchromatic chromosomes and untill now, only few molecular analyses have been conducted. In this study we examined A. flavicollis individuals with different number of Bs for presence of two genes, C-KIT and 18S rRNA. The C-KIT proto-oncogene was found on Bs in three Canidae species and one Cervidae species. This gene is a coding receptor critical for proliferation and cell differentiation of hematopoietic, melanoblast and primordial germ cells, and is highly conserved within mammals. While using semiquantitative PCR, we did not notice any difference in the C-KIT band intensity among animals with different number of Bs (0-3). The presence of only one copy of C- KIT gene was confirmed using real time-PCR on genomic DNA of A. flavicollis specimens with different number of Bs. rRNA genes in eukaryotes’ genome are organized like units of tandem repeated sequences. The units form distinct clusters on one to several chromosome pairs. rRNA genes were found on Bs in different species including two species of genus Apodemus. One particular sample with 2 Bs showed the number of 18S rRNA gene about three times that of the calibrator 0 B sample. This result can indicate the presence of 18S rRNA gene on Bs, but its confirmation requires the implementation of other methods. Still, we can neither confirm nor deny the existence of pseudogen of tested target genes, or lose of exon 1 of C-KIT protooncogen in Bs of A. flavicollis. Our findings are further discussed. [Projekat Ministarstva nauke Republike Srbije, br. 173003]
Jelena Blagojevic - One of the best experts on this subject based on the ideXlab platform.
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host b chromosomes as potential sex ratio distorters of intestinal nematode infrapopulations in the yellow necked mouse Apodemus flavicollis
Journal of Helminthology, 2019Co-Authors: Vladimir M Jovanovic, Jelena Blagojevic, Borislav Cabrilo, Olivera Bjeliccabrilo, Ivana Budinski, Tanja Adnađevic, Mladen VujosevicAbstract:The yellow-necked mouse, Apodemus flavicollis, can be considered as a model for genetic polymorphism produced by the frequent presence of supernumerary or B chromosomes (Bs). Host genetic background is rarely taken into account in studies of parasite sex ratio. The main aim of this study was to investigate the range of infrapopulation sex ratios for nematode parasites of the yellow-necked mouse and to determine which factors most influence variation in parasite sex ratios. Six nematode species found in the collected yellow-necked mice were analysed. We confirmed the predominant pattern of female-biased sex ratios in vertebrate parasite infrapopulations. The presence of B chromosomes in host genomes played an important role in infrapopulations of Heligmosomoides polygyrus, Syphacia stroma and Trichuris muris, as hosts with B chromosomes carried a higher proportion of males. The relative increase of males in infrapopulations could result from a shift in parasite life history strategy, induced by adaptation to the specific host genotypes (Bs present). In a meta-analysis with previously published data, the sex determination system was demonstrated to play a significant role in nematode sex ratio variation, as well as specific life history patterns, such as the place of egg hatching.
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the origin of b chromosomes in yellow necked mice Apodemus flavicollis break rules but keep playing the game
PLOS ONE, 2017Co-Authors: Marija Rajicic, Jelena Blagojevic, Ivana Budinski, Tanja Adnađevic, Svetlana A Romanenko, T V Karamysheva, A S Bogdanov, Vladimir A Trifonov, N B Rubtsov, Mladen VujosevicAbstract:B chromosomes (Bs) are known for more than hundred years but their origin, structure and pattern of evolution are not well understood. In the past few years new methodological approaches, involving isolation of Bs followed by whole DNA amplification, DNA probe generation, and fluorescent in situ hybridization (FISH) or the B chromosome DNA sequencing, has allowed detailed analysis of their origin and molecular structure in different species. In this study we explored the origin of Bs in the yellow-necked wood mouse, Apodemus flavicollis, using generation of microdissected DNA probes followed by FISH on metaphase chromosomes. Bs of A. flavicollis were successfully isolated and DNA was used as the template for B-specific probes for the first time. We revealed homology of DNA derived from the analyzed B chromosomes to the pericentromeric region (PR) of sex chromosomes and subtelomeric region of two pairs of small autosomes, but lower homology to the rest of the Y chromosome. Moreover, all analysed Bs had the same structure regardless of their number per individual or the great geographic distance between examined populations from the Balkan Peninsula (Serbia) and Eastern Europe (south region of Russia and central Belarus). Therefore, it was suggested that B chromosomes in A. flavicollis have a unique common origin from the PR of sex chromosomes, and/or similar evolutionary pattern.
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exploring supernumeraries a new marker for screening of b chromosomes presence in the yellow necked mouse Apodemus flavicollis
PLOS ONE, 2016Co-Authors: Vanja Bugarskistanojevic, Jelena Blagojevic, Marija Rajicic, Gorana Stamenkovic, Thomas Liehr, Nadezda Kosyakova, Mladen VujosevicAbstract:Since the density of simple sequence repeats (SSRs) may vary between different chromosomes of the same species in eukaryotic genomes, we screened SSRs of the whole genome of the yellow necked mouse, Apodemus flavicollis, in order to reveal SSR profiles specific for animals carrying B chromosomes. We found that the 2200 bp band was amplified by primer (CAG)4AC to a highly increased level in samples with B chromosomes. This quantitative difference (B-marker) between animals with (+B) and without (0B) B chromosomes was used to screen 20 populations (387 animals). The presence/absence of Bs was confirmed in 96.5% of 342 non mosaic individuals, which recommends this method for noninvasive B-presence detection. A group of 45 animals with mosaic and micro B (μB) karyotypes was considered separately and showed 55.6% of overall congruence between karyotyping and molecular screening results. Relative quantification by qPCR of two different targeted sequences from B-marker indicated that these B-specific fragments are multiplied on B chromosomes. It also confirms our assumption that different types of Bs with variable molecular composition may exist in the same individual and between individuals of this species. Our results substantiate the origin of Bs from the standard chromosomal complement. The B-marker showed 98% sequence identity with the serine/threonine protein kinase VRK1 gene, similarly to findings reported for Bs from phylogenetically highly distant mammalian species. Evolutionarily conserved protein-coding genes found in Bs, including this one in A. flavicollis, could suggest a common evolutionary pathway.
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diversity of nematodes in the yellow necked field mouse Apodemus flavicollis from the peripannonic region of serbia
Journal of Helminthology, 2016Co-Authors: Borislav Cabrilo, Jelena Blagojevic, Vladimir M Jovanovic, Olivera Bjeliccabrilo, Ivana Budinski, Mladen VujosevicAbstract:Up to six nematode species were identified from 86 specimens of the yellow-necked field mouse Apodemus flavicollis from three mountainous localities known as Avala, Cer and Liskovac in Serbia. The highest prevalence of infection of 97% was recorded from Mt. Avala. Only one nematode species, Syphacia frederici, occurred in all three localities. There was complete overlap in nematode species from Mts. Avala and Liskovac, whereas the taxonomic distinctness of Mt. Cer was seen in the presence of the insect-transmitted species Rictularia proni. Locality was a statistically significant factor in all the best-fitted generalized linear models of variation in abundances. The highest level of both species richness and parasite alpha diversity (Shannon's H= 1.47) was found in the easternmost Mt. Liskovac, whereas the diversity indices were lowest for the westernmost Mt. Cer (Shannon's H= 0.48). In view of this geographical difference, the beta diversity indices were calculated along a west to east longitudinal gradient.
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screening of b chromosomes for presence of two genes in yellow necked mice Apodemus flavicollis mammalia rodentia
Genetika, 2015Co-Authors: Marija Rajicic, Jelena Blagojevic, Tanja Adnadjevic, Gorana Stamenkovic, Mladen VujosevicAbstract:B chromosomes (Bs) are a very heterogeneous group of extra chromosomes. In various species Bs occur with different nucleotide sequences ranging from repetitive to protein coding. In yellow-necked field mice, Apodemus flavicollis Bs are small euchromatic chromosomes and untill now, only few molecular analyses have been conducted. In this study we examined A. flavicollis individuals with different number of Bs for presence of two genes, C-KIT and 18S rRNA. The C-KIT proto-oncogene was found on Bs in three Canidae species and one Cervidae species. This gene is a coding receptor critical for proliferation and cell differentiation of hematopoietic, melanoblast and primordial germ cells, and is highly conserved within mammals. While using semiquantitative PCR, we did not notice any difference in the C-KIT band intensity among animals with different number of Bs (0-3). The presence of only one copy of C- KIT gene was confirmed using real time-PCR on genomic DNA of A. flavicollis specimens with different number of Bs. rRNA genes in eukaryotes’ genome are organized like units of tandem repeated sequences. The units form distinct clusters on one to several chromosome pairs. rRNA genes were found on Bs in different species including two species of genus Apodemus. One particular sample with 2 Bs showed the number of 18S rRNA gene about three times that of the calibrator 0 B sample. This result can indicate the presence of 18S rRNA gene on Bs, but its confirmation requires the implementation of other methods. Still, we can neither confirm nor deny the existence of pseudogen of tested target genes, or lose of exon 1 of C-KIT protooncogen in Bs of A. flavicollis. Our findings are further discussed. [Projekat Ministarstva nauke Republike Srbije, br. 173003]
Peter J Hudson - One of the best experts on this subject based on the ideXlab platform.
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heligmosomoides polygyrus reduces infestation of ixodes ricinus in free living yellow necked mice Apodemus flavicollis
Parasitology, 2009Co-Authors: Nicola Ferrari, Annapaola Rizzoli, Isabella M Cattadori, Peter J HudsonAbstract:Free-living animals are usually inhabited by a community of parasitic species that can interact with each other and alter both host susceptibility and parasite transmission. In this study we tested the prediction that an increase in the gastrointestinal nematode Heligmosomoides polygyrus would increase the infestation of the tick Ixodes ricinus, in free-living yellow-necked mice, Apodemus flavicollis. An extensive cross-sectional trapping survey identified a negative relationship between H. polygyrus and I. ricinus counter to the prediction. An experimental reduction of the nematode infection through anthelmintic treatment resulted in an increase in tick infestation, suggesting that this negative association was one of cause and effect. Host characteristics (breeding condition and age) and habitat variables also contributed to affect tick infestation. While these results were counter to the prediction, they still support the hypothesis that interactions between parasite species can shape parasite community dynamics in natural systems. Laboratory models may act differently from natural populations and the mechanism generating the negative association is discussed.
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sex role as factor of heterogeneity transmission in host macroparasite system the case study of Apodemus flavicollis
Parassitologia, 2004Co-Authors: Nicola Ferrari, Annapaola Rizzoli, E Cattadori, Peter J HudsonAbstract:The predisposition of parasite to aggregate is generated by heterogeneity in exposure and susceptibility to infection. Among factors such age, body condition and diet that may influence the individual variations in transmission and establishment of parasite, sex is recognised to play a determinant role. Indeed in vertebrate, host parasite tend to be male biased. These evidences suggest sex differences in susceptibility, but whether sexes differs in their contribution in transmission is still debated. We analysed Apodemus flavicollis and its parasites Heligmosomoides polygyrus focusing whether sex is important in influencing the dynamics of infection in free living animal population. Methods: From April 2001 to September 2001 a field experiment was carried out on a population monitored with capture-mark-recapture live trapping (14 994 trap night) in 9 samples areas. The parasite burden was selectively reduced by anthelmintic treatment in all males of 3 areas in all females of other 3 areas while 3 remanding areas were used as control. During the experiment the dynamics of parasite infestations was monitored by individual faecal samples analysis. The multicapture data were analysed with generalised linear mixed models fitted with negative binomial errors and individual identification and temporal data as random factors. Results: A total of 143 A. flavicollis were trapped, with a total of 319 faecal samples analysed. During the experiments no significant changes in parasite prevalence and EPG was observed in control areas. In the manipulated areas the treated individual decreased the parasite burden. In the areas where females were treated males, compared with control males, did not change their parasite burden. While in areas where males were treated females decreased their parasites load respect to control females. Discussion: The experimental results suggests the role of the male A. flavicollis to drive the infection. Even if the mechanisms generating such pattern are not still clear, such findings suggest the importance of functional groups in maintaining the infections and thus their identification when programming control strategies.
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the role of host sex in parasite dynamics field experiments on the yellow necked mouse Apodemus flavicollis
Ecology Letters, 2003Co-Authors: Nicola Ferrari, Annapaola Rizzoli, Isabella M Cattadori, Javier Nespereira, Peter J HudsonAbstract:We investigated the role of host sex in parasite transmission and questioned: ‘Is host sex important in influencing the dynamics of infection in free living animal populations?’ We experimentally reduced the helminth community of either males or females in a yellownecked mice (Apodemus flavicollis) population using an anthelmintic, in replicated trapping areas, and subsequently monitored the prevalence and intensity of macroparasites in the untreated sex. We focussed on the dominant parasite Heligmosomoides polygyrus and found that reducing parasites in males caused a consistent reduction of parasitic intensity in females, estimated through faecal egg counts, but the removal of parasites in females had no significant influence on the parasites in males. This finding suggests that males are responsible for driving the parasite infection in the host population and females may play a relatively trivial role. The possible mechanisms promoting such patterns are discussed.
Simone Sommer - One of the best experts on this subject based on the ideXlab platform.
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heligmosomoides polygyrus infection is associated with lower mhc class ii gene expression in Apodemus flavicollis indication for immune suppression
Infection Genetics and Evolution, 2011Co-Authors: Jan Axtner, Simone SommerAbstract:Due to their key role in recognizing foreign antigens and triggering the subsequent immune response the genes of the major histocompatibility complex (MHC) provide a potential target for parasites to attack in order to evade detection and expulsion from the host. A diminished MHC gene expression results in less activated T cells and might serve as a gateway for pathogens and parasites. Some parasites are suspected to be immune suppressors and promote co-infections of other parasites even in other parts of the body. In our study we found indications that the gut dwelling nematode Heligmosomoides polygyrus might exert a systemic immunosuppressive effect in yellow-necked mice (Apodemus flavicollis). The amount of hepatic MHC class II DRB gene RNA transcripts in infected mice was negatively associated with infection intensity with H. polygyrus. The hepatic expression of immunosuppressive cytokines, such as transforming growth factor β and interleukin 10 was not associated with H. polygyrus infection. We did not find direct positive associations of H. polygyrus with other helminth species. But the prevalence and infection intensity of the nematodes Syphacia stroma and Trichuris muris were higher in multiple infected individuals. Furthermore, our data indicated antagonistic effects in the helminth community of A. flavicollis as cestode infection correlated negatively with H. polygyrus and helminth species richness. Our study shows that expression analyses of immune relevant genes can also be performed in wildlife, opening new aspects and possibilities for future ecological and evolutionary research.
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validation of internal reference genes for quantitative real time pcr in a non model organism the yellow necked mouse Apodemus flavicollis
BMC Research Notes, 2009Co-Authors: Jan Axtner, Simone SommerAbstract:Background Reference genes are used as internal standards to normalize mRNA abundance in quantitative real-time PCR and thereby allow a direct comparison between samples. So far most of these expression studies used human or classical laboratory model species whereas studies on non-model organism under in-situ conditions are quite rare. However, only studies in free-ranging populations can reveal the effects of natural selection on the expression levels of functional important genes. In order to test the feasibility of gene expression studies in wildlife samples we transferred and validated potential reference genes that were developed for lab mice (Mus musculus) to samples of wild yellow-necked mice, Apodemus flavicollis. The stability and suitability of eight potential reference genes was accessed by the programs BestKeeper, NormFinder and geNorm.
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number of mhc alleles is related to parasite loads in natural populations of yellow necked mice Apodemus flavicollis
Evolutionary Ecology Research, 2009Co-Authors: Yvonne Meyerlucht, Simone SommerAbstract:ABSTRACT Hypothesis: Low levels of immune gene variation (major histocompatibility complex) ina population are associated with increased parasite load and infection intensity. Organism: Different populations of the yellow necked mouse ( Apodemus flavicollis ),a common rodent in European deciduous and mixed forest habitats Methods: We assessed genetic diversity at selectively neutral, non-coding markers (micro-satellites) and adaptive genetic variation at a functionally important part of the immunecomplex MHC (major histocompatibility complex). We investigated the load with gastro-intestinal parasites non-invasively by faecal egg counts and assessed the influence of populationgenetic variation on parasite burden. Results: Both neutral and adaptive genetic diversity differed between mice populations. Wecould not detect an effect of neutral genetic diversity on the parasite burden in a population.Heterozygosity at the MHC did not reveal an effect on the parasite burden either. However, wedid identify significant effects of the number of different MHC alleles in a population onparasite burden. Mice populations with a large number of different MHC alleles displayedlower parasite loads than those populations with few different MHC alleles.
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mhc diversity and the association to nematode parasitism in the yellow necked mouse Apodemus flavicollis
Molecular Ecology, 2005Co-Authors: Yvonne Meyerlucht, Simone SommerAbstract:In vertebrates, the genes of the major histocompatibility complex (MHC) are among the most debated candidates accounting for co-evolutionary processes of host-parasite interaction at the molecular level. The exceptionally high allelic polymorphism found in MHC loci is believed to be maintained by pathogen-driven selection, mediated either through heterozygous advantage or rare allele advantage (= frequency dependent selection). While investigations under natural conditions are still very rare, studies on humans or mice under laboratory conditions revealed support for both hypotheses. We investigated nematode burden and allelic diversity of a functional important MHC class II gene (DRB exon2) in free-ranging yellow-necked mice (Apodemus flavicollis). Twenty-seven distinct Apfl-DRB alleles were detected in 146 individuals with high levels of amino acid sequence divergence, especially at the antigen binding sites (ABS), indicating selection processes acting on this locus. Heterozygosity had no influence on the infection status (being infected or not), the number of different nematode infections (NNI) or the intensity of infection, measured as the individual faecal egg count (FEC). However, significant associations of specific Apfl-DRB alleles to both nematode susceptibility and resistance were found, for all nematodes as well as in separate analyses of the two most common nematodes. Apodemus flavicollis individuals carrying the alleles Apfl-DRB*5 or Apfl-DRB*15 revealed significantly higher FEC than individuals with other alleles. In contrast, the allele Apfl-DRB*23 showed a significant association to low FEC of the most common nematode. Thus, our results provide evidence for pathogen-driven selection acting through rare allele advantage under natural conditions.
Annapaola Rizzoli - One of the best experts on this subject based on the ideXlab platform.
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ljungan virus detected in bank voles myodes glareolus and yellow necked mice Apodemus flavicollis from northern italy
Journal of Wildlife Diseases, 2010Co-Authors: Heidi Christine Hauffe, Therese Olsson, Annapaola Rizzoli, Bo Niklasson, A Bianchi, William KlitzAbstract:Identified in 1998, Ljungan virus (LV; Picornaviridae) causes type 1 diabetes–like symptoms and myocarditis in bank voles (Myodes glareolus) from Sweden and Denmark, and may be a zoonotic agent of several important diseases (e.g., intrauterine fetal death, type 1 diabetes, Guillain-Barre syndrome, and myocarditis). Using a real-time reverse transcriptase–polymerase chain reaction assay and sequence analysis, we detected LV in bank voles, and for the first time, in yellow-necked mice (Apodemus flavicollis) collected during 2006 from a site in northern Italy. The global distribution of LV and its role as a mammalian pathogen deserve further attention.
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heligmosomoides polygyrus reduces infestation of ixodes ricinus in free living yellow necked mice Apodemus flavicollis
Parasitology, 2009Co-Authors: Nicola Ferrari, Annapaola Rizzoli, Isabella M Cattadori, Peter J HudsonAbstract:Free-living animals are usually inhabited by a community of parasitic species that can interact with each other and alter both host susceptibility and parasite transmission. In this study we tested the prediction that an increase in the gastrointestinal nematode Heligmosomoides polygyrus would increase the infestation of the tick Ixodes ricinus, in free-living yellow-necked mice, Apodemus flavicollis. An extensive cross-sectional trapping survey identified a negative relationship between H. polygyrus and I. ricinus counter to the prediction. An experimental reduction of the nematode infection through anthelmintic treatment resulted in an increase in tick infestation, suggesting that this negative association was one of cause and effect. Host characteristics (breeding condition and age) and habitat variables also contributed to affect tick infestation. While these results were counter to the prediction, they still support the hypothesis that interactions between parasite species can shape parasite community dynamics in natural systems. Laboratory models may act differently from natural populations and the mechanism generating the negative association is discussed.
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temporal variation of ixodes ricinus intensity on the rodent host Apodemus flavicollis in relation to local climate and host dynamics
Vector-borne and Zoonotic Diseases, 2007Co-Authors: Roberto Rosa, Andrea Pugliese, Mini Ghosh, Sarah E Perkins, Annapaola RizzoliAbstract:The risk to humans of contracting tick-borne zoonotic diseases depends on the risk of a bite from an infected tick, which can be broken down into its component parts as the number of host-seeking ticks in the environment, in particular nymphs, and the prevalence of tick-borne pathogens they are carrying. In turn, the prevalence of tick-borne pathogens is dependent upon tick biting intensity on hosts that support transmission between ticks; namely rodents. These ticks once fed moult into the next life stage and search for the next blood meal, thus posing a zoonotic risk. Here, we analyse tick biting intensity on rodents in a known tick-borne encephalitis (TBE) focus in Trentino (northern Italy). We examine patterns of tick demography and the influence of host densities and climate on ticks' generation time, development rates, tick density and intensity. During the period 2000–2004, a population of the yellow-necked mouse, Apodemus flavicollis, the most important TBE transmission host, was intensively monit...
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sex role as factor of heterogeneity transmission in host macroparasite system the case study of Apodemus flavicollis
Parassitologia, 2004Co-Authors: Nicola Ferrari, Annapaola Rizzoli, E Cattadori, Peter J HudsonAbstract:The predisposition of parasite to aggregate is generated by heterogeneity in exposure and susceptibility to infection. Among factors such age, body condition and diet that may influence the individual variations in transmission and establishment of parasite, sex is recognised to play a determinant role. Indeed in vertebrate, host parasite tend to be male biased. These evidences suggest sex differences in susceptibility, but whether sexes differs in their contribution in transmission is still debated. We analysed Apodemus flavicollis and its parasites Heligmosomoides polygyrus focusing whether sex is important in influencing the dynamics of infection in free living animal population. Methods: From April 2001 to September 2001 a field experiment was carried out on a population monitored with capture-mark-recapture live trapping (14 994 trap night) in 9 samples areas. The parasite burden was selectively reduced by anthelmintic treatment in all males of 3 areas in all females of other 3 areas while 3 remanding areas were used as control. During the experiment the dynamics of parasite infestations was monitored by individual faecal samples analysis. The multicapture data were analysed with generalised linear mixed models fitted with negative binomial errors and individual identification and temporal data as random factors. Results: A total of 143 A. flavicollis were trapped, with a total of 319 faecal samples analysed. During the experiments no significant changes in parasite prevalence and EPG was observed in control areas. In the manipulated areas the treated individual decreased the parasite burden. In the areas where females were treated males, compared with control males, did not change their parasite burden. While in areas where males were treated females decreased their parasites load respect to control females. Discussion: The experimental results suggests the role of the male A. flavicollis to drive the infection. Even if the mechanisms generating such pattern are not still clear, such findings suggest the importance of functional groups in maintaining the infections and thus their identification when programming control strategies.
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the role of host sex in parasite dynamics field experiments on the yellow necked mouse Apodemus flavicollis
Ecology Letters, 2003Co-Authors: Nicola Ferrari, Annapaola Rizzoli, Isabella M Cattadori, Javier Nespereira, Peter J HudsonAbstract:We investigated the role of host sex in parasite transmission and questioned: ‘Is host sex important in influencing the dynamics of infection in free living animal populations?’ We experimentally reduced the helminth community of either males or females in a yellownecked mice (Apodemus flavicollis) population using an anthelmintic, in replicated trapping areas, and subsequently monitored the prevalence and intensity of macroparasites in the untreated sex. We focussed on the dominant parasite Heligmosomoides polygyrus and found that reducing parasites in males caused a consistent reduction of parasitic intensity in females, estimated through faecal egg counts, but the removal of parasites in females had no significant influence on the parasites in males. This finding suggests that males are responsible for driving the parasite infection in the host population and females may play a relatively trivial role. The possible mechanisms promoting such patterns are discussed.