Presence and identity of Babesia microti in Ireland

Babesia microti is a tick-transmitted protozoan parasite of wildlife that can also cause serious disease in humans. It is now well established that B. microti represents an assemblage of different strains or species, only some of which are important zoonotic pathogens. Therefore, in order to assess the potential public health risk associated with B. microti in any given location, it is important to determine the strains that are present. This is the first study on the presence and identity of B. microti in Ireland. Overall, 314 wood mice (Apodemus sylvaticus), 243 bank voles (Myodes glareolus) and 634 questing Ixodes ricinus nymphs collected in various locations across Ireland were screened for the presence of B. microti by metabarcoding and nested PCR, respectively. Overall 8 rodent spleen samples (1.4%) were positive for B. microti, while all tick samples tested negative. Rodent isolates were identified as the 'Munich' strain which rarely causes human disease and is chiefly transmitted by the mouse tick, Ixodes trianguliceps. Together with reports from the UK these results suggest that B. microti does not represent a significant public health risk in Britain or Ireland.

POS1204 SARS-CoV-2 INFECTION AFTER VACCINATION IN PATIENTS WITH RHEUMATIC DISEASES FROM ARGENTINA

Background

Patients with rheumatic diseases (RD) have been excluded from SARS-CoV-2 vaccine trials. Though data appear to show safety and efficacy, mostly evidence remains in mRNA vaccines. However in our country, adenovirus and inactivated vaccines, as well as heterologous schemes are frequently used.

Objectives

To describe clinical characteristics and outcomes of SARS-CoV-2 infection after vaccination in patients with RD from de the SAR-CoVAC registry and to compare them with patients who got infected before vaccination. Additionally, factors associated with COVID-19 unfavorable outcome were assessed.

Methods

Adult patients with RD who have been vaccinated for SARS-CoV-2 were consecutively included between June 1st and December 21st, 2021. Confirmed SARS-CoV-2 infection (RT-PCR o serology) was reported by the treated physician. Infection after an incomplete scheme was defined when the event was diagnosed at least 14 days after first dose; and after a complete scheme when it occurred > 14 days after second dose. Homologous scheme is defined by two same doses of vaccine and heterologous by two different doses. Patients with previous SARS-CoV-2 infection were excluded. To compare SARS-CoV-2 infection characteristics in not vaccinated patients, subjects from the SAR-COVID registry, which includes patients with RD and SARS-CoV-2 infection, were matched 2:1 by gender, age and RD.

WHO-Ordinal Scale ≥5 was used to define unfavorable infection outcome. Descriptive statics, Chi2 test, Fischer test, T test and ANOVA were used.

Results

A total of 1350 patients from the SAR COVAC registry were included, 67 (5%) presented SARS-CoV-2 infection after vaccination. The later were mostly (72%) females with a mean age of 57 (SD 15) years old. The most frequent RD were rheumatoid arthritis (41%), psoriatic arthritis (12%) and systemic lupus erythematosus (10%). At vaccination, most of them (75%) had low disease activity or remission, 19% were taking steroids, 39% methotrexate, 27% bDMARDs and 6% JAK inhibitors.

A total of 11 (16%) patients had SARS-CoV-2 infection <14 days after the first vaccine dose, 39 (58%) after an incomplete scheme and 17 (25 %) following a complete one. In the incomplete scheme group, 59% received Gam-COVID-Vac, 31% ChAdOx1 nCov-19 and 10% BBIBP-CorV; and in patients with complete scheme 47%, 24% and 29%, respectively. No event was reported after a complete heterologous scheme. No significant differences regarding sociodemoghraphic characteristics, RD, disease treatment, type of vaccine and regimen was found between in those with infection and those without it.

After vaccination only 8 (12%) of the patients who got infected had an unfavorable course, 88% of them following an incomplete scheme (5 received Gam-COVID-Vac, 1 ChAdOx1 nCov-19 and 1 BBIBP-CorV) and one subject after a complete homologous Gam-COVID-Vac scheme. Having an unfavorable outcome of SARS-CoV-2 infection was associated to: male gender [63% vs 24%, p=0.036], older age [mean 70 years (SD 7) vs 55 years (SD 15), p=0.005], being Caucasian [100% vs 54%, p=0.018], higher education [mean 17 years (SD 4) vs 12 years (SD 4), p=0.010], the presence of comorbidities [100% vs 39%, p=0.001, having pulmonary disease [37% vs 5%, p=0.019], dyslipidemia [63% vs 17%, p=0.011] and arterial hypertension [63% vs 24%, p=0.036], RD, treatments, disease activity and types of vaccines received were comparable between groups.

When comparing patients with and without vaccination prior SARS-CoV-2 infection, those who received at least one dose of vaccine had less frequently severe COVID-19 (12% vs 24%, p=0.067) and presented lower mortality due to COVID-19 (3% vs 6%, p=0.498). However these differences did not reach statistical significance.

Conclusion

In the SAR-CoVAC registry 5% of the patients had SARS-CoV-2 infection after vaccination, most of them mild and 25% after a complete scheme. Any vaccine was associated with severe COVID-19. When comparing with non-vaccinated patients, those with at least one dose, had less frequently severe disease and died due COVID-19.

Disclosure of Interests

None declared

Deciphering the fine nucleotide diversity of full HLA class I and class II genes in a well-documented population from sub-Saharan Africa

With the aim to understand how next‐generation sequencing (NGS) improves both our assessment of genetic variation within populations and our knowledge on HLA molecular evolution, we sequenced and analysed 8 HLA loci in a well‐documented population from sub‐Saharan Africa (Mandenka). The results of full‐gene NGS‐MiSeq sequencing compared with those obtained by traditional typing techniques or limited sequencing strategies showed that segregating sites located outside exon 2 are crucial to describe not only class I but also class II population diversity. A comprehensive analysis of exons 2, 3, 4 and 5 nucleotide diversity at the 8 HLA loci revealed remarkable differences among these gene regions, notably a greater variation concentrated in the antigen recognition sites of class I exons 3 and some class II exons 2, likely associated with their peptide‐presentation function, a lower diversity of HLA‐C exon 3, possibly related to its role as a KIR ligand, and a peculiar molecular diversity of HLA‐A exon 2, revealing demographic signals. Based on full‐length HLA sequences, we also propose that the most frequent DRB1 allele in the studied population, DRB1*13:04, emerged from an allelic conversion involving 3 potential alleles as donors and DRB1*11:02:01 as recipient. Finally, our analysis revealed a high occurrence of the DRB1*13:04‐DQA1*05:05:01‐DQB1*03:19 haplotype, possibly resulting from a selective sweep due to protection to Onchorcerca volvulus, a prevalent pathogen in West Africa. This study unveils highly relevant information on the molecular evolution of HLA genes in relation to their immune function, calling for similar analyses in other populations living in contrasting environments.

Design method for compact, achromatic, high-performance, solid catadioptric system (SoCatS), from visible to IR

Maresse described a classical solid catadioptric system (SoCatS) for a lens comprising a solid body and a single-focal Maksutov type construction, characterized by two refractive and two reflective surfaces. Due to ray propagation through the solid block twice, the design is feasible at a single wavelength, otherwise suffering on chromatic aberration induced by dispersion. We design a SoCatS for a telescope and describe a class of solutions to reduce and control chromatic and some spherical aberration in the solid catadioptric system.

Between-population differences in the genetic and maternal components of body mass in roe deer

Background

Understanding the genetic and environmental mechanisms governing variation in morphology or phenology in wild populations is currently an important challenge. While there is a general consensus that selection is stronger under stressful conditions, it remains unclear whether the evolutionary potential of traits should increase or decrease with increasingly stressful conditions. Here, we investigate how contrasting environmental conditions during growth may affect the maternal and genetic components of body mass in roe deer, the most abundant and widespread wild ungulate in Western Europe. Body mass is a key life history trait that strongly influences both survival and reproductive performance in large herbivores. We used pedigrees and animal models to determine the variance components of juvenile and adult winter body mass in two populations experiencing contrasting early-life conditions.

Results

Our analyses showed that roe deer at Chizé, where habitat was poor and unpredictable, exhibited very low genetic variance in juvenile body mass. Instead, variance in mass was mainly driven by among-cohort differences in early-life conditions and maternal environment. In contrast, roe deer at Bogesund, where resource availability during the critical period of fawn rearing was higher, displayed a substantial level of genetic variance in body mass. We discuss the potential role of past demography and viability selection on fawn body mass on the erosion of genetic variance in the poor habitat.

Conclusions

Our study highlights the importance of accounting for both spatial (i.e. between-population variation) and temporal (i.e. cohort variation) heterogeneity in environmental conditions, especially in early life, to understand the potential for adaptive responses of wild populations to selection.

Electronic supplementary material

The online version of this article (10.1186/s12862-018-1154-9) contains supplementary material, which is available to authorized users.

Assessment of a 16S rRNA amplicon Illumina sequencing procedure for studying the microbiome of a symbiont-rich aphid genus

The bacterial communities inhabiting arthropods are generally dominated by a few endosymbionts that play an important role in the ecology of their hosts. Rather than comparing bacterial species richness across samples, ecological studies on arthropod endosymbionts often seek to identify the main bacterial strains associated with each specimen studied. The filtering out of contaminants from the results and the accurate taxonomic assignment of sequences are therefore crucial in arthropod microbiome studies. We aimed here to validate an Illumina 16S rRNA gene sequencing protocol and analytical pipeline for investigating endosymbiotic bacteria associated with aphids. Using replicate DNA samples from 12 species (Aphididae: Lachninae, Cinara) and several controls, we removed individual sequences not meeting a minimum threshold number of reads in each sample and carried out taxonomic assignment for the remaining sequences. With this approach, we show that (i) contaminants accounted for a negligible proportion of the bacteria identified in our samples; (ii) the taxonomic composition of our samples and the relative abundance of reads assigned to a taxon were very similar across PCR and DNA replicates for each aphid sample; in particular, bacterial DNA concentration had no impact on the results. Furthermore, by analysing the distribution of unique sequences across samples rather than aggregating them into operational taxonomic units (OTUs), we gained insight into the specificity of endosymbionts for their hosts. Our results confirm that Serratia symbiotica is often present in Cinara species, in addition to the primary symbiont, Buchnera aphidicola. Furthermore, our findings reveal new symbiotic associations with Erwinia- and Sodalis-related bacteria. We conclude with suggestions for generating and analysing 16S rRNA gene sequences for arthropod-endosymbiont studies.

Preoperative levosimendan. A new way for organoprotection

Preoperative use of levosimendan in cardiac surgery patients is one of the most attractive therapeutic alternatives in subjects with left or right ventricular dysfunction. Our review explores the pharmacological bases and clinical evidence for the use of levosimendan, with the intention of making a series of recommendations regarding its use in preoperative optimization prior to cardiac surgery. We carried out a survey of 102 Spanish anesthesiologists in order to shed light on the grey areas regarding the use of this drug prior to surgery. Our findings suggest that levosimendan is recommended for patients with severe left or right ventricular dysfunction, moderate left ventricular dysfunction in which Intra-aortic Balloon Counterpulsation (IABC) is necessary and severe pulmonary hypertension. Administration of levosimendan prior to surgical cardiac intervention without an initial bolus reduces the likelihood of complications.

Landscape features and helminth co-infection shape bank vole immunoheterogeneity, with consequences for Puumala virus epidemiology

Heterogeneity in environmental conditions helps to maintain genetic and phenotypic diversity in ecosystems. As such, it may explain why the capacity of animals to mount immune responses is highly variable. The quality of habitat patches, in terms of resources, parasitism, predation and habitat fragmentation may, for example, trigger trade-offs ultimately affecting the investment of individuals in various immunological pathways. We described spatial immunoheterogeneity in bank vole populations with respect to landscape features and co-infection. We focused on the consequences of this heterogeneity for the risk of Puumala hantavirus (PUUV) infection. We assessed the expression of the Tnf-α and Mx2 genes and demonstrated a negative correlation between PUUV load and the expression of these immune genes in bank voles. Habitat heterogeneity was partly associated with differences in the expression of these genes. Levels of Mx2 were lower in large forests than in fragmented forests, possibly due to differences in parasite communities. We previously highlighted the positive association between infection with Heligmosomum mixtum and infection with PUUV. We found that Tnf-α was more strongly expressed in voles infected with PUUV than in uninfected voles or in voles co-infected with the nematode H. mixtum and PUUV. H. mixtum may limit the capacity of the vole to develop proinflammatory responses. This effect may increase the risk of PUUV infection and replication in host cells. Overall, our results suggest that close interactions between landscape features, co-infection and immune gene expression may shape PUUV epidemiology.

Antiviral properties against HIV of water soluble copper carbosilane dendrimers and their EPR characterization

We describe here the use of anionic carbosilane dendrimers to obtain new copper complexes. UV-Vis and a computer aided analysis of the EPR spectra provided information about the coordination modes of copper depending on the nature of the dendrimer and about the geometry and structure of the complexes in solution. Some of these metallo-dendrimers have been tested "in vitro" as antiviral compounds in the inhibition of HIV infection in pre and post-infection treatment.

Landscape genetics highlights the role of bank vole metapopulation dynamics in the epidemiology of Puumala hantavirus

Rodent host dynamics and dispersal are thought to be critical for hantavirus epidemiology as they determine pathogen persistence and transmission within and between host populations. We used landscape genetics to investigate how the population dynamics of the bank vole Myodes glareolus, the host of Puumala hantavirus (PUUV), vary with forest fragmentation and influence PUUV epidemiology. We sampled vole populations within the Ardennes, a French PUUV endemic area. We inferred demographic features such as population size, isolation and migration with regard to landscape configuration. We next analysed the influence of M. glareolus population dynamics on PUUV spatial distribution. Our results revealed that the global metapopulation dynamics of bank voles were strongly shaped by landscape features, including suitable patch size and connectivity. Large effective size in forest might therefore contribute to the higher observed levels of PUUV prevalence. By contrast, populations from hedge networks highly suffered from genetic drift and appeared strongly isolated from all other populations. This might result in high probabilities of local extinction for both M. glareolus and PUUV. Besides, we detected signatures of asymmetric bank vole migration from forests to hedges. These movements were likely to sustain PUUV in fragmented landscapes. In conclusion, our study provided arguments in favour of source-sink dynamics shaping PUUV persistence and spread in heterogeneous, Western European temperate landscapes. It illustrated the potential contribution of landscape genetics to the understanding of the epidemiological processes occurring at this local scale.

Preoperative gastric conditioning in cervical gastroplasty

To determine if ischemic conditioning of the stomach improves the morbidity, mortality, and the anastomotic failure in gastroplasties with cervical anastomosis. Analysis of all patients with indication for cervical gastroplasty during the period of study. In all cases, ischemic conditioning was performed by selective embolization. Anastomotic failure, morbidity, and mortality rates were studied. Thirty-nine consecutive patients were included. Angiography and selective embolization of the left gastric, right gastric, and splenic arteries were performed. Surgery was performed 2 weeks later. Four patients did not have a complete embolization; median hospital stay after conditioning was 1.24 ± 0.6 days. In two patients, surgery could not be completed. Of the 33 remaining, 29 had a posterior mediastinic gastroplasty and four through the anterior mediastinum. The most common morbidity was respiratory. Five patients had a reoperation and the mortality was 6%. One case of anastomotic leak was found (3%). The mean hospital stay was 17.5 days. Preoperative embolization is a technique with acceptable morbidity and a short hospital stay. In our experience it can reduce the incidence of the morbidity, mortality, and anastomotic leak in gastroplasties with cervical anastomosis. Prospective studies will be necessary to demonstrate the validity of this approach.

Characterization and PCR multiplexing of polymorphic microsatellite loci in the whipworm Trichuris arvicolae, parasite of arvicoline rodents and their cross-species utilization in T. muris, parasite of murines

Trichuris arvicolae and T. muris are gastro-intestinal nematodes of respectively arvicoline and murine rodents. We aim to investigate the ecology of these Trichuris species using population genetics. We sampled nematodes from rodents trapped in the East of France. After confirming the species identification of the nematodes using ITS1-5.8S-ITS2 ribosomal DNA sequences, we isolated and characterized twelve dinucleotide microsatellite loci in T. arvicolae. A multiplex panel was developed. Application to a set of 30 individuals allowed clear and easy characterization of allele sizes. The number of alleles ranged from 2 to 6 per locus with observed heterozygosities ranging from 0 to 0.93. A test on eleven T. muris revealed that eight loci among twelve amplified, and five were polymorphic. These sets of microsatellite loci provide high throughput capacity for population genetic studies.

Multiple parasites mediate balancing selection at two MHC class II genes in the fossorial water vole: insights from multivariate analyses and population genetics

We investigated the factors mediating selection acting on two MHC class II genes (DQA and DRB) in water vole (Arvicola scherman) natural populations in the French Jura Mountains. Population genetics showed significant homogeneity in allelic frequencies at the DQA1 locus as opposed to neutral markers (nine microsatellites), indicating balancing selection acting on this gene. Moreover, almost exhaustive screening for parasites, including gastrointestinal helminths, brain coccidia and antibodies against viruses responsible for zoonoses, was carried out. We applied a co-inertia approach to the genetic and parasitological data sets to avoid statistical problems related to multiple testing. Two alleles, Arte-DRB-11 and Arte-DRB-15, displayed antagonistic associations with the nematode Trichuris arvicolae, revealing the potential parasite-mediated selection acting on DRB locus. Selection mechanisms acting on the two MHC class II genes thus appeared different. Moreover, overdominance as balancing selection mechanism was showed highly unlikely in this system.

Efficacy of enteral decontamination in the prevention of anastomotic dehiscence and pulmonary infection in esophagogastric surgery

Our aim in this study is to evaluate the efficacy of decontamination of the high digestive tract in reducing the incidence of anastomotic dehiscence, pulmonary infection and mortality after resective gastro-esophageal surgery. A prospective randomized and double-blinded study was conducted in patients undergoing total gastrectomy for gastric cancer and esophagectomy for esophageal cancer. Two groups were studied: group A patients were given erythromycin + gentamicine + nistatine sulfate orally; group B patients were given placebo. Mortality, incidence of anastomotic dehiscence and incidence of pulmonary infection were the end points evaluated. One hundred and nine consecutive patients were randomized. Eighteen (16.5%) were excluded. From the 91 patients who were evaluated, 42 (46.2%) received an esophagectomy and 49 (53.8%) had a total gastrectomy. Esophagectomies showed: a 0% rate of anastomotic dehiscence in group A and 12.5% in group B, P = 0.176; a pulmonary infection rate of 22.2% in group A and 29.1% in group B, P = 0.443; and mortality rate was 0% in group A and 12.5% in group B, P = 0.176. After gastrectomy, anastomotic dehiscence rate was 4.5% in group A and 0% in group B, P = 0.449; pulmonary infection rate was 4.5% in group A and 11.1% in group B, P = 0.387 and mortality was 9% in group A and 0% in group B, P = 0.196. Decontamination protocol does not help in decreasing the incidence of anastomotic dehiscence, pulmonary infection and mortality in the present study. Nevertheless, there seems to be a tendency to low pulmonary infection after gastrectomy and esophagectomy and to improve the incidence of anastomotic dehiscence after esophagectomy. Further studies are needed to re-evaluate these findings.

Density-related changes in selection pattern for major histocompatibility complex genes in fluctuating populations of voles

Host-pathogen interactions are of particular interest in studies of the interplay between population dynamics and natural selection. The major histocompatibility complex (MHC) genes of demographically fluctuating species are highly suitable markers for such studies, because they are involved in initiating the immune response against pathogens and display a high level of adaptive genetic variation. We investigated whether two MHC class II genes (DQA1, DRB) were subjected to contemporary selection during increases in the density of fossorial water vole (Arvicola terrestris) populations, by comparing the neutral genetic structure of seven populations with that estimated from MHC genes. Tests for heterozygosity excess indicated that DQA1 was subject to intense balancing selection. No such selection operated on neutral markers. This pattern of selection became more marked with increasing abundance. In the low-abundance phase, when populations were geographically isolated, both overall differentiation and isolation-by-distance were more marked for MHC genes than for neutral markers. Model-based simulations identified DQA1 as an outlier (i.e. under selection) in a single population, suggesting the action of local selection in fragmented populations. The differences between MHC and neutral markers gradually disappeared with increasing effective migration between sites. In the high-abundance year, DQA1 displayed significantly lower levels of overall differentiation than the neutral markers. This gene therefore displayed stronger homogenization than observed under drift and migration alone. The observed signs of selection were much weaker for DRB. Spatial and temporal fluctuations in parasite pressure and locus-specific selection are probably the most plausible mechanisms underlying the observed changes in selection pattern during the demographic cycle.

Migration and recovery of the genetic diversity during the increasing density phase in cyclic vole populations

In cyclic populations, high genetic diversity is currently reported despite the periodic low numbers experienced by the populations during the low phases. Here, we report spatio-temporal monitoring at a very fine scale of cyclic populations of the fossorial water vole (Arvicola terrestris) during the increasing density phase. This phase marks the transition from a patchy structure (demes) during low density to a continuous population in high density. We found that the genetic diversity was effectively high but also that it displayed a local increase within demes over the increasing phase. The genetic diversity remained relatively constant when considering all demes together. The increase in vole abundance was also correlated with a decrease of genetic differentiation among demes. Such results suggest that at the end of the low phase, demes are affected by genetic drift as the result of being small and geographically isolated. This leads to a loss of local genetic diversity and a spatial differentiation among demes. This situation is counterbalanced during the increasing phase by the spatial expansion of demes and the increase of the effective migration among differentiated demes. We provide evidences that in cyclic populations of the fossorial water voles, the relative influence of drift operating during low density populations and migration occurring principally while population size increases interacts closely to maintain high genetic diversity.

Genetic structure is influenced by landscape features: empirical evidence from a roe deer population

The delimitation of population units is of primary importance in population management and conservation biology. Moreover, when coupled with landscape data, the description of population genetic structure can provide valuable knowledge about the permeability of landscape features, which is often difficult to assess by direct methods (e.g. telemetry). In this study, we investigated the genetic structuring of a roe deer population which recently recolonized a fragmented landscape. We sampled 1148 individuals from a 40 x 55-km area containing several putative barriers to deer movements, and hence to gene flow, namely a highway, rivers and several canals. In order to assess the effect of these landscape features on genetic structure, we implemented a spatial statistical model known as geneland which analyses genetic structure, explicitly taking into account the spatial nature of the problem. Two genetic units were inferred, exhibiting a very low level of differentiation (F(ST) = 0.008). The location of their boundaries suggested that there are no absolute barriers in this study area, but that the combination of several landscape features with low permeability can lead to population differentiation. Our analysis hence suggests that the landscape has a significant influence on the structuring of the population under study. It also illustrates the use of geneland as a powerful method to infer population structure, even in situations of young populations exhibiting low genetic differentiation.

Dispersal is not female biased in a resource-defence mating ungulate, the European roe deer

Dispersal is frequently more prevalent in one sex compared to the other. Greenwood proposed that patterns of sex-biased dispersal among birds and mammals are linked to their mating strategies. For species where males defend resources rather than females, he predicted female-biased dispersal, because males should remain at their birth site where they are familiar with the distribution of the resources that they must defend. Greenwood's hypothesis has been extensively supported among birds, where most species exhibit a resource-defence mating strategy. However, almost no equivalent information is available for mammals as males generally defend mates in this group. An exception is the European roe deer, a resource-defence mating ungulate. We thus tested Greenwood's hypothesis on this atypical mammalian model, looking for female-biased dispersal using sex-specific inter-individual genetic distances. We conclusively show that gene flow is not higher among females compared to males in the studied roe deer population, and hence that dispersal is not female-biased, suggesting that male mating strategy is not the primary selective force driving the evolution of dispersal in roe deer. We discuss the role of female mate choice and intra-sexual competition as possible alternative selective pressures involved.

Duplication, balancing selection and trans-species evolution explain the high levels of polymorphism of the DQA MHC class II gene in voles (Arvicolinae)

Major histocompatibility complex (MHC) genes play important role in host-parasite interactions and parasites are crucial factors influencing the population dynamics of hosts. We described the structure and diversity of exon 2 of the MHC class II DQA gene in three species of voles (Arvicolinae) exhibiting regular multi-annual fluctuations of population density and analysed the processes leading to the observed MHC polymorphism. By using cloning-sequencing methodology and capillary electrophoresis-single strand conformation polymorphism, we described seven sequences in the water, eight in the common, and seven in the bank voles coming from an area of 70 km(2) around the Nozeroy canton in the Jura Mountains (Franche Comté, France). All exon 2 sequences translate to give unique amino acid sequences and positive selection was found to act very intensively on antigen binding sites. We documented the presence of recombination at vole DQA region but its importance in generating allelic polymorphism seems to be relatively limited. For the first time within rodents, we documented the duplication of the DQA gene in all three species with both copies being transcriptionally active. Phylogenetic analysis of allelic sequences revealed extensive trans-species polymorphism within the subfamily although no alleles were shared between species in our data set. We discuss possible role of parasites in forming the recent polymorphism pattern of the DQA locus in voles.

Genetic structure of the cyclic fossorial water vole (Arvicola terrestris): landscape and demographic influences

Genetic structure can be strongly affected by landscape features and variation through time and space of demographic parameters such as population size and migration rate. The fossorial water vole (Arvicola terrestris) is a cyclic species characterized by large demographic fluctuations over short periods of time. The outbreaks do not occur everywhere at the same time but spread as a wave at a regional scale. This leads to a pattern of large areas (i.e. some hundreds of km2), each with different vole abundances, at any given time. Here, we describe the abundance and genetic structures in populations of the fossorial water vole. We use the data to try to understand how landscape and demographic features act to shape the genetic structure. The spatial variability of vole abundance was assessed from surface indices, collected in spring 2002 (April) in eastern central France. Genetic variability was analysed using eight microsatellite loci at 23 localities sampled between October 2001 and April 2002. We found some congruence between abundance and genetic structures. At a regional scale, the genetic disruptions were associated with both sharp relief and transition between an area of low abundance and another of high abundance. At a local scale, we observed a variation of the isolation-by-distance pattern according to the abundance level of vole populations. From these results we suggest that the dispersal pattern in cyclic rodent populations varies throughout the demographic cycle.

Landscape connectivity influences gene flow in a roe deer population inhabiting a fragmented landscape: an individual-based approach

Changes in agricultural practices and forest fragmentation can have a dramatic effect on landscape connectivity and the dispersal of animals, potentially reducing gene flow within populations. In this study, we assessed the influence of woodland connectivity on gene flow in a traditionally forest-dwelling species--the European roe deer--in a fragmented landscape. From a sample of 648 roe deer spatially referenced within a study area of 55 x 40 km, interindividual genetic distances were calculated from genotypes at 12 polymorphic microsatellite loci. We calculated two geographical distances between each pair of individuals: the Euclidean distance (straight line) and the 'least cost distance' (the trajectory that maximizes the use of wooded corridors). We tested the correlation between genetic pairwise distances and the two types of geographical pairwise distance using Mantel tests. The correlation was better using the least cost distance, which takes into account the distribution of wooded patches, especially for females (the correlation was stronger but not significant for males). These results suggest that in a fragmented woodland area roe deer dispersal is strongly linked to wooded structures and hence that gene flow within the roe deer population is influenced by the connectivity of the landscape.

Continuous-wave lasing of a stoichiometric Yb laser material: KYb(WO4)2

For the first time to the authors' knowledge, continuous-wave laser emission of the stoichiometric crystal KYb(WO4)2 was achieved at 1068 nm. The 125-microm-thin sample was directly water cooled and pumped at 1025 nm by a Ti:sapphire laser. The maximum output power at room temperature was 20 mW.