Evolution of the old world Arenaviridae and their rodent hosts : Generalized host-transfer orassociation by descent ?

The present article compares and discusses ten scenarios optimizing the number of cospeciation events between the respective phylogenies of the Old World Arenaviridae and their murine hosts. All scenarios support the previously proposed “diffuse coevolution” hypothesis, in which parallel phylogeny and/or host switches on closely related hosts can be considered as the most common mechanism of transmission. The scenarios also suggest that the diversity of the viruses and their rodent hosts could be higher than currently expected and that cophylogeny could have been underestimated. The transfer of viruses from their normal hosts to phylogenetically remote hosts could be due to changes in their regular mode of dispersion, a phenomenon which could correspond with their emergence as human parasites. The comparison of viral phylogeny with the host cladogram also suggests that the origin of Arenaviridae goes back a long time, probably to the origin of the Murinae. The origin of arenaviruses is currently thought to lie in AsiaDix scénarios optimisant le nombre d'événements de cospéciation entre les phylogénies respectives des arénavirus de l'Ancien monde et leurs hôtes murins sont comparés et discutés. Tous sont conciliables avec l'hypothèse de coévolution diffuse précédemment proposée. Cette hypothèse privilégie la cophylogénie (évolution parallèle) et/ou la transmission croisée à des hôtes proches parents des hôtes d'origine. La discussion de ces scénarios suggère également que la biodiversité des virus et celle de leurs hôtes pourraient être sous-estimées dans l'état actuel de nos connaissances. Le transfert des virus, de leurs hôtes habituels à des hôtes phylogénétiquement éloignés, pourrait résulter de perturbations de leur écologie et correspondre aux périodes durant lesquelles ils deviennent dangereux pour les humains. La comparaison des deux cladogrammes suggère également que l'origine des Arenaviridae est probablement ancienne : elle pourrait être contemporaine de l'origine des Muridae. On estime actuellement que l'origine de cette famille se situe en Asie

Peyer's Patches: The Immune Sensors of the Intestine

The gut-associated lymphoid tissue (GALT) consists of isolated or aggregated lymphoid follicles forming Peyer's patches (PPs). By their ability to transport luminal antigens and bacteria, PPs can be considered as the immune sensors of the intestine. PPs functions like induction of immune tolerance or defense against pathogens result from the complex interplay between immune cells located in the lymphoid follicles and the follicle-associated epithelium. This crosstalk seems to be regulated by pathogen recognition receptors, especially Nod2. Although TLR exerts a limited role in PP homeotasis, Nod2 regulates the number, size, and T-cell composition of PPs, in response to the gut flora. In turn, CD4+ T-cells present in the PP are able to modulate the paracellular and transcellular permeabilities. Two human disorders, Crohn's disease and graft-versus-host disease are thought to be driven by an abnormal response toward the commensal flora. They have been associated with NOD2 mutations and PP dysfunction

Body Size Evolution of Oxyurid (Nematoda) Parasites: The Role of Hosts

Studying the diversification of body size in a taxon of parasites allows comparison of patterns of variation observed in the parasites with patterns found in free-living organisms. The distributions of body size of oxyurid nematodes (obligate parasites of vertebrates and invertebrates) are lognormally right-skewed, except for male oxyurids in invertebrates which show left-skewed distributions. In these parasitic forms, speciose genera do not have the smallest body sizes. Parasite body size is positively correlated with host body size, the largest hosts possessing the largest parasites. This trend is shown to occur within one monophyletic group of oxyurids, those of Old World primates. Comparative methods are used to take account of the effects of phylogeny. The use of multiple linear regression on distance matrices allows measurements of the contribution of phylogeny to the evolution of body size of parasites. Evolution of body size in female pinworms of Old World primates appears to be dependent only on the body size of their hosts. The tendency of parasite body size to increase with host body size is discussed in the light of the evolution of life-history traits

NEW PARASITE RECORDS FROM Kerodon rupestris (RODENTIA, CAVIIDAE) AN ENDEMIC SPECIES TO NORTHEASTERN BRAZIL

The present study aimed to identify endoparasites from faecal samples of Kerodon rupestris, an endemic rodent of the Brazilian semiarid region. Samples collected from 10 locations at the Parque Nacional Serra da Capivara, Piauí State, Brazil were analyzed. Each faecal samples was processed, rehydrated, homogenized, and processed by spontaneous sedimentation. Morphological and morphometric characteristics of gastrointestinal parasites were observed using light microscopy. A total of three taxa from helminth and protozoan parasites were found. The results demonstrated parasite remains in 6/10 localities, and a high occurrence of Trichuris cf. gracilis, in 5/10 localities. Egg morphometric data was compared with Thichuris spp. egg Brazilian rodents. Two new parasite records were identified in K. rupestris, a nematode, Helminthoxys sp. (Oxyuridae) and a possible coccidian. The findings are discussed with taxonomic and ecological literature of intestinal parasites from rodents. The role of K. rupestris as source of ecological information in the region is suggested

Karyotype diversity suggests that Laonastes aenigmamus (Laotian rock rat) (Rodentia, Diatomyidae) is a multi-specific genus

International audienceLaonastes aenigmamus (Khanyou) is a recently described rodent species living in geographically separated limestone formations of the Khammuan Province in Lao PDR. Chromosomes of 21 specimens of L. aenigmamus were studied using chromosome banding as well as fluorescent in situ hybridization (FISH) techniques using human painting, telomere repeats , and 28S rDNA probes. Four different karyotypes were established. Study with human chromosome paints and FISH revealed that four large chromosomes were formed by multiple common tandem fusions, with persistence of some interstitial telomeres. The rearrangements separating the different karyotypes (I to IV) were also reconstructed. Various combinations of Robertsonian translocations or tandem fusions involving the same chromosomes differentiate these karyo-types. These rearrangements create a strong gametic barrier, which isolates specimens with karyotype II from the others. C-banding and FISH with telomere repeats also exhibit large and systematized differences between karyotype II and others. These data indicate an ancient reproductive separation and suggest that Laonastes is not a mono-specific genus

Laonastes aenigmamus, an enigmatic rodent recently discovered in Laos

The Laotian rock rat or kha-nyou (Laonastes aenigmamus), a small rodent the size of a rat discovered by chance on a Laotian market, is new to science. This small mammal lives in a very specific rocky habitat, in a seemingly limited territory. Its adaptations to a very specific biotope and lifestyle probably explain its survival and its late discovery.Le kanyou (Laonastes aenigmamus), petit rongeur de la taille d'un rat découvert par hasard sur un marché laotien, est une nouveauté scientifique. Ce petit mammifère vit dans un habitat rocheux très particulier, et il semble que son aire de distribution soit peu étendue. Ses adaptations à un biotope et à un mode de vie très particuliers expliquent probablement sa survie ainsi que sa découverte tardive

Toxoplasmosis in Rodents: Ecological Survey and First Evidences in Thailand.

International audienceDomestic and wild rodents known as the most abundant and diversified order of mammals have a key role in the ecological food chain and also in the transmission of parasites and pathogens to other animals. While foraging on the ground, they can get infected by Toxoplasma gondii, a protozoan parasite, which is the causative agent of toxoplasmosis. Therefore, they serve as intermediate hosts of T. gondii and can transmit it to their predators. To assess their role in the maintenance of T. gondii lifecycle in Thailand, we sampled rodents in a range of biotopes representative of the high biodiversity and conducted a serological survey with latex agglutination test to detect anti-T. gondii antibodies. Overall, 21 of 461 (4.6%) rodents had diagnostically significant antibody titers (cutoff, 1:64). Every species with at least 37 individuals captured tested positive, confirming the wide range of potential mammalian hosts of toxoplasmosis. None of the ecological traits (sex, maturity, morphology, season, or habitat) was found significant to predict the susceptibility to T. gondii both univariately and in a multivariate analysis. However, high prevalences were reported in either forested or anthropized areas. This survey constitutes the first confirmed serological investigation of T. gondii in rodents in Thailand. The rarity of both domestic and wild felids in Thailand emphasizes the importance of rodents in maintaining T. gondii, and questions the involvement of other carnivores in the life cycle

Note préliminaire: Talpa aquitania nov. sp. (Talpidae, Soricomorpha) une nouvelle espèce de taupe du sud-ouest de la France et du nord de l’Espagne

Une étude, basée sur le mtDNA, de la génétique des populations de taupes récemment capturées en France nous a permis de découvrir une espèce nouvelle, Talpa aquitania nov. sp. Nous donnons ici une description préliminaire de la nouvelle espèce et de sa distribution. Cette dernière couvre une région se situant au sud et à l’ouest du cours de la Loire et, au-delà des Pyrénées, dans le nord de la péninsule ibérique.A mtDNA based study of the population genetics of moles recently captured in France allowed us to discover a new species, Talpa aquitania nov. sp. We are giving here a preliminary description of the new species. Its distribution covers an area lying south and west of the course of the Loire river in France and beyond the Pyrenees, a part of Northern Spain

Relationship of parasites and pathogens diversity to rodents in Thailand

International audienceRodents have proven to be of increasing importance in transmitting diseases to humans in recent decades, through the emergence of worldwide epidemics and, in Thailand, through the emergence of leptospirosis and scrub typhus. Investigations of parasites and pathogens in murine rodents have helped to describe the implication of the main species and understand the different ways of transmission. From wild to anthropized habitats, rodents can be reservoirs, hosts or vectors of infectious organisms. Related species can react very differently to the same pathogens, with pivotal implications for the understanding of their natural circulation. Scrub typhus is transmitted to humans through the bites of trombiculid mites that have previously fed on infected rodents, generally occurring in wild habitats. Leptospirosis can affect people without any direct contact with infected rodents, but by indirect spread in agricultural areas. Parasitic diseases, such as toxoplasmosis and trypanosomiasis benefit from the proximity of rodents to domesticated animals to jump from one vector to another before reaching humans. By occupying almost all biotopes and by rapidly adapting to environmental changes, rodents are fundamental in the maintenance and transmission of an impressive number of infectious organisms to humans

Autophagy Genes (ATG16L1/IRGM) and IBD: Involvement of the ATG16L1 Gene in Algerian Patients with Crohn's Disease

Background: Chronic Inflammatory Bowel Diseases (IBD) including Crohn’s disease (CD) and ulcerative colitis (UC) are gastrointestinal disorders under the influence of a complex genetic basis. One hundred sixty-three predisposition loci were identified by genome-wide association (GWAS) studies, refocusing the pathogenesis of IBD on immunity genes. Autophagy is a fundamental mechanism in the maintenance of intestinal homeostasis. Failures of this mechanism appear to be a major risk factor in the setting up of chronic intestinal inflammation. Two single nucleotide polymorphisms (SNPs) within two genes, were selected namely (rs2241880 AàG) for ATG16L1 and (rs10065172 CàT) for IRGM.These two genes are both involved in the autophagy mechanism. We investigated these two SNP in an Algerian cohort for the first time since no previous association studies between IBD and the two studied genes were available for the Algerian population. Methods: A case-control study was performed on a cohort including 95 Algerian patients with Crohn's disease and ulcerative colitis versus 116 Controls. Genotyping of the cohort involved allelic discrimination by TaqMan SNP Genotyping Assay. Results: A statistically significant association of the rs2241880 AàGmutation of the ATG16L1 gene was demonstrated in IBD (p = 0.04) and, more particularly in Crohn's disease (p = 0.03).The presence of this mutation would increase the risk of Crohn's disease by a factor of 2 in its GG homozygous mutated form (OR = 2.11 95% CI (1.07-4.16)). No significant associations were found for the rs10065172 CàT mutation of the IRGM gene. Conclusion: Our data highlight the involvement of the ATG16L1 gene in the genesis and/or evolution of IBD cases, notably Crohn's disease, indicating the impact that deregulation of the autophagy mechanism could have on the Algerian population. Nevertheless, it would be interesting to expand the sampling and carry out the functional studies to elucidate the impact of the deregulation of the ATG16L1 gene in IBD