Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Geographical distribution of parasite species can provide insights into the evolution and diversity of parasiticcommunities. Biogeography of marine parasites is poorly known, especially because it requires anunderstanding of host-parasite interactions, information that is rare, especially over large spatial scales.Here, we have studied the biogeographical patterns of dactylogyrid parasites of chaetodontids, one of themost well-studied fish families, in the tropical Indo-west Pacific region. Dactylogyrid parasites were collectedfrom gills of 34 butterflyfish species (n = 560) at nine localities within an approximate area of62 million km2. Thirteen dactylogyrid species were identified, with richness ranging from 6 to 12 speciesat individual localities. Most dactylogyrid communities were dominated by Haliotrema angelopterum orHaliotrema aurigae, for which relative abundance was negatively correlated (q = !0.59). Parasite richnessand diversity were highest in French Polynesia and the Great Barrier Reef (Australia) and lowest in Palau.Three biogeographic regions were identified based on dactylogyrid dissimilarities: French Polynesia,characterised by the dominance of H. angelopterum, the western Pacific region dominated by H. aurigae,and Ningaloo Reef (Australia), dominated by Euryhaliotrema berenguelae. Structure of host assemblageswas the main factor explaining the dissimilarity (turnover and nestedness components of the Bray-Curtis dissimilarity and overall Bray-Curtis dissimilarity) of parasite communities between localities,while environment was only significant in the turnover of parasite communities and overall dissimilarity.Spatial structure of localities explained only 10% of the turnover of parasite communities. The interactionof the three factors (host assemblages, environment and spatial structure), however, explained the highestamounts of variance of the dactylogyrid communities, indicating a strong colinearity between the factors.Our findings show that spatial arrangement of chaetodontid dactylogyrids in the tropical Indo-westPacific is primarily characterised by the turnover of the main Haliotrema spp., which is mainly explainedby the structure of host assemblages.
ISSN: 0020-7519

hal-01562156
https://hal-univ-perp.archives-ouvertes.fr/hal-01562156
DOI : 10.1016/j.ijpara.2017.01.006

Éditeur(s) : HAL CCSD Cambridge University Press (CUP)
Résumé : International audience
We studied the monogenean communities of 34 species of butterflyfish from the tropical Indo-West Pacific, identifying 13 dactylogyrid species (including two species that are presently undescribed). Monogenean assemblages differed significantly between host species in terms of taxonomic structure, intensity and prevalence. Parasite richness ranged from 0 (Chaetodon lunulatus) to 11 (C. auriga, C. citrinellus and C. lunula). Host specificity varied between the dactylogyrids species, being found on 2-29 of the 34 chaetodontid species examined. Sympatric butterflyfish species were typically parasitized by different combinations of dactylogyrid species, suggesting the existence of complex host-parasite interactions. We identified six clusters of butterflyfish species based on the similarities of their dactylogyrid communities. Dactylogyrid richness and diversity were not related to host size, diet specialization, depth range or phylogeny of butterflyfish species. However, there was a weak positive correlation between monogenean richness and diversity and host geographical range. Most communities of dactylogyrids were dominated by Haliotrema aurigae and H. angelopterum, indicating the importance of the genus Haliotrema in shaping monogenean communities of butterflyfishes. This study casts light on the structure of the monogenean communities of butterflyfishes, suggesting that the diversity and complexity of community structures arises from a combination of host species-specific parameters.
ISSN: 0031-1820

hal-01380679
https://hal-univ-perp.archives-ouvertes.fr/hal-01380679
DOI : 10.1017/S0031182016001463

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
While the effects of deforestation and habitat fragmentation on parasite prevalence or richness are well investigated, host-parasite networks are still understudied despite their importance in understanding the mechanisms of these major disturbances. Because fragmentation may negatively impact species occupancy, abundance and co-occurrence, we predict a link between spatiotemporal changes in habitat and the architecture of host-parasite networks. For this, we used an extensive data set on 16 rodent species and 29 helminth species from seven localities of South-East Asia. We analysed the effects of rapid deforestation on connectance and modularity of helminth-parasite networks. We estimated both the degree of fragmentation and the rate of deforestation through the development of land uses and their changes through the last 20 to 30years in order to take into account the dynamics of habitat fragmentation in our statistical analyses. We found that rapid fragmentation does not affect helminth species richness per se but impacts host-parasite interactions as the rodent-helminth network becomes less connected and more modular. Our results suggest that parasite sharing among host species may become more difficult to maintain with the increase of habitat disturbance.
ISSN: 0021-8790

hal-01355307
https://hal.archives-ouvertes.fr/hal-01355307
DOI : 10.1111/1365-2656.12368
IRD : fdi:010064927

Éditeur(s) : HAL CCSD
Résumé : International audience
The host-parasite genera Proformica-Rossomyrmex present four pairs of species with a very wide range of distribution from China to Southeastern Spain, from huge extended plains to the top of high mountains. Here we review (1) the published data on these pairs in comparison to other slave-makers; (2) the different dispersal ability in hosts and parasites inferred from genetics (chance of migration conditions the evolutionary potential of the species); (3) the evolutionary potential of host and parasite determining the coevolutionary process in each host-parasite system that we treat to define using cuticular chemical data. We find a lower evolutionary potential in parasites than in hosts in fragmented populations, where selective pressures give advantage to a limited female parasite migration due to uncertainty of locating a host nest. A similar evolutionary potential is detected for hosts and parasites when the finding of host nests is likely (i.e., in continuous and extended populations). Moreover, some level of local adaptation at CHC profiles between host and parasite exists independently of the kind of geographic distribution and the ability of dispersal of the different populations. Similarity at CHC profiles appears to be a trait imposed by natural selection for the interaction between hosts and slave-makers.
Psyche

hal-01322574
https://hal.archives-ouvertes.fr/hal-01322574
DOI : 10.1155/2013/541804

Éditeur(s) : HAL CCSD Cambridge University Press (CUP)
Résumé : International audience
Leishmania parasites can escape the immune response by invading cell types lacking leishmanicidal mechanisms. Silent persistence of Leishmania parasites in the host organism is responsible for asymptomatic carriage and relapses after cured leishmaniasis. Here, we studied the interaction between Hepatic Stellate Cells (HSC) and Leishmania. An original model of human HSC in primary culture infected with L. donovani was developed. The presence of intracellular parasites was studied and quantified using optical and confocal microscopy. HSC characteristics were studied using microscopy, methylene blue assay, long-term cultures and qPCR. We showed for the first time that human HSC are permissive to L. donovani infection, with no modification of HSC survival, growth rate and proinflammatory and fibrogenic characteristics. Intracellular parasites did not replicate but HSC had no effect on their survival. Indeed, after a 40-day culture, infected HSC cultures transferred on NNN medium yielded new promastigotes that were able to proliferate and efficiently infect new cells. HSC are permissive to L. donovani, with neither parasite killing nor apparent cell damage. Thus, HSC could act as potent sanctuary cells for Leishmania in the liver, which could partially explain parasite reactivation after an asymptomatic carriage or a cured visceral leishmaniasis.
ISSN: 0031-1820

inserm-00825803
http://www.hal.inserm.fr/inserm-00825803
DOI : 10.1017/S0031182012001965
PUBMED : 23253952

Éditeur(s) : HAL CCSD Frontiers Media
Résumé : International audience
The Anopheles midgut hosts diverse bacterial communities and represents a complex ecosystem. Several evidences indicate that mosquito midgut microbiota interferes with malaria parasite transmission. However, the bacterial composition of salivary glands and ovaries, two other biologically important tissues, has not been described so far. In this study, we investigated the dynamics of the bacterial communities in the mosquito tissues from emerging mosquitoes until 8 days after a blood meal containing Plasmodium falciparum gametocytes and described the temporal colonization of the mosquito epithelia. Bacterial communities were identified in the midgut, ovaries, and salivary glands of individual mosquitoes using pyrosequencing of the 16S rRNA gene. We found that the mosquito epithelia share a core microbiota, but some bacteria taxa were more associated with one or another tissue at a particular time point. The bacterial composition in the tissues of emerging mosquitoes varied according to the breeding site, indicating that some bacteria are acquired from the environment. Our results revealed temporal variations in the bacterial community structure, possibly as a result of the mosquito physiological changes. The abundance of Serratia significantly correlated with P. falciparum infection both in the midgut and salivary glands of malaria challenged mosquitoes, which suggests that interactions occur between microbes and parasites. These bacteria may represent promising targets for vector control strategies. Overall, this study points out the importance of characterizing bacterial communities in malaria mosquito vectors.
ISSN: 1664-302X

hal-01546162
https://hal.archives-ouvertes.fr/hal-01546162
DOI : 10.3389/fmicb.2015.01500

Éditeur(s) : HAL CCSD American Society for Microbiology
Résumé : International audience
Summary: The apicomplexan parasite Toxoplasma gondii was discovered a little over 100 years ago, but knowledge of its biological life cycle and its medical importance has grown in the last 40 years. This obligate intracellular parasite was identified early as a pathogen responsible for congenital infection, but its clinical expression and the importance of reactivations of infections in immunocompromised patients were recognized later, in the era of organ transplantation and HIV infection. Recent knowledge of host cell-parasite interactions and of parasite virulence has brought new insights into the comprehension of the pathophysiology of infection. In this review, we focus on epidemiological and diagnostic aspects, putting them in perspective with current knowledge of parasite genotypes. In particular, we provide critical information on diagnostic methods according to the patient's background and discuss the implementation of screening tools for congenital toxoplasmosis according to health policies.
ISSN: 0893-8512

hal-00696903
https://hal.archives-ouvertes.fr/hal-00696903
https://hal.archives-ouvertes.fr/hal-00696903/document
https://hal.archives-ouvertes.fr/hal-00696903/file/Epidemiologysur and_Diagnostic-accepted.pdf
DOI : 10.1128/CMR.05013-11

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
In mutualisms, each interacting species obtains resources from its partner that it would obtain less efficiently if alone, and so derives a net fitness benefit. In exchange for shelter (domatia) and food, mutualistic plant-ants protect their host myrmecophytes from herbivores, encroaching vines and fungal pathogens. Although selective filters enable myrmecophytes to host those ant species most favorable to their fitness, some insects can by-pass these filters, exploiting the rewards supplied whilst providing nothing in return. This is the case in French Guiana for Cecropia obtusa (Cecropiaceae) as Pseudocabima guianalis caterpillars (Lepidoptera, Pyralidae) can colonize saplings before the installation of their mutualistic Azteca ants. The caterpillars shelter in the domatia and feed on food bodies (FBs) whose production increases as a result. They delay colonization by ants by weaving a silk shield above the youngest trichilium, where the FBs are produced, blocking access to them. This probable temporal priority effect also allows female moths to lay new eggs on trees that already shelter caterpillars, and so to occupy the niche longer and exploit Cecropia resources before colonization by ants. However, once incipient ant colonies are able to develop, they prevent further colonization by the caterpillars. Although no higher herbivory rates were noted, these caterpillars are ineffective in protecting their host trees from a pathogenic fungus, Fusarium moniliforme (Deuteromycetes), that develops on the trichilium in the absence of mutualistic ants. Therefore, the Cecropia treelets can be parasitized by two often overlooked species: the caterpillars that shelter in the domatia and feed on FBs, delaying colonization by mutualistic ants, and the fungal pathogen that develops on old trichilia. The cost of greater FB production plus the presence of the pathogenic fungus likely affect tree growth.
PLoS ONE

hal-00912399
https://hal.archives-ouvertes.fr/hal-00912399
https://hal.archives-ouvertes.fr/hal-00912399/document
DOI : 10.1371/journal.pone.0020538
OATAO : 10156

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
The development of Plasmodium falciparum within the Anopheles gambiae mosquito relies on complex vector-parasite interactions, however the resident midgut microbiota also plays an important role in mediating parasite infection. In natural conditions, the mosquito microbial flora is diverse, composed of commensal and symbiotic bacteria. We report here the isolation of culturable midgut bacteria from mosquitoes collected in the field in Cameroon and their identification based on the 16S rRNA gene sequencing. We next measured the effect of selected natural bacterial isolates on Plasmodium falciparum infection prevalence and intensity over multiple infectious feedings and found that the bacteria significantly reduced the prevalence and intensity of infection. These results contrast with our previous study where the abundance of Enterobacteriaceae positively correlated with P. falciparum infection (Boissiere et al. 2012). The oral infection of bacteria probably led to the disruption of the gut homeostasis and activated immune responses, and this pinpoints the importance of studying microbe-parasite interactions in natural conditions. Our results indicate that the effect of bacterial exposure on P. falciparum infection varies with factors from the parasite and the human host and calls for deeper dissection of these parameters for accurate interpretation of bacterial exposure results in laboratory settings.
ISSN: 1932-6203

hal-01546172
https://hal.archives-ouvertes.fr/hal-01546172
DOI : 10.1371/journal.pone.0081663

Éditeur(s) : HAL CCSD
Résumé : International audience
This paper investigates the narrative challenges and opportunities that contemporary virology offers to popular science and to fiction. The study of viruses reveals extremely complex relations, playing out over different physical and temporal scales. Viruses constitute a heterogeneous population whose interactions with living organisms occur on multiple levels, and whose numbers are vastly superior to human and even bacterial populations on earth. The resulting challenges for narration can be grouped into three main formal questions. The first is the problem of scale, since the numbers and sizes of virus and host populations are vastly different, as are the temporalities over which they transform and survive. The second is the complexity of actants, since viruses are involved in relations where destruction and mutual benefit can overlap, and genetic transformations are played out over many generations. The third is the choice of images through which to convey their behaviours: many existing metaphors in microbiology, such as “chimeras”, “parasites” or “kill-the-winner dynamics”, carry the narrative potential of a mythological and/or theatrical imagination.These questions will first be examined as challenges encountered in the narration of biology for vulgarization purposes, and effects on narrative forms will be outlined: shifts in focalization in order to create multiscalar perspectives; unstable actantial models as expressions of complex relations; and the use or resistance to narrative structures implied by several key metaphors in virological discourse. These formal characteristics will then be presented through two case studies drawn from contemporary fiction. In his “scientific fable” Conflits Intérieurs (2015), microbiologist Eric Bapteste creates a multiscalar narrative by using humans and viruses as both protagonists and narrators in a battle of ideas. In the graphic novel aâma (2011-2014), Frederik Peeters explores the ambiguous potential, both symbiotic and threatening, of a meta-organism uniting humans with microscopic agents. Both these novels play with scale, metaphor and actants so as to question the fundaments of human identity. They posit the act of narration as a defining human attribute, and consequently use the narrative voice as an arena in which we observe the weakening of the notion of the subject by microbiology.
“Narrative, Cognition & Science” Symposium
Erlangen, Germany

hal-01434744
https://hal.archives-ouvertes.fr/hal-01434744