Survey of ticks in French Guiana.

9 pagesInternational audienceIn this study, we examine the current pattern of tick diversity and host use in French Guiana, South America, from 97 sampling localities encompassing peri-urban, rural and natural habitats. We collected 3395 ticks, including 1485 specimens from 45 vertebrate species (humans, domestic and wild animals) and 1910 questing specimens from vegetation. Morphological examinations identified 22 species belonging to six genera: Amblyomma (16 species), Rhipicephalus (two species), Ixodes (one species), Dermacentor (one species), Haemaphysalis (one species), Ornithodoros (one species). To facilitate future identification, we produced a bank of pictures of different stages for all these species. Taxonomic identification was then confirmed by molecular characterization of two mitochondrial genes, cytochrome c oxidase CO1 and 16S rDNA. Eleven of the 22 reported species were collected on humans, six on domestic animals and 12 on wild animals. The most widespread tick species collected were A. cajennense sensu stricto and, to a lesser extent, A. oblongoguttatum; both of these species were frequently found on humans. We used these results to discuss the tick-associated risks for human and animal health in French Guiana

Phylogenetics of the <i>Spiroplasma ixodetis</i> endosymbiont reveals past transfers between ticks and other arthropods

International audienceThe bacterium Spiroplasma ixodetis is a maternally inherited endosymbiont primarily described from ticks but also found widespread across other arthropods. While it has been identified as a male-killing agent in some insect species, the consequences of infection with S. ixodetis in ticks are entirely unknown, and it is unclear how this endosymbiont spreads across tick species. Here, we have investigated this aspect through the examination of the diversity and evolutionary history of S. ixodetis infections in 12 tick species and 12 other arthropod species. Using a multi-locus typing approach, we identified that ticks harbor a substantial diversity of divergent S. ixodetis strains. Phylogenetic investigations revealed that these S. ixodetis strains do not cluster within a tick-specific subclade but rather exhibit distinct evolutionary origins. In their past, these strains have undergone repeated horizontal transfers between ticks and other arthropods, including aphids and flies. This diversity pattern strongly suggests that maternal inheritance and horizontal transfers are key drivers of S. ixodetis spread, dictating global incidence of infections across tick communities. We do not, however, detect evidence of S. ixodetis-based male-killing since we observed that infections were widely present in both males and females across populations of the African blue tick Rhipicephalus decoloratus

Detection of Anaplasma and Ehrlichia bacteria in humans, wildlife, and ticks in the Amazon rainforest.

International audienceTick-borne bacteria of the genera Ehrlichia and Anaplasma cause several emerging human infectious diseases worldwide. In this study, we conduct an extensive survey for Ehrlichia and Anaplasma infections in the rainforests of the Amazon biome of French Guiana. Through molecular genetics and metagenomics reconstruction, we observe a high indigenous biodiversity of infections circulating among humans, wildlife, and ticks inhabiting these ecosystems. Molecular typing identifies these infections as highly endemic, with a majority of new strains and putative species specific to French Guiana. They are detected in unusual rainforest wild animals, suggesting they have distinctive sylvatic transmission cycles. They also present potential health hazards, as revealed by the detection of Candidatus Anaplasma sparouinense in human red blood cells and that of a new close relative of the human pathogen Ehrlichia ewingii , Candidatus Ehrlichia cajennense, in the tick species that most frequently bite humans in South America. The genome assembly of three new putative species obtained from human, sloth, and tick metagenomes further reveals the presence of major homologs of Ehrlichia and Anaplasma virulence factors. These observations converge to classify health hazards associated with Ehrlichia and Anaplasma infections in the Amazon biome as distinct from those in the Northern Hemisphere

HLA-matched related donor hematopoietic stem cell transplantation is a suitable treatment in adolescents and adults with sickle cell disease: Comparison of myeloablative and non-myeloablative approaches

SCOPUS: le.jinfo:eu-repo/semantics/publishe

Evolutionary changes in symbiont community structure in ticks

International audienceEcological specialization to restricted diet niches is driven by obligate, and often maternally inherited, symbionts in many arthropod lineages. These heritable symbionts typically form evolutionarily stable associations with arthropods that can last for millions of years. Ticks were recently found to harbour such an obligate symbiont, Coxiella-LE, that synthesizes B vitamins and cofactors not obtained in sufficient quantities from blood diet. In this study, the examination of 81 tick species shows that some Coxiella-LE symbioses are evolutionarily stable with an ancient acquisition followed by codiversification as observed in ticks belonging to the Rhipicephalus genus. However, many other Coxiella-LE symbioses are characterized by low evolutionary stability with frequent host shifts and extinction events. Further examination revealed the presence of nine other genera of maternally inherited bacteria in ticks. Although these nine symbionts were primarily thought to be facultative, their distribution among tick species rather suggests that at least four may have independently replaced Coxiella-LE and likely represent alternative obligate symbionts. Phylogenetic evidence otherwise indicates that cocladogenesis is globally rare in these symbioses as most originate via horizontal transfer of an existing symbiont between unrelated tick species. As a result, the structure of these symbiont communities is not fixed and stable across the tick phylogeny. Most importantly, the symbiont communities commonly reach high levels of diversity with up to six unrelated maternally inherited bacteria coexisting within host species. We further conjecture that interactions among coexisting symbionts are pivotal drivers of community structure both among and within tick species