Biology subjects

Jourdan-Pineau, H.

Publications and source records attributed to Jourdan-Pineau, H..

8 recordsLinked to original sources

bioRxiv2026

Microbial communities in Ornithodoros phacochoerus ticks: spatial structure and influence of African swine fever virus infectious status

AO_SCPLOWBSTRACTC_SCPLOWOrnithodoros phacochoerus are nidicolous soft ticks of the Ornithodoros moubata complex of species known to be vectors of the African swine fever (ASF) virus. These Ornithodoros ticks depend on endosymbionts to produce essential nutrients necessary for their development. However, endosymbionts are only a part of the complex microbiota hosted by the tick. This microbiota often includes primary or secondary endosymbionts, commensal species from the environment, and, most of the time, some pathogens. The present study was performed to understand the organization and spatial distribution of the microbiota of O. phacochoerus. One of the objectives was to investigate if the pathogen of interest (ASF virus) is involved in the organization of the microbiota through pathogen-induced dysbiosis or other interactions. For this purpose, 704 O. phacochoerus ticks were collected from two conservation areas in Mozambique. Sequencing was performed targeting the V3-V4 region of the 16S rRNA gene, and the resulting dataset was processed using FROGS to characterize the bacterial microbiota hosted by the ticks. The results indicate that the microbiota of Ornithodoros phacochoerus contains very low bacterial diversity, with one primary endosymbiont (Francisella-like endosymbiont), one potential secondary endosymbiont (Rickettsiella), and very few environmental or pathogenic bacterial species. We found a clear spatial structure of the microbiota, with ticks from the same sampling site showing similar patterns. On the contrary, no association with the infectious status for African swine fever virus was detected, suggesting that this pathogen does not shape Ornithodoros microbial communities. Our results on tick - microbiota - pathogen - environment interactions in nidicolous soft ticks, showed patterns that differ from most hard tick studies.

microbiology↗

bioRxiv2025

Population genetics of the nidicolous soft tick Ornithodoros phacochoerus in the context of African swine fever sylvatic cycle

Ticks of the species Ornithodoros phacochoerus are endophilic soft ticks which infest warthog burrows. Like other Ornithodoros of the O. moubata species complex, O. phacochoerus is a vector of the African swine fever virus and participates in the maintenance of the virus among warthogs in the sylvatic cycle in Southern and Eastern African countries. In this study, the population genetic structure of O. phacochoerus was investigated using sixteen microsatellite markers. After sampling campaigns that took place between 2020 and 2022, we analyzed 684 ticks from 21 warthog burrows and resting sites from Coutada 9 Game Reserve, Macossa District, Mozambique, and 138 ticks from 3 warthog burrows and resting sites from Gorongosa National Park, Gorongosa District, Mozambique. Burrows and resting sites are regularly used by the common warthog Phacochoerus africanus which is thought to be responsible for the movements of O. phacochoerus between sites. After genotyping, the observed genetic variation followed a model of isolation by distance with a structure at the level of the sampling sites (burrows and resting sites). Gorongosa National Park and Coutada 9 Game Reserve appeared to be completely isolated from each other in terms of gene flow, and Coutada 9 Game Reserve showed a clear signature of a bottleneck effect. Effective population sizes within sampling sites were quite low (4.1 individuals), with an estimated migration rate of 35% and a mean dispersal distance of 209 meters per tick generation. These results suggested frequent tick movements between burrows at a small geographic scale, due to warthog movements between the burrows. As both wildlife conservation areas are positive for African swine fever virus, these results reinforce the suspected role of the ticks in the sylvatic cycle of the virus, as infected ticks could be moved from one burrow to another, maintaining the presence of the virus in several sites of the conservation areas. This confirms the importance of maintaining buffer zones around conservation areas, buffer zones that should remain free of any domestic pigs to prevent vector spillover from the sylvatic cycle to the domestic cycle.

ecology↗

bioRxiv2024

Comparative genomics of Rickettsiella bacteria reveal variable metabolic traits involved in symbiotic interactions with arthropods

Members of the Rickettsiella genus (order: Legionellales) are emerging as widespread bacteria associated with insects, arachnids, and crustaceans. While some Rickettsiella strains are highly virulent pathogens, others are maternally inherited endosymbionts that manipulate arthropod phenotypes, including the induction of defensive symbiosis and cytoplasmic incompatibility. However, the genomic diversity of Rickettsiella remains largely unexplored, and their genetic potential to induce complex phenotypes in arthropods is only partially understood. In this study, we sequenced five new Rickettsiella genomes isolated from three tick species. Through comparative genomics, we observed that Rickettsiella members share similar metabolic capabilities, and collectively lack virulence genes from pathogenic Legionellales. Additional analysis of Rickettsiella genomes revealed significant variability in metabolic properties related to endosymbiosis. Specifically, their capacity to biosynthesize certain B vitamins and heme varies, suggesting a functional role of some Rickettsiella strains in the nutrition of their arthropod hosts. Some Rickettsiella genomes harbour homologs of Wolbachia cif genes, the cause of Wolbachia-induced cytoplasmic incompatibility,, suggesting that Rickettsiella may use a similar molecular mechanism to manipulate the reproduction of their arthropod hosts. Phylogenomics further revealed that tick-borne Rickettsiella exhibit distinct evolutionary origins within the genus, indicating that Rickettsiella have undergone repeated horizontal transfers between ticks and other arthropods.

evolutionary biology↗

bioRxiv2024

Spatial patterns of Hyalomma marginatum-borne pathogens in the Occitanie region (France), a focus on the intriguing dynamics of Rickettsia aeschlimannii

Hyalomma marginatum is an invasive tick species recently established in mainland southern France. This tick is known to host a diverse range of human and animal pathogens such as Rickettsia aeschlimannii, Theileria equi, Anaplasma phagocytophilum, Anaplasma marginale, Ehrlichia minasensis, Crimean-Congo hemorrhagic fever and West Nile virus. While information about the dynamics of these pathogens is crucial to assess disease risk and develop effective monitoring strategies, few data on the spatial dynamics of these pathogens are currently available. We thus collected ticks in 27 sites in the Occitanie region to characterize spatial patterns of H. marginatum- borne pathogens. Several pathogens have been detected: Theileria equi (9.2%), Theileria orientalis (0.2%), Anaplasma phagocytophilum (1.6%), Anaplasma marginale (0.8%) and Rickettsia aeschlimannii (87.3%). Interestingly, we found a spatial clustered distribution for the pathogen R. aeschlimannii between two geographically isolated areas with infection rates and bacterial loads significantly lower in Herault/Gard departments (infection rate 78.6% in average) compared to Aude/Pyrenees-Orientales departments (infection rate 92.3% in average). At a smaller scale, R. aeschlimannii infection rates varied from one site to another, ranging from 29% to 100%. Overall, such high infection rates (87.3% in average) and the effective maternal transmission of R. aeschlimannii might suggest a role as a tick symbiont in H. marginatum. Moreover, currently identified as a human pathogen, such results also question about its pathogenic status in humans given the low number of human cases. Further studies are thus needed to understand both the status and the role of R. aeschlimannii in H. marginatum ticks. IMPORTANCETicks are obligatory hematophagous arthropods which transmit pathogens of medical and veterinary importance. Their infections cause serious health issues in humans and considerable economic loss in domestic animals. Information about the presence of pathogens in ticks and their dynamics is crucial to assess disease risk for public and animal health. Analysing tick-borne pathogens in ticks collected in 27 sites in the regions Occitanie, our results highlight clear spatial patterns in the Hyalomma marginatum-borne pathogen distribution and strengthen the postulate that it is essential to develop effective monitoring strategies and consider the spatial scale to better characterize the circulation of tick-borne pathogens.

microbiology↗

bioRxiv2023

The importance of experimental design for studying the vector competence of Ornithodoros ticks for African swine fever virus: a meta-analysis of published evaluations

African Swine Fever (ASF) is a highly economically devastating viral disease for swine. Soft ticks of the genus Ornithodoros are involved in its epidemiology, as vectors and natural reservoirs of African Swine Fever Virus (ASFV). The vector competence of Ornithodoros ticks for ASFV has been mainly studied by mimicking natural tick-to-pig transmission pathways through experimental infections in the laboratory. By reviewing the original research studies dating back to the 1960s on the vector competence of Ornithodoros for ASFV, we estimated the vector competence of 10 tick species in association with 38 viral strains resulting in 51 tick-virus associations. This assessment emphasized the extensive range of protocol designs employed and their impact on the success of tick infection with ASFV. Our results call for standardised procedures in vector competence experiments to facilitate further investigation and reduce potential experimental bias. In particular, we recommend the use of late nymphs or adult ticks from a laboratory colony to achieve efficient infection rates. In addition, viral inoculation should be carried out by blood meal rather than by injection, and preference should be given to high titre blood. Finally, detection of viral DNA should be performed 2 months after inoculation to distinguish between successful replication and residual virus in the tick.

ecology↗

bioRxiv2023

New insights into the role of the microbiota in Ornithodoros moubata: Influence of endosymbionts on the reproductive fitness of the tick

AO_SCPLOWBSTRACTC_SCPLOWOver the past decade, many studies have demonstrated the crucial role of the tick microbiome in tick biology. The soft tick Ornithodoros moubata is a hematophagous ectoparasite of Suidae, best known for transmitting the African swine fever virus. Its bacterial microbiota is characterized by a high prevalence of Francisella-like and Rickettsia endosymbionts. The present study aims to better understand the potential influence of these two major members of the tick microbiota on the reproductive fitness of O. moubata. A total of 132 adult female ticks were treated with antibiotics using gentamycin or rifampicin added to the blood meal. Half of the ticks were also supplemented with B vitamins to address the nutritional role of endosymbionts. Over two periods of 50 days, several traits related to the reproductive fitness were monitored to investigate the importance of Francisella and Rickettsia for these traits. It appeared that most of the reproductive parameters considered were not affected. However, antibiotic treatments induced an increase in the tick survival, indicating a potential fitness cost of harboring endosymbionts during the tick reproductive cycle. Similarly, 366 first stage nymphs of Ornithodoros moubata were exposed to the same treatments for molecular quantification of both endosymbionts. Results from qPCR suggested that the treatments had a bacteriostatic effect on endosymbionts without completely eliminating neither Francisella-like endosymbiont nor Rickettsia.

ecology↗

bioRxiv2022

Bimodal breeding phenology in the parsley frog Pelodytes punctatus as a bet-hedging strategy in an unpredictable environment despite strong priority effects

AO_SCPLOWBSTRACTC_SCPLOWWhen environmental conditions are unpredictable, expressing alternative phenotypes spreads the risk of failure, a mixed strategy called bet-hedging. In the southern part of its range, the Parsley Frog Pelodytes punctatus breeds both in autumn and in spring. Our aim was to study the breeding phenology and reproductive success associated with the use of those two seasonal niches to understand how this breeding strategy can be maintained. Field surveys revealed that breeding phenology was typically bimodal with a higher breeding effort in autumn. More importantly, in spring, the survival rate of offspring was severely reduced by the presence of autumn tadpoles, indicating a clear priority effect. However, the autumn cohort often failed to survive over winter, in which case spring cohorts were often successful. Based on those results, we constructed a model in which females can allocate a variable portion of eggs to each season and added a priority effect. We conclude that the existence of the two breeding seasons may indeed constitute a bet-hedging strategy.

evolutionary biology↗

bioRxiv2017

Challenges in estimating heritability of phase polyphenism: Insights from measured and simulated data in the desert locust

Quantitative genetics experiments aim at understanding and predicting the evolution of phenotypic traits. Running such experiments often bring the same questions: Should I bother with maternal effects? Could I estimate those effects? What is the best crossing scheme to obtain reliable estimates? Can I use molecular markers to spare time in the complex task of keeping track of the experimental pedigree?\n\nWe explored those practical issues in the desert locust, Schistocerca gregaria using morphologic and coloration traits, known to be influenced by maternal effects. We ran quantitative genetic analyses with an experimental dataset and used simulations to explore i) the efficiency of animal models to accurately estimate both heritability and maternal effects, ii) the influence of crossing schemes on the precision of estimates and iii) the performance of a marker-based method compared to the pedigree-based method.\n\nThe simulations indicated that maternal effects deeply affect heritability estimates and very large datasets are required to properly distinguish and estimate maternal effects and heritabilities. In particular, ignoring maternal effects in the animal model resulted in overestimation of heritabilities and a high rate of false positives whereas models specifying maternal variance suffer from lack of power. Maternal effects can be estimated more precisely than heritabilities but with low power. To obtain better estimates, bigger datasets are required and, in the presence of maternal effects, increasing the number of families over the number of offspring per families is recommended. Our simulations also showed that, in the desert locust, using relatedness based on available microsatellite markers may allow reasonably reliable estimates while rearing locusts in group.\n\nIn the light of the simulation results, our experimental dataset suggested that maternal effects affected various phase traits. However the statistical limitations, revealed by the simulation approach, didnt allow precise variance estimates. We stressed out that doing simulations is a useful step to design an experiment in quantitative genetics and interpret the outputs of the statistical models.

evolutionary biology↗