Gwenaël Vourc'h

Publications of Gwenaël Vourc'h

• Human risk of infection with Borrelia burgdorferi, the Lyme disease agent, in eastern United States.

  Authors: Maria A Diuk-Wasser, Anne Gatewood Hoen, Paul Cislo, Robert Brinkerhoff, Sarah A Hamer, Michelle Rowland, Roberto Cortinas, Gwenaël Vourc'h, Forrest Melton, Graham J Hickling, Jean I Tsao, Jonas Bunikis, Alan G Barbour, Uriel Kitron, Joseph Piesman, Durland Fish

  The American journal of tropical medicine and hygiene. 02/2012; 86(2):320-7.

  The geographic pattern of human risk for infection with Borrelia burgdorferi sensu stricto, the tick-borne pathogen that causes Lyme disease, was mapped for the eastern United States. The map isThe geographic pattern of human risk for infection with Borrelia burgdorferi sensu stricto, the tick-borne pathogen that causes Lyme disease, was mapped for the eastern United States. The map is based on standardized field sampling in 304 sites of the density of Ixodes scapularis host-seeking nymphs infected with B. burgdorferi, which is closely associated with human infection risk. Risk factors for the presence and density of infected nymphs were used to model a continuous 8 km×8 km resolution predictive surface of human risk, including confidence intervals for each pixel. Discontinuous Lyme disease risk foci were identified in the Northeast and upper Midwest, with a transitional zone including sites with uninfected I. scapularis populations. Given frequent under- and over-diagnoses of Lyme disease, this map could act as a tool to guide surveillance, control, and prevention efforts and act as a baseline for studies tracking the spread of infection.

• Reproducibility of local environmental factors for the abundance of questing Ixodes ricinus nymphs on pastures.

  Authors: Chloé Boyard, Jacques Barnouin, Séverine Bord, Patrick Gasqui, Gwenaël Vourc'h

  Ticks and tick-borne diseases. 06/2011; 2(2):104-10.

  In ecology and epidemiology, exploratory field studies based on multivariate statistical models commonly are used to identify factors that are associated with a phenomenon. The challenge is toIn ecology and epidemiology, exploratory field studies based on multivariate statistical models commonly are used to identify factors that are associated with a phenomenon. The challenge is to evaluate whether these factors are indeed correlated to the phenomenon or if the statistical significance results from fortuitous association or type 1 statistical error (probability of rejecting a null hypothesis when it is true). This is particularly the case when the phenomenon is linked to environmental factors that usually are more or less correlated to each other and when the phenomenon is itself highly variable. The abundance of Ixodes ricinus ticks, a major disease vector in Europe, is highly variable and depends on environmental conditions that define suitable habitat and host presence. Our objective was to identify reproducible factors in space and time that influenced the abundance of questing I. ricinus nymphs. We sampled questing nymphs in pastures in 4 settings, i.e. during 3 periods (2003, 2004, and 2006) in one region, and during one period (2006) in another region, both regions located in Central France. The same data collection, data selection, and model analysis using negative binomial distribution were applied independently in the 4 data sets to identify 'reproducible' factors, i.e. explanatory factors that were significant in different time periods and spaces. The 3 most reproducible factors suggested that woodland type vegetation and woodland vicinity constantly favoured nymph abundance on pastures. In addition, the presence of fruit trees was significantly associated with nymph abundance in one region. The other factors were not reproducible. The study confirmed the status of key factors for nymph abundance while avoiding having to redefine the statistical model to model the different sampling conditions. It also shows the difficulty to identify factors with general significance acting on a very variable phenomenon, based on a study made one year in one region. Relevant study design should consider appropriate repetitions based on the range of values of the studied factors. Furthermore, discussion of the results is essential to identify factors that have a general significance.

• Ecological factors characterizing the prevalence of bacterial tick-borne pathogens in Ixodes ricinus ticks in pastures and woodlands.

  Authors: Lénaïg Halos, Séverine Bord, Violaine Cotté, Patrick Gasqui, David Abrial, Jacques Barnouin, Henri-Jean Boulouis, Muriel Vayssier-Taussat, Gwenaël Vourc'h

  Applied and environmental microbiology. 07/2010; 76(13):4413-20.

  Ecological changes are recognized as an important driver behind the emergence of infectious diseases. The prevalence of infection in ticks depends upon ecological factors that are rarely taken intoEcological changes are recognized as an important driver behind the emergence of infectious diseases. The prevalence of infection in ticks depends upon ecological factors that are rarely taken into account simultaneously. Our objective was to investigate the influences of forest fragmentation, vegetation, adult tick hosts, and habitat on the infection prevalence of three tick-borne bacteria, Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum, and Rickettsia sp. of the spotted fever group, in questing Ixodes ricinus ticks, taking into account tick characteristics. Samples of questing nymphs and adults were taken from 61 pastures and neighboring woodlands in central France. The ticks were tested by PCR of pools of nymphs and individual adults. The individual infection prevalence was modeled using multivariate regression. The highest infection prevalences were found in adult females collected in woodland sites for B. burgdorferi sensu lato and A. phagocytophilum (16.1% and 10.7%, respectively) and in pasture sites for Rickettsia sp. (8.7%). The infection prevalence in nymphs was lower than 6%. B. burgdorferi sensu lato was more prevalent in woodlands than in pastures. Forest fragmentation favored B. burgdorferi sensu lato and A. phagocytophilum prevalence in woodlands, and in pastures, the B. burgdorferi sensu lato prevalence was favored by shrubby vegetation. Both results are probably because large amounts of edges or shrubs increase the abundance of small vertebrates as reservoir hosts. The Rickettsia sp. prevalence was maximal on pasture with medium forest fragmentation. Female ticks were more infected by B. burgdorferi sensu lato than males and nymphs in woodland sites, which suggests an interaction between the ticks and the bacteria. This study confirms the complexity of the tick-borne pathogen ecology. The findings support the importance of small vertebrates as reservoir hosts and make a case for further studies in Europe on the link between the composition of the reservoir host community and the infection prevalence in ticks.

• The Flying Fox Pteropus seychellensis of Mayotte (Comoros): Method of Capture and Blood Sampling.

  Authors: Amélie Desvars, Thomas Duval, Clément Punelle, Michel Pascal, Gwenaël Vourc'h

  Journal of wildlife diseases. 08/2009; 45(3):870-3.

  Pteropus seychellensis comorensis is the only Pteropodidae bat species on the island of Mayotte (Comoros Archipelago), and most aspects of its biology are unknown. In order to catch this large bat,Pteropus seychellensis comorensis is the only Pteropodidae bat species on the island of Mayotte (Comoros Archipelago), and most aspects of its biology are unknown. In order to catch this large bat, we used a simple and low-cost method, consisting of raised mist nets that were set close to foraging sites. Major factors driving catch success were high food availability, good positioning of mist nets, and careful observation of movement patterns to identify foraging sites where the chances of capture are high. Blood was collected from the alar and humeral veins, which appear to be more practical for this purpose than other parts of the venous system.

• Blood-Feeding Behavior of Aedes albopictus, a Vector of Chikungunya on La Réunion.

  Authors: Helene Delatte, Amelie Desvars, Anthony Bouétard, Séverine Bord, Geoffrey Gimonneau, Gwenaël Vourc'h, Didier Fontenille

  Vector borne and zoonotic diseases (Larchmont, N.Y.). 08/2009;

  Abstract Chikungunya virus (CHIKV) has long been considered to be transmitted to humans by the human-biting mosquito Aedes aegypti, especially in Africa. However, the recent outbreak of CHIKVAbstract Chikungunya virus (CHIKV) has long been considered to be transmitted to humans by the human-biting mosquito Aedes aegypti, especially in Africa. However, the recent outbreak of CHIKV involved another vector, Aedes albopictus, and serological data in the literature suggest that several species of domestic or human-related vertebrates can be contaminated by this virus. However, the role of Ae. albopictus mosquitoes as potential enzootic vectors for CHIKV has not yet been evaluated. Here we investigate Ae. albopictus feeding and resting behaviors in an area where a CHIKV epidemic recently occurred, which means deciphering host-seeking and feeding behaviors on several vertebrate species, measuring endophagous/exophagous (activity), endophilic/exophilic (resting) behaviors and its diel (24 h, day/night) biting activity. Ae. albopictus was found to have bimodal daily feeding activities and was found to have exophagic (89%) and exophilic (87%) behaviors. Ae. albopictus showed an opportunistic feeding behavior on a wide range of hosts (from cold-blooded to warm-blooded animals), supporting that it can be implicated in various vertebrate-virus pathosystems. However, with equal availability of one of the four vertebrate hosts (calf, chicken, dog, and goat) proposed against human, Ae. albopictus significantly preferred human, supporting earlier data about its high degree of anthropophily. Multiple blood feeding was also reported in every combination (animal/human) offered to Ae. albopictus, enlightening the higher risks to spread an arbovirus to human population because of interrupted feeding. Such catholic behavior suggests that Ae. albopictus may act as a bridge vector for zoonotic viruses. Further epidemiological implications of this issue are discussed.

• Climate and tick seasonality predict Borrelia burgdorferi genotype distribution.

  Authors: Anne G Gatewood, Kelly A. Liebman, Gwenaël Vourc'h, Jonas Bunikis, Sarah A. Hamer, Roberto Cortinas, Forrest Melton, Paul Cislo, Uriel Kitron, Jean Tsao, Alan G Barbour, Durland Fish, Maria A Diuk-Wasser

  Applied and environmental microbiology. 03/2009;

  The blacklegged tick, Ixodes scapularis, is of significant public health importance as a vector of Borrelia burgdorferi, the agent of Lyme borreliosis. The timing of seasonal activity of eachThe blacklegged tick, Ixodes scapularis, is of significant public health importance as a vector of Borrelia burgdorferi, the agent of Lyme borreliosis. The timing of seasonal activity of each immature I. scapularis life stage relative to the next is critical for the maintenance of B. burgdorferi because larvae must feed after an infected nymph to efficiently acquire the infection from reservoir hosts. Recent studies have shown that some strains of B. burgdorferi do not persist in the primary reservoir host for more than a few weeks, thereby shortening the window of opportunity between nymphal and larval feeding that sustains their enzootic maintenance. We tested the hypothesis that climate is predictive of geographic variation in the seasonal activity of I. scapularis, which in turn differentially influences the distribution of B. burgdorferi genotypes within the geographic range of I. scapularis. We analyzed the relationships between climate, seasonal activity of I. scapularis, and B. burgdorferi genotype frequency in 30 geographically diverse sites in the northeastern and Midwestern US. We found that the magnitude of the difference between summer and winter daily temperature maximums was positively correlated with the degree of seasonal synchrony of the two immature stages of I. scapularis. Genotyping revealed an enrichment of 16S-23S rRNA intergenic spacer restriction fragment length polymorphism sequence type 1 strains relative to others at sites with lower seasonal synchrony. We conclude that climate-associated variability in the timing of I. scapularis host-seeking contributes to geographic heterogeneities in the frequencies of B. burgdorferi genotypes, with potential consequences for Lyme borreliosis morbidity.

• Mammal and bird species distribution at the woodland-pasture interface in relation to the circulation of ticks and pathogens.

  Authors: Gwenaël Vourc'h, Chloé Boyard, Jacques Barnouin

  Annals of the New York Academy of Sciences. 01/2009; 1149:322-5.

  The tick vector Ixodes ricinus can be found in pastures in landscapes where pasture and woodland intermix, such as in the bocage. To identify which mammal or bird species could potentially transportThe tick vector Ixodes ricinus can be found in pastures in landscapes where pasture and woodland intermix, such as in the bocage. To identify which mammal or bird species could potentially transport ticks between woodland and pasture, we did a species inventory on four French bocage sites in 2005. Fifty-eight species were observed, 21 of which were found in three different habitats: the middle of the pasture, the hedgerow ecotone, and the woodland. Because the bocage is a meeting point for wildlife, domestic animals, and humans, species using the three habitats could potentially be epidemiologic agents for circulation of tick vectors as well as of pathogens. Thus, the bocage could be used as a model landscape for the study of epidemiologic cycles and potential emergence of multiple-host pathogens.

• The relationships between Ixodes ricinus and small mammal species at the woodland-pasture interface.

  Authors: Chloé Boyard, Gwenaël Vourc'h, Jacques Barnouin

  Experimental & applied acarology. 02/2008; 44(1):61-76.

  Ixodes ricinus, as vector, and small mammals, as reservoirs, are implicated in pathogen transmission between wild fauna, domestic animals and humans at the woodland-pasture interface. The ecologicalIxodes ricinus, as vector, and small mammals, as reservoirs, are implicated in pathogen transmission between wild fauna, domestic animals and humans at the woodland-pasture interface. The ecological relationship between ticks and small mammals was monitored in 2005 on four bocage (enclosed pastureland) sites in central France, where questing ticks were collected by dragging and small mammals were trapped. Questing I. ricinus tick and small mammal locations in the environment were assessed through correspondence analysis. I. ricinus larval burden on small mammals was modeled using a negative binomial law. The correspondence analyses underlined three landscape features: grassland, hedgerow, and woodland. Seven small mammal species were trapped, while questing ticks were all I. ricinus, with the highest abundance in woodland and the lowest in pasture. The small mammals were overall more abundant in hedgerow, less present in woodland and sparse in grassland. They carried mainly I. ricinus, and secondarily I. acuminatus and I. trianguliceps. The most likely profile for a tick-infested small mammal corresponded to a male wood mouse (Apodemus sylvaticus) in woodland or hedgerow during a dry day. A. sylvaticus, which was the only species captured in grassland, but was also present in hedgerow and woodland, may be a primary means of transfer of I. ricinus larvae from woodland to pasture.

• Borrelia burgdorferi Sensu Lato in Siberian chipmunks (Tamias sibiricus) introduced in suburban forests in France.

  Authors: Gwenaël Vourc'h, Julie Marmet, Michelle Chassagne, Séverine Bord, Jean-Louis Chapuis

  Vector borne and zoonotic diseases (Larchmont, N.Y.). 02/2007; 7(4):637-41.

  Numerous vertebrate reservoirs have been described for Borrelia burgdorferi sensu lato (sl), which includes the etiological agents of Lyme Borreliosis (LB). The Siberian chipmunk (Tamias sibiricus)Numerous vertebrate reservoirs have been described for Borrelia burgdorferi sensu lato (sl), which includes the etiological agents of Lyme Borreliosis (LB). The Siberian chipmunk (Tamias sibiricus) is a rodent originating from Asia, where it is suspected to be a B. burgdorferi reservoir. It has been intentionally released into the wild in Europe since the 1970s, but has not yet been subject to any study regarding its association with the LB agent. In this paper we studied Siberian chipmunk infestation with the LB vector (Ixodes ricinus) and infection prevalence by LB spirochetes in a suburban introduced population. We compared these findings with known competent reservoir hosts, the bank vole (Myodes [clethrionomys] glareolus) and wood mouse (Apodemus sylvaticus). All Siberian chipmunks were infested with larvae and larval abundance was higher in this species (mean number of larvae [95% Confidence Interval]: 73.5 [46.0, 117.2]) than in the two other rodent species (bank voles: 4.4 [3.0, 6.3] and wood mice: 10.2 [4.9, 21.2]). Significant factors affecting abundance of larvae were host species and sampling season. Nymphs were most prevalent on chipmunks (86.2%, mean: 5.1 [3.3, 8.0]), one vole carried only two nymphs, and none of the mice had any nymphs. Nymph abundance in chipmunks was affected by sampling season and sex. Furthermore, the infection prevalence of B. burgdorferi sl in the Siberian chipmunk was the highest (33.3%) and predominantly of B. afzelii. The infection prevalence was 14.1% in bank voles, but no wood mouse was found to be infected. Our results suggest that the Siberian chipmunk may be an important reservoir host for LB.

• Prevalence of Anaplasma phagocytophilum, Rickettsia sp. and Borrelia burgdorferi sensu lato DNA in questing Ixodes ricinus ticks from France.

  Authors: Lénaïg Halos, Gwenaël Vourc'h, Violaine Cotte, Patrick Gasqui, Jacques Barnouin, Henri-Jean Boulous, Muriel Vayssier-Taussat

  Annals of the New York Academy of Sciences. 11/2006; 1078:316-9.

  A total of 4701 Ixodes ricinus, collected during the summer of 2003, were analyzed for three pathogens. DNA was detected from the three pathogens. Co-detection of more than one pathogen was observed.

• Detecting emerging diseases in farm animals through clinical observations.

  Authors: Gwenaël Vourc'h, Victoria E Bridges, Jane Gibbens, Brad D De Groot, Lachlan McIntyre, Roger Poland, Jacques Barnouin

  Emerging infectious diseases. 03/2006; 12(2):204-10.

  Predicting emerging diseases is among the most difficult challenges facing researchers and health managers. We present available approaches and tools to detect emerging diseases in animals based onPredicting emerging diseases is among the most difficult challenges facing researchers and health managers. We present available approaches and tools to detect emerging diseases in animals based on clinical observations of farm animals by veterinarians. Three information systems are described and discussed: Veterinary Practitioner Aided Disease Surveillance in New Zealand, the Rapid Syndrome Validation Project-Animal in the United States, and "émergences" in France. These systems are based on syndromic surveillance with the notification of every case or of specific clinical syndromes or on the notification of atypical clinical cases. Data are entered by field veterinarians into forms available through Internet-accessible devices. Beyond challenges of implementing new information systems, minimizing economic and health effects from emerging diseases in animals requires strong synergies across a group of field partners, in research, and in international animal and public health customs and practices.

• Broad-range PCR-TTGE for the first-line detection of bacterial pathogen DNA in ticks.

  Authors: Lénaïg Halos, Maria Mavris, Gwenaël Vourc'h, Renaud Maillard, Jacques Barnouin, Henri-Jean Boulouis, Muriel Vayssier-Taussat

  Veterinary research. 37(2):245-53.

  Ticks are known or suspected vectors for a wide range of bacterial pathogens. One of the first steps for tick-borne risk assessment is the detection of these pathogens in their vectors. In theTicks are known or suspected vectors for a wide range of bacterial pathogens. One of the first steps for tick-borne risk assessment is the detection of these pathogens in their vectors. In the present study, a broad-range PCR amplification of the eubacterial gene encoding the 16S rRNA gene combined with Temporal Temperature Gradient gel Electrophoresis (TTGE) was evaluated as a method allowing the one-step detection of bacterial pathogen DNA in ticks. Firstly, DNA extracts from bacteria known to be tick-borne pathogens, i.e., Borrelia burgdorferi lato sensu, Anaplasma phagocytophilum, Spotted Fever Group (SFG) Rickettsia spp., were used to establish a TTGE pathogen DNA reference marker. Secondly, we used broad-range PCR-TTGE to detect the presence of DNA from these three pathogens in 55 DNA extracts from pools of 10 nymphal Ixodes ricinus ticks, which have been previously shown to carry DNA from at least one of those bacteria by specific PCR. Among the 20 B. burgdorferi specific-PCR samples, 15 (75%) were also found to be positive using PCR-TTGE. Sixteen of the seventeen (94%) Rickettsia spp. PCR-specific samples were positive using PCR-TTGE detection and all PCR-specific positive extracts (11/11, 100%) for A. phagocytophilum were also positive using PCR-TTGE. Moreover, we identified unexpected bacterial sequences that were not related to any of the three pathogens such as a sequence related to Spiroplasma sp. Thus, broad-range PCR-TTGE allowed the single step detection of DNA from up to 3 pathogens in the same co-infected samples as well as detection of DNA from unexpected bacteria.