Prevalence of Borrelia burgdorferi sensu lato and Anaplasmataceae members in Ixodes ricinus ticks in Alsace, a focus of Lyme borreliosis endemicity in France

Prevalence of Lyme Disease and Relapsing Fever Borrelia spp. in Vectors, Animals, and Humans within a One Health Approach in Mediterranean Countries

The genus Borrelia has been divided into Borreliella spp., which can cause Lyme Disease (LD), and Borrelia spp., which can cause Relapsing Fever (RF). The distribution of genus Borrelia has broadened due to factors such as climate change, alterations in land use, and enhanced human and animal mobility. Consequently, there is an increasing necessity for a One Health strategy to identify the key components in the Borrelia transmission cycle by monitoring the human-animal-environment interactions. The aim of this study is to summarize all accessible data to increase our understanding and provide a comprehensive overview of Borrelia distribution in the Mediterranean region. Databases including PubMed, Google Scholar, and Google were searched to determine the presence of Borreliella and Borrelia spp. in vectors, animals, and humans in countries around the Mediterranean Sea. A total of 3026 were identified and screened and after exclusion of papers that did not fulfill the including criteria, 429 were used. After examination of the available literature, it was revealed that various species associated with LD and RF are prevalent in vectors, animals, and humans in Mediterranean countries and should be monitored in order to effectively manage and prevent potential infections.

Multiple factors affecting Ixodes ricinus ticks and associated pathogens in European temperate ecosystems (northeastern France)

In Europe, the main vector of tick-borne zoonoses is Ixodes ricinus, which has three life stages. During their development cycle, ticks take three separate blood meals from a wide variety of vertebrate hosts, during which they can acquire and transmit human pathogens such as Borrelia burgdorferi sensu lato, the causative agent of Lyme borreliosis. In this study conducted in Northeastern France, we studied the importance of soil type, land use, forest stand type, and temporal dynamics on the abundance of ticks and their associated pathogens. Negative binomial regression modeling of the results indicated that limestone-based soils were more favorable to ticks than sandstone-based soils. The highest tick abundance was observed in forests, particularly among coniferous and mixed stands. We identified an effect of habitat time dynamics in forests and in wetlands: recent forests and current wetlands supported more ticks than stable forests and former wetlands, respectively. We observed a close association between tick abundance and the abundance of Cervidae, Leporidae, and birds. The tick-borne pathogens responsible for Lyme borreliosis, anaplasmosis, and hard tick relapsing fever showed specific habitat preferences and associations with specific animal families. Machine learning algorithms identified soil related variables as the best predictors of tick and pathogen abundance.

Cross-alteration of murine skin and tick microbiome concomitant with pathogen transmission after Ixodes ricinus bite

BACKGROUND

Ticks are major vectors of diseases affecting humans such as Lyme disease or domestic animals such as anaplasmosis. Cross-alteration of the vertebrate host skin microbiome and the tick microbiome may be essential during the process of tick feeding and for the mechanism of pathogen transmission. However, it has been poorly investigated.

METHODS

We used mice bitten by field-collected ticks (nymphs and adult ticks) in different experimental conditions to investigate, by 16S rRNA gene metabarcoding, the impact of blood feeding on both the mouse skin microbiome and the tick microbiome. We also investigated by PCR and 16S rRNA gene metabarcoding, the diversity of microorganisms transmitted to the host during the process of tick bite at the skin interface and the dissemination of the pathogen in host tissues (blood, heart, and spleen).

RESULTS

Most of the commensal bacteria present in the skin of control mice were replaced during the blood-feeding process by bacteria originating from the ticks. The microbiome of the ticks was also impacted by the blood feeding. Several pathogens including tick-borne pathogens (Borrelia/Borreliella, Anaplasma, Neoehrlichia, Rickettsia) and opportunistic bacteria (Williamsia) were transmitted to the skin microbiome and some of them disseminated to the blood or spleen of the mice. In the different experiments of this study, skin microbiome alteration and Borrelia/Borreliella transmission were different depending on the tick stages (nymphs or adult female ticks).

CONCLUSIONS

Host skin microbiome at the bite site was deeply impacted by the tick bite, to an extent which suggests a role in the tick feeding, in the pathogen transmission, and a potentially important impact on the skin physiopathology. The diversified taxonomic profiles of the tick microbiome were also modified by the blood feeding. Video Abstract.

Seroprevalence for Borrelia burgdorferi sensu lato and tick-borne encephalitis virus antibodies and associated risk factors among forestry workers in northern France, 2019 to 2020

BackgroundLyme borreliosis (LB) is the most common tick-borne disease (TBD) in France. Forestry workers are at high risk of TBD because of frequent exposure to tick bites.AimWe aimed to estimate the seroprevalence of Borrelia burgdorferi sensu lato and tick-borne encephalitis virus (TBEV) antibodies among forestry workers in northern France. We compared seroprevalence by geographical area and assessed factors associated with seropositivity.MethodsBetween 2019 and 2020, we conducted a randomised cross-sectional seroprevalence survey. Borrelia burgdorferi sl seropositivity was defined as positive ELISA and positive or equivocal result in western blot. Seropositivity for TBEV was defined as positive result from two ELISA tests, confirmed by serum neutralisation. We calculated weighted seroprevalence and adjusted prevalence ratios to determine association between potential risk factors and seropositivity.ResultsA total of 1,778 forestry workers participated. Seroprevalence for B. burgdorferi sl was 15.5% (95% confidence interval (CI): 13.9-17.3), 3.5 times higher in the eastern regions than in the western and increased with seniority and with weekly time in a forest environment. Seroprevalence was 2.5 times higher in forestry workers reporting a tick bite during past years and reporting usually not removing ticks rapidly. Seroprevalence for TBEV was 0.14% (95% CI: 0.05-0.42).ConclusionWe assessed for the first time seroprevalence of B. burgdorferi sl and TBEV antibodies among forestry workers in northern France. These results will be used, together with data on LB and tick-borne encephalitis (TBE) incidence and on exposure to tick-bites, to target prevention programmes.

15-year Borrelia prevalence and species distribution monitoring in Ixodes ricinus/inopinatus populations in the city of Hanover, Germany

Lyme borreliosis, caused by Borrelia burgdorferi sensu lato (s.l.) spirochaetes, is the most common tick-borne disease (TBD) in the Northern Hemisphere. Rising incidences indicate that its epidemiology may be affected by global changes. Therefore, the current study aimed to assess changes in tick infection rates with Borrelia spp. over a 15-year monitoring period in the city of Hanover, Germany, as a follow-up to previous prevalence studies (years 2005, 2010 and 2015). To assess the epidemiological risk, ticks of the Ixodes ricinus/inopinatus-complex were sampled from April to October 2020 by the flagging method at 10 frequently visited recreation areas in Hanover. Analysis by quantitative real-time PCR of 2100 individual ticks revealed an overall Borrelia prevalence of 25.5% (535/2100). Regarding different tick developmental stages, nymphs showed a significantly lower Borrelia prevalence (18.4% [193/1050]) than adult ticks (32.6% [342/1050]). Comparison with previous years revealed a stable total Borrelia prevalence along with consistent infection rates in the different developmental stages over the 15-year monitoring period. Borrelia species differentiation by Reverse Line Blot was successful in 67.3% of positive ticks collected in 2020, with B. afzelii being the dominating species (59.2% of the differentiated infections), besides B. burgdorferi sensu stricto (s.s.), B. garinii, B. valaisiana, B. spielmanii, B. bavariensis and B. bissettiae and the relapsing fever spirochaete B. miyamotoi. Additionally, the proportion of infections attributed to B. afzelii showed a significant increase in 2020 compared to 2005 and 2015 (59.2% vs. 37.6% and 32.0% of successfully differentiated infections, respectively). Coinfections with Anaplasma phagocytophilum and Rickettsia spp. stayed stable comparing 2020 with previous years. Therefore, although changes in the Borrelia prevalence in questing ticks were not observed throughout the 15-year monitoring period, shifts in Borrelia species distribution may alter the epidemiological risk.

Impact of Different Anthropogenic Environments on Ticks and Tick-Associated Pathogens in Alsace, a French Region Highly Endemic for Tick-Borne Diseases

Ticks and tick-borne diseases have spread over the last decades. In parallel, the incidence in humans, accidental hosts for most of these zoonotic diseases, has increased. This epidemiological intensification can be associated with anthropogenic alterations of forest ecosystems and animal biodiversity, but also with socioeconomic changes. Their proliferation is largely due to human-induced effects on the factors that favor the circulation of these infectious agents. We selected different types of anthropogenic environments in Alsace, a region endemic for tick-borne diseases in France, to better understand the impact of human interventions on tick populations and tick-borne disease incidence. Ticks were collected in one golf course, three urban parks, one mid-mountain forest, and one alluvial forest that is currently part of a protected natural area. Ixodes ricinus was found primarily in humid vegetation, which is favorable for tick survival, such as grounds populated with trees and covered with leaf litter. We also observed that reforestation and high animal biodiversity in a protected area such as the alluvial forest led to a greater number of ticks, including both Ixodes ricinus and Dermacentor reticulatus, as well as to a higher prevalence of pathogens such as Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum, Borrelia miyamotoi, and Rickettsia raoulti.

The emerging tick-borne pathogen Neoehrlichia mikurensis: first French case series and vector epidemiology

Neoehrlichia mikurensis is an intracellular bacterium transmitted in Europe and Asia by ticks of the Ixodes ricinus complex. Interest in this bacterium has increased since it was demonstrated to be responsible for febrile syndromes in patients. To date, most clinical cases have been reported in northern Europe, but case series have also been described in central Europe and China. Notably, thrombotic events occurred during the course of the disease. We investigated the presence of N. mikurensis in 10,885 I. ricinus nymphs in two regions of France (Alsace and Brittany) collected between 2013 and 2020 and in 934 patients suspected of human granulocytic anaplasmosis in Alsace, an endemic area for Lyme borreliosis, using a specific PCR assay. N. mikurensis was detected in 5.42% of the ticks from Alsace, whereas only one (0.03%) tick was found to be positive in Brittany. Spatiotemporal disparities were also noticed within the Alsace region over the four collection sites investigated, and a significant increase in the prevalence of nymphs carrying N. mikurensis was also observed in the last three years of collection. Four out of 934 screened patients were found to be positive for N. mikurensis. Two had malignancies, and the other two were apparently immunocompetent. Superficial thrombosis was noticed in one patient, and long-lasting bacteremia was noted in another patient. These four patients are the first clinical cases of neoehrlichiosis described in France. We suggest including N. mikurensis in the differential diagnosis of post-tick bite febrile syndromes to treat patients and prevent the occurrence of thrombotic complications.

Longitudinal study of prevalence and spatio-temporal distribution of Borrelia burgdorferi sensu lato in ticks from three defined habitats in Latvia, 1999-2010

Members of the Borrelia burgdorferi sensu lato (s.l.) species complex are known to cause human Lyme borreliosis. Because of longevity of some reservoir hosts and the Ixodes tick vectors' life cycle, long-term studies are required to better understand species and population dynamics of these bacteria in their natural habitats. Ticks were collected between 1999 and 2010 in three ecologically different habitats in Latvia. We used multilocus sequence typing utilizing eight chromosomally located housekeeping genes to obtain information about species and population fluctuations and/or stability of B. burgdorferi s.l. in these habitats. The average prevalence over all years was 18.9%. From initial high-infection prevalences of 25.5%, 33.1% and 31.8%, from 2002 onwards the infection rates steadily decreased to 7.3%. Borrelia afzelii and Borrelia garinii were the most commonly found genospecies but striking local differences were obvious. In one habitat, a significant shift from rodent-associated to bird-associated Borrelia species was noted whilst in the other habitats, Borrelia species composition was relatively stable over time. Sequence types (STs) showed a random spatial and temporal distribution. These results demonstrated that there are temporal regional changes and extrapolations from one habitat to the next are not possible.

Assessment of Borrelia miyamotoi in febrile patients and ticks in Alsace, an endemic area for Lyme borreliosis in France

Background

Borrelia miyamotoi is a relapsing fever Borrelia species transmitted by ticks of the Ixodes ricinus complex. Human disease caused by B. miyamotoi was first described in Russia and later in the USA and Japan. Additionally, five cases of meningoencephalitis in immunocompromised patients and one case in an apparently immunocompetent patient were described.

Methods

We investigated the presence of B. miyamotoi in I. ricinus nymphs and in patients suspected of human granulocytic anaplasmosis, in Alsace (France), an endemic area for I. ricinus ticks and Lyme borreliosis, using direct (PCR) and indirect diagnosis (glycerophosphoryldiester-phosphodiesterase (GlpQ) serology).

Results

Borrelia miyamotoi was found in 2.2% of 4354 ticks collected between 2013 and 2016. None of the 575 blood samples, collected from the patients suspected of HGA, was found positive for B. miyamotoi by PCR. Acute and late sera from 138 of these 575 patients were available. These paired sera were tested for IgM and IgG antibodies against the B. miyamotoi GlpQ antigen. A total of 14 out of 138 patients had at least one positive parameter (i.e. anti-GlpQ IgG and/or IgM). One patient seroconverted for IgG, and three had isolated IgM in the acute serum. These three patients were treated with doxycycline which could have prevented seroconversion. After reviewing clinical data and other biological tests performed, co-exposure among different microorganisms vectored by ticks or serological cross-reactivity could not be ruled out in these different cases. One patient had persistent IgG, which strongly suggests previous exposure to B. miyamotoi.

Conclusions

Humans can be exposed to B. miyamotoi through tick bites in Alsace. We present serological data for possible B. miyamotoi exposure or infection of patients with fever after tick bite. Future studies should determine the incidence, clinical course and burden of this emerging tick-borne disease in other parts of Western Europe.

Co-infection of bacteria and protozoan parasites in Ixodes ricinus nymphs collected in the Alsace region, France

Fifty nymphal Ixodes ricinus ticks collected in Alsace, France, identified by morphological criteria and using MALDI-TOF MS, were tested by PCR to detect tick-associated bacteria and protozoan parasites. Seventy percent (35/50) of ticks contained at least one microorganism; 26% (9/35) contained two or more species. Several human pathogens were identified including Borrelia burgdorferi s.s. (4%), Borrelia afzelii (2%), Borrelia garinii (2%), Borrelia valaisiana (4%), Borrelia miyamotoi (2%), Rickettsia helvetica (6%) and "Babesia venatorum" (2%). Bartonella spp. (10%) and a Wolbachia spp. (8%) were also detected. The most common co-infections involved Anaplasmataceae with Borrelia spp. (4%), Anaplasmataceae with Bartonella spp. (6%) and Anaplasmataceae with Rickettsia spp. (6%). Co-infection involving three different groups of bacteria was seen between bacteria of the family Anaplasmataceae, Borrelia spp. and Bartonella spp. (2%). Results highlight the panel of infectious agents carried by Ixodes ricinus. Co-infection suggests the possibility of transmission of more than one pathogen to human and animals during tick blood feeding.

Model of Risk of Exposure to Lyme Borreliosis and Tick-Borne Encephalitis Virus-Infected Ticks in the Border Area of the Czech Republic (South Bohemia) and Germany (Lower Bavaria and Upper Palatinate)

In Europe, Lyme borreliosis (LB) and tick-borne encephalitis (TBE) are the two vector-borne diseases with the largest impact on human health. Based on data on the density of host-seeking Ixodes ricinus ticks and pathogen prevalence and using a variety of environmental data, we have created an acarological risk model for a region where both diseases are endemic (Czech Republic-South Bohemia and Germany-Lower Bavaria, Upper Palatinate). The data on tick density were acquired by flagging 50 sampling sites three times in a single season. Prevalence of the causative agents of LB and TBE was determined. Data on environmental variables (e.g., altitude, vegetation cover, NDVI, land surface temperature) were obtained from various sources and processed using geographical information systems. Generalized linear models were used to estimate tick density, probability of tick infection, and density of infected ticks for the whole area. A significantly higher incidence of human TBE cases was recorded in South Bohemia compared to Bavarian regions, which correlated with a lower tick density in Bavaria. However, the differences in pathogen prevalence rates were not significant. The model outputs were made available to the public in the form of risk maps, indicating the distribution of tick-borne disease risk in space.

Factors responsible for Ixodes ricinus nymph abundance: Are soil features indicators of tick abundance in a French region where Lyme borreliosis is endemic?

In Europe, the hard tick Ixodes ricinus (Acari: Ixodidae) is the main vector of Lyme borreliosis spirochetes (Borrelia burgdorferi sensu lato group). A field study was conducted to evaluate the abundance of Ixodes nymphs in the French region of Alsace, where Lyme borreliosis is endemic, and to determine whether environmental factors such as soil moisture and composition may be associated with nymph abundance. In the ten sites studied, ticks were collected by drag sampling from March to October in 2013 and 2014. Temperature, relative humidity, saturation deficit, soil pH, humus composition and type of vegetation were recorded at each site. The abundance of I. ricinus was highly variable from one site to another. Inter-annual variations were also observed, since the nymph abundance were higher in 2013 than in 2014. This study shows that humus type can be indicative of nymph abundance. Three types of humus were observed: (1) moder, (2) mull, and (3) mull-moder humus. One of them, moder humus, which is characterized by a thick layer of fragmented leaves, was found in multivariate analyses to be strongly associated with the nymph abundance. This study demonstrates that factors such as saturation deficit do not suffice to explain the differences in nymph abundance among sites. The composition of the soil and especially the type of humus should also be taken into consideration when assessing acarological risk.

Effects of conservation management of landscapes and vertebrate communities on Lyme borreliosis risk in the United Kingdom

Landscape change and altered host abundance are major drivers of zoonotic pathogen emergence. Conservation and biodiversity management of landscapes and vertebrate communities can have secondary effects on vector-borne pathogen transmission that are important to assess. Here we review the potential implications of these activities on the risk of Lyme borreliosis in the United Kingdom. Conservation management activities include woodland expansion, management and restoration, deer management, urban greening and the release and culling of non-native species. Available evidence suggests that increasing woodland extent, implementing biodiversity policies that encourage ecotonal habitat and urban greening can increase the risk of Lyme borreliosis by increasing suitable habitat for hosts and the tick vectors. However, this can depend on whether deer population management is carried out as part of these conservation activities. Exclusion fencing or culling deer to low densities can decrease tick abundance and Lyme borreliosis risk. As management actions often constitute large-scale perturbation experiments, these hold great potential to understand underlying drivers of tick and pathogen dynamics. We recommend integrating monitoring of ticks and the risk of tick-borne pathogens with conservation management activities. This would help fill knowledge gaps and the production of best practice guidelines to reduce risks.

This article is part of the themed issue ‘Conservation, biodiversity and infectious disease: scientific evidence and policy implications’.

Assessment of MALDI-TOF MS biotyping for Borrelia burgdorferi sl detection in Ixodes ricinus

Matrix Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) has been demonstrated to be useful for tick identification at the species level. More recently, this tool has been successfully applied for the detection of bacterial pathogens directly in tick vectors. The present work has assessed the detection of Borrelia burgdorferi sensu lato in Ixodes ricinus tick vector by MALDI-TOF MS. To this aim, experimental infection model of I. ricinus ticks by B. afzelii was carried out and specimens collected in the field were also included in the study. Borrelia infectious status of I. ricinus ticks was molecularly controlled using half-idiosome to classify specimens. Among the 39 ticks engorged on infected mice, 14 were confirmed to be infected by B. afzelii. For field collection, 14.8% (n = 12/81) I. ricinus ticks were validated molecularly as infected by B. burgdorferi sl. To determine the body part allowing the detection of MS protein profile changes between non-infected and B. afzelii infected specimens, ticks were dissected in three compartments (i.e. 4 legs, capitulum and half-idiosome) prior to MS analysis. Highly reproducible MS spectra were obtained for I. ricinus ticks according to the compartment tested and their infectious status. However, no MS profile change was found when paired body part comparison between non-infected and B. afzelii infected specimens was made. Statistical analyses did not succeed to discover, per body part, specific MS peaks distinguishing Borrelia-infected from non-infected ticks whatever their origins, laboratory reared or field collected. Despite the unsuccessful of MALDI-TOF MS to classify tick specimens according to their B. afzelii infectious status, this proteomic tool remains a promising method for rapid, economic and accurate identification of tick species. Moreover, the singularity of MS spectra between legs and half-idiosome of I. ricinus could be used to reinforce this proteomic identification by submission of both these compartments to MS.

Infection of Ixodes ricinus by Borrelia burgdorferi sensu lato in peri-urban forests of France

Lyme borreliosis is the most common tick-borne disease in the northern hemisphere. In Europe, it is transmitted by Ixodes ticks that carry bacteria belonging to the Borrelia burgdorferi sensu lato complex. The objective of this work was to explore eco-epidemiological factors of Lyme borreliosis in peri-urban forests of France (Sénart, Notre-Dame and Rambouillet). We investigated whether the introduction of Tamias sibiricus in Sénart could alter the density of infected ticks. Moreover, the density and tick infection were investigated according to the tree species found in various patches of Sénart forest. For this purpose, ticks were sampled during 3 years. In the Sénart forest, the density of nymph and adult ticks showed no significant difference between 2008, 2009 and 2011. The nymph density varied significantly as a function of the month of collection. Regarding the nymphs, a higher rate of infection and infected density were found in 2009. Plots with chipmunks (C) presented a lower density of both nymphs and adult ticks than plots without chipmunks (NC) did. A higher rate of infection of nymphs with Borrelia was seen in C plots. The prevalence of the various species of Borrelia was also found to vary between C and NC plots with the year of the collect. The presence of chestnut trees positively influenced the density of both nymphs and adults. The infected nymph density showed a significant difference depending on the peri-urban forest studied, Sénart being higher than Rambouillet. The prevalence of Borrelia species also differed between the various forests studied. Concerning the putative role that Tamias sibiricus may play in the transmission of Borrelia, our results suggest that its presence is correlated with a higher rate of infection of questing ticks by Borrelia genospecies and if its population increases, it could play a significant role in the risk of transmission of Lyme borreliosis.

The enzootic life-cycle of Borrelia burgdorferi (sensu lato) and tick-borne rickettsiae: an epidemiological study on wild-living small mammals and their ticks from Saxony, Germany

BACKGROUND

Borrelia burgdorferi (sensu lato) and rickettsiae of the spotted fever group are zoonotic tick-borne pathogens. While small mammals are confirmed reservoirs for certain Borrelia spp., little is known about the reservoirs for tick-borne rickettsiae. Between 2012 and 2014, ticks were collected from the vegetation and small mammals which were trapped in Saxony, Germany. DNA extracted from ticks and the small mammals' skin was analyzed for the presence of Rickettsia spp. and B. burgdorferi (s.l.) by qPCR targeting the gltA and p41 genes, respectively. Partial sequencing of the rickettsial ompB gene and an MLST of B. burgdorferi (s.l.) were conducted for species determination.

RESULTS

In total, 673 small mammals belonging to eight species (Apodemus agrarius, n = 7; A. flavicollis, n = 214; Microtus arvalis, n = 8; Microtus agrestis, n = 1; Mustela nivalis, n = 2; Myodes glareolus, n = 435; Sorex araneus, n = 5; and Talpa europaea, n = 1) were collected and examined. In total, 916 questing ticks belonging to three species (Ixodes ricinus, n = 741; Dermacentor reticulatus, n = 174; and I. trianguliceps, n = 1) were collected. Of these, 474 ticks were further investigated. The prevalence for Rickettsia spp. and B. burgdorferi (s.l.) in the investigated small mammals was 25.3 and 31.2%, respectively. The chance of encountering Rickettsia spp. in M. glareolus was seven times higher for specimens infested with D. reticulatus than for those which were free of D. reticulatus (OR: 7.0; 95% CI: 3.3-14.7; P < 0.001). In total, 11.4% of questing I. ricinus and 70.5% of D. reticulatus were positive for Rickettsia spp. DNA of B. burgdorferi (s.l.) was detected only in I. ricinus (5.5%). Sequence analysis revealed 9 R. helvetica, 5 R. raoultii, and 1 R. felis obtained from 15 small mammal samples.

CONCLUSION

Small mammals may serve as reservoirs for Rickettsia spp. and B. burgdorferi (s.l.). While the prevalence for Rickettsia spp. in M. glareolus is most likely depending on the abundance of attached D. reticulatus, the prevalence for B. burgdorferi (s.l.) in small mammals is independent of tick abundance. Dermacentor reticulatus may be the main vector of certain Rickettsia spp. but not for Borrelia spp.

Seroprevalence of seven pathogens transmitted by the Ixodes ricinus tick in forestry workers in France

In order to assess the level of occupational exposure to the main pathogens transmitted by the Ixodes ricinus tick, a seroprevalence study was performed on serum samples collected in 2003 from 2975 forestry workers of northeastern France. The global seroprevalence estimated for the seven pathogens studied was 14.1% (419/2975) for Borrelia burgdorferi sl, 5.7% (164/2908) for Francisella tularensis, 2.3% (68/2941) for tick-borne encephalitis virus, 1.7% (50/2908) for Anaplasma phagocytophilum and 1.7% (48/2908) for Bartonella henselae. The seroprevalences of Babesia divergens and Babesia microti studied in a subgroup of participants seropositive for at least one of these latter pathogens were 0.1% (1/810) and 2.5% (20/810), respectively. Borrelia burgdorferi sl seroprevalence was significantly higher in Alsace and Lorraine and F. tularensis seroprevalence was significantly higher in Champagne-Ardenne and Franche-Comté. The results of this survey also suggest low rates of transmission of Bartonella henselae and F. tularensis by ticks and a different west/east distribution of Babesia species in France. The frequency and potential severity of these diseases justify continued promotion of methods of prevention of I. ricinus bites.

Co-infection of Ticks: The Rule Rather Than the Exception

Introduction

Ticks are the most common arthropod vectors of both human and animal diseases in Europe, and the Ixodes ricinus tick species is able to transmit a large number of bacteria, viruses and parasites. Ticks may also be co-infected with several pathogens, with a subsequent high likelihood of co-transmission to humans or animals. However few data exist regarding co-infection prevalences, and these studies only focus on certain well-known pathogens. In addition to pathogens, ticks also carry symbionts that may play important roles in tick biology, and could interfere with pathogen maintenance and transmission. In this study we evaluated the prevalence of 38 pathogens and four symbionts and their co-infection levels as well as possible interactions between pathogens, or between pathogens and symbionts.

Methodology/principal findings

A total of 267 Ixodes ricinus female specimens were collected in the French Ardennes and analyzed by high-throughput real-time PCR for the presence of 37 pathogens (bacteria and parasites), by rRT-PCR to detect the presence of Tick-Borne encephalitis virus (TBEV) and by nested PCR to detect four symbionts. Possible multipartite interactions between pathogens, or between pathogens and symbionts were statistically evaluated. Among the infected ticks, 45% were co-infected, and carried up to five different pathogens. When adding symbiont prevalences, all ticks were infected by at least one microorganism, and up to eight microorganisms were identified in the same tick. When considering possible interactions between pathogens, the results suggested a strong association between Borrelia garinii and B. afzelii, whereas there were no significant interactions between symbionts and pathogens.

Conclusion/significance

Our study reveals high pathogen co-infection rates in ticks, raising questions about possible co-transmission of these agents to humans or animals, and their consequences to human and animal health. We also demonstrated high prevalence rates of symbionts co-existing with pathogens, opening new avenues of enquiry regarding their effects on pathogen transmission and vector competence.

Ticks transmit more pathogens than any other arthropod, and one single species can transmit a large variety of bacteria and parasites. Because co-infection might be much more common than previously thought, we evaluated the prevalence of 38 known or neglected tick-borne pathogens in Ixodes ricinus ticks. Our results demonstrated that co-infection occurred in almost half of the infected ticks, and that ticks could be infected with up to five pathogens. Moreover, as it is well established that symbionts can affect pathogen transmission in arthropods, we also evaluated the prevalence of four symbiont species and demonstrated that all ticks were infected by at least one microorganism. This work highlights the co-infection phenomenon in ticks, which may have important implications for human and animal health, emphasizing the need for new diagnostic tests better adapted to tick-borne diseases. Finally, the high co-occurrence of symbionts and pathogens in ticks, reveals the necessity to also account for these interactions in the development of new alternative strategies to control ticks and tick-borne disease.

Mapping human risk of infection with Borrelia burgdorferi sensu lato, the agent of Lyme borreliosis, in a periurban forest in France

Lyme borreliosis is a major zoonosis in Europe, with estimates of over 26,000 cases per year in France alone. The etiological agents are spirochete bacteria that belong to the Borrelia burgdorferi sensu lato (s. l.) complex and are transmitted by hard ticks among a large range of vertebrate hosts. In Europe, the tick Ixodes ricinus is the main vector. In the absence of a vaccine and given the current difficulties to diagnose and treat chronic Lyme syndromes, there is urgent need for prevention. In this context, accurate information on the spatial patterns of risk of exposure to ticks is of prime importance for public health. The objective of our study was to provide a snapshot map of the risk of human infection with B. burgdorferi s. l. pathogens in a periurban forest at a high resolution, and to analyze the factors that contribute to variation in this risk. Field monitoring took place over three weeks in May 2011 in the suburban Sénart forest (3,200ha; southeast of Paris), which receives over 3 million people annually. We sampled ticks over the entire forest area (from 220 forest stands with a total area of 35,200m(2)) and quantified the density of questing nymphs (DON), the prevalence of infection among nymphs (NIP), and the density of infected nymphs (DIN), which is the most important predictor of the human risk of Lyme borreliosis. For each of these response variables, we explored the relative roles of weather (saturation deficit), hosts (abundance indices of ungulates and Tamias sibiricus, an introduced rodent species), vegetation and forest cover, superficial soil composition, and the distance to forest roads. In total, 19,546 questing nymphs were collected and the presence of B. burgdorferi s. l. was tested in 3,903 nymphs by qPCR. The mean DON was 5.6 nymphs per 10m(2) (standard deviation=10.4) with an average NIP of 10.1% (standard deviation=0.11). The highest DIN was 8.9 infected nymphs per 10m(2), with a mean of 0.59 (standard deviation=0.6). Our mapping and modeling revealed a strong heterogeneity of risk within the forest. The highest risk was found in the eastern part of the forest and localized patches in the northwestern part. Lyme borreliosis risk was positively associated with stands of deciduous trees (mainly oaks) and roe deer abundance. Contrary to expectations, DIN actually increased with distance from the point of introduction of T. sibiricus (i.e., DIN was higher in areas with potentially lower abundances of T. sibiricus). Thus, despite the fact that T. sibiricus is an important reservoir host for B. burgdorferi s. l., our study found that other explanatory factors played a more important role in determining the density of infected ticks. Precise mapping of the risk of exposure to Lyme borreliosis in a highly visited forest represents an important tool for targeting prevention and control measures, as well as making the general public and local health officials aware of the risks.

Coexistence of Borrelia burgdorferi s.l. genospecies within Ixodes ricinus ticks from central and eastern Poland

The purpose of the study was to assess the prevalence and coinfection rates of Borrelia burgdorferi sensu lato genotypes in Ixodes ricinus (L.) ticks sampled from diverse localities in central and eastern regions of Poland. In years 2009-2011, questing nymphs and adults of I. ricinus were collected using a flagging method at 18 localities representing distinct ecosystem types: urban green areas, suburban forests and rural woodlands. Molecular detection of B. burgdorferi s.l. genospecies was based on amplification of a fla gene using nested PCR technique, subsequent PCR-RFLP analysis and bidirectional sequencing. It was revealed that 45 samples (2.1%) harboured two different B. burgdorferi s.l. genospecies, whereas triple infections with various spirochetes was found in 11 (0.5%) individuals. Generally, the highest average coinfection rates were evidenced in arachnids gathered at rural woodlands, intermediate at suburban forests, while the lowest were recorded at urban green areas. Overall, single spirochete infections were noted in 16.3% (n = 352/2,153) ticks. Importantly, it is the first report evidencing the occurrence of Borrelia miyamotoi (0.3%, n = 7/2153) in I. ricinus populations within central Poland. Circumstantial variability of B. burgdorferi s.l. genospecies in the common tick individuals sampled at various habitat types in central and eastern Poland was displayed. The coexistence of two or three different spirochete genospecies in single adult ticks, as well as the presence of B. miyamotoi were demonstrated. Therefore, further studies uncovering the co-circulation of the tested bacteria and other human pathogens in I. ricinus ticks are required.

Comparative population genomics of the Borrelia burgdorferi species complex reveals high degree of genetic isolation among species and underscores benefits and constraints to studying intra-specific epidemiological processes

Lyme borreliosis, one of the most frequently contracted zoonotic diseases in the Northern Hemisphere, is caused by bacteria belonging to different genetic groups within the Borrelia burgdorferi species complex, which are transmitted by ticks among various wildlife reservoirs, such as small mammals and birds. These features make the Borrelia burgdorferi species complex an attractive biological model that can be used to study the diversification and the epidemiology of endemic bacterial pathogens. We investigated the potential of population genomic approaches to study these processes. Sixty-three strains belonging to three species within the Borrelia burgdorferi complex were isolated from questing ticks in Alsace (France), a region where Lyme disease is highly endemic. We first aimed to characterize the degree of genetic isolation among the species sampled. Phylogenetic and coalescent-based analyses revealed clear delineations: there was a ∼50 fold difference between intra-specific and inter-specific recombination rates. We then investigated whether the population genomic data contained information of epidemiological relevance. In phylogenies inferred using most of the genome, conspecific strains did not cluster in clades. These results raise questions about the relevance of different strategies when investigating pathogen epidemiology. For instance, here, both classical analytic approaches and phylodynamic simulations suggested that population sizes and migration rates were higher in B. garinii populations, which are normally associated with birds, than in B. burgdorferi s.s. populations. The phylogenetic analyses of the infection-related ospC gene and its flanking region provided additional support for this finding. Traces of recombination among the B. burgdorferi s.s. lineages and lineages associated with small mammals were found, suggesting that they shared the same hosts. Altogether, these results provide baseline evidence that can be used to formulate hypotheses regarding the host range of B. burgdorferi lineages based on population genomic data.

Anaplasma phagocytophilum--a widespread multi-host pathogen with highly adaptive strategies

The bacterium Anaplasma phagocytophilum has for decades been known to cause the disease tick-borne fever (TBF) in domestic ruminants in Ixodes ricinus-infested areas in northern Europe. In recent years, the bacterium has been found associated with Ixodes-tick species more or less worldwide on the northern hemisphere. A. phagocytophilum has a broad host range and may cause severe disease in several mammalian species, including humans. However, the clinical symptoms vary from subclinical to fatal conditions, and considerable underreporting of clinical incidents is suspected in both human and veterinary medicine. Several variants of A. phagocytophilum have been genetically characterized. Identification and stratification into phylogenetic subfamilies has been based on cell culturing, experimental infections, PCR, and sequencing techniques. However, few genome sequences have been completed so far, thus observations on biological, ecological, and pathological differences between genotypes of the bacterium, have yet to be elucidated by molecular and experimental infection studies. The natural transmission cycles of various A. phagocytophilum variants, the involvement of their respective hosts and vectors involved, in particular the zoonotic potential, have to be unraveled. A. phagocytophilum is able to persist between seasons of tick activity in several mammalian species and movement of hosts and infected ticks on migrating animals or birds may spread the bacterium. In the present review, we focus on the ecology and epidemiology of A. phagocytophilum, especially the role of wildlife in contribution to the spread and sustainability of the infection in domestic livestock and humans.

Improved PCR/nested PCR approaches with increased sensitivity and specificity for the detection of pathogens in hard ticks

Most epidemiological studies on tick-borne pathogens employ PCR approaches. Prevalences determined by this method particularly depend on the efficiency and sensitivity of the applied protocol, which can be influenced by various factors. In the current study, we examined crucial points to improve PCR strategies with respect to sensitivity as well as specificity and developed optimized and easily practicable PCR/nested PCR approaches for the detection of different tick-borne pathogens. Among them were Anaplasma phagocytophilum, Borrelia burgdorferi sensu lato complex, and Babesia spp., for which the novel protocol was successfully applied to perform species determination by direct sequencing of PCR amplicons. The occurrence of double and multiple infections of different species of the same genus were detected by chromatogram analyses exhibiting mixed sequences. Furthermore, we suggest employing a standard plasmid containing the appropriate target sequence followed by verification of the encountered detection limit with an addition of tick DNA spiked with the appropriate pathogen DNA. Approaches standardized in this manner would facilitate the comparison of prevalence studies.

Prevalence of tick-borne pathogens in adult Dermacentor spp. ticks from nine collection sites in France

The importance of Dermacentor spp. in the transmission of tick-borne pathogens is not well recognized in Europe. To investigate the role of Dermacentor spp. in the transmission of tick-borne pathogens, questing ticks were collected in 9 sites from southern to northwestern France (Camargue Delta to Eastern Brittany) where Dermacentor spp. exist and tick-borne diseases had occurred previously. Three tick species were collected during the spring and autumn of 2009. Collected ticks (both males and females) included D. marginatus (n=377), D. reticulatus (n=74), and I. ricinus (n=45). All ticks were analyzed by PCR or reverse line blot for the presence of pathogens' DNA. Pathogens analyzed were based on veterinarian reports and included Anaplasma phagocytophilum, Coxiella burnetii, Anaplasma marginale, Borrelia burgdorferi, Bartonella spp., Babesia spp., Theileria spp., and Francisella sp. Francisella tularensis was not detected in any of the analyzed ticks. In D. marginatus, infection prevalence for A. phagocytophilum (3%) was similar to that found in I. ricinus in Europe. Other pathogens present in D. marginatus included A. marginale (0.5%), Bartonella spp. (9%), C. burnetii (12%), F. philomiragia (1.3%), and Theileria annulata/Babesia bovis (0.3%), which were detected for the first time in France. Pathogens detected in D. reticulatus included A. marginale (1%), Bartonella spp. (12%), C. burnetii (16%), Borrelia spp. (1.5%), and F. philomiragia (19%). Pathogens detected in I. ricinus included A. phagocytophilum (41%), Bartonella spp. (9%), C. burnetii (18%), A. marginale (1%), Borrelia spp. (4.5%), and Babesia sp. (7%). This study represents the first epidemiological approach to characterize tick-borne pathogens infecting Dermacentor spp. in France and that may be transmitted by ticks from this genus. Further experiments using experimental infections and transmission may be now conducted to analyze vector competency of Dermacentor spp. for these pathogens and to validate such hypothesis.

Anaplasma phagocytophilum in horses and ticks in Tunisia

Background

Anaplasma phagocytophilum , the causative agent of granulocytic anaplasmosis, affects several species of wild and domesticated mammals, including horses. We used direct and indirect methods to compare and evaluate exposure to A. phagocytophilum in horses in northern Tunisia.

Methods

Serum from 60 horses was tested by IFA for antibodies to A. phagocytophilum , and whole blood was tested for A. phagocytophilum 16S rRNA gene using a nested-PCR. To examine the risk of A. phagocytophilum transmission, 154 ticks that had been collected from horses were examined for the presence of A. phagocytophilum by nested-PCR targeting 16S rRNA gene.

Results

This is the first time that A. phagocytophilum has been detected in horses in Tunisia, with an overall seroprevalence of 40/60 (67%). Six of the seroreactive samples (10%) had an IFA titer of 1:80, 14 (23%) of 1:160, 8 (13%) of 1:320 and 12 (20%) a titer 1 ≥ 640. The seroprevalence revealed no significant regional and sex differences. In contrast, a significant difference was observed between breeds. Eight (13%) of the horses were positive for A. phagocytophilum in the PCR, with no significant breed and age differences. Hyalomma marginatum was a predominant tick species (130/154), and 3 were infected by A. phagocytophilum (a prevalence of 2.3%). The concordance rate of A. phagocytophilum detection between IFA and PCR had a k value of −0.07.

Conclusions

The results presented in this study suggest that horses infested by ticks in Tunisia are exposed to A. phagocytophilum.

Dual presence of Anaplasma phagocytophilum and its closely related Anaplasma sp. in ixodid ticks in Hokkaido, Japan, and their specific molecular detection

Anaplasma phagocytophilum causes human granulocytic anaplasmosis (HGA) and tick-borne fever in ruminants. A closely related and potentially novel Anaplasma sp. in Japan was recently characterized. The aims of the study were to provide molecular evidence for the presence of these 2 species in Japan, and to develop a reliable PCR method based on the nucleotide differences within the citrate synthase (gltA) gene. DNA samples from 182 ixodid ticks (134 Ixodes persulcatus, 35 Haemaphysalis douglasii and 13 I. ovatus) collected from 2 sites in Hokkaido, Japan, were screened for A. phagocytophilum and its closely related Anaplasma sp. (herein designated as Anaplasma sp. Japan) using 16S rRNA PCR, revealing a combined prevalence rate of 27.5% (50 samples). The positive samples were then used to evaluate a newly developed gltA-based nested PCR method. Selected positive samples were further characterized using the groEL gene for confirmation and phylogenetic analyses. Two groups of sequence results were obtained: those that had closer identities with (1) A. phagocytophilum (99.5-99.6% for 16S rRNA, 97.5% for gltA and 98.4% for groEL), and those that had closer identities with (2) Anaplasma sp. closely related to A. phagocytophilum in Japan (99.3% for 16S rRNA, 96.4-98.7% for gltA and 97.5-97.9% for groEL). The present study confirmed the distinct presence of A. phagocytophilum and its closely related Anaplasma sp. in Japan, and developed a new PCR detection method based on gltA that can distinguish the 2 organisms.

Which forest bird species are the main hosts of the tick, Ixodes ricinus, the vector of Borrelia burgdorferi sensu lato, during the breeding season?

Wild birds are important hosts for vector-borne pathogens, especially those borne by ticks. However, few studies have been conducted on the role of different bird species within a community as hosts of vector-borne pathogens. This study addressed individual and species factors that could explain the burden of Ixodes ricinus on forest birds during the reproductive periods of both vectors and hosts. The goal was to identify which bird species contribute the most to the tick population at the community level. Birds were mist-netted on four plots in 2008 and on seven plots in 2009 in two forests (Sénart and Notre Dame, near Paris, France). The dependence of the tick load per bird upon environmental conditions (questing nymph density, year and plot) and on host species traits (species, age, sex, body size, vertical space use, level of innate and acquired immunity) was analysed. Finally, the relative contribution of each bird species to the local dynamics of ticks was estimated, while accounting for their respective abundance. Tick burden differed markedly between bird species and varied according to questing nymph density. Bird species with a high body mass, those that forage low in the vegetation, and those that had a high innate immune response and a high spleen mass were more likely to have a high tick burden. Four species (the Common Blackbird, Turdus merula, the European Robin, Erithacus rubecula, the Song Thrush, Turdus philomelos, and the Winter Wren, Troglodytes troglodytes) hosted more than 90% of the ticks in the local bird community. These species, and particularly T. merula which was host to a high proportion of the nymphs, are likely to contribute significantly to the circulation of pathogens for which they are competent, such as the agent of Lyme borreliosis.

Human granulocytic anaplasmosis in eastern France: clinical presentation and laboratory diagnosis

Human granulocytic anaplasmosis (HGA) is a tick-borne infection characterised by an acute, nonspecific febrile illness. To date, few clinical cases have been supported by both a positive polymerase chain reaction (PCR) assay and subsequent seroconversion against Anaplasma phagocytophilum antigen all over Europe. We report here 3 consecutive cases of HGA that occurred during the summer of 2009 which fulfilled the epidemiologic, clinical, and biological criteria for HGA. These data highlight PCR assay on ethylenediaminetetraacetic acid blood rather than serology as the diagnostic test of choice during the acute phase of the disease. In endemic areas, HGA should be investigated in patients presenting an undifferentiated febrile illness with cytopenia, elevated rates of liver enzymes, and increased C-reactive protein values.

Study on ticks and tick-borne zoonoses in public parks in Italy

A survey on tick density and on tick-borne zoonoses was carried out in four public parks in the outskirts of Imola (northern Italy) from June to October 2006. All stages of Ixodes ricinus and only larvae of Riphicephalus sanguineus were recovered by dragging, performed on 100-m transects. Almost all ticks (99%) were harvested in one park. I. ricinus density (nymphs/100 m(2) ) ranged from 0 in park L to 6.3 in park F. Nymphs and adults of I. ricinus were subjected to PCR for Anaplasma phagocytophilum, Bartonella spp., Borrelia burgdorferi s. l. and Rickettsia spp. The observed prevalences were 38.3% for Bartonella henselae, 5.2% for Bartonella clarridgeiae, 10.4% for B. burgdorferi s. l., 2.6% for Rickettsia helvetica and 13% for Rickettsia monacensis, respectively. No DNA of A. phagocytophilum was found. Acarological risks (AR) were calculated as probabilities of collecting at least one infected nymph per transect. The AR values calculated for the various zoonotic agents were 11.4% for R. helvetica, 27.7% for B. clarridgeiae, 49.7% for B. burgdorferi s. l., 57.2% for R. monacensis and 90.4% for B. henselae, respectively. In this study, B. clarridgeiae was for the first time identified in I. ricinus ticks.

A Vegetation Index qualifying pasture edges is related to Ixodes ricinus density and to Babesia divergens seroprevalence in dairy cattle herds

Babesia divergens, transmitted by the tick Ixodes ricinus, is the main agent of bovine piroplasmosis in France. This Apicomplexa often is present in asymptomatic carriers; however, clinical cases are rare. While numerous factors are known to influence tick density, no risk factor of contact with B. divergens has been identified for cattle. Our study aimed to explore whether a Vegetation Index could serve as an indirect indicator of within-herd B. divergens seroprevalence. In February 2007, blood samples were taken from all of the cows in 19 dairy cattle herds in Western France and IFAT serology was performed individually to measure B. divergens seroprevalence. The following spring, I. ricinus nymphs were collected by drag sampling along transects on the vegetation of each farm's pasture perimeters. Tick density was related significantly to a Vegetation Index (V.I., ranging from 1 to 5) that took into account the abundance of trees and bushes on the edge of pastures: most ticks (57%) were found in transects with the highest V.I. (covering 15% of the explored surface in the study area). At the farm level, the proportion of transects presenting I. ricinus nymphs was significantly related to B. divergens seroprevalence: the farms with more than 15% of transects with I. ricinus had a significantly higher risk of high seroprevalence. The proportion of pasture perimeters where the V.I.=5 also was significantly related to B. divergens seroprevalence: the farms where more than 20% of transects had a V.I.=5 had a significantly higher risk of high seroprevalence. Given that the Vegetation Index is a steady indicator of the potential I. ricinus density in the biotope, we recommend that the risk of high B. divergens seroprevalence in cows be evaluated using this tool rather than drag samplings.

Cryptic vector divergence masks vector-specific patterns of infection: an example from the marine cycle of Lyme borreliosis

Vector organisms are implicated in the transmission of close to a third of all infectious diseases. In many cases, multiple vectors (species or populations) can participate in transmission but may contribute differently to disease ecology and evolution. The presence of cryptic vector populations can be particularly problematic as differences in infection can be difficult to evaluate and may lead to erroneous evolutionary and epidemiological inferences. Here, we combine site-occupancy modeling and molecular assays to evaluate patterns of infection in the marine cycle of Lyme borreliosis, involving colonial seabirds, the tick Ixodes uriae, and bacteria of the Borrelia burgdorferi s.l. complex. In this cycle, the tick vector consists of multiple, cryptic (phenotypically undistinguishable but genetically distinct) host races that are frequently found in sympatry. Our results show that bacterial detection varies strongly among tick races leading to vector-specific biases if raw counts are used to calculate Borrelia prevalence. These differences are largely explained by differences in infection intensity among tick races. After accounting for detection probabilities, we found that overall prevalence in this system is higher than previously suspected and that certain vector-host combinations likely contribute more than others to the local dynamics and large-scale dispersal of Borrelia spirochetes. These results highlight the importance of evaluating vector population structure and accounting for detection probability when trying to understand the evolutionary ecology of vector-borne diseases.

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

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 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.

Prevalence and seasonality of tick-borne pathogens in questing Ixodes ricinus ticks from Luxembourg

In Europe, ixodid ticks are important arthropod vectors of human and animal pathogens, but comprehensive studies of the prevalence of all relevant pathogens in Central Europe are scarce. As a result of ecological changes, the incidences of tick-borne infections are expected to increase. In this study, 1,394 nymphal and adult Ixodes ricinus ticks sampled monthly during the active season from 33 ecologically distinct collection sites throughout Luxembourg were screened for all human tick-borne pathogens relevant in Central Europe. Species were identified by sequence analysis of detection PCR amplicons. Mean infection rates of ticks were 11.3% for Borrelia burgdorferi sensu lato, 5.1% for Rickettsia sp., 2.7% for Babesia sp., and 1.9% for Anaplasma phagocytophilum. No tick was found to be infected with Coxiella sp., Francisella tularensis subsp., or Tick-borne encephalitis virus (TBEV). A total of 3.2% of ticks were infected with more than one pathogen species, including mixed Borrelia infections (1.5%). Seasonal variations of tick infection rates were observed for Borrelia, Babesia, and Anaplasma, possibly reflecting a behavioral adaptation strategy of questing ticks. A positive correlation between the grade of urbanization and Borrelia infection rate of ticks was observed, suggesting an established urban zoonotic cycle. We also found Hepatozoon canis (0.1%) and Bartonella henselae (0.3%), which so far have not been found in questing Ixodes ricinus ticks in Central Europe.

[Seroprevalence of Lyme Borreliosis and tick-borne encephalitis in workers at risk, in eastern France]

OBJECTIVE

The aim of this article was to assess the seroprevalence of Lyme Borreliosis and tick-borne encephalitis (TBE) among occupationally exposed forest workers.

METHODS

Workers exposed to tick bites in Eastern France were interviewed by occupational health physicians of the mutualité sociale agricole (MSA) on their sociodemographic features, their occupational activity, their last tick bite, their clinical history, and their means of prevention. Blood sampling was carried out for antibody detection.

RESULTS

Among the 2975 subjects included in the study, the observed seroprevalence was 14.1% for Lyme borreliosis and 3.4% for TBE. Age, occupational activity, and place of residence significantly influenced the serological status of Lyme borreliosis. The seroprevalence was significantly higher among woodcutters (17.5%) than among other occupational categories (p<.001). Seroprevalence in Alsace (26.9%) and Lorraine (16.5%) were significantly higher than in other regions (p<0.001 and p<0.01, respectively). The seroprevalence of TBE was significantly higher in Alsace (5.5%; p<0.001). The rates of seroprevalence for both infections varied according to forest areas. The multifactorial analysis of prevention practices revealed three types of behaviors as far as protection was concerned: "rigorous", "partial", or "insufficient".

CONCLUSION

These results do not change the present French indications for use of TBE vaccine. They highlight the importance of information on these diseases and the need for further studies on microbial ecology and risk-factors identification.

Detection of Anaplasma dna in Ixodes ricinus ticks: pitfalls

A total of 150 nymphal Ixodes ricinus (L., 1758) (Acari: Ixodidae) from the Czech Republic were examined for Anaplasma phagocytophilum (Foggie, 1949) Dumler et al., 2001 by PCR using EHR521/747 primers: 22 of 50 pools were positive (minimum prevalence, 14.7%). However, sequencing of the PCR products did not show complete homology with A. phagocytophilum (91%) while the closest relationship (95%) was found to "Candidatus Ehrlichia walkefii". The results indicate a need for care in interpretation of Anaplasma PCR results and for PCR optimization for detecting A. phagocytophilum in ticks.

Tick infestation risk and Borrelia burgdorferi s.l. infection-induced increase in host-finding efficacy of female Ixodes ricinus under natural conditions

An investigation of the risk of human tick infestation, together with the prevalence of Borrelia burgdorferi s.l. infection, was conducted in a sylvatic habitat in western Germany to provide data needed for future risk-benefit evaluations of acaricides used for clothing impregnation. Additionally, data were collected on behavioural changes in Borrelia burgdorferi s.l.-infected adult female I. ricinus ticks and the possible impact of such changes on host-finding efficacy. The risk of I. ricinus-infestation was determined by collecting from the protective clothing of volunteers and by dragging in known tick-infested sites in the Kühkopf Mountain area, Koblenz, Germany, from June through October 2006. The overall tick infestation rate per person per hour was 7.4+/-5.5, with the following sex- and stage-specific differences: males 0.32+/-0.37, females 1.1+/-1.2, nymphs 3.6+/-4.4, larvae 2.4+/-3.5. Concurrent dragging revealed an average 19.4+/-16.2 times higher infestation rate as well as a markedly lower infection rate with borreliae in adult I. ricinus ticks when compared to ticks collected from exposed human volunteers. Although the difference in infection rates was statistically significant (P<0.023) only in adult female ticks, our data indicate that B. burgdorferi s.l. infection may increase host-finding efficacy in adult I. ricinus. The overall exposure risk was 1.0 B. burgdorferi s.l.-infected ticks per person per hour of exposure, or 0.25 ticks per 100 m walking distance in the study area.

Phenology of Ixodes ricinus and infection with Borrelia burgdorferi sensu lato along a north- and south-facing altitudinal gradient on Chaumont Mountain, Switzerland

Questing Ixodes ricinus L. ticks were collected monthly from 2003 to 2005 on the north- and south-facing slopes of Chaumont Mountain in Neuchâtel, Switzerland, at altitudes varying from 620 to 1,070 m. On the south-facing slope, questing tick density was higher than on the north-facing slope, and it decreased with altitude. Density tended to increase with altitude on the north-facing slope. Saturation deficit values higher than 10 mmHg and lasting for >2 mo were often recorded on the south-facing slope, explaining seasonal patterns of questing tick activity. The overall prevalence of Borrelia burgdorferi sensu lato was 22.4%, and prevalence differed according to exposure and among years. No difference was noticed between nymphs and adults. Four Borrelia species were identified. Mixed infections were detected in 52 ticks, B. garinii and B. valaisiana (n = 21) and B. afzelii and B. burgdorferi s.s. (n = 20) were the most frequent associations observed. The density of infected ticks varied from 3.6 to 78.7 infected nymphs per 100 m2 and from 0.6 to 16.9 infected adults per 100 m2, both slopes combined. The study on the south-facing slope was a follow-up of a previous study carried out at the same location during 1999-2001. Comparison of climatic data between the two periods showed a marked increase in saturation deficit. Substantial differences in density and phenology of ticks also were observed. At high elevations, ticks were significantly more abundant during the current study. This can be explained by rising temperatures recorded during summer at altitude, reaching values similar to those registered in the first study beneath. At the lowest altitude, adults were significantly less abundant, probably due to long-lasting high saturation deficits that impaired nymphal survival. The density of Borrelia-infected ticks was higher than in the previous study.

Le diagnostic clinique des manifestations articulaires et musculaires de la borréliose de Lyme

The diagnosis of Lyme borreliosis in case of joint and muscular presentations is generally suggested by epidemiological factors. However, as a rule, laboratory testing is required to confirm the diagnosis. When considering the epidemiology of Lyme borreliosis in France, the only areas free of ticks infected by Borrelia burgdorgeri sl, are those close to the Mediterranean sea or at high altitude. The risk is greatest in the Alsace region. Exposure is particularly high among forest workers and people who use the countryside for their leisure activities. The likelihood of infection following a tick bite is difficult to assess; indeed, the bite site may remain unnoticed. A medical history of erythema migrans, if untreated, is a major diagnostic clue, although the association appears to be less consistent in France than in the US. Lyme arthritis generally arises apparently spontaneously. It is characteristically mono- or oligo-articular, asymmetrical, predominantly affects the knee, and has an intermittent course. Synovial cysts and enthesitis are common. Myositis is rare, polymorphic, and has been linked to other symptoms in the same localizations. Minor arthralgia and myalgia frequently occur, principally early in the course of the infection. It was suggested that sequels of the disease include so-called fibromyalgic syndromes. The principal differential diagnosis as far as arthritis is concerned, is made on spondylarthropathy and chronic juvenile arthritis. Rheumatoid arthritis is another pathology, although Lyme arthritis does sometimes evolve to chronicity.

Ixodes ricinus density and infection prevalence of Borrelia burgdorferi sensu lato along a North-facing altitudinal gradient in the Rhône Valley (Switzerland)

Questing Ixodes ricinus ticks were sampled monthly along a north-facing altitudinal gradient in the canton of Valais, Switzerland, from March 2004 to February 2005. Tick density and infection with Borrelia burgdorferi sensu lato were monitored. Ticks were collected by flagging vegetation at three different altitudes (750 m, 880 m, and 1020 m above sea level). Ticks were examined for Borrelia by polymerase chain reaction (PCR) followed by reverse line blot. At the three altitudes, questing tick activity was not observed under 10 degrees C and was reduced when saturation deficit was higher than 5 mm Hg, most questing tick activity was occurred between 2 mm Hg and 7 mm Hg. Tick density and peak tick density were highest at 1020 m. High saturation deficits at the lowest altitudes appear to impair the tick population. The prevalence of B. burgdorferi infection in nymphs and adults decreased with altitude. The prevalence of infection was higher in adult ticks (47%) than in nymphs (29%). Four B. burgdorferi sensu lato genospecies were detected: B. afzelii (40%), B. garinii (22%), B. valaisiana (12%) and B. burgdorferi sensu stricto (6%). Mixed infections were detected in 13% of infected ticks.

[Lyme disease: basis for treatment strategy, primary preventive care and secondary preventive care]

Lyme disease is the most common tick borne disease and is caused by Borrelia burgdorferi sensu lato. Ticks of the genus Ixodes are the vectors that transmit the infection to host mammals in endemic foci. Ixodes is infected by Borrelia at larval stage when it feeds on infected mammals. Man is an occasional host. The infection risk is linked to interaction between human and the natural environment. Strategies for prevention are closely related to the enzootic cycle of the Ixodes tick. Environmental measures to reduced tick density or host mammals are expensive, need to be repeated annually and cannot be applied to large areas. The primary prevention could be reduced to personal preventive measures such as reducing the amount of exposed skin and frequent checking for ticks. The risk of Lyme disease transmission after a tick bite is relatively low, and remains under 4%. The transmission rate depends on the duration of feeding. A rapide tick removal with fine tweezers or preferably special forceps and disinfection of the bite site appear to be the best technique. The absence of scientific evidence, and the risk of adverse events does not lead to recommending antimicrobial prophylaxis. Follow-up and educating the patients on the disease, clinical manifestation, and later primary prevention should be undertaken.

[Lyme disease: prophylaxis after tick bite]

Lyme disease is a bacterial infection caused by Borrelia burgdorferi, which is transmitted by infected ticks. The transmission depends on several factors, especially on the duration of the tick's presence in the host body (the nymph which is smaller than the adults and thus less visible, is in this case the most frequently involved) and on whether the tick is infected or not. The interpretation of results in the few available studies is made difficult by the lack of information obtained (due to difficulty to collect information and examination costs). The comparison is made even more difficult by the difference between Borrelia ticks species in various regions. Today, the best methods are preventive: protective clothing, tick repellents, checking and removal of ticks after a journey in an endemic zone, and in case of tick bite, regular examination of the bite site during the following weeks in order to initiate an early curative treatment if ECM is diagnosed. The currently available data seems to be insufficient to suggest systematic antimicrobial prophylaxis in case of tick bite.