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Table S1. Descriptive statistics of nymph density for spring semesters. Table S2. Descriptive statistics of nymph density for autumn semesters. (DOCX 19 kb)

Figure S1. The sampling area with the circular footpath. Figure S2. The sampling area with the maximal temperature threshold for nymph activity. Figure S3. The sampling area with the cumulated nymph density for spring semesters. Figure S4. The sampling area with the cumulated nymph density for autumn semesters. Figure S5. The sampling area with the linear correlations between Climap-net data and field measures for temperature and humidity. Figure S6. Parallel plots of nymph density and relevant climatic variables (1 plot by year). Figure S7. Parallel plots of nymph density and the number of days of each year during which the upper threshold of maximal temperature was reached. (DOCX 8766 kb)

A total of 874 Ixodes ricinus ticks were collected in Switzerland to investigate the genetic diversity of the Borrelia population. We integrated to the RT-PCR method the DNA sequence analysis of a 162-bp fragment of the recA gene. Five genospecies were detected: Borrelia afzelii, Borrelia burgdorferi s.s., Borrelia garinii, Borrelia valaisiana, and Borrelia lusitaniae. A heterogeneous distribution was observed within the B. burgdorferi s.l. genospecies. The most prevalent and diverse genospecies found in Switzerland was Borrelia afzelii, which might suggest a rapid evolution of this genospecies

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

We studied the relationship between climate and Ixodes ricinus L. tick behavior by following every day the proportion of ticks questing in a tick population placed in polyamide mesh-delimited arenas in the field. Simultaneously, the phenology of the questing density of nymphs and adults was studied by sampling ticks in a close location. At any time during the year, the proportion of questing adults was significantly higher (mean 24%) than the proportion of questing nymphs (mean 12%). The proportion of questing nymphs and adults decreased stepwise with time. The proportion of questing adults partially recovered after each decrease. In contrast, the proportion of questing nymphs was strongly reduced during a single short period in June and did not recover even partially. Decrease in the proportion of questing ticks was strongly related either to a peak in saturation deficit or to a drop in maximal relative humidity. No increase in the proportion of questing nymphs was observed in the arenas during autumn, although an autumn peak of nymphs was observed at the sampling location close to the arenas. This suggests that the autumn peak of nymphs observed in nature was due to newly emerged spring-fed larvae and not to reactivated spring active nymphs

Lyme disease is caused by genetically divergent spirochetes, including 3 pathogenic genospecies: Borrelia burgdorferi sensu stricto, B. garinii, and B. afzelii. Serodiagnosisis complicated by this genetic diversity. A synthetic peptide (C6), based on the 26-mer invariable region (IR6) of the variable surface antigen of B. burgdorferi (VlsE), was used as ELISA antigen, to test serum samples collected from mice experimentally infected with the 3 genospecies and from European patients with Lyme disease. Regardless of the infecting strains, mice produced a strong antibody response to C6, which indicates that IR6 is antigenically conserved among the pathogenic genospecies. Twenty of 23 patients with culture-confirmed erythema migrans had a detectable antibody response to C6. A sensitivity of 95.2% was achieved, with serum samples collected from patients with well-defined acrodermatitis chronica atrophicans. Fourteen of 20 patients with symptoms of late Lyme disease also had a positive anti-IR6 ELISA. Thus, it is possible that C6 may be used to serodiagnose Lyme disease universally

La borréliose de Lyme qui est, dans l'hémisphère nord, la plus répandue des maladies à transmission vectorielle, est due à des bactéries appartenant au genre Borrelia burgdorferi. Il s'agit d'une maladie plurisystémique qui affecte essentiellement la peau, le système nerveux le cœur et les articulations. En Europe, le vecteur de la maladie est la tique Ixodes ricinus; aux États -Unis d'Amérique les deux vecteurs principaux sont la tique I. scapularis dans les régions du nord-est et du centre-ouest et I. pacificus sur la Côte Ouest. Plusieurs espèces de petits et moyens mammifères ou d'oiseaux terrestres servent de réservoirs à la bactérie dans les zones endémiques. Le pronostic est excellent, surtout lorsque la maladie de Lyme est diagnostiquée en phase initiale et traitée immédiatement. La prophylaxie repose sur deux méthodes: l'immunisation préventive, d'une part, et la mise en œuvre de mesures permettant d'éviter les piqûres de tiques et de lutter contre ces vecteurs, d'autre part. Lyme borreliosis, the most common vector-bome disease in the northern hemisphere, is caused by bacteria belonging to the Borrelia burgdorferi complex. The disease is multisystemic, affecting mainly the skin, nervous system, heart and joints. In Europe, the vector of the disease is the tick Ixodes ricinus, whereas in the United States of America, two primary tick vectors exist, namely: I. scapularis in the north-eastern and mid-western regions and I. pacificus on the west coast. Several species of small and medium-sized mammals and ground-feeding birds serve as reservoirs for the bacteria in endemic areas. The prognosis for patients with Lyme borreliosis is excellent, particularly when diagnosed and treated early in the course of infection. Prevention of Lyme borreliosis can be achieved using two approaches, either prevention of infection by immunisation, or prevention of tick bites through avoidance, personal protection and tick control. De todas las enfermedades vehiculadas por vectores, la borreliosis de Lyme, causada por bacterias pertenecientes al complejo Borrelia burgdorferi, es la más común en el hemisferio norte. Esta enfermedad de carácter multisistémico afecta principalmente la piel, el sistema nervioso, el corazón y las articulaciones. En Europa, el vector de la enfermedad es la garrapata Ixodes ricinus. En los Estados Unidos de América, por su parte, existen dos garrapatas que ejercen de vectores primarios: I.scapularis en las regiones del noreste y el medio oeste, e I.pacificus en la costa oeste. En las áreas endémicas varias especies de mamíferos pequeños y medianos y de aves de alimentación terrestre sirven de reservorio de las bacterias. Los pacientes afectados de borreliosis de Lyme presentan un pronóstico excelente, sobre todo cuando se diagnostica y trata la infección en sus fases iniciales. Para prevenir esta enfermedad caben dos procedimientos distintos: prevenir la infección con medidas de inmunización; o impedir la mordedura de la garrapata previniendo esta posibilidad, protegiéndose del contacto y luchando contra sus poblaciones.

The purpose of this study was to assess the number of cases and the clinical aspects of Lyme borreliosis in French-speaking Switzer- land. From July 1996 to December 1997, all laboratories performing serological tests for Lyme borreliosis sent a questionnaire to the treating physicians whenever the tests were positive. In addition, the physicians who diagnosed a case on clinical grounds only were also asked to report these cases. During this period, 1460 positive serological tests were recorded among approximately 10 360 performed (14%). A total of 775 questionnaires were returned (53%). In 3 ⁄ 4 of the cases, the test was ordered because of an acute clinical manifestation or a tick bite. The rest related to chronic symptoms or follow-up. In 504 cases (65%), diagnosis was considered certain or probable. These were erythema migrans in 46%, clinical manifestations of stage II in 33% (26 facial palsy, 20 acute arthritis, 5 benign cutaneous lymphocytoma) and chronic symptoms in 21% (23 acrodermatitis, 26 neuropathies, and 8 arthritis). The adjusted incidence, estimated on the basis of the treating physician’s place of residence, ranged from 9/100 000 in Valais to 95/100 000 in Neuchâtel. This study indicates that Lyme borreliosis is a diagnosis frequently looked for and established in French-speaking Switzerland. Although erythema migrans is the main clinical manifestation, symptoms of stage II and III indicate that Lyme borreliosis is also responsible for relatively major systemic morbidity.

Lyme borreliosis is a zoonosis: its causative agent, B: burgdorferi, circulates between ticks and a large range of vertebrates. Identification of the hosts which are responsible for the infection of the vectors is extremely important to determine the potential risk of infection in an habitat. Various small mammals and bird species are considered reservoirs for the Lyme disease spirochetes. Grey and red squirrels, hedgehogs as well as hares and rabbits can develop an infection and transmit B. burgdorferi sensu lato to feeding ticks. In Eurasian endemic areas, many different Borrelia species circulate between ticks and vertebrate hosts. Studies have shown that European and Asian genospecies are associated with specific groups of vertebrate hosts, such as B. valaisiana and B. garinii with birds, B. afzelii with small mammals and B. burgdorferi ss and B. afzelii with red squirrels. However, such associations are not always observed as in Japan where B. garinii, B. afzelii and unidentified Borrelia species are found in small mammals. Some enzootic cycles involving tick species which do not feed at all on humans or which rarely feed on humans have been described in Europe and USA. It is likely that many existing enzootic foci have yet to be discovered. The circulation of B. burgdorferi in silent foci does not have important implications for human health, but it demonstrates the complexity of the ecology of this microorganism and the variety of ecological niches this spirochete can occupy.

The contribution of woodmice (Apodemus sylvaticus), yellow-necked mice (Apodemus flavicollis) and bank voles (Clethrionomys glareolus) was compared in a focus of Lyme borreliosis in Switzerland during a 7 months' study. All three species of mice and one species of shrews (Sorex araneus) were shown parasitized by infected Ixodes ricinus immatures. About 14% of larvae and 50% of nymphs collected on small mammals were infected with B. burgdorferi. Spirochetes were isolated from blood of 3 woodmice and one yellow-necked mouse. The infectious status of rodents was estimated by tick xenodiagnosis. Prevalence of infected rodents ranged from 20% to 44%. Mice presented a higher potential infectivity than voles. The prevalence of infected rodents showed a seasonal variation.

Vaccination with outer surface protein A (OspA) of Borrelia burgdorferi prevents subsequent infection and disease in both laboratory animals and humans with high efficacy. OspA-based immunity, however, does not affect established infection due to the loss of OspA expression in the vertebrate host. We show here that repeated passive transfer of mouse and/or rabbit immune sera to recombinant GST-OspC fusion protein resulted in a dose-dependent resolution (1) of fully established arthritis and carditis as well as infection in needle-challenged C.B-17 SCID and (2) of infection in both experimentally and tick-infected BALB/c mice. Unexpectedly, active immunization of disease-susceptible AKR/N mice with GST-OspC only led to prevention but not resolution of disease and infection, in spite of high serum titers of OspC-specific Ab and the expression of ospC in tissue-derived spirochetes. The data suggest that the efficacy of OspC antibody-mediated immunity depends on the immunological history of the recipient and/or environment-dependent regulation of OspC surface expression by spirochetes in vivo. The results encourage further attempts to develop therapeutic vaccination protocols against Lyme disease.

Cherix, Daniel, Freitag, Anne, Gern, Lise (2014): Prédation des tiques Ixodes ricinus par les fourmis des bois Formica pratensis - expérience préliminaire. Entomo Helvetica 7: 41-45, DOI: 10.5169/seals-985958