Biomedical subjects

L Gern

Publications and source records attributed to L Gern.

At least 19 recordsLinked to original sources

PubMed2006

Widespread distribution and high prevalence of an alpha-proteobacterial symbiont in the tick Ixodes ricinus.

The tick Ixodes ricinus is responsible for the transmission of a number of bacterial, protozoan and viral diseases to humans and animals in Europe and Northern Africa. Female I. ricinus from England, Switzerland and Italy have been found to harbour an intracellular alpha-proteobacterium, designated IricES1, within the cells of the ovary. IricES1 is the only prokaryote known to exist within the mitochondria of any animal or multicellular organism. To further examine the distribution, prevalence and mode of transmission of IricES1, we performed polymerase chain reaction screening of I. ricinus adults from 12 countries across its geographic distribution, including tick colonies that have been maintained in the laboratory for varying periods of time. IricES1 was detected in 100% of field-collected female ticks from all countries examined (n = 128), while 44% of males were found to be infected (n = 108). Those males that are infected appear to harbour fewer bacteria than females. Sequencing of fragments of the 16S rRNA and gyrB genes revealed very low nucleotide diversity among various populations of IricES1. Transmission of IricES1 from engorged adult females to eggs was found to be 100% (n = 31). In tick colonies that had been maintained in the laboratory for several years, a relatively low prevalence was found in females (32%; n = 25). To our knowledge, IricES1 is the most widespread and highly prevalent of any tick-associated symbiont.

Alphaproteobacteria↗

PubMed2005

[The biology of the Ixodes ricinus tick].

More than 800 tick species have been reported world-wide however only about 30 tick species feed on humans, among them Ixodes ricinus, which is the most frequent tick species biting humans in Europe. It is the vector of Borrelia burgdorferi, which causes Lyme disease and of the tick-borne encephalitis virus. I. ricinus ticks pass through three developmental stages: larvae, nymphs and adults (females and males). More than 300 animal species have been reported as natural hosts for I. ricinus and 50 vertebrate species have been identified as reservoir hosts for B. burgdorferi. The density of this tick species may be very high, reaching in some places more than 300 ticks/100 m2. Attached ticks should be removed without delay with a blunt forceps.

Animals↗

PubMed2004

Risk of Borrelia burgdorferi infection in western Switzerland following a tick bite.

The aim of this study was to define the risk of developing Lyme borreliosis after a tick bite. A survey was conducted from 1993 to 1995 in the western part of Switzerland in a group of patients who presented for treatment of a recent tick bite. Only patients with negative serological tests (enzyme-linked fluorescent assay screening test, and IgG and IgM immunoblots) at the first consultation and for whom a second blood sample was available 2 months later were included in the study. Of the 376 patients included, 266 had no clinical manifestation (group 1) and 110 had a small local cutaneous reaction (<2 cm) (group 2). The tick was available for 160 patients. Seroconversion was observed in 4.5% of 376 patients, 3.4% in group 1 and 7.2% in group 2. Typical erythema migrans, confirmed by seroconversion, was observed in three of 376 (0.8%) patients, while five of 376 (1.3%) patients developed a skin lesion without seroconversion. No other clinical manifestation of Lyme borreliosis was observed among these 376 patients. Borrelia detection in ticks did not correlate significantly with the risk of Lyme borreliosis. In conclusion, the risk of developing Lyme borreliosis in western Switzerland after a tick bite is low, and therefore, prophylactic antibiotics are not required.

Adolescent↗

PubMed2004

Lyme borreliosis in Europe and North America.

Since the discovery of the Lyme disease spirochete in North America in 1982 and in Europe in 1983, a plethora of studies on this unique group of spirochetes that comprise Borrelia burgdorferi sensu lato has been accumulated. In an attempt to compare and contrast Lyme borreliosis in Europe and North America we have reviewed the biology of the aetiologic agents, as well as the clinical aspects, diagnosis and treatment of this disease on both continents. Moreover, we have detailed the ecology of the Ixodes ticks that transmit this infection and the reservoir hosts that maintain the spirochete cycle in nature. Finally, we have examined the transmission dynamics of the spirochete on both continents, as well as the available prevention strategies. Although it has been over two decades since the discovery of the Lyme disease spirochete, Lyme borreliosis is an expanding public health problem that has defied our attempts to control it. By comparing the accumulated experience of investigators in North America and Europe, where the disease is most frequently reported, we hope to advance the cause of developing novel approaches to combat Lyme borreliosis.

Animals↗

PubMed2002

Apodemus species mice are reservoir hosts of Borrelia garinii OspA serotype 4 in Switzerland.

Among Borrelia burgdorferi sensu lato isolates, seven outer surface protein A (OspA) serotypes have been described: serotypes 1 and 2 correspond to B. burgdorferi sensu stricto and Borrelia afzelii, respectively, and serotypes 3 to 7 correspond to Borrelia garinii. In Europe, serotype 4 has never been isolated from Ixodes ricinus ticks until recently, although this serotype has been frequently isolated from cerebrospinal fluid from patients. In Europe, B. afzelii and B. burgdorferi sensu stricto were found associated with rodents and B. garinii was found associated with birds. In this study, the reservoir role of Apodemus mice for B. garinii OspA serotype 4 was demonstrated by xenodiagnosis. Apodemus mice are the first identified reservoir hosts for B. garinii OspA serotype 4.

Animals↗

PubMed2002

Coinoculation of Borrelia spp. with tick salivary gland lysate enhances spirochete load in mice and is tick species-specific.

C3H/HeN mice were inoculated with 10(6) spirochetes, either Borrelia burgdorferi strain N40 or the Portuguese strain of B. lusitaniae, PotiB2. Mice receiving spirochetes coinoculated with salivary gland lysate (SGL) demonstrated significantly higher spirochete loads in target organs as measured by quantitative real-time polymerase chain reaction. This effect was tick dependent, in that Ixodes ricinus SGL specifically enhanced B. lusitaniae load, whereas I. scapularis SGL specifically increased B. burgdorferi N40 load, but did not significantly affect the dissemination of B. lusitaniae. Protein profile analysis indicated at least 5 major protein differences between I. scapularis and I. ricinus SGL, which can possibly account for this specific tick-spirochete interaction.

Animals↗

PubMed2001

Transmission of Borrelia garinii OspA serotype 4 to BALB/c mice by Ixodes ricinus ticks collected in the field.

In Europe, Borrelia garinii OspA serotype 4 has been isolated from the cerebrospinal fluid of patients but, up to now, has never been identified among culture isolates from Ixodes ricinus ticks. This information raises the question of whether OspA serotype 4 is transmitted by I. ricinus in nature. In the present study, I. ricinus nymphs collected in an area of endemicity in southern Germany were allowed to feed on mice. Cultivation of ear biopsy specimens showed that six of seven B. garinii-infected mice were infected by OspA serotype 4. In contrast, very few B. garinii OspA serotype 4 organisms were isolated directly from the ticks which infected the mice; most isolates were B. afzelii. The infected mice transmitted mainly OspA serotype 4 to xenodiagnostic ticks, preferentially in combination with B. afzelii.

Animals↗

PubMed2000

[Epidemiology of Lyme borreliosis in French-speaking Switzerland].

The purpose of this study was to assess the number of cases and the clinical aspects of Lyme borreliosis in French-speaking Switzerland. 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.

Adolescent↗

PubMed2000

Antigenic conservation of an immunodominant invariable region of the VlsE lipoprotein among European pathogenic genospecies of Borrelia burgdorferi SL.

Lyme disease is caused by genetically divergent spirochetes, including 3 pathogenic genospecies: Borrelia burgdorferi sensu stricto, B. garinii, and B. afzelii. Serodiagnosis is complicated by this genetic diversity. A synthetic peptide (C(6)), based on the 26-mer invariable region (IR(6)) 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 C(6), which indicates that IR(6) is antigenically conserved among the pathogenic genospecies. Twenty of 23 patients with culture-confirmed erythema migrans had a detectable antibody response to C(6). 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-IR(6) ELISA. Thus, it is possible that C(6) may be used to serodiagnose Lyme disease universally.

Amino Acid Sequence↗

PubMed2000

Influence of saturation deficit and temperature on Ixodes ricinus tick questing activity in a Lyme borreliosis-endemic area (Switzerland).

Questing Ixodes ricinus ticks were sampled monthly in a periurban mixed forest at Neuchâtel, Switzerland, in 1996, 1997, and 1998. A total of 5,530 I. ricinus nymphs and 1,385 adults were collected. The emergence of questing tick populations in spring varied among years in relation to the air temperature. The monthly variation in questing nymph density was negatively correlated with the saturation deficit; there was a strong decrease in tick numbers in late spring and summer as soon as the saturation deficit increased. A variation in tick density in relation to the saturation deficit was also observed between years; the tick density was high when the saturation deficit was low during spring and summer (1997) and was low when the saturation deficit was high (1998). During the 3-year study period, marked climatic differences among years highlighted the influence of temperature and saturation deficit on the phenology of ticks.

Animals↗

PubMed2000

The wild hidden face of Lyme borreliosis in Europe.

Lyme borreliosis is a zoonosis affecting humans in the Northern hemisphere. The pathogen, Borrelia burgdorferi sensu lato (sl), persists in endemic areas through a maintenance cycle involving ticks and wild animals. The description of different genospecies associated with Lyme borreliosis in Europe has generated the question concerning the maintenance of these pathogens in nature: how do closely related bacterial species like B. burgdorferi sl circulate between one main tick species, Ixodes ricinus, and several vertebrate host species? Recent studies have provided evidence that specific associations exist in some areas between Borrelia species and vertebrate hosts. The present paper based on this recent knowledge discusses various aspects of the ecology of the disease in Western Europe, in particular the maintenance and dispersal of the pathogens, and brings up some interesting questions.

Animals↗

PubMed2000

PCR detection of granulocytic ehrlichiae in Ixodes ricinus ticks and wild small mammals in western Switzerland.

The presence of granulocytic ehrlichiae was demonstrated by PCR in Ixodes ricinus ticks and wild small mammals in Switzerland in two areas of endemicity for bovine ehrlichiosis. Six ticks (three females and three nymphs) (1.4%) of 417 I. ricinus ticks collected by flagging vegetation contained ehrlichial DNA. A total of 201 small mammals from five species, wood mouse (Apodemus sylvaticus), yellow-necked mouse (Apodemus flavicollis), earth vole (Pitymys subterraneus), bank vole (Clethrionomys glareolus), and common shrew (Sorex araneus), were trapped. The analysis of I. ricinus ticks [corrected] collected on 116 small mammals showed that nine C. glareolus voles and two A. sylvaticus mice hosted infected tick larvae. In these rodents, granulocytic ehrlichia infection was also detected in blood, spleen, liver, and ear samples. Further examinations of 190 small mammals without ticks or with noninfected ticks showed the presence of ehrlichial DNA in spleen and other tissues from six additional C. glareolus, three A. flavicollis, and one S. araneus mammals. This study suggests that A. sylvaticus, A. flavicollis, S. araneus, and particularly C. glareolus are likely to be natural reservoirs for granulocytic ehrlichiae. Partial 16S rRNA gene sequences of granulocytic ehrlichiae from ticks and rodents showed a high degree of homology (99 to 100%) with granulocytic ehrlichiae isolated from humans. In contrast, groESL heat shock operon sequence analysis showed a strong divergence (approximately 5%) between the sequences in samples derived from rodents and those derived from samples from questing ticks or from other published ehrlichia sequences. Dual infections with granulocytic ehrlichia and Borrelia burgdorferi were found in ticks and small mammals.

Animals↗

PubMed2000

Lyme disease.

Lyme borreliosis, the most common vector-borne 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.

Animals↗

PubMed1999

Resolution of experimental and tick-borne Borrelia burgdorferi infection in mice by passive, but not active immunization using recombinant OspC.

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.

Animals↗

PubMed1999

Transmission of Borrelia afzelii from Apodemus mice and Clethrionomys voles to Ixodes ricinus ticks: differential transmission pattern and overwintering maintenance.

This study deals with the ecology of Lyme borreliosis in Europe. The relationships between Borrelia burgdorferi sensu lato spirochetes, Clethrionomys and Apodemus rodent reservoirs and the Ixodes ricinus tick vector were investigated during 16 consecutive months in an enzootic area in Switzerland. Cultivation of ear skin biopsies was used to isolate spirochetes from C. glareolus, A. sylvaticus, A. flavicollis and Glis glis. Borrelia infection was more frequently observed in Clethrionomys than in Apodemus. Tick xenodiagnosis was used to determine the infectivity of rodents. The infection rate in ticks fed on Clethrionomys was higher than that in ticks fed on Apodemus, but Apodemus yielded more infected ticks than Clethrionomys because of a better tick moulting success. Xenodiagnostic ticks were placed into BSK medium to obtain isolates. Isolates from rodents and rodent-feeding ticks were all identified as B. afzelii. The follow-up of the infectivity status of repeatedly recaptured rodents clearly demonstrated that these hosts remained infective for ticks during winter till the following spring. Comparing C. glareolus and A. sylvaticus, each rodent species showed different host infection, different host infectivity and contributed differently to the moulting success of feeding ticks. These factors influence differentially the pattern of transmission of B. afzelii from Clethrionomys voles and Apodemus mice to I. ricinus ticks.

Animals↗

PubMed1999

Genetic diversity of Borrelia burgdorferi sensu lato isolates obtained from Ixodes ricinus ticks collected in Slovakia.

In Europe, Borrelia burgdorferi sensu lato is diverse, including B. burgdorferi s.s., B. garinii, B. afzelii, B. valaisiana and B. lusitaniae. In this study, we focused on the distribution of the different B. burgdorferi species among Ixodes ricinus adult ticks collected in an endemic area within Slovakia. We compared results of prevalence of B. burgdorferi infection in ticks obtained by immunofluorescence (IF) and by isolation. Isolates were characterized by restriction fragment length polymorphism (RFLP) of the rrf-rrl intergenic spacer genes using MseI. Using immunofluorescence we observed that 56/114 (49%) ticks were infected by B. burgdorferi s.l. Males were found to be more often infected (32/57, 56%) than females (24/57, 42%) but the difference was not significant (p = 0.1895). From the same 114 ticks a total of 37 isolates were obtained: 19 from males (33%) and 18 from females (32%). The RFLP identification revealed 25 B. afzelii (68%), 5 B. garinii (14%), 5 B. valaisiana (14%) and 2 B. lusitaniae (5%). The infection in ticks was more often detected by IF than by isolation (p = 0.0153) and isolation success was higher when the infection degree in ticks was high (p = 0.0397). The infection prevalence observed in this area is among the highest observed in Europe.

Animals↗

PubMed1999

Infection of Ixodes ricinus (Acari: Ixodidae) by Borrelia burgdorferi sensu lato in North Africa.

Free-living adult Ixodes ricinus L, were collected in Amdoun, situated in the Kroumiry mountains in northwestern Tunisia (North Africa). Using direct fluorescence antibody assay, the infection rate of field-collected I. ricinus by Borrelia burgdorferi sensu lato was 30.5% (n = 72). No difference in infection rate was observed between male and female ticks. Spirochetes that had been isolated from I. ricinus from Ain Drahim (Kroumiry Mountains) in 1988 were identified as Borrelia lusitaniae (formerly genospecies PotiB2). This is the first identification of a genospecies of Borrelia burgdorferi sensu lato from the continent of Africa.

Africa, Northern↗

PubMed1998

Natural history of Borrelia burgdorferi sensu lato.

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.

Animals↗