Borrelia-infected Ticks Research Articles

Spatial and Temporal Variability in Prevalence Rates of Members of the Borrelia burgdorferi Species Complex in Ixodes ricinus Ticks in Urban, Agricultural and Sylvatic Habitats in Slovakia.

Lyme borreliosis (LB) is the most prevalent tick-borne human infection in Europe, with increasing incidence during the latest decades. Abundant populations of Ixodes ricinus, the main vector of the causative agent, spirochetes from the Borrelia burgdorferi sensu lato (Bbsl) complex, have been observed in urban and suburban areas of Europe, in general, and Slovakia, particularly. Understanding the spread of infectious diseases is crucial for implementing effective control measures. Global changes affect contact rates of humans and animals with Borrelia-infected ticks and increase the risk of contracting LB. The aim of this study was to investigate spatial and temporal variation in prevalence of Bbsl and diversity of its species in questing I. ricinus from three sites representing urban/suburban, natural and agricultural habitat types in Slovakia. Ixodes ricinus nymphs and adults were collected by dragging the vegetation in green areas of Bratislava town (urban/suburban habitat), in the Small Carpathians Mountains (natural habitat) (south-western Slovakia) and in an agricultural habitat at Rozhanovce in eastern Slovakia. Borrelia presence in ticks was detected by PCR and Bbsl species were identified by restriction fragment length polymorphism (RFLP). Borrelia burgdorferi s.l. species in coinfected ticks were identified by reverse line blot. Significant spatial and temporal variability in prevalence of infected ticks was revealed in the explored habitats. The lowest total prevalence was detected in the urban/suburban habitat, whereas higher prevalence was found in the natural and agricultural habitat. Six Bbsl species were detected by RFLP in each habitat type -B. burgdorferi sensu stricto (s.s.), B. afzelii, B. garinii, B. valaisiana, B. lusitaniae and B. spielmanii. Coinfections accounted for 3% of the total infections, whereby B. kurtenbachii was identified by RLB and sequencing in mixed infection with B. burgdorferi s.s, B. garinii and B. valaisiana. This finding represents the first record of B. kurtenbachii in questing I. ricinus in Slovakia and Europe. Variations in the proportion of Bbsl species were found between nymphs and adults, between years and between habitat types. Spatial variations in prevalence patterns and proportion of Bbsl species were also confirmed between locations within a relatively short distance in the urban habitat. Habitat-related and spatial variations in Borrelia prevalence and distribution of Bbsl species are probably associated with the local environmental conditions and vertebrate host spectrum. Due to the presence of Borrelia species pathogenic to humans, all explored sites can be ranked as areas with high epidemiological risk.

Monitoring Risk: Tick and Borrelia burgdorferi Public Participatory Surveillance in the Canadian Maritimes, 2012-2020.

Ticks are vectors of many diseases, including Lyme disease (Ld). Lyme disease is an emerging disease in Canada caused by infection with the Lyme borreliosis (Lb) members of the Borrelia genus of spirochaete bacteria, of which Borrelia burgdorferi is regionally the most prevalent. The primary tick vector in central and eastern Canada, Ixodes scapularis, is increasing in numbers and in the geographical extent of established populations. This study documents the distribution of ticks recovered by passive surveillance, and their B. burgdorferi infection prevalence, in three Canadian Maritime provinces from 2012–2020. These regions represent areas in which tick populations are widely established, establishing, and considered non-established. Using a community science approach by partnering with veterinarians and members of the public, we collected over 7000 ticks from the 3 provinces. The three species found most often on companion animals and humans were I. scapularis (76.9%), Ixodes cookei (10.4%) and Dermacentor variabilis (8.9%). The most common hosts were dogs (60.5%), cats (16.8%) and humans (17.6%). As is typical of passive surveillance tick collections, the majority of ticks recovered were adult females; for I. scapularis 90.2%, 5.3%, 3.9% and 0.6% of the total of 5630 ticks recovered for this species were adult females, adult males, nymphs and larvae, respectively. The majority of B. burgdorferi-infected ticks were I. scapularis, as expected. Borrelia infection prevalence in I scapularis was higher in Nova Scotia (20.9%), the province with the most endemic regions, than New Brunswick (14.1%) and Prince Edward Island (9.1%), provinces thought to have established and non-established tick populations, respectively. The province-wide Borrelia infection prevalence generally increased in these latter tow provinces over the course of the study. The host did not have a significant effect on B. burgdorferi infection prevalence; I. scapularis ticks from dogs, cats, humans was, 13.3% (n = 3622), 15.6% (n = 817), 17.9% (n = 730), respectively. No I. scapularis larvae were found infected (n = 33) but B. burgdorferi was detected in 14.8% of both adults (n = 5140) and nymphs (n = 215). The incidence of B. burgdorferi infection also did not differ by engorgement status 15.0% (n = 367), 15.1% (n = 3101) and 14.4% (n = 1958) of non-engorged, engorged and highly engorged ticks, respectively, were infected. In New Brunswick, at the advancing front of tick population establishment, the province-wide infection percentages generally increased over the nine-year study period and all health district regions showed increased tick recoveries and a trend of increased percentages of Borrelia-infected ticks over the course of the study. Within New Brunswick, tick recoveries but not Borrelia infection prevalence were significantly different from endemic and non-endemic regions, suggesting cryptic endemic regions existed prior to their designation as a risk area. Over the 9 years of the study, tick recoveries increased in New Brunswick, the primary study region, and I. scapularis recoveries spread northwards and along the coast, most but not all new sites of recoveries were predicted by climate-based models, indicating that ongoing tick surveillance is necessary to accurately detect all areas of risk. Comparison of tick recoveries and public health risk areas indicates a lag in identification of risk areas. Accurate and timely information on tick distribution and the incidence of Borrelia and other infections are essential for keeping the public informed of risk and to support disease prevention behaviors.

Prevalence of <i>Borrelia burgdorferi sensu</i> lato genetic markers in blood-sucking ticks in suburban park zones in Saint Petersburg

Tick-borne bacterial and viral infections are widespread in middle latitudes of the Northern hemisphere. Natural foci of such infections coincide with geographic areas inhabited by ixodid ticks. Ixodid tick-borne borreliosis is a pressing issue for some territories of Russia, especially for the North-Western Federal District and St. Petersburg megalopolis as well as adjacent areas of the Leningrad District, where people may become infected after tick bite in recreational zones in suburban park areas. Currently, very few publications regarding prevalence of tick-borne pathogens in St. Petersburg area are available. In our study, questing ticks flagged in park zone (northern coast of Finnish Gulf, Kurortny District) were examined with PCR for carriage of pathogenic B. burgdorferi sensu lato complex. In addition, samples positive for Borrelia DNA signal were further genotyped with species-specific primers against rpoBgene fragment. It was found that Ixodes persulcatus dominated in this area. Prevalence of Borrelia burgdorferi s.l. complex comprised 9.33%. Genospecies B. afzelii and less frequently B. garinii were detected. A mixt-infection with two Borel-lia species was detected in one sample. Interestingly, all Borrelia-infected ticks belonged to I. persulcatus suggesting a closer association for certain species in «pathogen-vector» system. Our findings are essential in investigating distribution of ixodid borreliosis foci in St. Petersburg and suburbs, obtaining new data regarding epidemiology, diagnostics, treatment and prevention of this infection. It is noteworthy than prevalence of pathogenic Borrelia spp. vs. tick-borne encephalitis virus in vectors was higher thereby accounting for its higher morbidity. Comparing our data with those published elsewhere by European researchers allows to note that prevalence of pathogenic Borrelia spp. in ticks varies broadly in diverse geographic regions. It is necessary to take into consideration that prevalence of Borrelia markers achieves ~10% in ticks given frequent attendance of park areas near St. Petersburg that point at risk of developing bor-reliosis in recreational zones.

First records of tick-borne pathogens in populations of the taiga tick Ixodes persulcatus in Sweden

BackgroundThe common tick Ixodes ricinus and the taiga tick I. persulcatus are the main tick vectors of Borrelia spirochaetes, TBE virus (TBEV) and of several other zoonotic pathogens in the western and eastern areas, respectively of the Palaearctic region. Recently, populations of the taiga tick were, for the first time, detected in northern Sweden. This prompted us to investigate if they harbour human pathogens.MethodsA total of 276 I. persulcatus ticks (136 males, 126 females and 14 nymphs) and one I. ricinus nymph was collected by the cloth-dragging method in northern Sweden in July–August 2015 and May–July 2016. In addition, 8 males and 10 females of I. persulcatus were collected from two dogs (16 and 2 ticks, respectively) in two of the localities. All ticks were microscopically and molecularly identified to developmental stage and species and screened for B. burgdorferi (sensu lato), B. miyamotoi, Anaplasma phagocytophilum, Rickettsia spp., Neoehrlichia mikurensis, Babesia spp. and TBEV using real-time PCR followed by species identification by sequencing the PCR-products of conventional PCR assays.ResultsOf the ticks collected by the cloth-dragging method, 55% (152/277) were positive for Borrelia. There was no significant difference between the proportions of Borrelia-infected nymphs (33%, 5/15) and Borrelia-infected adult ticks (56%, 147/262), and no significant difference between the proportions of Borrelia-infected males (54%, 74/136) and Borrelia-infected females (58%, 73/126). Three different Borrelia species were identified. Borrelia afzelii was the predominant species and detected in 46% of all Borrelia-infected ticks followed by B. garinii, 35%, B. valaisiana, 1%, and mixed infections of different Borrelia species, 1%; 17% of all Borrelia-infections were untypeable. One I. persulcatus female contained Rickettsia helvetica, and one nymph contained Rickettsia sp. Of the 277 ticks analysed, all were negative for A. phagocytophilum, Babesia spp., Borrelia miyamotoi, N. mikurensis and TBEV. The ticks collected from the two dogs were negative for all pathogens examined except for Borrelia spp., that was detected in 5 out of 16 ticks removed from one of the dogs.ConclusionsTo our knowledge, this is the first time that I. persulcatus from Sweden has been analysed for the presence of tick-borne pathogens. The examined tick populations had a low diversity of tick-borne pathogens but a high prevalence of B. burgdorferi (s.l.).

Anti-OspA DNA-Encoded Monoclonal Antibody Prevents Transmission of Spirochetes in Tick Challenge Providing Sterilizing Immunity in Mice

We recently developed anti-OspA human immunoglobulin G1 monoclonal antibodies (HuMAbs) that are effective in preventing Borrelia transmission from ticks in a murine model. Here, we investigated a novel approach of DNA-mediated gene transfer of HuMAbs that provide protection against Lyme disease. Plasmid DNA-encoded anti-OspA HuMAbs inoculated in mice achieved a serum antibody concentration of >6 μg/mL. Among mice injected with DNA-encoded monoclonal antibodies, 75%-77% were protected against an acute challenge by Borrelia-infected ticks. Our results represent the first demonstration of employing DNA transfer as a delivery system for antibodies that block transmission of Borrelia in animal models.

Pathogen communities of songbird-derived ticks in Europe\u2019s low countries

BackgroundBirds play a major role in the maintenance of enzootic cycles of pathogens transmitted by ticks. Due to their mobility, they affect the spatial distribution and abundance of both ticks and pathogens. In the present study, we aim to identify members of a pathogen community [Borrelia burgdorferi (s.l.), B. miyamotoi, ‘Ca. Neoehrlichia mikurensis’, Anaplasma phagocytophilum and Rickettsia helvetica] in songbird-derived ticks from 11 locations in the Netherlands and Belgium (2012–2014).ResultsOverall, 375 infested songbird individuals were captured, belonging to 35 species. Thrushes (Turdus iliacus, T. merula and T. philomelos) were trapped most often and had the highest mean infestation intensity for both Ixodes ricinus and I. frontalis. Of the 671 bird-derived ticks, 51% contained DNA of at least one pathogenic agent and 13% showed co-infections with two or more pathogens. Borrelia burgdorferi (s.l.) DNA was found in 34% of the ticks of which majority belong to so-called avian Borrelia species (distribution in Borrelia-infected ticks: 47% B. garinii, 34% B. valaisiana, 3% B. turdi), but also the mammal-associated B. afzelii (16%) was detected. The occurrence of B. miyamotoi was low (1%). Prevalence of R. helvetica in ticks was high (22%), while A. phagocytophilum and ‘Ca. N. mikurensis’ prevalences were 5% and 4%, respectively. The occurrence of B. burgdorferi (s.l.) was positively correlated with the occurrence of ‘Ca. N. mikurensis’, reflecting variation in susceptibility among birds and/or suggesting transmission facilitation due to interactions between pathogens.ConclusionsOur findings highlight the contribution of European songbirds to co-infections in tick individuals and consequently to the exposure of humans to multiple pathogens during a tick bite. Although poorly studied, exposure to and possibly also infection with multiple tick-borne pathogens in humans seems to be the rule rather than the exception.

Virulence of recurrent infestations with Borrelia-infected ticks in a Borrelia-amplifying bird

Lyme disease cases caused by Borrelia burgdorferi s.l. bacteria is increasing steadily in Europe, in part due to the expansion of the vector, Ixodes ricinus. Wild reservoir hosts are typically recurrently infested. Understanding the impact of these cumulative parasite exposures on the host’s health is, therefore, central to predict the distribution of tick populations and their pathogens. Here, we have experimentally investigated the symptoms of disease caused by recurrent infestations in a common songbird (Parus major). Birds were exposed three times in succession to ticks collected in a Borrelia endemic area. Health and immune measures were analyzed in order to investigate changes in response to tick infestation and Borrelia infection rate. Nitric oxide levels increased with the Borrelia infection rate, but this effect was increasingly counteracted by mounting tick infestation rates. Tick infestations equally reduced haematocrit during each cycle. But birds overcompensated in their response to tick feeding, having higher haematocrit values during tick-free periods depending on the number of ticks they had been previously exposed to. Body condition showed a similar overshooting response in function of the severity of the Borrelia infection. The observed overcompensation increases the bird’s energetic needs, which may result in an increase in transmission events.

A prospective study on the incidence of Borrelia burgdorferi sensu lato infection after a tick bite in Sweden and on the Åland Islands, Finland (2008–2009)

Lyme borreliosis (LB) is a common and increasing tick-borne disease in Europe. The risk of acquiring a Borrelia infection after a tick bite is not fully known. Therefore, we investigated the incidence of Borrelia infection after a bite by a Borrelia-infected tick and if the Borrelia load and/or the duration of tick-feeding influenced the risk of infection. During 2008–2009, ticks and blood samples were collected from 1546 tick-bitten persons from Sweden and the Åland Islands, Finland. Follow-up blood samples were taken 3 months after the tick bite. The duration of tick feeding was microscopically estimated and Borrelia was detected and quantified in ticks by real-time PCR. Anti-Borrelia antibodies were detected in sera using ELISA tests and immunoblot.Five percent (78/1546) of the study participants developed Borrelia infection (LB diagnosis and/or seroconversion) after a tick bite (45% bitten by Borrelia-infected ticks and 55% bitten by uninfected ticks). Of these, 33 developed LB (whereof 9 also seroconverted) while 45 participants seroconverted only. Experience of non-specific symptoms was more frequently reported by Borrelia-infected participants compared to uninfected participants. All who seroconverted removed “their” ticks significantly later than those who did not. The Borrelia load in the ticks did not explain the risk of seroconversion. Regional and sex differences in the Borrelia seroprevalence were found. The risk of developing a Borrelia infection after a bite by a Borrelia-infected tick is small but increases with the duration of tick feeding.

Survival of Ixodes ricinus (Acari: Ixodidae) nymphs under cold conditions is negatively influenced by frequent temperature variations

In this study, we tested the survival of Ixodes ricinus under cold conditions in the laboratory. We investigated how the frequency of temperature variations (from −5°C or −10°C to 13°C), and infection with Borrelia burgdorferi sensu lato (s.l.) influenced survival of questing nymphs collected in spring and autumn 2011. In experiment 1, survival of 1760 nymphs was tested at −10°C over a short period of time to simulate very cold winter conditions. In experiment 2, survival of 1600 nymphs was tested under cold condition (−5°C) over a long period of time to simulate common winter conditions. Ticks used for survival tests at −5°C were screened for Borrelia by quantitative PCR, and genospecies identification was achieved by reverse line blotting. Tick age and frequency of temperature variations had a highly significant effect on I. ricinus survival while Borrelia infection was marginally significant. Hence, survival rate was higher in younger (autumn) than older (spring) nymphs and in nymphs exposed to low rather than high-frequency temperature variations. Borrelia-infected ticks tended to survive better than their uninfected counterparts. These findings suggest that in nature (i) frequent temperature changes in winter threaten tick survival more importantly than very low temperatures, (ii) older (spring) ticks are less resistant to cold than younger (autumn) individuals, and (iii) Borrelia infection plays a marginal role in I. ricinus survival during winter conditions.

Prevalence of Borrelia burgdorferi sensu stricto, Borrelia afzelii, Borrelia garinii, and Borrelia valaisiana in Ixodes ricinus ticks from the northwest of Norway

Over a 3-y period, Ixodes ricinus ticks were randomly collected to study the prevalence of 4 Borrelia species: B. burgdorferi sensu stricto, B. afzelii, B. garinii and B. valaisiana. While B. burgdorferi s. s., B. afzelii, and B. garinii have been associated with human borreliosis in Norway for several years, B. valaisiana was reported in a Norwegian tick for the first time in 2010. A real-time polymerase chain reaction (qPCR) was developed as an easy-to-use method, with high sensitivity and specificity, to detect and genospecies-type B. burgdorferi s. s., B. afzelii, B. garinii, and B. valaisiana in I. ricinus ticks. A combination of species-specific primers and TaqMan MGB probes labelled with fluorescents with different emission spectra, ensured a highly specific method with the potential to detect more than 1 genospecies in 1 run. Sequencing of the housekeeping gene recG from 48 Borrelia-positive samples was used to confirm specificity. Denaturing gradient gel electrophoresis profiling of tick-borne bacteria was used to help optimize the assay sensitivity. The qPCR assay was applied to analyze 1808 I. ricinus ticks collected in the field, which resulted in an overall infection rate of 14.8%, 18.7%, and 14.3% in 2010, 2011, and 2012, respectively. The majority of the Borrelia-infected ticks were infected with B. afzelii. The overall infection rate is somewhat lower than that reported in the most recent study of the infection rate in southern Norway in 2010, and this study indicates that the infection rate varies from one year to another.

First detection of Borrelia burgdorferi-antibodies in free-living birds of prey from Eastern Westphalia, Germany

Borrelia (B.) burgdorferi sensu lato, the causative agent of Lyme disease, is the most important arthropod-borne zoonosis-pathogen in the Northern hemisphere. Besides small mammals, birds, primarily Passeriformes and sea birds, play an important role in the transmission, distribution and maintenance of this disease. Previous studies on birds have focused mainly on the detection of Borrelia-infected ticks. However, the presence or absence of an infected tick cannot be taken as an indicator of the infective status of the avian host; to date this area of research has not been explored. In this study, serological analyses of blood collected from free-living birds of prey (n = 29) at the rehabilitation centre in Eastern Westphalia, Germany, highlights that birds of prey are also susceptible to B. burgdorferi and react immunologically to an infection. Increased antibody-levels could be found by using a modified Indirect Immunofluorescent-testing in two common buzzards, Buteo buteo, and two eagle owls, Bubo bubo. Further research regarding the serological diagnostics of B. burgdorferi within the avian host is required. In the future, it should be taken into account that birds of prey can be reservoirs for B. burgdorferi, as well as carriers of infected ticks; although at present their epidemiological importance is still to be confirmed.

Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum in Ixodes ricinus ticks in Brønnøysund in northern Norway

Ticks are important vectors of disease for both humans and animals. In Europe, Lyme borreliosis is the most abundant tick-borne human disease, whereas anaplasmosis, or tick-borne fever, is the most widespread tick-borne infection in domestic animals. However, knowledge about the prevalence of the causative disease agents in questing ticks in the northern range of their distribution in Norway is missing. Ixodes ricinus ticks were therefore collected by flagging vegetation in Brønnøysund, an area near the Arctic Circle in Norway where ticks have been abundant for decades. Ticks were analysed for infection with Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum by real-time PCR amplification of the 16S rRNA gene of B. burgdorferi and the msp2 gene of A. phagocytophilum. B. burgdorferi s.l. were subsequently genotyped by conducting a melt curve analysis of the PCR-amplified hbb gene or by directly sequencing the PCR-amplified rrs (16S)-rrl (23S) intergenetic spacer. A. phagocytophilum was genotyped by msp2 gene sequencing. B. burgdorferi s.l. isolates were detected in 11.3% (15/133) of the nymphal ticks and in 33.3% (29/87) of the adult ticks. Of the 44 Borrelia-infected ticks collected, B. afzelii was identified in 42 ticks (95.5%), whereas B. garinii was detected in only 2 ticks (4.5%). A. phagocytophilum was detected in 0.8% of nymphal ticks (1/133) and in 4.6% of adult ticks (4/87). Mixed infections of more than one B. burgdorferi genospecies were not observed. One adult tick was co-infected with B. afzelii and A. phagocytophilum.

Circumstantial evidence for an increase in the total number and activity of borrelia-infected ixodes ricinus in the Netherlands

BackgroundBetween 1994 and 2009, a threefold increase has been observed in consultations of general practitioners for tick bites and Lyme disease in The Netherlands. The objective of this study was to determine whether an increase in the number of questing ticks infected with B. burgdorferi sensu lato is a potential cause of the rise in Lyme disease incidence.MethodsHistoric data on land usage, temperature and wildlife populations were collected and analyzed together with data from two longitudinal field studies on density of questing ticks. Effective population sizes of Borrelia burgdorferi s.l. were calculated.ResultsLong-term trend analyses indicated that the length of the annual tick questing season increased as well as the surface area of tick-suitable habitats in The Netherlands. The overall abundances of feeding and reproductive hosts also increased. Mathematical analysis of the data from the field studies demonstrated an increase in mean densities/activities of questing ticks, particularly of larvae between 2006 and 2009. No increase in infection rate of ticks with Borrelia burgdorferi sensu lato was found. Population genetic analysis of the collected Borrelia species points to an increase in B. afzelii and B. garinii populations.ConclusionsTogether, these findings indicate an increase in the total number of Borrelia-infected ticks, providing circumstantial evidence for an increase in the risk of acquiring a bite of a tick infected with B. burgdorferi s.l. Due to the high spatiotemporal variation of tick densities/activities, long-term longitudinal studies on population dynamics of I. ricinus are necessary to observe significant trends.

Geographic and Temporal Variations in Population Dynamics ofIxodes ricinusand AssociatedBorreliaInfections in The Netherlands

In a countrywide investigation of the ecological factors that contribute to Lyme borreliosis risk, a longitudinal study on population dynamics of the sheep tick Ixodes ricinus and their infections with Borrelia burgdorferi sensu lato (s.l.) was undertaken at 24 sites in The Netherlands from July 2006 to December 2007. Study sites were mature forests, dune vegetations, or new forests on land reclaimed from the sea. Ticks were sampled monthly and nymphal ticks were investigated for the presence of Borrelia spp. I. ricinus was the only tick species found. Ticks were found in all sites, but with significant spatial and temporal variations in density between sites. Peak densities were found in July and August, with lowest tick numbers collected in December and January. In some sites, questing activities of I. ricinus nymphs and adults were observed in the winter months. Mean monthly Borrelia infections in nymphs varied from 0% to 29.0% (range: 0%-60%), and several sites had significantly higher mean nymphal Borrelia infections than others. Four genospecies of Borrelia burgdorferi s.l. were found, with B. afzelii being dominant at most sites. Borrelia infection rates in nymphal ticks collected in July, September, and November 2006 were significantly higher (23.7%, p<0.01) than those in the corresponding months of 2007 (9.9%). The diversity in Borrelia genospecies between sites was significantly different (p<0.001). Habitat structure (tree cover) was an effective discriminant parameter in the determination of Borrelia infection risk, as measured by the proportion of nymphal ticks infected with B. burgdorferi s.l. Thickness of the litter layer and moss cover were positively related to nymphal and adult tick densities. The study shows that Borrelia-infected ticks are present in many forest and dune areas in The Netherlands and suggests that in such biotopes, which are used for a wide variety of recreational activities, the infection risk is high.

Prevalence of avian-associated Borrelia burgdorferi s.l. genospecies in Ixodes ricinus ticks collected from blackbirds ( Turdus merula) and song thrushes ( T. philomelos)

Between May and September of 2002, forest passerine birds and immature Ixodes ricinus ticks infesting them were surveyed for infection with Borrelia burgdorferi s.l. in a sylvatic habitat in west-central Poland. A total of 738 feeding I. ricinus ticks were recovered from 114 birds belonging to 9 species. The majority of ticks (65.7%) were collected from two thrush species, the blackbird ( Turdus merula) and the song thrush ( T. philomelos). Since only the two Turdus species proved to be parasitized by Borrelia-infected ticks, this study focused mainly on these birds. Immature ticks were removed from 53 of the 54 captured thrushes. A total of 304 partially or fully engorged ticks (110 larvae and 194 nymphs), and 53 bird-derived blood samples were tested for borreliae. B. burgdorferi s.l. DNA was detected by PCR in 11% of the larval ticks and in 7.2% of the nymphs. The PCR-positive ticks were found on 8 of 53 tick-infested thrushes. B. garinii and B. valaisiana accounted for 88.5% and 11.5% of the infections detected in Borrelia-positive ticks, respectively. Only one out of 53 of Turdus blood samples were PCR-positive for borreliae. The blood-positive thrush was infected with B. burgdorferi s.s. B. afzelii was the most frequently identified genospecies in PCR-positive questing I. ricinus ticks, followed by B. valaisiana (89% and 11%, respectively). The absence of B. afzelii infection in ticks feeding on passerine birds, despite its strong predominance in local questing nymph populations, indicates that avian hosts are not reservoirs of this genospecies and consequently that the rodent-adapted B. afzelii is negatively selected in ticks feeding on these hosts. These results validate the concept of some avian-associated genospecies within the B. burgdorferi s.l. complex and demonstrate that thrush species may support the circulation of B. garinii and B. valaisiana under natural conditions.

Phenology of &lt;I&gt;Ixodes ricinus&lt;/I&gt; and Infection with &lt;I&gt;Borrelia burgdorferi&lt;/I&gt; 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.

Abiotic parameters and diel and seasonal activity of Borrelia-infected and uninfected Ixodes persulcatus (Acarina: Ixodidae).

During the 1997 season of Ixodes persulcatus Schulze tick activity, 579 specimens were collected by flagging in the vicinity of St. Petersburg (Morskaja, Lisy Nos). Collections were made from April to July, and at each collection time the following measurements were recorded: light intensity (in lux); temperature of soil 1-1.5 cm below leaf litter, at the soil surface, and in the air 1.5 m above the soil surface; and relative humidity. The gradient between soil at a depth of 1-1.5 cm and soil surface temperatures appeared to be the main physical parameter that initiated tick migration out of the leaf litter. At soil temperature intervals of 5-10 degrees C and 21-26 degrees C, ticks were found only when the soil temperature 1-1.5 cm below the soil surface was colder than at its surface. When temperature ranged from 11 to 20 degrees C, 24% of the ticks were collected when the surface temperature was colder than that below the soil surface. Sixty percent of the ticks, especially nymphs, were collected when the soil surface and subsoil temperature difference ranged from 0 to 2.0 degrees C. The gradient between soil temperature and relative humidity appeared to increase the importance of the gradient between the soil and surface temperature at which time the maximum number of ticks were caught. Borrelia burgdorferi sensu lato infected ticks were collected only after 1100 hours. Prior to and just after 1100 h the mean difference between soil temperatures was 4.7 degrees C, whereas the mean difference between soil and surface temperatures was 6.4 degrees C at this time. The most important factors that influenced the appearance of Borrelia-infected ticks were the temperature gradients that existed between the surface and soil temperatures and the soil and air relative humidity. Greater numbers of infected nymphs were collected when temperature intervals ranged from 10 to 14 degrees C and lower numbers were collected between 15 and 20 degrees C. No Borrelia-infected nymphs were captured when the temperature interval ranged from 21 to 26 degrees C. Infected adults appeared to be more tolerant of higher temperatures than Borrelia-infected nymphs. A significant relationship was found between the activity of Borrelia-infected I. persulcatus and the temperature of the air, soil below the surface, at the soil surface, and relative humidity.

A monoclonal antibody generated by antigen inoculation via tick bite is reactive to the Borrelia burgdorferi Rev protein, a member of the 2.9 gene family locus.

Murine monoclonal antibodies directed against proteins of Borrelia burgdorferi B31 (low passage) were generated by the administration of antigen via the bite of borrelia-infected ticks. This strategy was employed as a mechanism to create antibodies against antigens presented by the natural route of tick transmission versus those presented by inoculation with cultured borreliae. One of the resultant antibodies reacted with a 17-kDa antigen from cultured B. burgdorferi, as seen by immunoblot analysis. This antibody was used to screen a B. burgdorferi genomic DNA lambda vector expression library, and an immunoreactive clone was isolated. DNA sequence analysis of this clone, containing a 2.7-kb insert, revealed several open reading frames. These open reading frames were found to be homologs of genes discovered as a multicopy gene family in the 297 strain of B. burgdorferi by Porcella et al. (S. F. Porcella, T. G. Popova, D. R. Akins, M. Li, J. D. Radolf, and M. V. Norgard, J. Bacteriol. 178:3293-3307, 1996). By selectively subcloning genes found in this insert into an Escherichia coli plasmid expression vector, the observation was made that the rev gene product was the protein reactive with the 17-kDa-specific monoclonal antibody. The rev gene product was found to be expressed in low-passage, but not in high-passage, B. burgdorferi B31. Correspondingly, the rev gene was not present in strain B31 genomic DNA from cultures that had been passaged >50 times. Serum samples from Lyme disease patients demonstrated an antibody response against the Rev protein. The generation of an anti-Rev response in Lyme disease patients, and in mice by tick bite inoculation, provides evidence that the Rev protein is expressed and immunogenic during the course of natural transmission and infection.

Prevalence of Borrelia burgdorferi sensu lato-infected ticks on migrating birds.

The prevalence of Lyme disease Borrelia-infected ticks on migrating birds was studied in Scandinavia. A total of 22,998 birds were caught at eight different bird observatories and examined for ticks. Five different species of ticks were found infesting the birds. The dominant species, Ixodesricinus, constituted 98.3% of the ticks collected. The presence of spirochetes was determined by an immunofluorescence assay of tick larvae and DNA amplification by PCR on all ticks. To determine which Borrelia burgdorferi sensu lato species were present, a species classification was performed by DNA amplification with species-specific 16S rDNA primers and by DNA sequencing (rDNA is DNA coding for rRNA). Flagellin gene sequences of all species of B. burgdorferi sensu lato previously recorded in Europe were observed. Borrelia garinii was the most prevalent Lyme disease Borrelia species in ticks collected from birds arriving from the South or Southeast in the spring, whereas the distribution was more heterogeneous in ticks from birds migrating from the Southwest. These data support the notion that birds are partly responsible for the heterogeneous distribution of Lyme disease Borrelia spirochetes in Europe.