Borrelia burgdorferi sensu lato in the female cement plug of Ixodes persulcatus ticks (Acari,Ixodidae)

Borrelia burgdorferi sensu lato was detected in one out of five cement plugs of female Ixodes persulcatus ticks. The spirochetes were found by dark field microscopy as early as 18 h after attachment of the ticks to the skin of a white mouse. The relevance of this finding is discussed in relation to the epidemiology of Lyme Borreliosis.     

Borrelia burgdorferi sensu lato in ticks (Acari: Ixodidae) from two different foci in Spain

The prevalence of Borrelia burgdorferi sensu lato in several tick species was studied over a 2 year period in two ecologically different areas in Spain. One area was an endemic area for Lyme disease, with a number of autochthonous human cases and supported large populations of Ixodes ricinus on cattle and birds; the second area was characterized by the absence of I. ricinus together with the presence of foxes and their associated tick species. While I. ricinus was the main vector of B. burgdoreri in the endemic area (with a mean prevalence of 14% in adults and 51% in nymphs), adults of both Ixodes canisuga and Ixodes hexagonus had high rates of B. burgdorferi prevalence (30 and 28%, respectively) in the zone where I. ricinus was absent. Immatures of Ixodes frontalis were found to be carriers of the spirochete only in those zones where I. ricinus is present, suggesting evidence for reservoir competence in a tick-bird cycle.     

First report of Anaplasma phagocytophilum and its co-infections with Borrelia burgdorferi sensu lato in Ixodes ricinus ticks (Acari: Ixodidae) from Republic of Moldova

We examined 198 questing Ixodes ricinus ticks collected in Chisinau City, Republic of Moldova by PCR assays for Anaplasma phagocytophilum, Borrelia burgdorferi sensu lato and co-infection of both pathogens, which were detected in 9%, 25.2% and 2.5% of tested ticks, respectively. B. burgdorferi s.l. genotyping revealed the presence of five genospecies with dominance of B. garinii. Our preliminary study provides evidence about occurrence of both pathogens in this populated area, which represent a potential health risk for inhabitants.     

Physiological Age of Field-collected Female Taiga Ticks, Ixodes persulcatus (Acari: Ixodidae), and their Infection with Borrelia burgdorferi Sensu Lato

In some studies the prevalence of tick infection (infection rate) and the intensity of infection are negatively correlated with unfed tick age (in the broad sense of this term). However, no special research has been carried out to consider the phenomenon thoroughly. The infection indices of the female taiga ticks, Ixodes persulcatus, infected with Borrelia burgdorferi s.l. were related to tick physiological age, an index that more precisely reflects tick physiological state than the time of tick collection in the field or the duration of tick survival under laboratory conditions. A novel quantitative technique of physiological age determination based on the evaluation of the ratios between sizes of the stable (scutum) and the changing (alloscutum) structures of the tick body was used. The age was estimated in accordance with the classical age-grade scale introduced by Balashov and a more fractional scale determined by the new technique. In total, 131 female ticks were examined for their infection and physiological age, 46 of which were infected with B. burgdorferi s.l. (mean infection rate 35.1%). The minimal intensity of infection was 0.4 bacterial cells per 100 fields of view whereas the maximal infection was 172 cells. There was no difference between the prevalence of infection in ticks of different physiological age. The intensity of infection obviously differed between ticks of different age groups in the scale introduced by Balashov but did not significantly differ between ticks of different age groups according to the fractional age-grade scale. The data concerning the relationships between Borrelia burgdorferi and unfed Ixodes ticks are considered.     

Ixodes (Pholeoixodes) hexagonus, an efficient vector of Borrelia burgdorferi in the laboratory

Borrelia burgdorferi Johnson et al. was first isolated from the midgut of Ixodes dammini Spielman et al. in the U.S.A. and from the midgut of I.ricinus (L.) in Europe. I.ricinus was considered to be the only tick vector of this borrelia, in Europe, until I.hexagonus Leach, the hedgehog tick, was found to harbour spirochaetes. This paper reports an evaluation of the vector competence of I.hexagonus for the spirochaete B.burgdorferi. Transovarial and trans-stadial survival were demonstrated and the spirochaete was transmitted to laboratory mice via the bites of trans-stadially infected I.hexagonus females.     

Differences in Borrelia infections in adult Ixodes persulcatus and Ixodes ricinus ticks (Acari: Ixodidae) in populations of north-western Russia

Dark-field microscopy was used to determine the number of Borrelia spirochetes in 630 standard preparations obtained from adult ixodid ticks (344 Ixodes persulcatus and 286 I. ricinus) collected in 1989-92 in the Leningrad region of Russia. The average numbers of Borrelia in I. persulcatus and I. ricinus preparations were 34.7 and 23.3 per 100 microscopic fields, respectively. The maximal individual values registered each year for ticks of both species were several hundred times greater than the minimal values. Ticks carrying relatively small numbers of Borrelia generally predominated. Proportions of more heavily infected ticks varied considerably from year to year. These parameters were significantly higher in foci with predominance of I. persulcatus ticks. As a consequence, risk to acquire Lyme borreliosis in such foci is considered greater than in foci where I. ricinus predominates.     

Acquisition of Borrelia burgdorferi by Ixodes ricinus ticks fed on the European hedgehog,Erinaceus europaeus L

A hedgehog, Erinaceus europaeus, was found to be heavily infested with larval and nymphal Ixodes ricinus in a forest park in Co. Galway, Ireland. A large proportion of the ticks that engorged and detached were infected with the spirochacte, Borrelia burgdorferi, the causative agent of human Lyme borreliosis. The identity of these spirochaetes was confirmed by immunofluorescent assay with B. burgdorferi-specific monoclonal antibody and by polymerase chain reaction test and they were transmitted from the hedgehog to laboratory-reared ticks and from the ticks obtained from the hedgehog to gerbils (Meriones unguiculatus). The high infection rate of the larvae that fed on the hedgehog in comparison with unfed larvae from the same habitat was interpreted as strong evidence that this host species is reservoir competent. Since hedgehogs can evidently feed adult ticks as well as many immature stages, they may well have an important role in the ecology of Lyme borreliosis in some habitats.     

Dynamics of Borrelia burgdorferi infection in nymphal Ixodes ricinus ticks during feeding

We report the sequential developmental events of Borrelia burgdorferi in histological sections of Ixodes ricinus nymphs before, during and after feeding. During the blood meal a decrease of approximately 50% in the number of infected ticks was recorded (eight out of 76, 11%) in comparison with the infection rate of unfed ticks (12 out of 56, 21%). Spirochetes were detected in tick salivary glands only after 2 days of attachment. From day 3 until drop-off, the number of infected ticks increased to 31% (15 out of 49). A quadratic logistic regression analysis showed that the variation in the number of infected ticks was significant, but only during the blood meal. The drop in the percentage of infected ticks during the first hours following attachment to the host is explained by our observation of spirochetes in the faeces of the ticks. The increase in the infection rate of replete ticks may be due to an uptake of spirochetes from the host skin at the feeding site.     

Sexual transmission of Borrelia garinii by male Ixodes persulcatus ticks (Acari, Ixodidae)

We investigated the transmission of Borrelia garinii and Borrelia afzelii between male and female Ixodes persulcatus ticks. For this purpose the infection rate of partners from tick couples was determined by polymerase chain reaction and reverse line blot. In couples, where the male tick was infected with B. garinii, four out of nine female partners carried B. garinii. In eight couples, male ticks had a dual infection of B. afzelii and B. garinii and three female partners were infected by Borrelia spirochetes. Two female ticks carried B. garinii, and one female tick had a dual infection. No evidence for transmission of B. afzelii from male to female ticks was found among seven couples. In 45 couples where the female tick was infected, not one male tick carried spirochetes. The difference in the B. garinii infection rate between male and female ticks among these couples is highly significant. Our data suggest that transmission of B. garinii from male ticks to female ticks does occur. Sexual transmission of this pathogen may play an important role in the maintenance of B. garinii in I. persulcatus. © Rapid Science Ltd. 1998     

Infection rates of Borrelia burgdorferi in different instars of Ixodes ricinus ticks from the Dutch North Sea Island of Ameland

Between 1988 and 1993, a total of 7173 I. ricinus ticks, predominantly nymphs, were collected from the vegetation on the Dutch North Sea Island of Ameland. A proportion of the ticks (n=547) was screened for the presence of Borrelia by immunofluorescence. Infection rates of Borrelia varied, in nymphs (n=347) from 13% to 46% and in adults, (n=122) from 20% to 43%. The infection rate in larvae (n=84) collected in 1993 was 21%, showing that transovarial transmission of B. burgdorferi occurs in the I. ricinus population on Ameland. Two tick-naive sheep seroconverted for B. burgdorferi after field-collected adult or nymphal I. ricinus were allowed to feed on them. Larval progeny (n=168) of 15 female adult ticks fed on one of these sheep were free from B. burgdorferi. B. burgdorferi was isolated in culture from field-collected adult ticks. Serotyping using monoclonal antibodies against outer surface proteins A and C indicated that both isolates belonged to genospecies B. garinii, and this was confirmed by DraI restriction analysis of the variable DNA sequence between the 5S and 23S rRNA genes.     

Risk indicators for the tick Ixodes ricinus and Borrelia burgdorferi sensu lato in Sweden

The distributional area of the tick Ixodes ricinus (L.), the primary European vector to humans of Lyme borreliosis spirochaetes (Borrelia burgdorferi sensu lato) and tick‐borne encephalitis virus, appears to be increasing in Sweden. It is therefore important to determine which environmental factors are most useful to assess risk of human exposure to this tick and its associated pathogens. The geographical distribution of I. ricinus in Sweden was analysed with respect to vegetation zones and climate. The northern limit of I. ricinus and B. burgdorferi s.l. in Sweden corresponds roughly to the northern limit of the southern boreal vegetation zone, and is characterized climatically by snow cover for a mean duration of 150 days and a vegetation period averaging 170 days. The zoogeographical distribution of I. ricinus in Sweden can be classified as southerly–central, with the centre of the distribution south of the Limes Norrlandicus. Ixodes ricinus nymphs from 13 localities in different parts of Sweden were examined for the presence of B. burgdorferi s.l. and found to be infected with Borrelia afzelii and Borrelia garinii. Tick sampling localities were characterized on the basis of the density of Borrelia‐infected I. ricinus nymphs, presence of specific mammals, dominant vegetation and climate. Densities of I. ricinus nymphs and Borrelia‐infected nymphs were significantly correlated, and nymphal density can thus serve as a general indicator of risk for exposure to Lyme borreliosis spirochaetes. Analysis of data from this and other studies suggests that high densities of Borrelia‐infected nymphs typically occur in coastal, broadleaf vegetation and in mixed deciduous/spruce vegetation in southern Sweden. Ixodes ricinus populations consistently infected with B. burgdorferi s.l. can occur in: (a) biotopes with shrews, rodents, hares and birds; (b) biotopes with shrews, rodents, hares, deer and birds, and (c) island locations where the varying hare (Lepus timidus) is the only mammalian tick host.     

Questing behaviour of Ixodes ricinus ticks (Acari: Ixodidae)

The vertical distribution in the vegetation of questing Ixodes ricinus ticks was investigated in two different vegetation types (high and low vegetation) at two localities in south-central Sweden during 1992-1993 (Toro) and 1995 (Bogesund). Significant correlations were found between the vertical distribution of immature ticks and the height of the vegetation. The greatest mean availabilities of the larvae and nymphs in low vegetation were in the intervals 0-9 and 30-39 cm, respectively. The larval numbers were greatest close to the ground (0-29 cm) in both high and low vegetation. The larval : nymphal ratio, at ground level at localities free of ground vegetation, varied between 8 : 1 and 32 : 1. In high vegetation, the greatest mean numbers of nymphal and adult ticks were at height intervals of 50-59 and 60-79 cm, respectively. These ranges are within the estimated height interval (40-100 cm) of the main part of the body surface of their preferred host, the roe deer (Capreolus capreolus). The presence of most questing I. ricinus larvae at ground level would favour the transmission of Borrelia burgdorferi s.l., since this is where the highly reservoir-competent rodents and shrews usually occur.     

Detection of Lyme disease spirochete,Borrelia burgdorferi sensu lato,including three novel genotypes in ticks (Acari: Ixodidae) collected from songbirds (Passeriformes) across Canada

Lyme disease is reported across Canada, but pinpointing the source of infection has been problematic. In this three‐year, bird‐tick‐pathogen study (2004–2006), 366 ticks representing 12 species were collected from 151 songbirds (31 passerine species/subspecies) at 16 locations Canada‐wide. Of the 167 ticks/pools tested, 19 (11.4%) were infected with Borrelia burgdorferi sensu lato (s.l.). Sequencing of the rrf‐rrl intergenic spacer gene revealed four Borrelia genotypes: B. burgdorferi sensu stricto (s.s.) and three novel genotypes (BC genotype 1, BC genotype 2, BC genotype 3). All four genotypes were detected in spirochete‐infected Ixodes auritulus (females, nymphs, larvae) suggesting this tick species is a vector for B. burgdorferi s.l. We provide first‐time records for: ticks in the Yukon (north of 60° latitude), northernmost collection of Amblyomma americanum in North America, and Amblyomma imitator in Canada. First reports of bird‐derived ticks infected with B. burgdorferi s.l. include: live culture of spirochetes from Ixodes pacificus (nymph) plus detection in I. auritulus nymphs, Ixodes scapularis in New Brunswick, and an I. scapularis larva in Canada. We provide the first account of B. burgdorferi s. l. in an Ixodes muris tick collected from a songbird anywhere. Congruent with previous data for the American Robin, we suggest that the Common Yellowthroat, Golden‐crowned Sparrow, Song Sparrow, and Swainson's Thrush are reservoir‐competent hosts. Song Sparrows, the predominant hosts, were parasitized by I. auritulus harboring all four Borrelia genotypes. Our results show that songbirds import B. burgdorferi s.l.‐infected ticks into Canada. Bird‐feeding I. scapularis subadults were infected with Lyme spirochetes during both spring and fall migration in eastern Canada. Because songbirds disperse millions of infected ticks across Canada, people and domestic animals contract Lyme disease outside of the known and expected range.     

Development of the salivary glands in embryos of Ixodes ricinus (Acari: Ixodidae)

We examined Ixodes ricinus embryos between 18 and 28 days of development with light, scanning and transmission electron microscopy. The differences in inner structure attested to establish three successive developmental stages: days 18–20, day 23, and days 26–28. Between 18 and 20 days the embryos are at early stages of organogenesis. Salivary glands cannot be identified at that stage. In 23-day-old embryos salivary glands are already outlined but the structure of alveoles is still different from that in larvae in which the embryonic development has been completed. Gland cells start to form alveoles and become active between 26 and 28 days of the development. This revised version was published online in July 2006 with corrections to the Cover Date.     

Interstadial and Infestation Level-dependent Variation in the Transmission Efficiency of Borrelia Burgdorferi from Mice to Ixodes Ricinus Ticks

The efficiency with which the spirochaete Borrelia burgdorferi sensu stricto was transmitted from laboratory mice to larval and nymphal Ixodes ricinus ticks was assessed, using the polymerase chain reaction. The transmission efficiency to nymphs was significantly greater than to larvae when both fed together on the same host. Increased tick infestation levels of mice were correlated with significantly greater engorgement weights and higher B. burgdorferi transmission coefficients from mice to nymphs. These observations indicate that both the feeding success of ticks and the transmission coefficients from host to tick may be influenced by the tick infestation level of an infected host. The infestation level and the relative numbers of each life stage of the tick are factors which should be considered in the design of transmission experiments.     

Densities of Ixodes ricinus ticks (Acari: Ixodidae) on moorland vegetation communities in the UK

Unfed (questing) Ixodes ricinus ticks were collected by blanket dragging on a monthly basis from heather-dominated, Vaccinium-dominated and bracken-dominated vegetation communities from two different biogeographical regions of the UK (the Quantock Hills in Somerset, south west England and the North York Moors, north east England) throughout the spring and summer months of 1991 and 1992. Eighteen sites were monitored across the two regions and a total of 1920 blanket drags were carried out. Vaccinium sites showed high tick densities at all life stages, as did bracken sites. Significantly lower numbers of larval and nymphal ticks per drag were collected on heather sites than were collected on either Vaccinium (bilberry/whortleberry) or bracken sites, while similar numbers of adult ticks per drag were collected from each of the three vegetation communities. There was no significant difference between the mean numbers of any tick life stage collected on the Quantock Hills and those collected on the North York Moors on these vegetation communities or between the mean numbers of any tick life stage collected in 1991 and those collected in 1992 on these vegetation communities.     

Coinfection with Borrelia burgdorferi sensu stricto and Borrelia garinii alters the course of murine Lyme borreliosis

Ixodes ricinus ticks and mice can be infected with both Borrelia burgdorferi sensu stricto and Borrelia garinii. The effect of coinfection with these two Borrelia species on the development of murine Lyme borreliosis is unknown. Therefore, we investigated whether coinfection with the nonarthritogenic B. garinii strain PBi and the arthritogenic B. burgdorferi sensu stricto strain B31 alters murine Lyme borreliosis. Mice simultaneously infected with PBi and B31 showed significantly more paw swelling and arthritis, long-standing spirochetemia, and higher numbers of B31 spirochetes than did mice infected with B31 alone. However, the number of PBi spirochetes was significantly lower in coinfected mice than in mice infected with PBi alone. In conclusion, simultaneous infection with B. garinii and B. burgdorferi sensu stricto results in more severe Lyme borreliosis. Moreover, we suggest that competition of the two Borrelia species within the reservoir host could have led to preferential maintenance, and a rising prevalence, of B. burgdorferi sensu stricto in European I. ricinus populations.     

Invasion of human neuronal and glial cells by an infectious strain of Borrelia burgdorferi

Human infection by Borrelia burgdorferi, the etiological agent for Lyme disease, can result in serious acute and late-term disorders including neuroborreliosis, a degenerative condition of the peripheral and central nervous systems. To examine the mechanisms involved in the cellular pathogenesis of neuroborreliosis, we investigated the ability of B. burgdorferi to attach to and/or invade a panel of human neuroglial and cortical neuronal cells. In all neural cells tested, we observed B. burgdorferi in association with the cell by confocal microscopy. Further analysis by differential immunofluorescent staining of external and internal organisms, and a gentamicin protection assay demonstrated an intracellular localization of B. burgdorferi. A non-infectious strain of B. burgdorferi was attenuated in its ability to associate with these neural cells, suggesting that a specific borrelial factor related to cellular infectivity was responsible for the association. Cytopathic effects were not observed following infection of these cell lines with B. burgdorferi, and internalized spirochetes were found to be viable. Invasion of neural cells by B. burgdorferi provides a putative mechanism for the organism to avoid the host's immune response while potentially causing functional damage to neural cells during infection of the CNS.     

The role of fat dormouse (Glis glis L.) as reservoir host for spirochete Borrelia burgdorferi sensu lato in the region of Gorski Kotar, Croatia

To determine whether some of the B. burgdorferi sensu lato genospecies associate with fat dormouse as a reservoir host, we investigated the prevalence of infection in questing animals. A total of 45 adult fat dormice (30 female and 15 male) were captured by hunters during their hunting season in the region of Gorski Kotar, Croatia. Dead animals were aseptically dissected, and the urinary bladder tissue was used for isolation attempt and for deoxyribonucleic acid (DNA) extraction. Out of 45 DNA samples extracted from urine bladder tissue, we found four (8.88%) to be polymerase chain reaction (PCR) positive. The RFLP analysis of the PCR product after cleavage with DraI and MseI distinguished between the three major genospecies: B. burgdorferi sensu stricto, B. garinii and B. afzelii. All positive samples were typed as B. afzelii with a unique DraI or MseI pattern. The results of the analysis of urinary bladder tissue samples culture for the presence of Borrelia were negative. Results showed that a prevalence of the Borrelia infection among population of fat dormice indicated their epizootiological involvement as a reservoir of Borrelia spirochetes. Furthermore, this work is an initial step in the investigation of the molecular epidemiology/epizootiology of Lyme borreliosis in Croatia.     

The spatial distribution of Borrelia burgdorferi-infected Ixodes ricinus in the Connemara region of County Galway,Ireland

Studies were carried out in the Connemara area of County Galway in the west of Ireland in order to determine the abundance and distribution of the tick, Ixodes ricinus and the prevalence of its infection with Borrelia burgdorferi. The tick was very abundant locally, in particular when associated with cattle, sheep and enclosed red deer. Large numbers of ticks not only occurred on the pastures, but also on adjacent roadside verges. No infections with B. burgdorferi could be demonstrated when nymphal ticks were sampled from central areas of the pastures, suggesting that livestock and red deer are probably not significant reservoirs of the spirochaete. Small numbers of infected nymphal and adult ticks were associated with hedges, dry stone walls, the margins of woodland adjoining infested pastures and in woodland from which livestock were excluded. Woodmice (Apodemus sylvaticus) were most numerous in such habitats and the majority were infected with B. burgdorferi.