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PubMed2006

Determining the tick scutal index allows assessment of tick feeding duration and estimation of infection risk with Borrelia burgdorferi sensu lato in a person bitten by an Ixodes ricinus nymph.

The risk of Borrelia burgdorferi sensu lato transmission from an infected vector tick to a host increases with increasing duration of tick feeding. In Ixodes ricinus nymphs, the main vector of B. burgdorferi s.l. in most parts of Europe, the transmission risk appears low to moderate within the first 24h of feeding but increases to >70% after only 36 h. In this study, the so-called scutal index, the ratio between tick abdominal length and scutum width, a very good measure of the level of tick engorgement, was investigated for its potential to assess the feeding duration of detached I. ricinus nymphs, thereby indicating the level of human infection risk with B. burgdorferi s.l. I. ricinus nymphs were allowed to feed in capsules on tick-naive Mongolian gerbils for 0, 12, 24, 36 h, or to repletion, in groups of up to 9 individuals. After tick removal, the scutal index of each tick (n=516) was determined using a stereomicroscope with an ocular micrometer. This was also possible, if the tick mouthparts were damaged. Although the scutal indices determined at 24 h versus 36 h post-attachment (a critical interval for B. burgdorferi transmission) differ significantly, there was some overlap between the two groups. However, by choosing a scutal index of 1.1 as a cut-off, it was possible to assign 93.2% of the ticks attached for 24h (n=310) to one group (low-risk group ticks) and 85.6% of those attached for 36 h (n=97) to the other (high-risk group ticks). This means that those people from whom I. ricinus nymphs with a scutal index >1.1 detached have a distinctly elevated risk of Borrelia infection and therefore more likely require medical attention.

Animals↗
PubMed2006

The paralogous salivary anti-complement proteins IRAC I and IRAC II encoded by Ixodes ricinus ticks have broad and complementary inhibitory activities against the complement of different host species.

Several observations suggest that inhibition of the host complement alternative pathway by Ixodes tick saliva is crucial to achieve blood feeding. We recently described two paralogous anti-complement proteins called Ixodes ricinus anti-complement (IRAC) proteins I and II co-expressed in I. ricinus salivary glands. Phylogenetic analyses suggested that these sequences were diversifying by a process of positive Darwinian selection, possibly leading to molecules with different biological properties. In the present study, we tested the hypothesis that each paralogue may have different inhibitory activities against the complement of different natural host species, thereby contributing to broaden the host range of I. ricinus ticks. IRAC I and IRAC II were tested against the complement of eight I. ricinus natural host species (six mammals and two birds). The results demonstrate that IRAC I and IRAC II have broad and complementary inhibition activities against the complement of different host species. This report is the first description of paralogous anti-complement molecules encoded by a pathogen with broad and complementary inhibitory activities against the complement of different host species.

Animals↗
PubMed2005

Spatial distribution of Dermacentor reticulatus and Ixodes ricinus in Hungary: evidence for change?

A survey was conducted to investigate the spatial distribution of Ixodes ricinus and Dermacentor reticulatus in Hungary and to compare these data with the results of a previous large-scale survey. In the survey conducted in the 1950s, D. reticulatus adults were detected in two isolated areas of two counties, and the presence of these ticks in the collection was explained by accidental introduction. In the present survey, D. reticulatus became the second most common species occurring in all 16 counties involved in the monitoring and showed high prevalence. The change in the spatial distribution of this tick species, the increase of incidence of Babesia canis infection in Hungary, and the increasing number of canine babesiosis case reports from other Central and Central Eastern European countries since the 1970s suggest an expansion of the geographic range of D. reticulatus and intensification of the transmission rate of B. canis and probably other D. reticulatus-borne diseases (e.g. tularemia and tick-borne lymphadenopathy) in the region. The spatial distribution of I. ricinus was roughly in line with the results of the earlier survey. I. ricinus was the most common tick species being present in all 16 counties with the highest prevalence. Nevertheless, the comparison of the data of the previous and current survey cannot be used for fine-scale analysis; thus, it cannot be dismissed that the spatial distribution of I. ricinus also changed during the past decades. The spatial distribution patterns of tick-borne encephalitis in Hungary and other Central Eastern European countries may indicate such a change.

Animals↗
PubMed1997

Cold hardiness, supercooling ability and causes of low-temperature mortality in the soft tick, Argas reflexus, and the hard tick, Ixodes ricinus (Acari: Ixodoidea) from Central Europe.

Seasonal supercooling points (SCPs=temperature of crystallization) and cold hardiness were investigated in the indigenous hard tick, I. ricinus, and in A. reflexus, a soft tick introduced to Central Europe from the South. Both species proved to be freeze-susceptible as well as highly susceptible to inoculative freezing. None of the postembryonic developmental stages of either species showed any distinct seasonal pattern of SCP. Unexpectedly, the introduced A. reflexus exhibited a distinctly higher degree of cold hardiness in terms of lower lethal temperature (LT(50): 24h exposure) as well as lethal time (T(50): time of survival at -10.1 degrees C) than I. ricinus. Engorged I. ricinus larvae as well as engorged summer acclimatized A. reflexus larvae showed some mortality at temperatures well above the SCP. This mortality was generally expressed as a failure of the following stage to eclose properly. A 10-day cold acclimation at +3 degrees C eliminated that kind of mortality in summer acclimatized A. reflexus larvae, but not in I. ricinus larvae. It was frequently observed that freezing of ticks resulted-possibly via leakage from the midgut-in a subsequent reddish brown discoloration of the ticks after thawing. Taking into account that discoloration was an indication of previous freezing, it was concluded, that after long-term exposure (for >/=30 days) at -10.1 degrees C, a temperature well above the SCP, some tick mortality could be observed that was not caused by previous freezing. Weighing experiments clearly demonstrated, that the level of dehydration was not critical for survival of A. reflexus during long-term cold exposure, even at low RH. This indicates, that cold-related factors other than freezing and dehydration were detrimental to this species.

Journal Article↗
PubMed1998

Ixodes ricinus strains in Europe.

An analysis of cuticular hydrocarbons (CH) of unfed adult Ixodes ricinus ticks collected throughout Europe showed that there are 10 distinct I. ricinus groups. Studies on the seasonal and annual consistency of CH composition and possible effects of host and environmental factors suggested that CHs may be used as a genuine genetic marker for I. ricinus. Preliminary studies compared the vector competence of ticks from three of the most separated I. ricinus groups and the results suggested that there may be significant differences in tick susceptibility to Borrelia afzelii.

Animals↗
PubMed2001

Risk factors in habitats of the tick Ixodes ricinus influencing human exposure to Ehrlichia phagocytophila bacteria.

Ixodes ricinus L. (Acari: Ixodida) were sampled during 1996-99 in southern Scotland, on vegetation using cloth drags, on humans by removal from clothing and on roe deer (Capreolus capreolus L.) by searching legs of culled deer. Developmental microclimate was recorded by automatic recorders and questing microclimate by portable instruments during tick collections. Ticks and deer were examined for infection with Ehrlichia phagocytophila bacteria (Rickettsiales) using microscopy and polymerase chain reaction. This pathogen causes tick-borne fever of sheep in Europe and human granulocytic ehrlichiosis in North America, but in Europe human clinical ehrlichiosis due to E. phagocytophila has not been recorded despite serological evidence of exposure. Among three types of habitat, coniferous woodland was most infested with questing ticks (560 ticks/km of drag; mean numbers collected on long trousers: 24.3 larvae, 13.5 nymphs and 0.8 adult ticks/km walked), deciduous woodland had slightly lower infestation (426 ticks/km drag) and upland sheep pasture had much lower infestation (220 ticks/km drag). Of the three main vegetation types, bracken was least infested (360 ticks/km drag), ericas most (430 ticks/km drag) and grassland had intermediate infestation density (413 ticks/km drag). Questing and developmental microclimates were poor predictors of exposure within these habitats, except lower infestation of pastures was attributed to greater illumination there. Collectors who walked a total of 300 km through all habitats (taking 360 h in all seasons), wearing cotton trousers hanging outside rubber boots, were bitten by only four nymphs and 11 larvae of I. ricinus (but no adult ticks). There was a negative correlation between densities of deer and ticks collected, although presence of deer remains a major indicator of exposure. The proportion of infected ticks was fairly uniform at four sites studied. Overall prevalence of E. phagocytophila in I. ricinus was 3.3% in nymphs (40/1203) but only approximately 1.5% in adults of both sexes (although males do not bite). It was estimated that nymphs of I. ricinus gave 4.4% probability of one infected bite/person/year (for occupational exposure during this research) due to presence in all seasons and habitats, their human biting rate of 0.011 nymphs/h or 0.013 nymphs/km and widespread infection with E. phagocytophila. The frequency distribution of intensity of infection in ticks was approximately normal (mean 98 morulae/nymph infected), thus there is a high risk of receiving a high dose from any one infected tick bite.

Animals↗
PubMed2006

Sympatric Ixodes trianguliceps and Ixodes ricinus ticks feeding on field voles (Microtus agrestis): potential for increased risk of Anaplasma phagocytophilum in the United Kingdom?

The importance of wild rodents as reservoirs of zoonotic tick-borne pathogens is considered low in the United Kingdom because, in studies to date, those parasitized by exophilic Ixodes ricinus ticks carry almost exclusively larvae and thus have a minor role in transmission cycles. In a cross-sectional study, 11 (6.7%) of 163 field voles (Microtus agrestis) captured at field sites in Northern England were PCR-positive for Anaplasma phagocytophilum. The voles were found to act as hosts for both larval and nymphal I. ricinus and all stages of the nidicolous tick I. trianguliceps, and eight individuals were infested with ticks of both species at the same time. Two of 158 larval and one of 13 nymphal I. ricinus, as well as one of 14 larval and one of 15 nymphal I. trianguliceps collected from the rodents were PCR-positive. These findings suggest that habitats where field voles are abundant in the United Kingdom may pose a risk of A. phagocytophilum infection because (i) field voles, the most abundant terrestrial mammal in the United Kingdom, may be a competent reservoir; (ii) the field voles are hosts for both nymphal and larval ixodid ticks so they could support endemic cycles of A. phagocytophilum; and (iii) they are hosts for nidicolous I. trianguliceps, which may alone maintain endemic cycles, and exophilic I. ricinus ticks, which could act as a bridge vector and transmit infections to humans and domesticated animals.

Anaplasma phagocytophilum↗
PubMed1996

Lyme borreliosis spirochetes in Ixodes ricinus (Acari:Ixodidae) and the varying hare on isolated islands in the Baltic, Sea.

We investigated isolated ecosystems to determine if Lyme borreliosis is maintained in the absence of reservoir-competent small mammals. Human cases of Lyme disease have been reported on the isolated islands of Gotska Sandön and Stora Karlsö in the Baltic Sea. The varying hare, Lepus timidus, is the only terrestrial vertebrate species capable of serving as a host for all stages of Ixodes ricinus (L.) on these islands. In August, mean larval infestation on 5 hares from each island was 548 with a maximum of 2,276 larvae on 1 hare. Smaller numbers of nymphal and female ticks were also engorging on the hares. During August-September, B. burgdorferi s.l. was detected in 11-24% of nymphal I. ricinus fed as larvae on hares and in 8-19% of host-seeking nymphal I. ricinus collected from the vegetation. We conclude that L. timidus serves as a maintenance host for B. burgdorferi s.l. and its vector, I. ricinus, on both islands.

Animals↗
PubMed1996

Borreliae in immature Ixodes ricinus (Acari:Ixodidae) ticks parasitizing birds in the Czech Republic.

Of 411 forest birds of 33 species examined near Valtice, Czech Republic, 29% were infested with Ixodes ricinus (L.); 2.2% were parasitized by Haemaphysalis concinna Koch. Borreliae were detected in 5.1 and 11.7% of larval and nymphal I. ricinus, respectively. None of the 13 H. concinna tested was infected. In total, 3.2% of the birds examined were parasitized by I. ricinus immatures infected by borreliae. Borreliae-containing ticks parasitized European robin, Erithacus rubecula (L.); Eurasian blackbird, Turdus merula L.; Blackcap, Sylvia atricapilla (L.); Eurasian chiffchaff, Phylloscopus collybita (Vieillot); Great tit, Parus major L.; and Eurasian jay, Garrulus glandarius (L.). The isolate BR-34 from a nymphal I. ricinus off a Eurasian blackbird had a sodium dodecyl sulfate-polyacrylamide gel electrophoresis protein pattern, reactions to monoclonal antibodies, and fragments of HindIII digested DNA probed with fla and ospA genes that suggested to us that it belongs to the genospecies Borrelia garinii. Free-living birds may be involved in the circulation of B. burgdorferi sensu lato principally as disseminators of infected ixodid ticks to new area.

Animals↗
PubMed2005

Borrelia burgdorferi sensu lato infection in larval Ixodes ricinus (Acari: Ixodidae) feeding on blackbirds in northwestern Italy.

Birds belonging to 59 species (n = 1,206) were live captured in Piemonte, northwestern Italy, in 2001. Ixodes ricinus (L.) larvae were collected from 59 birds belonging to nine species, and nymphs were recovered on 79 birds belonging to 10 species. Eurasian blackbirds, Turdus merula L., had significantly higher levels of infestation by ticks than other passerine species. Larval I. ricinus of blackbirds peaked in summer, when prevalence was 39% (95% confidence interval 24.2-55.5) and mean number of ticks per host was 3.3 (1.6-7.2), whereas nymphs peaked in spring, when prevalence was 72.2% (54.8-85.8) and mean number of ticks per host was 6.9 (4.4-10.7). Immature I. ricinus were coincidentally aggregated on blackbirds, with 15 blackbirds feeding 67.4% of nymphs and 40.3% of larvae, and coinfestation by both stages was relatively high in summer: Kappa = 0.64 (0.40-0.88). Borrelia burgdorferi sensu lato was identified by polymerase chain reaction (PCR) in 58.3% (35.9-78.5) of larvae with engorgement ratio > or = 3 that were collected from blackbirds. Larvae that were collected from other passerine species gave negative PCR results. Sixteen of 21 PCR-positive samples belonged to B. garinii (76.2%), and five (23.8%) were Borrelia valaisiana. Results of this study suggest that blackbirds play an important role as hosts for immature I. ricinus and as reservoir of Borrelia garinii in northwestern Italy.

Animals↗
PubMed2003

Darkness induces mobility, and saturation deficit limits questing duration, in the tick Ixodes ricinus.

The behaviour of Ixodes ricinus nymphs was recorded in 10-day experiments using computer-assisted video-tracking, in the absence of any host stimuli. These ticks switch spontaneously from questing in a desiccating atmosphere to quiescence in a water-saturated atmosphere after dark. Quantification of both questing and quiescence duration demonstrates that questing duration is inversely related to saturation deficit whereas quiescence duration is not. Distance walked after quiescence increased with desiccating conditions, while the distance walked after questing remained unchanged. Almost all locomotor activities of I. ricinus occurred during darkness under either a 14 h:10 h L:D or a 8 h:4 h L:D cycle. We established that all life stages of I. ricinus are equipped to sense shifts in light intensity with bilaterally placed strings of photoreceptors. This permits I. ricinus to use onset of darkness to trigger mobility when desiccation risk is reduced in nature.

Animals↗
PubMed2000

Peculiarities of behaviour of taiga (Ixodes persulcatus) and sheep (Ixodes ricinus) ticks (Acarina: Ixodidae) determined by different methods.

A comparison of the behavioural peculiarities of Ixodes persulcatus Schulze, 1930 (north-western population, Russia) and Ixodes ricinus (L., 1758) from western Russia and Denmark was determined by using two methods. Method 1 involved a sojourn of ticks on vertical plastic sticks and showed that the questing behaviour of I. ricinus nymphs was dependent on temperature and relative humidity (RH). A significantly greater number of nymphs quested at 22 degrees C and 100% RH than at 18 degrees C. When the humidity was reduced to 30% all of the nymphs departed. In the second method, the activity of ticks on an inclined "ticksdrome" was estimated. The activity of I. ricinus adults from the Danish population was 1.2 times greater than that of ticks from Russia. Females of the species studied and specimens from all study areas were more active than all other stages of development. The locomotor activity of both adult and immature I. ricinus that were infected with Borrelia burgdorferi sensu lato was suppressed when compared with uninfected specimens. The locomotor activity of I. persulcatus females infected by borreliae with exoskeleton anomalies was 1.3 times greater (P<0.05) than that of infected ticks without anomalies. Our data showed that infected females with exoskeleton anomalies could crawl faster on a human and reach uncovered parts of the body that are vulnerable for attachment and feeding. A study of locomotor activity and questing behaviour may be useful for comparing the risk for different tick species and populations to transmit tick-borne pathogens.

Animals↗
PubMed2006

Borrelia lusitaniae and spotted fever group rickettsiae in Ixodes ricinus (Acari: Ixodidae) in Tuscany, central Italy.

Prevalence of infection by Borrelia burgdorferi s.l. and spotted fever group (SFG) rickettsiae was estimated in host-seeking ticks in an area in Tuscany, central Italy, where Lyme borreliosis was reported in a forestry worker. B. burgdorferi s.l. was identified by polymerase chain reaction in 16.7% (95% CI = 10.3, 24.8) of Ixodes ricinus (L.) nymphs and 39.6% (95% CI = 26.5, 54.0) of adults. Borrelia lusitaniae accounted for 82.9% of positive samples, followed by Borrelia garinii (9.8%), Borrelia afzelii (2.4%), and Borrelia burgdorferi s.s. (2.4%). One Rhipicephalus spp. adult was infected with B. garinii (prevalence = 8.3%; 95% CI = 0.21, 38.5). Prevalence of infection by SFG rickettsiae was 38.5% (95% CI = 26.7, 51.4) in I. ricinus nymphs, 34.6% (95% CI = 22.0, 49.1) in I. ricinus adults, and 50% (95% CI = 21.1, 78.9) in Rhipicephalus spp. adults. Phylogenetic analysis showed the similarity of B. lusitaniae strains that were identified in this study and of a strain that was previously isolated from a human patient in Portugal. Results of this study confirm the dominance of B. lusitaniae in areas in the Mediterranean basin and the infection by SFG rickettsiae in I. ricinus.

Animals↗
PubMed1991

Hosts on which nymphal Ixodes ricinus most abundantly feed.

To identify hosts that may serve as European reservoirs for the agent of Lyme disease, Borrelia burgdorferi, we determined whether nymphal Ixodes ricinus feed mainly on particular mice (Apodemus flavicollis or A. agrarius), voles (Clethrionomys glareolus) or on sand lizards (Lacerta agilis) and whether the abundance of these hosts corresponds to the seasonal activity of the subadult stages of the vector tick. In all sites, the mice appeared most heavily infested by larvae; at least seven parasitized each mouse, about three per vole and four per lizard. Many fewer nymphal I. ricinus parasitized A. flavicollis and C. glareolus than did larvae. Although more than 30 times as many larval than nymphal ticks parasitized the two most abundant hosts (C. glareolus and A. flavicollis), about 15 times as many fed on A. agrarius and twice as many on lizards. Nymphal and larval ticks fed on rodents at about the same time. Lizards were most abundantly parasitized by nymphs somewhat earlier than by larvae. Early in the season of transmission of Lyme disease, virtually all A. agrarius as well as lizards were potentially exposed to spirochetes borne by nymphal I. ricinus. We concluded that larval and nymphal I. ricinus differentially parasitize different hosts. Because so many of these nymphs feed on them, A. agrarius may more effectively serve as reservoirs for the agent of Lyme disease than do other putative reservoir hosts. The presence of lizards may inhibit transmission.

Animals↗
PubMedDate not supplied

[Experience in the study of the peculiarities of the distribution of the tick Ixodes ricinus in a large territory].

Attempts were undertaken to study the character of the distribution of I. ricinus over a large territory. Methodic principles of the land survey of arthropods distribution and laboratory processing of its results, that were used before for I. persulcatus, were found to be quite suitable for I. ricinus. It was established that hungry adults of I. ricinus have at least three types of the distribution throughout the forests of Lithuania. Types of the distribution can be ascertained by the results of the record of I. ricinus nymphs with a flag.

Animals↗
PubMedDate not supplied

[Study of characteristics of distribution of the tick Ixodes ricinus over a large territory].

Attempts were undertaken to study the character of the distribution of I. ricinus over a large territory. Methodic principles of the land survey of arthropods distribution and laboratory processing of its results, that were used before for I. persulcatus, were found to be quite suitable for I. ricinus. It was established that hungry adults of I. ricinus have at least three types of the distribution throughout the forests of Lithuania. Types of the distribution can be ascertained by the results of the record of I. ricinus nymphs with a flag.

Animals↗
PubMed2004

Prevalence of Borrelia burgdorferi sensu lato genospecies in host-seeking Ixodes ricinus ticks in selected South Bohemian locations (Czech Republic).

In selected localities of Ceské Budĕjovice and Ceský, Krumlov districts, well known by stable high incidence of tick-borne encephalitis (TBE) human cases but with low incidence of Lyme borreliosis, monitoring of Borrelia burgdorferi sensu lato (s.l.) in Ixodes ricinus ticks was performed. Research was also aimed at the spread of I. ricinus to mountain areas of this region (National Park Sumava), as well as at investigating this tick for B. burgdorferi s.l. genospecies and TBE virus infection. Altogether 498 nymphs, 88 females and 11 males of I. ricinus from lower locations and 58 nymphs from mountain locations (760-1080 m above sea level) were tested by polymerase chain reaction. In lower locations total prevalence of Borrelia burgdorferi s.l. in Ixodes ricinus ticks was 35%. Single infection of Borrelia afzelii, B. garinii and B. burgdorferi sensu stricto (s.s.) was found in 59, 50 and 63 ticks, respectively (i.e. in 12.8, 11.2 and 14.1%). Double infection was found in 42 ticks (6.0%) and triple infection in three ticks (0.4%). The high frequency of B. burgdorferi s.s. exceeds the as yet reported occurrence in Central Europe. These circumstances are discussed. In mountain locations B. afzelii was found in five ticks, that including two co-infection with B. garinii, in elevations of 762 m and 1024 m above sea level, respectively. This fact signals a real danger of human infections in a region that was previously deemed to be without risk. Moreover, this region is more and more the target destination of tourist activities. The results also suggest that the penetration of infection can be rapid and formation and establishment of natural focus of Lyme borreliosis might be rather quick.

Animals↗
PubMed2004

[Participation of Ixodes ricinus developmental stages in transmission of Anaplasma (Ehrlichia) phagocytophila].

The present study constitutes a survey on the prevalence of human granulocytic ehrlichiosis agent, Anaplasma (Ehrlichia) phagocytophila, infecting ticks, Ixodes ricinus. I. ricinus were collected in the spring and autumn of the years 2000-2002 in western Pomerania (Poland), on vegetation using cloth drags. In all, 3340 individuals of I. ricinus were collected from the sampling sites. This total comprised of 511 females, 525 males, and 1998 nymphs. The prevalence of this pathogen in ticks was assessed using the PCR technique (a fragment of 16S rDNA gene amplified with EHR 521 and EHR 747 primers). The overall prevalence of A. phagocytophila in I. ricinus was 3 % in adults but only 1.6% in nymphs.

Anaplasma phagocytophilum↗