Influence of selected meteorological variables on the questing activity of Ixodes ricinus ticks in Lower Silesia,SW Poland

The relationship between climate data and tick questing activity is crucial for estimation of the spatial and temporal distribution of the risk of ticks and tick‐borne diseases. This study establishes correlations between selected meteorological variables provided by the Weather Research and Forecasting model (WRF) and the questing activity of Ixodes ricinus nymphs and adults on a regional scale across Lower Silesia, Poland. Application of Generalized Linear Mixed Models (GLMM), built separately for adults and nymphs, showed that solar radiation, air temperature, and saturation deficit appeared to be the meteorological variables of prime importance, whereas the wind speed was less important. However, the effect of meteorological parameters was different for adults and nymphs. The adults are also more influenced by forest cover and the percentage of forest type if compared to nymphs. The WRF model providing meteorological variables separately for each location and day of tick sampling can be useful in studies of questing activity of ticks on a regional scale.     

Models of temporal variation in questing activity in individuals of Ixodes recinus (Acari: Ixodidae)

Intensive observations of the questing activity of Ixodes ricinus ticks in the field were made to provide data on the range of durations of periods of continuous questing activity, and of the variation in questing activity between individuals. Continuous periods of questing were observed to extend to a maximum of 28 hours. Substantial variation in questing activity between individuals was observed. Models fitted to the distribution of durations of bouts of questing activity provide insights into the questing ecology of I. ricinus. Results suggest that questing duration may not be solely dependent on the state of hydration of the tick. A function fitted to the frequency distribution of the proportions of active life that individuals spend on questing, provides an empirically-based model that can be used to generate a stochastic expression of variation of questing activity in individuals in a questing population.     

Activity periods and questing behavior of the seabird tick Ixodes uriae (Acari: Ixodidae) on Gull Island, Newfoundland: the role of puffin chicks

Questing behavior of Ixodes uriae and their associated seasonal, host-feeding patterns are crucial to our understanding of tick life history strategies and the ecology of diseases that they transmit. Consequently, we quantified questing behavior of nymphs and adult female I. uriae ticks at Gull Island, a seabird colony in Newfoundland, Canada, to examine seasonal variation of off-host and on-host tick activity. We sampled a total of 133 adult Atlantic puffins (Fratercula arctica), 152 puffin chicks, and 145 herring gull (Larus argentatus) chicks for ticks during the breeding seasons of 2004 and 2005. Questing ticks were sampled by dragging a white flannel cloth across the grassy breeding areas during the mo of May, June, July, and August. Nymph questing activity reached a peak during mid-July (79 and 110 individuals/hr in 2004 and 2005, respectively). The prevalence of nymphs and adult female ticks on different seabird hosts varied between years and during the seasons. Puffin chicks had the highest prevalence (above 70% in July) of nymphs in both years and this was correlated with questing activity. Female ticks rarely fed on puffin chicks, but were prevalent on adult puffins and gulls, although prevalence and questing of ticks were not correlated in these hosts. These patterns of off-host and on-host tick activity suggests that I. uriae ticks likely use a combination of questing and passive waiting, e.g., in puffin burrows, to detect hosts, depending on the tick stage and the host species.     

Expression of heat shock proteins and subolesin affects stress responses, Anaplasma phagocytophilum infection and questing behaviour in the tick, Ixodes scapularis

We characterized the effects of subolesin and heat shock protein (HSP) expression on Ixodes scapularis Say (Acari: Ixodidae) stress responses to heat shock and feeding, questing behaviour and Anaplasma phagocytophilum (Rickettsiales: Anaplasmataceae) infection. Ticks and cultured tick cells were analysed before and after subolesin, hsp20 and hsp70 gene knock-down by RNA interference. The results of these studies confirm that HSPs are involved in the tick cell response to heat stress and that subolesin and HSPs are both involved in the tick response to blood-feeding stress and A. phagocytophilum infection. Subolesin and hsp20 are involved in the tick protective response to A. phagocytophilum infection and hsp70 expression may be manipulated by the pathogen to increase infectivity. Importantly, these results demonstrate that subolesin, hsp20 and hsp70 expression also affect tick questing behaviour. Overall, this research demonstrates a relationship between hsp and subolesin expression and tick stress responses to heat shock and blood feeding, A. phagocytophilum infection and questing behaviour, thereby extending our understanding of the tick-host-pathogen interface.     

Monitoring the diel activity of Ixodes ricinus ticks in Hungary over three seasons

Ixodes ricinus is the most common tick species in Europe and vector of many diseases of humans. The risk of contracting such a disease is influenced by many factors, but one of the crucial points is questing activity of unfed ticks. In order to supplement the few literature data on patterns of diel activity of this tick species and to examine the correlations between data on diel activity of ticks and their small mammal hosts and some meteorological variables, a survey was performed. Diel activity of questing I. ricinus and small rodents was studied in a known natural tick-borne encephalitis virus focus over 7 months at one sampling day monthly. 1,063 I. ricinus ticks and 25 rodents were sampled. Air temperature and humidity data were also recorded in the 24 study plots at time of sampling. From April to October questing activity of nymphs increased in the 3-h-period after sunrise, comparing to activity of the 3 h before sunrise. Proportion of nymphs sampled 3 h after sunset compared to total sampled nymphs 3 h before and 3 h after sunset showed correlation to activity of rodents. In the period of April–July both nymphs and larvae showed stronger activity from sunrise to sunset, this turned to dominant nighttime activity in August–September, whereas activity changed to equal in day and night in October. Our results indicate that natural light and rodent population have positive effect on questing activity of I. ricinus.     

Towards an Evolutionary Understanding of Questing Behaviour in the Tick Ixodes ricinus

The tick Ixodes ricinus finds its hosts by climbing vegetation and adopting a sit-and-wait tactic. This “questing” behaviour is known to be temperature-dependent, such that questing increases with temperature up to a point where the vapor pressure deficit (drying effect) forces ticks down to rehydrate in the soil or mat layer. Little if any attention has been paid to understanding the questing of ticks from an evolutionary perspective. Here we ask whether populations from colder climatic conditions respond differently in terms of the threshold temperature for questing and the rate of response to a fixed temperature. We find significant variation between populations in the temperature sensitivity of questing, with populations from cooler climates starting questing at lower temperatures than populations from warmer temperatures. Cool climate populations also quest sooner when the temperature is held constant. These patterns are consistent with local adaptation to temperature either through direct selection or acclimation and challenge the use of fixed thresholds for questing in modeling the spread of tick populations. Our results also show how both time and temperature play a role in questing, but we are unable to explain the relationship in terms of degree-time used to model Arthropod development. We find that questing in response to temperature fits well with a quantitative genetic model of the conditional strategy, which reveals how selection on questing may operate and hence may be of value in understanding the evolutionary ecology of questing.     

Morphological and molecular identification of medically important questing Dermacentor species collected from some recreational areas of Peninsular Malaysia

Systematic Parasitology - Questing is a situation when a tick is seeking to get closer or ambush its potential host. However, information on questing tick species in Malaysia is still lacking, thus...     

Climate impacts on blacklegged tick host-seeking behavior

The nymph of the blacklegged tick (Ixodes scapularis), the primary North American vector of the causative agent of Lyme disease, must attach to a host by the end of its questing season in order to feed and subsequently molt into an adult. The proper timing of this behavior is critical both for the tick’s survival and for perpetuating the transmission of tick-borne pathogens. Questing also depletes limited nymphal lipid reserves and increases desiccation risk. Given this tradeoff, questing behavior and its environmental influences can be expressed in a dynamic state variable model. We develop what we believe to be the first such model for a tick, and investigate the influence of climate on nymph fitness predictions. We apply these results to the hypothesized inland migration of I. scapularis from island refugia, evaluating fitness under suboptimal questing strategies and uncertain environmental conditions.     

Climate,satellite imagery and the seasonal abundance of the tick Rhipicephalus appendiculatus in southern Africa: a new perspective

Abstract. Recent predictive models for the distribution of the African tick Rhipicephalus appendiculatus Neumann, based on the computer packages CLIMEX and BIOCLIM and data derived from meteorological satellites, and for the seasonal dynamics of the same tick using the computer simulation models ECFXPERT and T3HOST, all have their limitations. Statistical analysis of the relationships between the seasonal abundance of all three life stages of this tick and climatic and satellite-derived data from five sites in southern Africa, taken from the literature, supports a new perspective that it is the timing of the questing activity of the desiccation-vulnerable larvae that determines the pattern of the tick's seasonal dynamics. The timing of the activity of nymphs and adults is determined by temperature-dependent development rates plus the delaying phenomenon of photoperiod-sensitive diapause, the timing and duration of which have evolved to achieve maximum generation survival by ensuring the occurrence of eggs and larvae during periods of optimal climatic conditions. The most important environmental factor appears to be night-time minimum temperature, determining condensation and saturation deficit and thus the tick's ability to replenish moisture lost during the daytime and so to survive while questing for hosts. It is the larvae whose numbers are correlated most closely with these factors, consistent with earlier experimental results showing larvae to be most susceptible to desiccating conditions. There is a statistical linkage between larval tick numbers and satellite imagery, arising from the correlation between larval numbers and minimum temperature and saturation deficit conditions, and in turn the relationship between these climatic conditions and the subsequent vegetational changes monitored by the satellites. Moisture availability to larvae is likely to be the critical factor throughout the geographical range of R.appendiculatus, but the precise combination of climatic conditions that optimize moisture availability and questing tick survival can be expected to vary geographically. The relationships between ticks, temperatures and satellite data in parts of equatorial Africa have yet to be established. These correlative patterns highlight both the critical life stage and environmental factors when trying to understand temporal, and ultimately spatial, variations in tick abundance.     

No distributional association between the tick Haemaphysalis longicornis (Acari: Ixodidae) and plant surface area

The questing height of the tick Haemaphysalis longicornis Neumann was studied on the plant species Solidago altissima L., Pteridium aquilinum Kuhn, Miscanthus sinensis Anderss, and Pleioblastus chino Makino in an abandoned rice field and in an ume (Japanese Apricot) orchard in a forest. On all plant species, the vertical distribution of tick adults and nymphs was not significantly correlated with the distribution of plant surface area. This result suggests that the questing height of this tick is related to the body height of its main animal host, the sika deer.     

Introduced Siberian chipmunks are more heavily infested by ixodid ticks than are native bank voles in a suburban forest in France

By serving as hosts for native vectors, introduced species can surpass native hosts in their role as major reservoirs of local pathogens. During a 4-year longitudinal study, we investigated factors that affected infestation by ixodid ticks on both introduced Siberian chipmunks Tamias sibiricus barberi and native bank voles Myodes glareolus in a suburban forest (Forêt de Sénart, Ile-de-France). Ticks were counted on adult bank voles and on adult and young chipmunks using regular monthly trapping sessions, and questing ticks were quantified by dragging. At the summer peak of questing Ixodes ricinus availability, the average tick load was 27-69 times greater on adult chipmunks than on adult voles, while average biomass per hectare of chipmunks and voles were similar. In adult chipmunks, individual effects significantly explained 31% and 24% of the total variance of tick larvae and nymph burdens, respectively. Male adult chipmunks harboured significantly more larvae and nymphs than adult females, and than juveniles born in spring and in summer. The higher tick loads, and more specifically the ratio of nymphs over larvae, observed in chipmunks may be caused by a higher predisposition - both in terms of susceptibility and exposure - to questing ticks. Tick burdens were also related to habitat and seasonal variation in age- and sex-related space use by both rodents. Introduced chipmunks may thus have an important role in the dynamics of local vector-borne pathogens compared with native reservoir hosts such as bank voles.     

Effects of deer density on tick infestation of rodents and the hazard of tick-borne encephalitis. I: empirical assessment

Tick borne encephalitis (TBE) is endemic to eastern and central Europe with broad temporal and spatial variation in infection risk. Although many studies have focused on understanding the environmental and socio-economic factors affecting exposure of humans to TBE, comparatively little research has been devoted to assessing the underlying ecological mechanisms of TBE occurrence in enzootic cycles, and therefore TBE hazard. The aim of this study was to evaluate the effect of the main ungulate tick hosts on the pattern of tick infestation in rodents and TBE occurrence in rodents and questing adult ticks. In this empirical study, we considered three areas where endemic human TBE occurs and three control sites having no reported human TBE cases. In these six sites located in Italy and Slovakia, we assessed deer density using the pellet group count-plot sampling technique, collected questing ticks, live-trapped rodents (primarily Apodemus flavicollis and Myodes glareolus) and counted ticks feeding on rodents. Both rodents and questing ticks were screened for TBE infection. TBE infection in ticks and rodents was positively associated with the number of co-feeding ticks on rodents and negatively correlated with deer density. We hypothesise that the negative relationship between deer density and TBE occurrence on a local scale (defined by the minimum overlapping area of host species) could be attributed to deer (incompetent hosts) diverting questing ticks from rodents (competent hosts), know as the 'dilution effect hypothesis'. We observed that, after an initial increase, the number of ticks feeding on rodents reached a peak for an intermediate value of estimated deer density and then decreased. Therefore, while at a regional scale, tick host availability has already been shown to be directly correlated with TBE distribution, our results suggest that the interactions between deer, rodents and ticks are much more complex on a local scale, supporting the possibility of a dilution effect for TBE.     

Density of Ixodes scapularis ticks on Monhegan Island after complete deer removal: A question of avian importation?

Questing adult blacklegged tick (Ixodes scapularis Say) abundance declined markedly three years after the 1999 removal of white‐tailed deer (Odocoileus virginianus Zimmermann) from Monhegan Island, ME. Since 2000, subadult ticks have not been found on Norway rats (Rattus norvegicus Berkenhout); questing nymphs have not been found since 2002. This suggested I. scapularis was reintroduced annually via bird importation of subadult ticks, but unable to complete its two‐year life cycle on the island due to lack of deer. To investigate this, we used uncertainty analysis to estimate 1) questing adult ticks/ha that would result from avian importation of nymphs, and 2) questing adult ticks/ha on Monhegan Island, using bird capture and tick burden data from Appledore Island, ME, flagged tick data from Monhegan Island, and ten uncertain parameters. During the deer‐fed period (1990–2001), estimated tick density on Monhegan Island was 18 times greater than that of imported ticks. During the post‐deer‐fed period (2002–2008), Monhegan Island tick density was equivalent to imported tick density. This supported the premise that all I. scapularis ticks on Monhegan Island have been bird‐derived since 2002.     

Modelling the effect of temperature variation on the seasonal dynamics of Ixodes ricinus tick populations

Seasonal variation in temperature is known to drive annual patterns of tick activity and can influence the dynamics of tick-borne diseases. An age-structured model of the dynamics of Ixodes ricinus populations was developed to explore how changes in average temperature and different levels of temperature variability affect seasonal patterns of tick activity and the transmission of tick-borne diseases. The model produced seasonal patterns of tick emergence that are consistent with those observed throughout Great Britain. Varying average temperature across a continuous spectrum produced a systematic pattern in the times of peak emergence of questing ticks which depends on cumulative temperature over the year. Examination of the effects of between-year stochastic temperature variation on this pattern indicated that peak emergence times are more strongly affected by temperature stochasticity at certain levels of average temperature. Finally the model was extended to give a simple representation of the dynamics of a tick-borne disease. A threshold level of annual cumulative temperature was identified at which disease persistence is sensitive to stochastic temperature variation. In conclusion, the effect of changing patterns of temperature variation on the dynamics of I. ricinus ticks and the diseases they transmit may depend on the cumulative temperature over the year and will therefore vary across different locations. The results also indicate that diapause mechanisms have an important influence on seasonal patterns of tick activity and require further study.     

Host-odour recognition in two tick species is coded in a blend of vertebrate volatiles

The questing behaviour of ixodid ticks serves for identification and localisation of approaching hosts and is evoked by carbon dioxide, vibrations, visual and odour stimuli. In an olfactometer, we examined the specificity of the questing response of larvae of Boophilus microplus, a one-host tick which develops mainly on cattle, and Ixodes ricinus, a three-host tick with a broader host spectrum. While all mammalian odours tested were equally stimulatory for I. ricinus, B. microplus was clearly more activated by bovine odours. A phenolic fraction of bovine odour stimulated B. microplus only. Attractive components of the host odours were identified by exposing the ticks to single chemicals and mixtures. Single chemicals stimulated questing responses only at levels higher than the levels detected in the bovine odour. However, an artificial odour blend of 37 pure chemicals, diluted to concentrations at which the individual components were inactive, proved to be as effective as natural host odour for both tick species. Further fractionation of the blend revealed that the combinatory effect was achieved by only 7 compounds in both species. Although B. microplus responded to the same synergistic mixture of volatiles as I. ricinus, it showed significant higher sensitivity to the cattle-associated compounds 1-octen-3-ol and 2-nitrophenol and this might contribute to its host-specificity. Accepted: 20 March 1999     

Diversity and seasonal patterns of ticks parasitizing wild birds in western Portugal

The diversity and abundance of questing ticks and ticks parasitizing birds was assessed during 1?year in two recreational forests in western Portugal, a suburban forest and an enclosed game area. The aim of this study was to assess the distribution and seasonality of tick species and to understand the role of bird species as hosts for ticks. Ixodes ricinus was the most abundant questing tick collected in the enclosed game area, whereas in the suburban forest, only three ticks were collected by blanket dragging. Tick species parasitizing birds included I. ricinus, I. frontalis, I. arboricola, I. acuminatus, Haemaphysalis punctata, Hyalomma marginatum and H. lusitanicum. This is the first record of I. arboricola in Portugal. Tick prevalence and intensity of infestation differed between study areas and was higher in birds from the game area where a large population of deer and wild boar may support tick populations. Ground and shrub dwelling bird species such as Turdus merula, Erithacus rubecula and Sylvia melanocephala were the most heavily parasitized by ticks, but the importance of different bird species as hosts of larvae and nymphs of I. ricinus and I. frontalis differed. Therefore, different bird species may contribute differently for tick population maintenance.     

Interspecific and intraspecific associations of two species of hard ticks, Haemaphysalis longicornis and Haemaphysalis megaspinosa, in relation to questing site

The effects of intraspecific and interspecific interactions on preferred questing sites of ticks, specifically nymphs and larvae of Haemaphysalis longicornis and Haemaphysalis megaspinosa, were examined in Boso Peninsula of central Japan from October 1996 to September 1999. Haemaphysalis longicornis were primarily segregated from H. megaspinosa by season. All stages of the 2 tick species preferred sedges. Three-way contingency tables and log-linear models were used to test for independence of occurrence and to quantify associations between species and stages with similar host ranges. The shifts of questing site from leaves to stem tips and from 40-49 cm to greater heights were observed in both species, which suggests that these sites are more suitable for ticks and that aggregation may serve as protection from severe conditions. In contrast, a shift to a lower height was observed in H. longicornis nymphs and larvae when other species were present, suggesting that they were driven away by other species, especially H. megaspinosa. Heterospecific clusters composed of at least 2 species were formed on stem tips more frequently. It is concluded that questing site was affected by both aggregation pattern and the presence of other species.     

Woodland biodiversity management as a tool for reducing human exposure to Ixodes ricinus ticks: A preliminary study in an English woodland

This paper presents preliminary findings towards developing a UK‐specific approach to reducing public exposure to woodland questing Ixodes ricinus tick populations by harnessing existing biodiversity‐enhancing woodland ride (i.e., linear non‐wooded herbaceous habitat either side of track within woodland) management strategies. This preliminary study in an English woodland firstly assesses whether ecological and environmental factors determine presence and density of questing Ixodes ricinus along woodland rides. Secondly, it sets these findings in the context of woodland ride management guidelines in England in order to understand what impact ride management strategies might have on numbers of questing ticks and tick survival. Nymph and adult I. ricinus presence and abundance were modelled in relation to relevant microclimate and ecological parameter variables. Predictor variables for increased questing nymph abundance included ride orientation, mat depth, occurrence of bracken/bramble and animal tracks, ride/path width, and sward height. Ticks thrive in the ecotonal habitat of a woodland ride, therefore we urge woodland managers to consider the impact of their ride management on ticks and human exposure to ticks. Possible recommendations for mitigating questing I. ricinus in line with biodiversity management guidelines rides are discussed in this paper and include seasonal mowing regimes, management of mulch/mat, and bracken/bramble management through use of scalloped ride edges.     

Spatial distribution of the Karoo paralysis tickIxodes rubicundus (Acari: Ixodidae) within a false upper Karoo veld type

Spatial distribution of the Karoo paralysis tick (Ixodes rubicundus) has been studied in a paralysis enzootic area of the southwestern Orange Free state. Significantly more females than males were collected from the vegetation. Most ticks (99%) used grass as questing sites at a height of approximately 45 cm (range 10–97 cm), which correlates with the size of host animals. No significant differences between the questing height of male and fermale ticks were evident. The ticks were found on most of the grass species present and, except for the genusEragrostis no specific preference was evident. When questing, the capitulum ofI. rubicundus is usually (90%) directed towards the ground. Seventy-eight percent of the ticks occurred singly on a specific grassblade or flowerhead. In those cases where two ticks occurred together, no sexual aggregation was evident. Most ticks occurred under or close ( =62 cm) to the corwn cover of specific shrub or tree species. These plant species were characterized by a dense crown cover with a mat of decaying leaf litter underneath. The preference of the tick for wild olive trees (Olea europaea fricana) suggests that except for the physical characteristics of this tree species, host factors may also be important. Significantly more ticks were distributed on the cooler, more protected southern sides of vegetation in comparison to the northern sides.     

An empirical quantitative framework for the seasonal population dynamics of the tick Ixodes ricinus

The wide geographic and climatic range of the tick Ixodes ricinus, and the consequent marked variation in its seasonal population dynamics, have a direct impact on the transmission dynamics of the many pathogens vectored by this tick species. We use long-term observations on the seasonal abundance and fat contents (a marker of physiological ageing) of ticks, and contemporaneous microclimate at three field sites in the UK, to establish a simple quantitative framework for the phenology (i.e. seasonal cycle of development) of I. ricinus as a foundation for a generic population model. An hour-degree tick inter-stadial development model, driven by soil temperature and including diapause, predicts the recruitment (i.e. emergence from the previous stage) of a single cohort of each stage of ticks each year in the autumn. The timing of predicted emergence coincides exactly with the new appearance of high-fat nymphs and adults in the autumn. Thereafter, fat contents declined steadily until unfed ticks with very low energy reserves disappeared from the questing population within about 1 year from their recruitment. Very few newly emerged ticks were counted on the vegetation in the autumn, but they appeared in increasing numbers through the following spring. Larger ticks became active and subsequently left the questing population before smaller ones. Questing tick population dynamics are determined by seasonal patterns of tick behaviour, host-contact rates and mortality rates, superimposed on a basal phenology that is much less complex than has hitherto been portrayed.