Borrelia burgdorferi sensu stricto isolates from patients with erythema migrans in Europe and the United States were compared by genotype, clinical features of infection, and inflammatory potential. ...Analysis of outer surface protein C and multilocus sequence typing showed that strains from these 2 regions represent distinct genotypes. Clinical features of infection with B. burgdorferi in Slovenia were similar to infection with B. afzelii or B. garinii, the other 2 Borrelia spp. that cause disease in Europe, whereas B. burgdorferi strains from the United States were associated with more severe disease. Moreover, B. burgdorferi strains from the United States induced peripheral blood mononuclear cells to secrete higher levels of cytokines and chemokines associated with innate and Th1-adaptive immune responses, whereas strains from Europe induced greater Th17-associated responses. Thus, strains of the same B. burgdorferi species from Europe and the United States represent distinct clonal lineages that vary in virulence and inflammatory potential.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The invasive, human-biting Asian longhorned tick, Haemaphysalis longicornis, was detected in New Jersey in the eastern United States in August of 2017 and by November of 2018 this tick had been ...recorded from 45 counties across 9 states, primarily along the Eastern Seaboard. The establishment of H. longicornis in the United States has raised the questions of how commonly it will bite humans and which native pathogens may naturally infect this tick. There also is a need for experimental vector competence studies with native pathogens to determine if H. longicornis can acquire a given pathogen while feeding, pass it transstadially, and then transmit the pathogen in the next life stage. In this experimental study, we evaluated the vector competence of a population of H. longicornis originating from the United States (New York) for a native isolate (B31) of the Lyme disease spirochete, Borrelia burgdorferi sensu stricto (s.s.). In agreement with a previous experimental study on the vector competence of H. longicornis for Borrelia garinii, we found that uninfected H. longicornis larvae could acquire B. burgdorferi s.s. while feeding on infected Mus musculus mice (infection prevalence >50% in freshly fed larvae) but that the infection was lost during the molt to the nymphal stage. None of 520 tested molted nymphs were found to be infected, indicating that transstadial passage of B. burgdorferi s.s. is absent or rare in H. longicornis; and based on the potential error associated with the number of nymphs testing negative in this study, we estimate that the upper 95% limit for infection prevalence was 0.73%. An Ixodes scapularis process control showed both effective acquisition of B. burgdorferi s.s. from infected mice by uninfected larvae and transstadial passage to the nymphal stage (infection prevalence of 80–82% for both freshly fed larvae and molted nymphs). We also observed that although H. longicornis larvae could be compelled to feed on mice by placing the ticks within feeding capsules, attachment and feeding success was minimal (<0.5%) when larvae were placed freely on the fur of the mice. We conclude that H. longicornis is unlikely to contribute more than minimally, if at all, to transmission of Lyme disease spirochetes in the United States.
The geographic range of the blacklegged tick, Ixodes scapularis, is expanding northward from the United States into southern Canada, and studies suggest that the lone star tick, Amblyomma americanum, ...will follow suit. These tick species are vectors for many zoonotic pathogens, and their northward range expansion presents a serious threat to public health. Climate change (particularly increasing temperature) has been identified as an important driver permitting northward range expansion of blacklegged ticks, but the impacts of host movement, which is essential to tick dispersal into new climatically suitable regions, have received limited investigation. Here, a mechanistic movement model was applied to landscapes of eastern North America to explore 1) relationships between multiple ecological drivers and the speed of the northward invasion of blacklegged ticks infected with the causative agent of Lyme disease, Borrelia burgdorferi sensu stricto, and 2) its capacity to simulate the northward range expansion of infected blacklegged ticks and uninfected lone star ticks under theoretical scenarios of increasing temperature. Our results suggest that the attraction of migratory birds (long-distance tick dispersal hosts) to resource-rich areas during their spring migration and the mate-finding Allee effect in tick population dynamics are key drivers for the spread of infected blacklegged ticks. The modeled increases in temperature extended the climatically suitable areas of Canada for infected blacklegged ticks and uninfected lone star ticks towards higher latitudes by up to 31% and 1%, respectively, and with an average predicted speed of the range expansion reaching 61 km/year and 23 km/year, respectively. Differences in the projected spatial distribution patterns of these tick species were due to differences in climate envelopes of tick populations, as well as the availability and attractiveness of suitable habitats for migratory birds. Our results indicate that the northward invasion process of lone star ticks is primarily driven by local dispersal of resident terrestrial hosts, whereas that of blacklegged ticks is governed by long-distance migratory bird dispersal. The results also suggest that mechanistic movement models provide a powerful approach for predicting tick-borne disease risk patterns under complex scenarios of climate, socioeconomic and land use/land cover changes.
The literature on Lyme disease includes a lively debate about the paradoxical role of changing deer populations. A decrease in the number of deer will both (1) reduce the incidence of Lyme disease by ...decreasing the host populations for ticks and therefore tick populations, and (2) enhance the incidence of Lyme disease by offering fewer reservoir-incompetent hosts for ticks, forcing the vector to choose reservoir-competent, and therefore possibly diseased, hosts to feed on. A review of field studies exploring the net impact of changing deer populations shows mixed results. In this manuscript, we investigate the hypothesis that the balance of these two responses to changing deer populations depends on the relative population sizes of reservoir-competent vs. reservoir-incompetent hosts and the presence of host preference in larval and adult stages.
A temperature driven seasonal model of Borrelia burgdorferi sensu stricto (cause of Lyme disease) transmission among three host types (reservoir-competent infected and uninfected hosts, and reservoir-incompetent hosts) is constructed as a system of nonlinear ordinary differential equations. The model, which produces biologically reasonable results for both the tick vector Ixodes scapularis Say 1921 and the hosts, is used to investigate the effects of reservoir-incompetent host removal on both tick populations and disease prevalence for various relative population sizes of reservoir-competent hosts vs. reservoir-incompetent hosts.
In summary, the simulation results show that the model with host preference appears to be more accurate than the one with no host preference. Given these results, we found that removal of adult I. scapularis(Say) hosts is likely to reduce questing nymph populations. At very low levels questing adult abundance may rise with lack of adult hosts. There is a dilution effect at low reservoir-competent host populations and there is an amplification effect at high reservoir-competent host populations.
Deer management (e.g., reduction) has been proposed as a tool to reduce the acarological risk of Lyme disease. There have been few opportunities to investigate Ixodes scapularis (blacklegged tick) ...and Borrelia burgdorferi sensu stricto dynamics in the absence of white-tailed deer (Odocoileus virginianus) in midwestern North America. A pair of islands in Lake Michigan presented a unique opportunity to study the role of alternative hosts for the adult stage of the blacklegged tick for maintaining a tick population as a deer herd exists on North Manitou Island but not on South Manitou Island, where coyotes (Canis latrans) and hares (Lepus americanus) are the dominant medium mammals. Additionally, we were able to investigate the maintenance of I. scapularis and B. burgdorferi in small mammal communities on both islands, which were dominated by eastern chipmunks (Tamias striatus). From 2011 to 2015, we surveyed both islands for blacklegged ticks by drag cloth sampling, bird mist netting, and small and medium-sized mammal trapping. We assayed questing ticks, on-host ticks, and mammal biopsies for the Lyme disease pathogen, B. burgdorferi. We detected all three life stages of the blacklegged tick on both islands. Of the medium mammals sampled, no snowshoe hares (Lepus americanus, 0/23) were parasitized by adult blacklegged ticks, but 2/2 coyotes (Canis latrans) sampled on South Manitou Island in 2014 were parasitized by adult blacklegged ticks, suggesting that coyotes played a role in maintaining the tick population in the absence of deer. We also detected I. scapularis ticks on passerine birds from both islands, providing support that birds contribute to maintaining as well as introducing blacklegged ticks and B. burgdorferi to the islands. We observed higher questing adult and nymphal tick densities, and higher B. burgdorferi infection prevalence in small mammals and in adult ticks on the island with deer as compared to the deer-free island. On the islands, we also found that 25% more chipmunks were tick-infested than mice, fed more larvae and nymphs relative to their proportional abundance compared to mice, and thus may play a larger role compared to mice in the maintenance of B. burgdorferi. Our investigation demonstrated that alternative hosts could maintain a local population of blacklegged ticks and an enzootic cycle of the Lyme disease bacterium in the absence of white-tailed deer. Thus, alternative adult blacklegged tick hosts should be considered when investigating deer-targeted management tools for reducing tick-borne disease risk, especially when the alternative host community may be abundant and diverse.
A promising alternative approach to conventional vector control practices is the use of systemic insecticides/acaricides orally administered to relevant mammalian host species to control blood ...feeding disease vectors. In the United States, Lyme disease continues to be the most prevalent vector-borne disease with the Centers for Disease Control and Prevention estimating approximately 500,000 Lyme disease infections each year. Previous research has demonstrated the potential usefulness of a low dose fipronil bait in controlling Ixodes scapularis larvae feeding on white-footed mice. However, no such acaricide-only product is approved for use in treating white-footed mice to control I. scapularis. The purpose of the study was to evaluate the use of a federally approved fipronil flea control bait (Grain Bait) in controlling I. scapularis parasitizing white-footed mice (Peromyscus leucopus). A simulated field trial was conducted in which Grain Bait was presented to grouped white-footed mice alongside an alternative diet for 168 h. Mice were fitted with capsules and manually parasitized with I. scapularis larvae. Replete larvae detaching from each mouse were collected and monitored for molting to nymphs. The inside of each capsule was observed to evaluate tick attachment. Blood was collected from all Treatment group mice via cardiac puncture to determine the fipronil sulfone concentration in plasma (CP) for each animal. Results indicated that Grain Bait would be consumed in the presence of an alternative diet and that bait acceptance was greater for males, relative to females. Treatment with Grain Bait prevented 100% larvae from feeding to repletion at Day 7 post-exposure and prevented 80% of larvae from feeding to repletion and 84% from molting at Day 21 post-exposure, relative to Control groups. Molted nymphs were not recovered from mice that had CP detectable ≥18.4 ng/ml. The results suggest that this federally approved flea product could be utilized for tick control and that other medically important vector-host relationships should be considered.
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•Fipronil grain bait fed to white-footed mice was effective against blacklegged ticks.•Controlling parasitizing larval and nymphal ticks can reduce Borrelia burgdorferi transmission to humans and wildlife.•Low doses and application rates could reduce environmental risk and acaricide resistance.•Fipronil grain bait controlled 100% ticks at 1-week post exposure and 84% ticks at 21-days post-exposure.
In northeastern North America, the blacklegged tick, Ixodes scapularis, is the vector of numerous tick-borne pathogens, including the agent of Lyme disease, Borrelia burgdorferi sensu stricto. Since ...1990, there has been a rapid spread of I. scapularis northward into the province of Ontario, Canada. Climate change has been implicated as one of the driving factors for the spread of this vector. Other ecological factors also influence survival of I. scapularis populations and may facilitate invasion. The objective of this study was to identify local abiotic and biotic factors of significance for the invasion of I. scapularis in Ontario. The presence of ticks was determined by drag sampling at 154 sites in southern, eastern and central Ontario from May to October in 2014 and 2015. At each site, data on site aspect, forest cover, understory density and composition, soil moisture and composition, and the depth of litter layer were collected. Cumulative degree days above zero °C, total precipitation and elevation were attributed to each site using a geographic information system. A mixed multi-variable logistic regression model was created to assess the impact of the ecological factors on the presence of I. scapularis. In total, I. scapularis was found at 29 sites (18.8%) across the study area. The density of the understory, the presence of shrubs and the interaction of these two ecological factors were statistically significant, as well as longitude and cumulative degree days above zero. Our findings illustrate that local ecological factors are of importance for the invasion of I. scapularis into Ontario, and may be used to enhance local public health interventions and current predictive models and risk maps for I. scapularis.
Assessing the risk of tick-borne disease in areas with high visitor numbers is important from a public health perspective. Evidence suggests that tick presence, density, infection prevalence and the ...density of infected ticks can vary between habitats within urban green space, suggesting that the risk of Lyme borreliosis transmission can also vary. This study assessed nymph density,
Borrelia
prevalence and the density of infected nymphs across a range of habitat types in nine parks in London which receive millions of visitors each year.
Ixodes ricinus
were found in only two of the nine locations sampled, and here they were found in all types of habitat surveyed. Established
I. ricinus
populations were identified in the two largest parks, both of which had resident free-roaming deer populations. Highest densities of nymphs (15.68 per 100 m
2
) and infected nymphs (1.22 per 100 m
2
) were associated with woodland and under canopy habitats in Richmond Park, but ticks infected with
Borrelia
were found across all habitat types surveyed. Nymphs infected with
Borrelia
(7.9%) were only reported from Richmond Park, where
Borrelia burgdorferi
sensu stricto and
Borrelia afzelii
were identified as the dominant genospecies. Areas with short grass appeared to be less suitable for ticks and maintaining short grass in high footfall areas could be a good strategy for reducing the risk of Lyme borreliosis transmission to humans in such settings. In areas where this would create conflict with existing practices which aim to improve and/or meet historic landscape, biodiversity and public access goals, promoting public health awareness of tick-borne disease risks could also be utilised.
Human Lyme disease–primarily caused by the bacterium Borrelia burgdorferi sensu stricto (s.s.) in North America–is the most common vector-borne disease in the United States. Research on risk ...mitigation strategies during the last three decades has emphasized methods to reduce densities of the primary vector in eastern North America, the blacklegged tick (Ixodes scapularis). Controlling white-tailed deer populations has been considered a potential method for reducing tick densities, as white-tailed deer are important hosts for blacklegged tick reproduction. However, the feasibility and efficacy of white-tailed deer management to impact acarological risk of encountering infected ticks (namely, density of host-seeking infected nymphs; DIN) is unclear. We investigated the effect of white-tailed deer density and management on the density of host-seeking nymphs and B. burgdorferi s.s. infection prevalence using surveillance data from eight national parks and park regions in the eastern United States from 2014–2022. We found that deer density was significantly positively correlated with the density of nymphs (nymph density increased by 49% with a 1 standard deviation increase in deer density) but was not strongly correlated with the prevalence of B. burgdorferi s.s. infection in nymphal ticks. Further, while white-tailed deer reduction efforts were followed by a decrease in the density of I. scapularis nymphs in parks, deer removal had variable effects on B. burgdorferi s.s. infection prevalence, with some parks experiencing slight declines and others slight increases in prevalence. Our findings suggest that managing white-tailed deer densities alone may not be effective in reducing DIN in all situations but may be a useful tool when implemented in integrated management regimes.
Altitudinal distributions, population structures and seasonal dynamics of tick fauna at three localities in Continental Croatia (Medvednica and Papuk) and an alpine biogeographic region (Gorski ...Kotar) were studied. Sampling of questing ticks was performed twice a year (spring and autumn, from 2019 to 2021) at different altitudes (200, 400, 600, 800 and 1000 m above sea level) using the flagging method. In total, 2942 ticks (53.9% larvae, 40.1% nymphs, 6.0% adults) were sampled and 2937 (99.83%) were determined as Ixodes ricinus, 4 (0.14%) as Haemaphysalis concinna and 1 (0.03%) as Ixodes frontalis. Ixodes ricinus was the only species found at all altitudes and sampling sites. The highest tick abundance was recorded at higher altitudes (800–1000 m asl.) on Medvednica and in Gorski Kotar within mixed forests of European beech and European silver fir, while on Papuk most of the ticks were sampled at lower altitudes (200 m asl.) in Sessile oak forest. From 27 pools containing 305 ticks, 1 (3.7%) was positive for Borrelia burgdorferi sensu lato infection. Borrelia burgdorferi s.l. was detected in 20% (1/5) of the pools containing nymphs and adults collected in Gorski Kotar (600 and 800 m asl.). Sequencing of the ospA gene and phylogenetic analysis revealed the presence of the Borrelia burgdorferi sensu stricto genotype.
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