Identification of Anaplasma marginale adhesins for entry into Dermacentor andersoni tick cells using phage display.

Anaplasma marginale is an obligate, intracellular, tick-borne bacterial pathogen that causes bovine anaplasmosis, an often severe, production-limiting disease of cattle found worldwide. Methods to control this disease are lacking, in large part due to major knowledge gaps in our understanding of the molecular underpinnings of basic host-pathogen interactions. For example, the surface proteins that serve as adhesins and, thus, likely play a role in pathogen entry into tick cells are largely unknown. To address this knowledge gap, we developed a phage display library and screened 66 A. marginale proteins for their ability to adhere to Dermacentor andersoni tick cells. From this screen, 17 candidate adhesins were identified, including OmpA and multiple members of the Msp1 family, including Msp1b, Mlp3, and Mlp4. We then measured the transcript of ompA and all members of the msp1 gene family through time, and determined that msp1b, mlp2, and mlp4 have increased transcript during tick cell infection, suggesting a possible role in host cell binding or entry. Finally, Msp1a, Msp1b, Mlp3, and OmpA were expressed as recombinant protein. When added to cultured tick cells prior to A. marginale infection, all proteins except the C-terminus of Msp1a reduced A. marginale entry by 2.2- to 4.7-fold. Except OmpA, these adhesins lack orthologs in related pathogens of humans and animals, including Anaplasma phagocytophilum and the Ehrlichia spp., thus limiting their utility in a universal tick transmission-blocking vaccine. However, this work greatly advances efforts toward developing methods to control bovine anaplasmosis and, thus, may help improve global food security.

Comparison of the supercooling points of questing Dermacentor variabilis adults in two populations on the Canadian prairies and implications for overwinter survival.

A comparison was made of the supercooling points (SCPs) of questing Dermacentor variabilis adults from two populations located ca. 800 km apart on the Canadian prairies. This is also the first study to examine whether there are seasonal fluctuations in the SCP of questing D. variabilis adults. The SCPs of adult ticks from Lizard Lake Community Pasture, a recently established population in west-central Saskatchewan, varied over spring and summer, with the median SCP warming over time. In addition, the SCPs of ticks from Lizard Lake Community Pasture were significantly higher than those of adult ticks collected from Sandy Hook in Manitoba, a population that has been established for decades. The off-host survival of adults from Sandy Hook between summer and spring has been shown previously to be significantly greater than that of adults from Lizard Lake Community Pasture. The findings of the present study suggest that there may be geographical variation in the SCPs of D. variabilis adults which may be associated with differences in overwinter survival. The relatively low SCPs of questing D. variabilis adults, and the ability of some adults to survive off-host during winter, may be factors contributing to the range expansion of this tick species in Canada.

Ticks and spirochetes of the genus Borrelia in urban areas of Central-Western Poland.

Due to the extensive use of green urban areas as recreation places, city residents are exposed to tick-borne pathogens. The objectives of our study were (i) to determine the occurrence of ticks in urban green areas, focussing on areas used by humans such as parks, schools and kindergartens, and urban forests, and (ii) to assess the prevalence of Borrelia infections in ticks in Zielona Góra, a medium-sized city in western Poland. A total of 161 ticks representing the two species Ixodes ricinus (34 males, 51 females, 30 nymphs) and Dermacentor reticulatus (20 males, 26 females) were collected from 29 of 72 (40.3%) study sites. In total, 26.1% of the ticks (85.7% of I. ricinus and 14.3% of D. reticulatus) yielded DNA of Borrelia. The difference in the infection rate between I. ricinus and D. reticulatus was significant. Among infected ticks, the most frequent spirochete species were B. lusitaniae (50.0%) and B. afzelii (26.2%), followed by B. spielmanii (9.5%), B. valaisiana (7.1%), B. burgdorferi sensu stricto, (4.8%) and B. miyamotoi (2.4%). No co-infections were found. We did not observe a correlation in the occurrence of Borrelia spirochetes in ticks found in individual study sites that differed in terms of habitat type and height of vegetation. Our findings demonstrate that the Borrelia transmission cycles are active within urban habitats, pointing the need for monitoring of tick-borne pathogens in public green areas. They could serve as guidelines for authorities for the proper management of urban green spaces in a way that may limit tick populations and the potential health risks posed by tick-borne pathogens.

Anaplasma bovis-Like Infections in Humans, United States, 2015-2017.

We detected the DNA of an Anaplasma bovis-like bacterium in blood specimens from 4 patients from the United States with suspected tickborne illnesses. Initial molecular characterization of this novel agent reveals identity to A. bovis-like bacteria detected in Dermacentor variabilis ticks collected from multiple US states.

Powassan Virus Lineage I in Field-Collected Dermacentor variabilis Ticks, New York, USA.

Powassan virus is a tickborne flavivirus that can cause lethal or debilitating neurologic illness. It is canonically transmitted by Ixodes spp. ticks but might spill over to sympatric Dermacentor species. We detected Powassan virus lineage I from a pool of field-collected D. variabilis ticks in New York, USA.

Novel Orthonairovirus Isolated from Ticks near China-North Korea Border.

We isolated a new orthonairovirus from Dermacentor silvarum ticks near the China-North Korea border. Phylogenetic analysis showed 71.9%-73.0% nucleic acid identity to the recently discovered Songling orthonairovirus, which causes febrile illness in humans. We recommend enhanced surveillance for infection by this new virus among humans and livestock.

Comparative analysis of the mitochondrial genome of Dermacentor steini from different regions in China.

Ticks are a group of blood-sucking ectoparasites that play an important role in human health and livestock production development as vectors of zoonotic diseases. The phylogenetic tree of single genes cannot accurately reflect the true kinship between species. Based on the complete mitochondrial genome analysis one can help to elucidate the phylogenetic relationships among species. In this study, the complete mitochondrial genome of Dermacentor steini (isolate Longyan) was sequenced and compared with the mitochondrial genes of 3 other Chinese isolates (Nanchang, Jinhua and Yingtan). In Dermacentor steini 4 isolates had identical or similar mitochondrial genome lengths and an overall variation of 0.76% between sequences. All nucleotide compositions showed a distinct AT preference. The most common initiation and stop codons were ATG and TAA, respectively. Fewer base mismatches were found in the tRNA gene of D. steini (isolate Longyan), and the vicinity of the control region and tRNA gene was a hot rearrangement region of the genus Dermacentor. Maximum likelihood trees and Bayesian trees indicate that D. steini is most closely related to Dermacentor auratus. The results enrich the mitochondrial genomic data of species in the genus Dermacentor and provide novel insights for further studies on the phylogeographic classification and molecular evolution of ticks.

Do ticks exhibit repeatable individual behaviors?

Diseases caused by ticks are often addressed as a traditional epidemiological mathematical puzzle, i.e., how many identical infected vectors, how many uniform potential hosts, and a dependable rate of transmission, etc. Although often useful at the population level, at the individual level disease transmission occurs when one tick bites one person. Just as we assign agency to people in their outdoor behavior and use of prophylactics against arthropods, perhaps we should also see ticks as individual actors? Are all ticks automatons that just quest and attach, or do they exhibit repeatable individual behaviors that affect transmission? We wanted to determine whether Dermacentor andersoni and D. variabilis adult ticks exhibited repeatable behaviors in four experiments. The experiments focused on left/right movement, attraction to CO2, photophilic tendencies, and avoidance of a repellant. We hypothesized that over two seasons we would find repeatable behavior patterns. In 2021, but not 2022, we found that within an experiment, individuals exhibited repeatable behaviors between trials and between experiments, i.e., if an animal showed repeatable 'adventurous' behavior in one experiment, this predicted adventurous behavior in a separate experiment. This strong evidence of predictable trait-like behavior was present in 2021 but was absent when we repeated the same experiments, with the same collection site, in 2022. This illustrates the importance of multiyear experimentation when testing for repeatable individual behaviors. Incidental to the study, we also observed that a major heat wave in 2021 altered the tick species composition (toward a more dry-adapted population) at our study site.

Differences in the reproductive output and larval survival of Rocky Mountain wood ticks (Dermacentor andersoni) and American dog ticks (Dermacentor variabilis) from prairie populations near their northern distributional limits in western Canada.

The effects of temperature and relative humidity (RH) on female reproductive output, egg development and larval survival were determined for Rocky Mountain wood ticks (Dermacentor andersoni) from a prairie population (Chin Lakes, Alberta, Canada) near the northern distribution limit of this species. The responses of D. andersoni eggs and unfed larvae to different temperature (25 or 32 °C) and RH (35, 55, 75, 85 or 95%) regimes were compared to our previously published data (Diyes et al. 2021) for a northern prairie population of American dog ticks (Dermacentor variabilis). Oviposition by D. andersoni females took 21-30 days at 25 °C and 95% RH compared to 10-21 days for D. variabilis. The number of eggs laid by female ticks was strongly dependent on their engorgement weight, and D. andersoni females produced more eggs than D. variabilis females of an equivalent body weight. Eggs of D. andersoni took less time to develop at 32 °C than 25 °C with ≥ 85% RH, and hatched faster than those of D. variabilis. Larval survival times declined as temperature increased and RH decreased, but D. andersoni survived longer at 32 °C and ≤ 75% RH than D. variabilis. The interspecific differences in responses to the same temperature and humidity regimes indicate that D. andersoni is xerophilic, whereas D. variabilis is hydrophilic. Hence, 'prairie' populations of the Rocky Mountain wood tick occur in the drier grassland ecoregions but are absent in Aspen Parklands Ecoregion which is located to the north and east of the distributional range of D. andersoni.

Interspecific differences in the behavioral response of ticks exposed to radiofrequency electromagnetic radiation.

Artificial electromagnetic radiation is a new environmental factor that affects animals. Experiments with the effect of radio frequency electromagnetic radiation were focused on both vertebrates and invertebrates. Ticks showed a significant affinity to radiation. Our study is a continuation of this research and its aim was to monitor the effect of radiation on the behavior of four tick species: Ixodes ricinus, Dermacentor reticulatus, Dermacentor marginatus and Haemaphysalis inermis. In total 1,200 ticks, 300 of each species, were tested in modules allowing the choice of an exposed or shielded area. During the test, the ticks were exposed to electro-magnetic radiation of 900 MHz for 24 h. The position of the individuals was recorded and we evaluated the obtained data statistically. We observed a significant preference to the exposed area in both sexes of I. ricinus. Males of D. reticulatus and D. marginatus also showed an affinity to radiation, but not females of both species, nor females and males of H. inermis. The results of the study support the assumption that ticks perceive the electromagnetic field and the observed differences in their response have the potential to help understand the mechanism of perception.

Common yarrow (Achillea millefolium) essential oil and main components as potential repellents and acaricides against Ixodes scapularis and Dermacentor variabilis (Acari: Ixodidae) ticks.

Repellent and acaricidal activities of essential oils (EO) extracted from common yarrow (Achillea millefolium L.) and main chemical components were evaluated against Ixodes scapularis and Dermacentor variabilis adult ticks and nymphs. Flowers and leaves were collected from two locations, Harvest Moon trail (HMT) and Port Williams (PW) in Nova Scotia (Canada), and EO were extracted via hydro-distillation. Samples were analyzed using GC-MS, and differences in chemical composition and quantity of compounds detected were reported in relation to the collection site and plant parts. EO were both rich in germacrene D (HMT EO 21.5 ± 1.31% wt; PW EO 25.5 ± 0.76% wt); however, HMT flower EO has a higher concentration of camphor (9.9 ± 0.08% wt) compared to PW flower EO (3.0 ± 0.01% wt). Significant acaricidal activity was reported against I. scapularis adult ticks, particularly for HMT flower EO with a LD50 of 2.4% v/v (95% confidence interval = 1.74-3.35) at 24 h post-exposure. Germacrene D had the lowest LD50 of 2.0% v/v (95% CI 1.45-2.58) among the four compounds after 7 days. No significant acaricidal effect was observed on D. variabilis adult ticks. Yarrow PW flower EO exerted repellent activity towards I. scapularis nymphs (100% repellency up to 30 min); however, repellency significantly declined over time. Yarrow EO exert promising acaricidal and repellent properties, that may be used to manage Ixodes ticks and the diseases they vector.

High Prevalence and Low Diversity of Rickettsia in Dermacentor reticulatus Ticks, Central Europe.

We collected 1,671 Dermacentor reticulatus ticks from 17 locations in the Czech Republic, Slovakia, and Hungary. We found 47.9% overall prevalence of Rickettsia species in ticks over all locations. Sequence analysis confirmed that all tested samples belonged to R. raoultii, the causative agent of tick-borne lymphadenopathy.

The Microbiota of Ixodes ricinus and Dermacentor reticulatus Ticks Collected from a Highly Populated City of Eastern Europe.

Recent investigations have examined, through sequencing the V6 region of 16S rRNA gene, the microbiota of questing Ixodes ricinus and Dermacentor reticulatus ticks collected from rural areas of Central (Dnipropetrovs'k (region D) and Poltava (region P)) and Northeastern (Kharkiv (region K)) Ukraine. In addition to defining the bacterial microbiota of both tick species, the previous investigations also revealed a high degree of inter-sex and inter-regional variations in the tick microbiota. As a continuation of the two studies, the present investigation has analyzed individual microbiota of questing I. ricinus (n = 50) and D. reticulatus (n = 50) ticks originating from Kyiv, the largest city of Ukraine. The Kyiv tick microbiota were compared between males and females for each tick species. Additionally, a cross-regional analysis was performed to compare the microbiota of Kyiv ticks to those from regions D, K, and P. Numerous statistically significant inter-sex and inter-regional variations were detected when alpha diversity, beta diversity, the bacterial relative and differential abundances were assessed. The overall results demonstrated that the microbiota of Kyiv ticks were statistically different compared to the ticks of the other three regions. Besides existing climatic and geographical differences between the four regions, the authors hypothesize that various anthropogenic factors of the megapolis (e.g., animal species translocation, land management, ecology) could have contributed to the distinct microbiota of Kyiv ticks observed in this study.

Mortality of various-age larval winter ticks, Dermacentor albipictus, following surface contact with entomopathogenic fungi.

The larval stage of the one-host tick, Dermacentor albipictus Packard (Acari: Ixodidae), the winter tick, is spent aggregated on the ground in summer until they quest for hosts in the autumn. Metarhizium brunneum (Petch) and Beauveria bassiana (Balsamo-Crivelli) Vuillemin are promising fungal biocontrol agents of ticks. The success of tick biocontrol using entomopathogenic fungi relies on infective propagule contact with a susceptible host at the right time within their life cycle and stage. The susceptibility of various-age D. albipictus larvae to commercial isolates of M. brunneum strain F52 (Mb-F52) and B. bassiana strain GHA (Bb-GHA) was assessed over a three-week period after contact with surfaces treated with 1.3 × 106 conidia/cm2. Larvae of four ages were examined (a) upon eclosion from eggs, (b) 2-weeks, (c) 1.5-months and (d) 3-months-old. Mortality of larvae exposed to fungus-treated surfaces ranged from 4 to 51% for Bb-GHA and 64-100% for Mb-F52 after three weeks. Significantly greater mortality was observed when larvae were exposed to Mb-F52 than Bb-GHA. Larval susceptibility was significantly greater within 2 weeks of eclosion from eggs and after 3 months of age. These results demonstrate the varying susceptibility of larvae to mycoacaricides at different times within their non-parasitic larval life stage.

Ticks on the move-climate change-induced range shifts of three tick species in Europe: current and future habitat suitability for Ixodes ricinus in comparison with Dermacentor reticulatus and Dermacentor marginatus.

Tick-borne diseases are a major health problem worldwide and could become even more important in Europe in the future. Due to changing climatic conditions, ticks are assumed to be able to expand their ranges in Europe towards higher latitudes and altitudes, which could result in an increased occurrence of tick-borne diseases.There is a great interest to identify potential (new) areas of distribution of vector species in order to assess the future infection risk with vector-borne diseases, improve surveillance, to develop more targeted monitoring program, and, if required, control measures.Based on an ecological niche modelling approach we project the climatic suitability for the three tick species Ixodes ricinus, Dermacentor reticulatus and Dermacentor marginatus under current and future climatic conditions in Europe. These common tick species also feed on humans and livestock and are vector competent for a number of pathogens.For niche modelling, we used a comprehensive occurrence data set based on several databases and publications and six bioclimatic variables in a maximum entropy approach. For projections, we used the most recent IPCC data on current and future climatic conditions including four different scenarios of socio-economic developments.Our models clearly support the assumption that the three tick species will benefit from climate change with projected range expansions towards north-eastern Europe and wide areas in central Europe with projected potential co-occurrence.A higher tick biodiversity and locally higher abundances might increase the risk of tick-borne diseases, although other factors such as pathogen prevalence and host abundances are also important.

Iron Reduction in Dermacentor andersoni Tick Cells Inhibits Anaplasma marginale Replication.

Anaplasma spp. are obligate intracellular, tick-borne, bacterial pathogens that cause bovine and human anaplasmosis. We lack tools to prevent these diseases in part due to major knowledge gaps in our fundamental understanding of the tick-pathogen interface, including the requirement for and molecules involved in iron transport during tick colonization. We determine that iron is required for the pathogen Anaplasma marginale, which causes bovine anaplasmosis, to replicate in Dermacentor andersoni tick cells. Using bioinformatics and protein modeling, we identified three orthologs of the Gram-negative siderophore-independent iron uptake system, FbpABC. Am069, the A. marginale ortholog of FbpA, lacks predicted iron-binding residues according to the NCBI conserved domain database. However, according to protein modeling, the best structural orthologs of Am069 are iron transport proteins from Cyanobacteria and Campylobacterjejuni. We then determined that all three A. marginale genes are modestly differentially expressed in response to altered host cell iron levels, despite the lack of a Ferric uptake regulator or operon structure. This work is foundational for building a mechanistic understanding of iron uptake, which could lead to interventions to prevent bovine and human anaplasmosis.

Repellent and acaricidal activities of basil (Ocimum basilicum) essential oils and rock dust against Ixodes scapularis and Dermacentor variabilis ticks.

Repellent and acaricidal activity of essential oils extracted from three varieties of basil (Ocimum basilicum L.) were evaluated on blacklegged ticks (Ixodes scapularis Say) and American dog ticks (Dermacentor variabilis Say) in laboratory conditions. Essential oils were extracted and characterized through gas chromatography-mass spectrometry, and tested at different concentrations for long-term repellent activity using horizontal bioassays. In addition, basil essential oils were combined with an inert material (i.e., granite rock dust) with known insecticidal and miticidal properties to assess acaricidal activities against adult ticks. Among the tested basil varieties, var. Jolina essential oil at 15% vol/vol concentration repelled 96% of tested ticks up to 2 h post-treatment. The EC50 for I. scapularis nymphs was 4.65% vol/vol (95% confidence interval: 4.73-4.57). In acaricidal tests, the combination of essential oil from var. Aroma 2 at 10% wt/wt with rock dust resulted in 100% tick mortality after only 24 h post-exposure, with a LD50 of 3.48% wt/wt (95% CI 4.05-2.91) for freshly prepared treatment tested on I. scapularis adults. The most common compounds detected in basil essential oils by GC-MS were linalool (52.2% in var. Nu Far, 48.2% in Aroma 2, 43.9% in Jolina), sabinene (6.71% in Nu Far, 8.99% in Aroma 2, 8.11% in Jolina), eugenol (11.2% in Jolina, 8.71% in Aroma 2), and estragole (18.2% in Nu Far). The use of essential oils alone and in combination with rock dust provides an innovative and environmentally friendly approach for managing ticks and inhibiting vector-borne disease transmission.

Tick-borne pathogens in Dermacentor reticulatus collected from dogs in eastern Poland.

In recent years, the distribution of Dermacentor reticulatus ticks has expanded into new territories in many European countries, including Poland, with increased population densities in areas of their regular occurrence. The spread of D. reticulatus enhances the risk of exposure of domestic animals and their owners to tick-borne diseases. The objective of this study was to assess the prevalence of infection of D. reticulatus ticks feeding on dogs with the pathogens Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum. The study material comprised 152 D. reticulatus ticks collected from dogs in the northeastern part of Lublin Province (eastern Poland). A ready-made AmpliSens® TBEV, B.burgdorferi sl, A.phagocytophilum, E.chaffeensis/E.muris-FRT PCR kit was used for qualitative detection and differentiation of tick-borne infections. The assessment of the degree of infection of the analyzed ticks with the two pathogens revealed that 9.2% (14/152) of the examined ticks were infected with one of the pathogens. No co-infections with the pathogens were detected in any of the ticks. The highest specific percentage of infections (8.6%, 13/152) was associated with A. phagocytophilum. The presence of B. burgdorferi s.l. was detected in only one of the examined ticks (0.7%). The spread of D. reticulatus to new territories and the increase in population density in areas of their regular occurrence implies the need for further studies of the prevalence of pathogens with medical and veterinary importance in order to assess the risk of tick-borne diseases.

Autochthonous Case of Rickettsia slovaca Infection in Russia.

We describe an autochthonous case of Rickettsia slovaca infection in a man 35 years of age from Russia who had tickborne lymphadenopathy. We used ELISA and quantitative PCR testing to further identify DNA and confirm diagnosis. Physicians in Russia should consider similar diseases in differential diagnoses after tick bites.

Scalp eschar and neck lymphadenopathy by Rickettsia slovaca after Dermacentor marginatus tick bite case report: multidisciplinary approach to a tick-borne disease.

BACKGROUND: Scalp Eschar and Neck LymphAdenopathy after Tick bite is a zoonotic non-pathogen-specific disease most commonly due to Rickettsia slovaca and Rickettsia raoultii. Diagnosis is mostly based only on epidemiological and clinical findings, without serological or molecular corroboration. We presented a clinical case in which diagnosis was supported by entomological identification and by R. slovaca DNA amplifications from the tick vector. CASE PRESENTATION: A 6-year-old child presented with asthenia, scalp eschar and supraclavicular and lateral-cervical lymphadenopathy. Scalp Eschar and Neck LymphAdenopathy After Tick bite syndrome following a Dermacentor marginatus bite was diagnosed. Serological test on serum revealed an IgG titer of 1:1024 against spotted fever group rickettsiae, polymerase chain reaction assays on tick identified Rickettsia slovaca. Patient was successfully treated with doxycycline for 10 days. CONCLUSIONS: A multidisciplinary approach including epidemiological information, clinical evaluations, entomological identification and molecular investigations on tick, enabled proper diagnosis and therapy.