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Worldwide, ticks are important vectors of human and animal pathogens. Besides Lyme Borreliosis, a variety of other bacterial and protozoal tick-borne infections are of medical interest in Europe. In this study, 553 questing and feeding Ixodes ricinus (n = 327) and Dermacentor reticulatus ticks (n = 226) were analysed by PCR for Borrelia, Rickettsia, Anaplasma, Coxiella, Francisella and Babesia species. Overall, the pathogen prevalence in ticks was 30.6% for I. ricinus and 45.6% for D. reticulatus. The majority of infections were caused by members of the spotted-fever group rickettsiae (24.4%), 9.4% of ticks were positive for Borrelia burgdorferi sensu lato, with Borrelia afzelii being the most frequently detected species (40.4%). Pathogens with low prevalence rates in ticks were Anaplasma phagocytophilum (2.2%), Coxiella burnetii (0.9%), Francisella tularensis subspecies (0.7%), Bartonella henselae (0.7%), Babesia microti (0.5%) and Babesia venatorum (0.4%). On a regional level, hotspots of pathogens were identified for A. phagocytophilum (12.5-17.2%), F. tularensis ssp. (5.5%) and C. burnetii (9.1%), suggesting established zoonotic cycles of these pathogens at least at these sites. Our survey revealed a high burden of tick-borne pathogens in questing and feeding I. ricinus and D. reticulatus ticks collected in different regions in Belarus, indicating a potential risk for humans and animals. Identified hotspots of infected ticks should be included in future surveillance studies, especially when F. tularensis ssp. and C. burnetii are involved.

Recently, a two-year study found that long-term prescribed fire significantly reduced tick abundance at sites with varying burn regimes (burned surrounded by burned areas [BB], burned surrounded by unburned areas [BUB], and unburned surrounded by burned areas [UBB]). In the current study, these ticks were tested for pathogens to more directly investigate the impacts of long-term prescribed burning on human disease risk. A total of 5,103 ticks (4,607  Amblyomma americanum , 76  Amblyomma maculatum , 383 Ixodes scapularis , two Ixodes brunneus , and 35 Dermacentor variabilis ) were tested for Borrelia spp., Rickettsia spp., Ehrlichia spp., and Anaplasma phagocytophilum . Long-term prescribed fire did not significantly impact pathogen prevalence except that A. americanum from burned habitats had significantly lower prevalence of Rickettsia (8.7% and 4.6% for BUB and UBB sites, respectively) compared to ticks from control sites (unburned, surrounded by unburned [UBUB])(14.6%). However, during the warm season (spring/summer), encounter rates with ticks infected with pathogenic bacteria was significantly lower (98%) at burned sites than at UBUB sites. Thus, despite there being no differences in pathogen prevalence between burned and UBUB sites, risk of pathogen transmission is lower at sites subjected to long-term burning due to lower encounter rates with infected ticks.

Rationale Tick paralysis has not been reported in horses in North America. Clinical Findings Two American Miniature horses were examined for progressive weakness and recumbency. Numerous ticks (Dermacentor variabilis) were found on both horses. Horse 1 was recumbent (grade 5/5 gait deficit) on presentation, whereas Horse 2 was standing but ataxic (grade 4/5 gait deficit) and tetraparetic. Both horses had decreased tongue and tail muscle tone, and had normal spinal reflexes. Cerebrospinal fluid cytology was normal. Equine herpesvirus‐1 testing was negative. Pertinent Interventions Ticks were removed within 24 hours of presentation. Both horses were treated topically with permethrin. Supportive care included fluid therapy, treatment for corneal ulceration, and frequent repositioning during recumbency. Outcome Within 48 hours of tick removal, both horses were neurologically normal. Clinical Relevance Ours is the first reported case of presumptive tick paralysis in horses in North America. Although rare, tick paralysis should be considered in horses presented with acute‐onset weakness progressing to recumbency.

Background An imidacloprid/flumethrin collar (Seresto®) was previously shown to prevent infection with Babesia canis , transmitted by Dermacentor reticulatus , in dogs for up to 1 month after application. The present study evaluated the prevention of transmission throughout the claimed efficacy period of 8 months. Methods Eight animals each were randomly included in groups 1 (negative control) and 2 (Seresto® collar), respectively. Animals in group 2 received the Seresto® collar on Day 0. Tick challenges were performed monthly from the 2nd to the 8th month. Assessment criteria included in situ tick counts 48 hours post-challenge, polymerase chain reaction (PCR) analyses and immunofluorescence assays (IFA). Whenever dogs were diagnosed with babesiosis they were “rescue-treated”, excluded and replaced. Consequently, 24 replacement animals were introduced at various time points throughout the study in the control group; thus data for a total of 32 dogs were available in the latter group at study termination. Results Acaricidal efficacy for in situ counts was 93% on Day 30, and ranged from 97 to 100% thereafter. No B. canis specific DNA or antibodies were detected in any Seresto®-treated dog at any time. Babesia canis -specific DNA and antibodies were detected in 2–6 of 8 control dogs after each challenge, confirming the validity of the challenge model. Conclusions The Seresto® collar was highly effective against challenges with D. reticulatus ticks for up to 8 months. The high sustained acaricidal efficacy over this period prevented transmission of B. canis , thus fully protecting dogs against infection in this experimental infestation model.

Ticks are of medical importance owing to their ability to transmit pathogens to humans and animals. The Rocky Mountain wood tick, Dermacentor andersoni , is a vector of a number of pathogens, including Anaplasma marginale, which is the most widespread tick-borne pathogen of livestock. Although ticks host pathogenic bacteria, they also harbor bacterial endosymbionts that have a role in tick physiology, survival, as well as pathogen acquisition and transmission. The goal of this study was to characterize the bacterial microbiome and examine the impact of microbiome disruption on pathogen susceptibility. The bacterial microbiome of two populations of D. andersoni with historically different susceptibilities to A. marginale was characterized. In this study, the microbiome was disrupted and then ticks were exposed to A. marginale or Francisella novicida to determine whether the microbiome correlated with pathogen susceptibility. Our study showed that an increase in proportion and quantity of Rickettsia bellii in the microbiome was negatively correlated to A. marginale levels in ticks. Furthermore, a decrease in Francisella endosymbionts was associated with lower F. novicida infection levels, demonstrating a positive pathogen–endosymbiont relationship. We demonstrate that endosymbionts and pathogens have varying interactions, and suggest that microbiome manipulation may provide a possible method for biocontrol by decreasing pathogen susceptibility of ticks.

Extracellular vesicles are thought to facilitate pathogen transmission from arthropods to humans and other animals. Here, we reveal that pathogen spreading from arthropods to the mammalian host is multifaceted. Extracellular vesicles from Ixodes scapularis enable tick feeding and promote infection of the mildly virulent rickettsial agent Anaplasma phagocytophilum through the SNARE proteins Vamp33 and Synaptobrevin 2 and dendritic epidermal T cells. However, extracellular vesicles from the tick Dermacentor andersoni mitigate microbial spreading caused by the lethal pathogen Francisella tularensis . Collectively, we establish that tick extracellular vesicles foster distinct outcomes of bacterial infection and assist in vector feeding by acting on skin immunity. Thus, the biology of arthropods should be taken into consideration when developing strategies to control vector-borne diseases. Extracellular vesicles have been implicated in the transmission of pathogens from the arthropod to the human host. Here the authors show that tick-derived extracellular vesicles play a role in feeding and modulate the outcome of bacterial infection.

Background The American dog tick, Dermacentor variabilis , is an important vector of pathogens to humans, wildlife and domestic animals in North America. Although this tick species is widely distributed in the USA and Canada, knowledge of its range-wide phylogeographic patterns remains incomplete. Methods We carried out a phylogenetic analysis of D. variabilis using samples collected from 26 USA states and five Canadian provinces. Tick samples ( n = 1053 in total) originated from two main sources: existing archives (2000–2011), and new collections made from 2012 to 2013. We sequenced a 691 bp fragment of the cox 1 gene from a subset ( n = 332) of geographically diverse D. variabilis . DNA extracted from individual ticks ( n = 1053) was also screened for a Francisella -like endosymbiont, using a targeted 16S rRNA sequencing approach, and important pathogens ( Rickettsia spp. and Coxiella burnetii ), using species-specific quantitative PCR assays. Results Maximum parsimony analysis of cox 1 sequences revealed two major groups within D. variabilis with distinct geographical distributions: one from the eastern USA/Canada (Group 1) and one from the west coast states of the USA (California and Washington; Group 2). However, genetic subdivisions within both of these two major groups were weak to moderate and not tightly correlated with geography. We found molecular signatures consistent with Francisella -like endosymbionts in 257 of the DNA extracts from the 1053 individual ticks, as well as Rickettsia spp. and Coxiella burnetii in a small number of ticks ( n = 29 and 2, respectively). Phylogenetic patterns for Francisella -like endosymbionts, constructed using sequence data from the bacterial 16S rRNA locus, were similar to those for D. variabilis , with two major groups that had a nearly perfect one-to-one correlation with the two major groups within D. variabilis . Conclusions Our findings reveal a distinct phylogenetic split between the two major D. variabilis populations. However, high levels of genetic mixture among widely separated geographical localities occur within each of these two major groups. Furthermore, our phylogenetic analyses provide evidence of long-term tick-symbiont co-evolution. This work has implications for understanding the dispersal and evolutionary ecology of D. variabilis and associated vector-borne diseases.

Background Species of Canidae in Russia can be infested with up to 24 different tick species; however, the frequency of different tick species infesting domestic dogs across Russia is not known. In addition, tick-borne disease risks for domestic dogs in Russia are not well quantified. The goal of this study was to conduct a nationwide survey of ticks collected from infested dogs admitted to veterinary clinics in Russian cities and to identify pathogens found in these ticks. Methods Ticks feeding on dogs admitted to 32 veterinary clinics in 27 major cities across Russia were preserved in ethanol and submitted to a central facility for examination. After identification, each tick was evaluated for infection with known tick-borne pathogens using PCR. Results There were 990 individual ticks collected from 636 dogs. All collected ticks belonged to the Ixodidae (hard ticks) and represented 11 species of four genera, Dermacentor , Ixodes , Rhipicephalus and Haemaphysalis . Four most common tick species were D. reticulatus , followed by I. persulcatus , I. ricinus and R. sanguineus . Ixodes persulcatus ticks were found to be infected with 10 different pathogens, and ticks of this species were more frequently infected than either D. reticulatus or I. ricinus . Ixodes persulcatus females were also more frequently co-infected with two or more pathogens than any other tick. Pathogenic species of five genera were detected in ticks: Anaplasma centrale , A . phagocytophilum and A . marginale ; Babesia canis , B. microti , B. venatorum , B. divergens , B. crassa and B. vogeli ; Borrelia miyamotoi , B. afzelii and B .  garinii ; Ehrlichia muris , E. canis and E . ruminantum ; and Theileria cervi . Anaplasma marginale , E. canis , B. crassa , B. vogeli and T. cervi were detected in I. persulcatus , and Babesia canis in D. marginatum , for the first time in Russia. Conclusions Multiple ticks from four genera and 11 species of the family Ixodidae were collected from domestic dogs across Russia. These ticks commonly carry pathogens and act as disease vectors. Ixodes persulcatus ticks present the greatest risk for transmission of multiple arthropod-borne pathogens.

Insect vitellogenin (Vg) has been considered to be synthesized in the fat body. Here, we found that abundant Vg protein is synthesized in Laodelphax striatellus hemocytes as well. We also determined that only the hemocyte-produced Vg binds to Rice stripe virus (RSV) in vivo. Examination of the subunit composition of L. striatellus Vg (LsVg) revealed that LsVg was processed differently after its expression in different tissues. The LsVg subunit able to bind to RSV exist stably only in hemocytes, while fat body-produced LsVg lacks the RSV-interacting subunit. Nymph and male L. striatellus individuals also synthesize Vg but only in hemocytes, and the proteins co-localize with RSV. We observed that knockdown of LsVg transcripts by RNA interference decreased the RSV titer in the hemolymph, and thus interfered with systemic virus infection. Our results reveal the sex-independent expression and tissue-specific processing of LsVg and also unprecedentedly connect the function of this protein in mediating virus transmission to its particular molecular forms existing in tissues previously known as non-Vg producing.