Prevalence Of Infected Ticks Research Articles

Lime for Lyme: Treatment of Leaf Litter with Dolomitic Lime Powder Impairs Activity of Immature Ixodes scapularis Ticks.

Background: Tick-borne diseases are an emerging threat to public health throughout the temperate world, leading to a growing field of research aimed at developing and testing intervention strategies for reducing human-tick encounters or prevalence of infection in ticks. Various wide-spectrum chemical acaricides have proven effective for controlling tick populations, but many of these have potential deleterious side-effects on health and the environment. In addition to chemical acaricides, certain compounds such as diatomaceous earth have been shown to have physical acaricidal properties. We hypothesized that dolomitic lime (CaMg(CO3)2, a corrosive, desiccant mineral that is already used extensively in agricultural and forestry contexts to balance the pH of soils, may affect ticks' locomotory activity, habitat position, or survival and that this should manifest as a reduction in the number of questing ticks collected by dragging. Objective: This study aimed to formally assess this hypothesis in a controlled laboratory setting. Methods: We carried out a microcosm experiment, with one control and three treated microcosm trays, each replicating the natural substrate characterizing I. scapularis habitat in northeastern North America. Each tray was infested with 200 living larvae and 50 nymphs, and then treated with 0 (control), 50, 100, or 500 g/m2 of lime powder. Ticks were collected by microdragging 24 and 72 h postliming. Results: Efficacy of liming at reducing the number of collected questing ticks ranged from 87% to 100% for larvae and 0% to 69% for nymphs 24 h postliming and from 91% to 93% for larvae and -47% to 65% for nymphs 72 postliming. Conclusion: This study provides the first experimental evidence of the potential efficacy of liming for impairing activity of questing immature ticks. Given that lime is a low-cost material, that methods for widespread application in deciduous woodlands already exist, and that it has been documented as having a limited negative impact on the environment, further assessment of lime application as a public health risk reduction intervention for tick-borne diseases is warranted.

Effects of rodent abundance on ticks and Borrelia: results from an experimental and observational study in an island system

BackgroundLyme borreliosis is the most common tick-borne disease in Europe and is often caused by Borrelia afzelii, which is transmitted by Ixodes ricinus ticks. The prevalence and abundance of infected ticks fluctuate in time and space, influencing human infection risk. Rodents are reservoir hosts for B. afzelii and important feeding hosts for larval ticks. In the study reported here, we examined how variation in rodent abundance is associated with B. afzelii infection prevalence in ticks, the density of nymphs (DON) and the density of infected nymphs (DIN) in the following year. We further analysed the relationships between the abundance of infected rodents and nymphal infection prevalence (NIP) and DIN.MethodsWe conducted a study that combined experimental and observational approaches on 15 islands (10 small islands and 5 large islands) in Finland. On all of the islands, ticks and rodents were monitored and sampled during the summer of 2019, with the monitoring of tick abundance and sampling continuing into the spring of 2020. On five of the 10 small islands, captured rodents were removed from the island (“removal” islands), and on the other five small islands, captured rodents were released back to the trapping site after marking and sampling (“control” islands). On the five large islands, captured rodents were released back to the trapping site after marking and sampling. The presence of B. afzelii from nymph and rodent samples was examined.ResultsThe results of the experimental study showed that neither treatment (removal), rodent abundance index nor abundance index of infected rodents in 2019 was associated with DON, NIP or DIN in 2020. Based on data from the observational study, the NIP in 2020 decreased with increasing rodent abundance index and abundance index of infected rodents in 2019. However, the DIN in 2020 was not associated with the rodent abundance index or the abundance index of infected rodents in 2019. In addition, in the observational study, DON in 2020 increased with increasing rodent abundance index.ConclusionsOur results suggest that low rodent abundance during the tick activity period is not sufficient for reducing the disease hazard and, hence, rodent removal may not be a feasible control measure in natural ecosystems.Graphical abstract

First detection of Candidatus Rickettsia tarasevichiae in Hyalomma marginatum ticks.

Ticks are important vectors of zoonotic diseases and play a major role in the circulation and transmission of many rickettsial species. The aim of this study was to investigate the carriage of Candidatus Rickettsia tarasevichiae (CRT) in a total of 1168 ticks collected in Inner Mongolia to elucidate the potential public health risk of this pathogen, provide a basis for infectious disease prevention, control and prediction and contribute diagnostic ideas for clinical diseases that present with fever in populations exposed to ticks. A total of four tick species, Haemaphysalis concinna (n = 21), Dermacentor nuttalli (n = 122), Hyalomma marginatum (n = 148), and Ixodes persulcatus (n = 877), were collected at nine sampling sites in Inner Mongolia, China, and identified by morphological and molecular biological methods. Reverse transcription PCR targeting the 16S ribosomal RNA (rrs), gltA, groEL, ompB and Sca4 genes was used to detect CRT DNA. Sequencing was used for pathogen species confirmation. The molecular epidemiological analysis showed that three species of ticks were infected with CRT, and the overall positive rate was as high as 42%. The positive rate of I. persulcatus collected in Hinggan League city was up to 96%, and that of I. persulcatus collected in Hulun Buir city was 50%. The pool positive rates of D. nuttalli and H. marginatum collected in Bayan Nur city and H. concinna collected in Hulun Buir city were 0%, 28% and 40%, respectively. This study revealed the high prevalence of CRT infection in ticks from Inner Mongolia and the first confirmation of CRT detected in H. marginatum in China. The wide host range and high infection rate in Inner Mongolia may dramatically increase the exposure of CRT to humans and other vertebrates. The role of H. marginatum in the transmission of rickettsiosis and its potential risk to public health should be further considered.

Spatial and Temporal Variability in Prevalence Rates of Members of the Borrelia burgdorferi Species Complex in Ixodes ricinus Ticks in Urban, Agricultural and Sylvatic Habitats in Slovakia.

Lyme borreliosis (LB) is the most prevalent tick-borne human infection in Europe, with increasing incidence during the latest decades. Abundant populations of Ixodes ricinus, the main vector of the causative agent, spirochetes from the Borrelia burgdorferi sensu lato (Bbsl) complex, have been observed in urban and suburban areas of Europe, in general, and Slovakia, particularly. Understanding the spread of infectious diseases is crucial for implementing effective control measures. Global changes affect contact rates of humans and animals with Borrelia-infected ticks and increase the risk of contracting LB. The aim of this study was to investigate spatial and temporal variation in prevalence of Bbsl and diversity of its species in questing I. ricinus from three sites representing urban/suburban, natural and agricultural habitat types in Slovakia. Ixodes ricinus nymphs and adults were collected by dragging the vegetation in green areas of Bratislava town (urban/suburban habitat), in the Small Carpathians Mountains (natural habitat) (south-western Slovakia) and in an agricultural habitat at Rozhanovce in eastern Slovakia. Borrelia presence in ticks was detected by PCR and Bbsl species were identified by restriction fragment length polymorphism (RFLP). Borrelia burgdorferi s.l. species in coinfected ticks were identified by reverse line blot. Significant spatial and temporal variability in prevalence of infected ticks was revealed in the explored habitats. The lowest total prevalence was detected in the urban/suburban habitat, whereas higher prevalence was found in the natural and agricultural habitat. Six Bbsl species were detected by RFLP in each habitat type -B. burgdorferi sensu stricto (s.s.), B. afzelii, B. garinii, B. valaisiana, B. lusitaniae and B. spielmanii. Coinfections accounted for 3% of the total infections, whereby B. kurtenbachii was identified by RLB and sequencing in mixed infection with B. burgdorferi s.s, B. garinii and B. valaisiana. This finding represents the first record of B. kurtenbachii in questing I. ricinus in Slovakia and Europe. Variations in the proportion of Bbsl species were found between nymphs and adults, between years and between habitat types. Spatial variations in prevalence patterns and proportion of Bbsl species were also confirmed between locations within a relatively short distance in the urban habitat. Habitat-related and spatial variations in Borrelia prevalence and distribution of Bbsl species are probably associated with the local environmental conditions and vertebrate host spectrum. Due to the presence of Borrelia species pathogenic to humans, all explored sites can be ranked as areas with high epidemiological risk.

Effective Methods of Estimation of Pathogen Prevalence in Pooled Ticks.

Since tick-borne diseases (TBDs) incidence, both in human and animal populations, is increasing worldwide, there is the need to assess the presence, distribution and prevalence of tick-borne pathogens. Reliable estimates on tick-borne pathogens (TBPs) prevalence represent the public health foundation to create risk maps and take effective prevention and control actions against TBDs. Tick surveillance consists of collecting and testing (usually in pools) thousands of specimens. Construction and analysis of tick pools represent a challenge due to the complexity of tick-borne pathogens and tick-borne diseases ecology. The aim of this study is to provide a practical guideline on appropriate pooling strategies and statistical analysis of infection prevalence through: (i) reporting the different pooling strategies and statistical methodologies commonly used to calculate pathogen prevalence in tick populations and (ii) practical comparison between statistical methods utilising a real dataset of infection prevalence in ticks collected in Northern Italy. Reporting detailed information on tick pool composition and size is as important as the correct TBPs prevalence estimation. Among the prevalence indexes, we suggest using maximum-likelihood estimates of pooled prevalence instead of minimum infection rate or pool positivity rate given the merits of the method and availability of software.

Effects of Neighborhood-Scale Acaricidal Treatments on Infection Prevalence of Blacklegged Ticks (Ixodes scapularis) with Three Zoonotic Pathogens.

Acaricides are hypothesized to reduce human risk of exposure to tick-borne pathogens by decreasing the abundance and/or infection prevalence of the ticks that serve as vectors for the pathogens. Acaricides targeted at reservoir hosts such as small mammals are expected to reduce infection prevalence in ticks by preventing their acquisition of zoonotic pathogens. By reducing tick abundance, reservoir-targeted or broadcast acaricides could reduce tick infection prevalence by interrupting transmission cycles between ticks and their hosts. Using an acaricide targeted at small-mammal hosts (TCS bait boxes) and one sprayed on low vegetation (Met52 fungal biocide), we tested the hypotheses that infection prevalence of blacklegged ticks with zoonotic pathogens would be more strongly diminished by TCS bait boxes, and that any effects of both acaricidal treatments would increase during the four years of deployment. We used a masked, placebo-controlled design in 24 residential neighborhoods in Dutchess County, New York. Analyzing prevalence of infection with Borrelia burgdorferi, Anaplasma phagocytophilum, and Babesia microti in 5380 nymphal Ixodes scapularis ticks, we found little support for either hypothesis. TCS bait boxes did not reduce infection prevalence with any of the three pathogens compared to placebo controls. Met52 was associated with lower infection prevalence with B. burgdorferi compared to placebo controls but had no effect on prevalence of infection with the other two pathogens. Although significant effects of year on infection prevalence of all three pathogens were detected, hypothesized cumulative reductions in prevalence were observed only for B. burgdorferi. We conclude that reservoir-targeted and broadcast acaricides might not generally disrupt pathogen transmission between reservoir hosts and tick vectors or reduce human risk of exposure to tick-borne pathogens.

1373. Using Geospatial Analysis to Describe the Association between Active Tick Surveillance Data and Clinical Cases of Anaplasmosis

Abstract Background Anaplasmosis is a vector-borne disease spread by Ixodes scapularis ticks mainly in the Northeastern United States. The Connecticut Department of Public Health (CT DPH) made anaplasmosis a state-wide reportable disease in 2008 and a large increase in reportable cases was seen in Connecticut between 2014 and 2019. Methods This study used clinical cases of anaplasmosis reported to the CT DPH and tick infection prevalence data to understand emerging geographic hotspots for the disease in the state and to evaluate the association between the human and tick infections. Human incidence rates (IR) were calculated per 100,000 in the population by county. Tick infection prevalence was calculated as an acarological risk index (ARI) using active tick surveillance data from the Connecticut Agricultural Experiment Station (CAES). These two calculations were analyzed with a Spearman rank correlation in SAS version 9.4 and overlaid on ArcMap. Results During the 2019-2020 period, 420 human cases of anaplasmosis were included and 148 infected ticks were identified. There was a significant positive correlation between IR and ARI identified (Spearman correlation 0.54, p = 0.03). Litchfield County had the highest number of human cases (128) and Fairfield County had the highest proportion of infected ticks (11.25%). The area with the greatest increase in both ARI and IR in Connecticut from 2019-2020 was New London County (ARI increased from 0.073 to 0.108, IR increased from 2.64 to 8.57). Conclusion This study supports the use of active tick surveillance in identifying geographic areas high incidence of human anaplasmosis and provides a strategy to evaluate tick surveillance for anaplasma infection. Active tick surveillance can be useful in guiding public health interventions and inform public health and clinician education on anaplasmosis. Disclosures All Authors: No reported disclosures.

Fluralaner Baits Reduce the Infestation of Peromyscus spp. Mice (Rodentia: Cricetidae) by Ixodes scapularis (Acari: Ixodidae) Larvae and Nymphs in a Natural Environment.

The development of interventions that reduce Lyme disease incidence remains a challenge. Reservoir-targeted approaches aiming to reduce tick densities or tick infection prevalence with Borrelia burgdorferi have emerged as promising ways to reduce the density of infected ticks. Acaricides of the isoxazoline family offer high potential for reducing infestation of ticks on small mammals as they have high efficacy at killing feeding ticks for a long period. Fluralaner baits were recently demonstrated as effective, in the laboratory, at killing Ixodes scapularis larvae infesting Peromyscus mice, the main reservoir for B. burgdorferi in northeastern North America. Here, effectiveness of this approach for reducing the infestation of small mammals by immature stages of I. scapularis was tested in a natural environment. Two densities of fluralaner baits (2.1 baits/1,000 m2 and 4.4 baits/1,000 m2) were used during three years in forest plots. The number of I. scapularis larvae and nymphs per mouse from treated and control plots were compared. Fluralaner baiting reduced the number of larvae per mouse by 68% (CI95: 51-79%) at 2.1 baits/1,000 m2 and by 86% (CI95: 77-92%) at 4.4 baits/1,000 m2. The number of nymphs per mouse was reduced by 72% (CI95: 22-90%) at 4.4 baits/1,000 m2 but was not significantly reduced at 2.1 baits/1,000 m2. Reduction of Peromyscus mouse infestation by immature stages of I. scapularis supports the hypothesis that an approach targeting reservoirs of B. burgdorferi with isoxazolines has the potential to reduce tick-borne disease risk by decreasing the density of infected ticks in the environment.

A comparison of horizontal and transovarial transmission efficiency of Borrelia miyamotoi by Ixodes scapularis

Borrelia miyamotoi is a relapsing fever spirochete carried by Ixodes spp. ticks throughout the northern hemisphere. The pathogen is acquired either transovarially (vertically) or horizontally through blood-feeding and passed transtadially across life stages. Despite these complementary modes of transmission, infection prevalence of ticks with B. miyamotoi is typically low (<5%) in natural settings and the relative contributions of the two transmission modes have not been studied extensively. Horizontal transmission of B. miyamotoi (strain CT13–2396 or wild type strain) was initiated using infected Ixodes scapularis larvae or nymphs to expose rodents, which included both the immunocompetent CD-1 laboratory mouse (Mus musculus) and a natural reservoir host, the white-footed mouse (Peromyscus. leucopus), to simulate natural enzootic transmission. Transovarial transmission was evaluated using I. scapularis exposed to B. miyamotoi as either larvae or nymphs feeding on immunocompromised SCID mice (M. musculus) and subsequently fed as females on New Zealand white rabbits. Larvae from infected females were qPCR-tested individually to assess transovarial transmission rates. Tissue tropism of B. miyamotoi in infected ticks was demonstrated using in situ hybridization. Between 1 and 12% of ticks were positive (post-molt) for B. miyamotoi after feeding on groups of CD-1 mice or P. leucopus with evidence of infection, indicating that horizontal transmission was inefficient, regardless of whether infected larvae or nymphs were used to challenge the mice. Transovarial transmission occurred in 7 of 10 egg clutches from infected females. Filial infection prevalence in larvae ranged from 3 to 100% (median 71%). Both larval infection prevalence and spirochete load were highly correlated with maternal spirochete load. Spirochetes were disseminated throughout the tissues of all three stages of unfed ticks, including the salivary glands and female ovarian tissue. The results indicate that while multiple transmission routes contribute to enzootic maintenance of B. miyamotoi, transovarial transmission is likely to be the primary source of infected ticks and therefore risk assessment and tick control strategies should target adult female ticks.

Inter-annual variation in prevalence of Borrelia burgdorferi sensu stricto and Anaplasma phagocytophilum in host-seeking Ixodes scapularis (Acari: Ixodidae) at long-term surveillance sites in the upper midwestern United States: Implications for public health practice

The geographic range of the blacklegged tick, Ixodes scapularis, and its associated human pathogens have expanded substantially over the past 20 years putting an increasing number of persons at risk for tick-borne diseases, particularly in the upper midwestern and northeastern United States. Prevention and diagnosis of tick-borne diseases rely on an accurate understanding by the public and health care providers of when and where persons may be exposed to infected ticks. While tracking changes in the distribution of ticks and tick-borne pathogens provides fundamental information on risk for tick-borne diseases, metrics that incorporate prevalence of infection in ticks better characterize acarological risk. However, assessments of infection prevalence are more labor intensive and costly than simple measurements of tick or pathogen presence. Our objective was to examine whether data derived from repeated sampling at longitudinal sites substantially influences public health recommendations for Lyme disease and anaplasmosis prevention, or if more constrained sampling is sufficient. Here, we summarize inter-annual variability in prevalence of the agents of Lyme disease (Borrelia burgdorferi s.s.) and anaplasmosis (Anaplasma phagocytophilum) in host-seeking I. scapularis nymphs and adults at 28 longitudinal sampling sites in the Upper Midwestern US (Michigan, Minnesota, and Wisconsin). Infection prevalence was highly variable among sites and among years within sites. We conclude that monitoring infection prevalence in ticks aids in describing coarse acarological risk trends, but setting a fixed prevalence threshold for prevention or diagnostic decisions is not feasible given the observed variability and lack of temporal trends. Reducing repeated sampling of the same sites had minimal impact on regional (Upper Midwest) estimates of average infection prevalence; this information should be useful in allocating scarce public health resources for tick and tick-borne pathogen surveillance, prevention, and control activities.

Mechanistic movement models reveal ecological drivers of tick-borne pathogen spread.

Identifying ecological drivers of tick-borne pathogen spread has great value for tick-borne disease management. However, theoretical investigations into the consequences of host movement behaviour on pathogen spread dynamics in heterogeneous landscapes remain limited because spatially explicit epidemiological models that incorporate more realistic mechanisms governing host movement are rare. We built a mechanistic movement model to investigate how the interplay between multiple ecological drivers affects the risk of tick-borne pathogen spread across heterogeneous landscapes. We used the model to generate simulations of tick dispersal by migratory birds and terrestrial hosts across theoretical landscapes varying in resource aggregation, and we performed a sensitivity analysis to explore the impacts of different parameters on the infected tick spread rate, tick infection prevalence and infected tick density. Our findings highlight the importance of host movement and tick population dynamics in explaining the infected tick spread rate into new regions. Tick infection prevalence and infected tick density were driven by predictors related to the infection process and tick population dynamics, respectively. Our results suggest that control strategies aiming to reduce tick burden on tick reproduction hosts and encounter rate between immature ticks and pathogen amplification hosts will be most effective at reducing tick-borne disease risk.

Why Lyme disease is common in the northern US, but rare in the south: The roles of host choice, host-seeking behavior, and tick density.

Lyme disease is common in the northeastern United States, but rare in the southeast, even though the tick vector is found in both regions. Infection prevalence of Lyme spirochetes in host-seeking ticks, an important component to the risk of Lyme disease, is also high in the northeast and northern midwest, but declines sharply in the south. As ticks must acquire Lyme spirochetes from infected vertebrate hosts, the role of wildlife species composition on Lyme disease risk has been a topic of lively academic discussion. We compared tick–vertebrate host interactions using standardized sampling methods among 8 sites scattered throughout the eastern US. Geographical trends in diversity of tick hosts are gradual and do not match the sharp decline in prevalence at southern sites, but tick–host associations show a clear shift from mammals in the north to reptiles in the south. Tick infection prevalence declines north to south largely because of high tick infestation of efficient spirochete reservoir hosts (rodents and shrews) in the north but not in the south. Minimal infestation of small mammals in the south results from strong selective attachment to lizards such as skinks (which are inefficient reservoirs for Lyme spirochetes) in the southern states. Selective host choice, along with latitudinal differences in tick host-seeking behavior and variations in tick densities, explains the geographic pattern of Lyme disease in the eastern US.

The species distribution of ticks & the prevalence of Kyasanur forest disease virus in questing nymphal ticks from Western Ghats of Kerala, South India.

Background & objectives:Kyasanur forest disease (KFD) is a zoonotic tick-borne disease across the Western Ghats of India. With the discovery of a cluster of human KFD cases in the Wayanad district of Kerala, the present study was focused on detecting KFD virus (KFDV) in tick populations. To manage this disease, it is necessary to understand the diversity of the tick species and factors influencing the distribution, abundance and prevalence of infected ticks in Wayanad district.Methods:Surveys were conducted from November 2016 to May 2018 in four forest ranges of Wayanad district. Ticks were collected by the dragging method and were identified to species level and assayed for virus detection using real-time polymerase chain reaction.Results:A total of 25,169 ticks were collected from 64 sites. Of the identified species, Haemaphysalis spinigera was the most abundant (56.64%), followed by H. turturis 9047 (35.94%), H. bispinosa 999 (3.96%), Amblyomma integrum 691 (2.74%), H. kyasanurensis (0.55%), Rhipicephalus sanguineus (0.08%), Hyalomma marginatum (0.02%), H. cuspidata (0.01%), R.microplus (0.01%) and Dermacentor auratus (0.003%). The nymphal stage was predominant from December to February having peak activity in January. A total of 572 pools were screened for the presence of KFDV, of which 21 pools were positive. The infection rates in H. spinigera and H. turturis tick were 2.62 and 1.04 per cent, respectively.Interpretation & conclusions:The circulation of KFDV was detected and its correlation with the prevalence in ticks near the fragmented forest and teak plantation areas of Wayanad district. Residents and visitors of these regions may become vulnerable to tick bites and to an increased risk of KFD as the distribution of established, infected tick populations continues to expand.

1338. Development of a Novel Application for Differential Diagnosis of Tick-borne Diseases

BackgroundEarly diagnosis and treatment of tick-borne diseases (TBDs) is critical for mitigating their adverse health outcomes, but the differential diagnosis of TBDs is challenging because many symptoms are nonspecific and commonly used diagnostic assays have significant shortcomings. Furthermore, although the local incidence of TBDs is recognized as an important factor in diagnosis, tools to help clinicians formally consider surveillance data in their decision-making are not available. To address these gaps, Gryphon Scientific developed a differential diagnosis application (app) for TBDs that calculates a patient’s likelihood of infection with specific TBDs based on their symptoms, risk factors, and state of suspected tick exposure.MethodsA differential diagnosis model for TBDs was developed using data on: (1) TBD symptom and risk factor prevalence in TBD patient populations, collected from clinical studies; and (2) human TBD incidence data from notifiable disease surveillance systems and tick infection prevalence data from reports and public databases, which were combined to develop an environmental risk measure. These data were used to build a Bayesian Belief Network (BBN) model that predicts TBD infection probabilities based on a patient’s symptoms, risk factors, and state of suspected tick exposure. Performance of the model was validated using case studies from the biomedical literature. The model was incorporated into an app developed using R-shiny, called TBD-DDx (Figures 1 and 3).ResultsA pilot application was developed that includes 10 states (AR, CT, MA, ME, MN, MO, NH, RI, VT, and WI) and the 11 TBDs endemic to those states. The differential diagnosis model identified the patient’s true disease as the top-predicted disease in 56% of cases and within the top three predicted TBD in 84% of cases. The inclusion of incidence factors in the model improved performance (Figure 4).ConclusionThese results demonstrate that the TBD-DDx app is a promising tool for informing clinical diagnoses of TBDs to guide selection of diagnostic testing and treatment. This study represents the first use of a BBN modeling approach that incorporates an environmental risk measure and could be adapted for differential diagnosis of other diseases with environmental or other exposure risks. Disclosures All authors: No reported disclosures.

Molecular investigation and phylogeny of species of the Anaplasmataceae infecting animals and ticks in Senegal

BackgroundOur study aimed to assess the diversity of the species of Anaplasmataceae in Senegal that infect animals and ticks in three areas: near Keur Momar Sarr (northern region), Dielmo and Diop (Sine Saloum, central region of Senegal), and in Casamance (southern region of Senegal).MethodsA total of 204 ticks and 433 blood samples were collected from ruminants, horses, donkeys and dogs. Ticks were identified morphologically and by molecular characterization targeting the 12S rRNA gene. Molecular characterization of species of Anaplasmataceae infecting Senegalese ticks and animals was conducted using the 23S rRNA, 16S rRNA, rpoB and groEL genes.ResultsTicks were identified as Rhipicephalus evertsi evertsi (84.3%), Hyalomma rufipes (8.3%), Hyalomma impeltatum (4.9%), R. bursa (1.5%) and R. muhsamae (0.9%). The overall prevalence of Anaplasmataceae infection in ticks was 0.9%, whereas 41.1% of the sampled animals were found infected by one of the species belonging to this family. We identified the pathogen Anaplasma ovis in 55.9% of sheep, A. marginale and A. centrale in 19.4% and 8.1%, respectively, of cattle, as well as a putative new species of Anaplasmataceae. Two Anaplasma species commonly infecting ruminants were identified. Anaplasma cf. platys, closely related to A. platys was identified in 19.8% of sheep, 27.7% of goats and 22.6% of cattle, whereas a putative new species, named here provisionally “Candidatus Anaplasma africae”, was identified in 3.7% of sheep, 10.3% of goats and 8.1% of cattle. Ehrlichia canis and Anaplasma platys were identified only from dogs sampled in the Keur Momar Sarr area. Ehrlichia canis was identified in 18.8% of dogs and two R. e. evertsi ticks removed from the same sheep. Anaplasma platys was identified in 15.6% of dogs. Neither of the dogs sampled from Casamance region nor the horses and donkeys sampled from Keur Momar Sarr area were found infected by an Anaplasmataceae species.ConclusionsThis study presents a summary of Anaplasmataceae species that infect animals and ticks in three areas from the northern, central and southern regions of Senegal. To our knowledge, our findings demonstrate for the first time the presence of multiple Anaplasmataceae species that infect ticks and domestic animals in Senegal. We recorded two potentially new species commonly infecting ruminants named here provisionally as Anaplasma cf. platys and “Candidatus Anaplasma africae”. However, E. canis was the only species identified and amplified from ticks. None of the other Anaplasmataceae species identified in animals were identified in the tick species collected from animals.

The role of juvenile Dermacentor reticulatus ticks as vectors of microorganisms and the problem of \u2018meal contamination\u2019

Juvenile Dermacentor reticulatus ticks inhabit nests and burrows of their rodent hosts and cannot be collected from vegetation. To detect vertical transmission of Babesia canis in D. reticulatus, we studied larvae and nymphs collected from rodents. However, the molecular techniques used for detection of pathogen DNA are sensitive enough to detect not only pathogens vectored by ticks but also those taken up with current or previous blood meals (‘meal contamination’) or just present in the environment and on the tick or host surface (‘environmental contaminations’). Thus, an additional aim of our study was to evaluate the extent of such contamination while studying feeding ticks collected from rodents. Juvenile D. reticulatus were collected from 140 rodents: 91 bank voles trapped in two forest sites in the Mazury Lake District and 49 rodents (Apodemus and Microtus spp.) from an open habitat near the town of Białobrzegi in Central Poland. Altogether 504 D. reticulatus ticks, comprising 266 individually evaluated nymphs and 238 larvae assigned to 50 larval pools, were studied for the presence of Babesia, Bartonella and Rickettsia spp. DNA. Statistical analyses were conducted to (1) evaluate the effect of rodent host factors (species, sex and age) on prevalence of infection in ticks, and (2) to compare the frequency of positive samples between groups of pathogen-positive and pathogen-negative rodent hosts. To complete the last aim, blood samples obtained from 49 rodents from Białobrzegi were studied for the presence of Babesia and Bartonella DNA. Infestation of rodent hosts with juvenile ticks ranged between 46 and 78%, with a mean abundance of 3.6 ticks/rodent for D. reticulatus and 4.8 ticks/rodent for Ixodes ricinus. The highest prevalence of PCR-positive D. reticulatus samples was obtained for Rickettsia spp. (28%) and R. raoultii was identified in 22 sequenced PCR products. Babesia DNA was detected in 20 (7.5%), including B. microti in 18 (6.8%) and B. canis in two (0.8%) of 266 D. reticulatus nymphs that were analyzed. Babesia microti DNA was also detected in four pools of D. reticulatus larvae (4/50 pools = 8%). The detection success of B. microti in D. reticulatus was associated with the species of the rodent hosts of the ticks (much higher for typical B. microti-host-species such as Microtus spp. than for Apodemus spp.) and host age (3 × higher in ticks collected from adult hosts in comparison to juvenile ones). Moreover, the DNA of B. microti was detected in 68% of D. reticulatus nymphs collected from B. microti-positive rodents in comparison to only 1.6% of nymphs collected from B. microti-negative rodents. Bartonella DNA was detected in 18% of D. reticulatus tick samples (38% of larval pools, 14% of nymphs). Again, host factors played important roles for ‘tick positivity’-the highest prevalence of positive ticks was on Apodemus spp., which are regarded as Bartonella reservoirs. Bartonella DNA was detected in 42% of nymphs and 57% of larval pools collected from Bartonella-positive rodents in comparison to 28% of nymphs and 11% of larvae collected from Bartonella-negative rodents. Vertical transmission of B. canis in D. reticulatus ticks was confirmed in the field. Additionally, we demonstrated that ‘meal contamination’ generates a confounding signal in molecular detection of pathogen DNA extracted from ticks collected from infected hosts and must be taken into account in evaluating the competence of tick species as vectors.

The Transcriptome of the Salivary Glands of Amblyomma aureolatum Reveals the Antimicrobial Peptide Microplusin as an Important Factor for the Tick Protection Against Rickettsia rickettsii Infection.

The salivary glands (SG) of ixodid ticks play a pivotal role in blood feeding, producing both the cement and the saliva. The cement is an adhesive substance that helps the attachment of the tick to the host skin, while the saliva contains a rich mixture of antihemostatic, anti-inflammatory, and immunomodulatory substances that allow ticks to properly acquire the blood meal. The tick saliva is also a vehicle used by several pathogens to be transmitted to the vertebrate host, including various bacterial species from the genus Rickettsia. Rickettsia rickettsii is a tick-borne obligate intracellular bacterium that causes the severe Rocky Mountain spotted fever. In Brazil, the dog yellow tick Amblyomma aureolatum is a vector of R. rickettsii. In the current study, the effects of an experimental infection with R. rickettsii on the global gene expression profile of A. aureolatum SG was determined by next-generation RNA sequencing. A total of 260 coding sequences (CDSs) were modulated by infection, among which 161 were upregulated and 99 were downregulated. Regarding CDSs in the immunity category, we highlight one sequence encoding one microplusin-like antimicrobial peptide (AMP) (Ambaur-69859). AMPs are important effectors of the arthropod immune system, which lack the adaptive response of the immune system of vertebrates. The expression of microplusin was confirmed to be significantly upregulated in the SG as well as in the midgut (MG) of infected A. aureolatum by a quantitative polymerase chain reaction preceded by reverse transcription. The knockdown of the microplusin expression by RNA interference caused a significant increase in the prevalence of infected ticks in relation to the control. In addition, a higher rickettsial load of one order of magnitude was recorded in both the MG and SG of ticks that received microplusin-specific dsRNA. No effect of microplusin knockdown was observed on the R. rickettsii transmission to rabbits. Moreover, no significant differences in tick engorgement and oviposition were recorded in ticks that received dsMicroplusin, demonstrating that microplusin knockdown has no effect on tick fitness. Further studies must be performed to determine the mechanism of action of this AMP against R. rickettsii.

Different Competence as a Lyme Borreliosis Causative Agent Reservoir Found in Two Thrush Species: The Blackbird (Turdus merula) and the Song Thrush (Turdus philomelos).

Passerine birds are significantly involved in the dissemination of Borreliella spp. bacteria (formerly Borrelia burgdorferi sensu lato complex), the causative agent of most common and important tick-spread disease Lyme borreliosis. Among several dozen investigated passerine bird species, thrushes (Turdidae) have been reported as a relatively good pathogen reservoirs and disseminators. The principal aim of the study was to identify the differences in Borreliella spp. reservoir competence between two widespread and showing similar behavior thrush species. A total of 157 Ixodes ricinus ticks (19 larvae, 138 nymphs) were collected from 26 blackbirds (Turdus merula) and 20 song thrushes (Turdus philomelos) living in the same forest habitat (northeastern Poland). All, at least partially engorged ectoparasites, were tested for the presence of Borreliella spp. DNA using the nested-PCR technique. No significant difference of tick prevalence was found, with 88.5% blackbirds and 70% of song thrushes infested. Screening for Borreliella spp. in ticks revealed that both tick infection prevalence (49.2% vs. 18.9%) and mean number of infected individuals engorging on birds (2.27 vs. 0.35) were higher in blackbirds. Both the investigated thrush species presumably could participate in the pathogen circulation, although with different efficiencies. The greater reservoir competence of blackbirds suggests the differentiated dynamics of host-pathogen interactions among selected species, and consequently their potentially disparate role in the ecology of Lyme borreliosis.

High burdens of Ixodes scapularis larval ticks on white-tailed deer may limit Lyme disease risk in a low biodiversity setting

An inverse relationship between biodiversity and human health has been termed the ‘dilution effect’ paradigm. In the case of tick-borne infections such as Lyme disease, the key assumption is that Borrelia burgdorferi sensu lato abundance is increased by the loss of less competent (dilution) hosts as biodiversity declines. White-tailed deer play a dual role in the pathogen cycle, as key reproductive hosts for adult ticks and incompetent hosts for the pathogen. While the role of deer as hosts of adult ticks is well established, the extent to which deer also feed immature ticks and reduce the proportion infected is unknown because of logistic constraints in measuring this empirically. We estimated the proportion of larvae that fed on deer in an extremely species-poor community on Block Island, RI, where tick nymphal infection prevalence was found to be lower than expected. In 2014, we measured the density, larval tick burdens, and realized reservoir competence of small mammal and bird hosts on Block Island, RI. In 2015, we measured the infection prevalence of host-seeking Ixodes scapularis nymphs resulting from larvae fed on available hosts in 2014. We back-estimated the proportion of larvae expected to have fed on deer in 2014 (the only unknown parameter) to result in the nymphal infection prevalence observed in 2015. Back-estimation predicted that 29% of larval ticks must have fed on deer to yield the observed 30% nymphal infection prevalence. In comparison, the proportion of larvae feeding on mice was 44% and 27% on birds. Our study identified an influential role of deer in reducing nymphal tick infection prevalence and a potential role as dilution hosts if the reduction in nymphal infection prevalence outweighs the role of deer as tick population amplifiers. Because both deer and competent hosts may increase in anthropogenic, fragmented habitats, the links between fragmentation, biodiversity, and Lyme disease risk may be complex and difficult to predict. Furthermore, a nonlinear relationship between deer abundance and Lyme disease risk would reduce the efficacy of deer population reduction efforts to control Lyme disease.

Tick-borne disease risk in a forest food web.

Changes to the community ecology of hosts for zoonotic pathogens, particularly rodents, are likely to influence the emergence and prevalence of zoonotic diseases worldwide. However, the complex interactions between abiotic factors, pathogens, vectors, hosts, and both food resources and predators of hosts are difficult to disentangle. Here we (1) use 19yr of data from six large field plots in southeastern New York to compare the effects of hypothesized drivers of interannual variation in Lyme disease risk, including the abundance of acorns, rodents, and deer, as well as a series of climate variables; and (2) employ landscape epidemiology to explore how variation in predator community structure and forest cover influences spatial variation in the infection prevalence of ticks for the Lyme disease bacterium, Borrelia burgdorferi, and two other important tick-borne pathogens, Anaplasma phagocytophilum and Babesia microti. Acorn-driven increases in the abundance of mice were correlated with a lagged increase in the abundance of questing nymph-stage Ixodes scapularis ticks infected with Lyme disease bacteria. Abundance of white-tailed deer 2 yr prior also correlated with increased density of infected nymphal ticks, although the effect was weak. Density of rodents in the current year was a strong negative predictor of nymph density, apparently because high current abundance of these hosts can remove nymphs from the host-seeking population. Warm, dry spring or winter weather was associated with reduced density of infected nymphs. At the landscape scale, the presence of functionally diverse predator communities or of bobcats, the only obligate carnivore, was associated with reduced infection prevalence of I.scapularis nymphs with all three zoonotic pathogens. In the case of Lyme disease, infection prevalence increased where coyotes were present but smaller predators were displaced or otherwise absent. For all pathogens, infection prevalence was lowest when forest cover within a 1km radius was high. Taken together, our results suggest that a food web perspective including bottom-up and top-down forcing is needed to understand drivers of tick-borne disease risk, a result that may also apply to other rodent-borne zoonoses. Prevention of exposure based on ecological indicators of heightened risk should help protect public health.