A national case-control study identifies human socio-economic status and activities as risk factors for tick-borne encephalitis in Poland

High habitat richness reduces the risk of tick-borne encephalitis in Europe: A multi-scale study

Background

The natural transmission cycle of tick-borne encephalitis (TBE) virus is enhanced by complex interactions between ticks and key hosts strongly connected to habitat characteristics. The diversity of wildlife host species and their relative abundance is known to affect transmission of tick-borne diseases. Therefore, in the current context of global biodiversity loss, we explored the relationship between habitat richness and the pattern of human TBE cases in Europe to assess biodiversity's role in disease risk mitigation.

Methods

We assessed human TBE case distribution across 879 European regions using official epidemiological data reported to The European Surveillance System (TESSy) between 2017 and 2021 from 15 countries. We explored the relationship between TBE presence and the habitat richness index (HRI1) by means of binomial regression. We validated our findings at local scale using data collected between 2017 and 2021 in 227 municipalities located in Trento and Belluno provinces, two known TBE foci in northern Italy.

Findings

Our results showed a significant parabolic effect of HRI on the probability of presence of human TBE cases in the European regions included in our dataset, and a significant, negative effect of HRI on the local presence of TBE in northern Italy. At both spatial scales, TBE risk decreases in areas with higher values of HRI.

Interpretation

To our knowledge, no efforts have yet been made to explore the relationship between biodiversity and TBE risk, probably due to the scarcity of high-resolution, large-scale data about the abundance or density of critical host species. Hence, in this study we considered habitat richness as proxy for vertebrate host diversity. The results suggest that in highly diverse habitats TBE risk decreases. Hence, biodiversity loss could enhance TBE risk for both humans and wildlife. This association is relevant to support the hypothesis that the maintenance of highly diverse ecosystems mitigates disease risk.

Neuroinvasion of emerging and re-emerging arboviruses: A scoping review

Background

Arboviruses are RNA viruses and some have the potential to cause neuroinvasive disease and are a growing threat to global health.

Objectives

Our objective is to identify and map all aspects of arbovirus neuroinvasive disease, clarify key concepts, and identify gaps within our knowledge with appropriate future directions related to the improvement of global health.

Methods

Sources of Evidence: A scoping review of the literature was conducted using PubMed, Scopus, ScienceDirect, and Hinari. Eligibility Criteria: Original data including epidemiology, risk factors, neurological manifestations, neuro-diagnostics, management, and preventive measures related to neuroinvasive arbovirus infections was obtained. Sources of evidence not reporting on original data, non-English, and not in peer-reviewed journals were removed. Charting Methods: An initial pilot sample of 30 abstracts were reviewed by all authors and a Cohen's kappa of κ = 0.81 (near-perfect agreement) was obtained. Records were manually reviewed by two authors using the Rayyan QCRI software.

Results

A total of 171 records were included. A wide array of neurological manifestations can occur most frequently, including parkinsonism, encephalitis/encephalopathy, meningitis, flaccid myelitis, and Guillain-Barré syndrome. Magnetic resonance imaging of the brain often reveals subcortical lesions, sometimes with diffusion restriction consistent with acute ischemia. Vertical transmission of arbovirus is most often secondary to the Zika virus. Neurological manifestations of congenital Zika syndrome, include microcephaly, failure to thrive, intellectual disability, and seizures. Cerebrospinal fluid analysis often shows lymphocytic pleocytosis, elevated albumin, and protein consistent with blood-brain barrier dysfunction.

Conclusions

Arbovirus infection with neurological manifestations leads to increased morbidity and mortality. Risk factors for disease include living and traveling in an arbovirus endemic zone, age, pregnancy, and immunosuppressed status. The management of neuroinvasive arbovirus disease is largely supportive and focuses on specific neurological complications. There is a need for therapeutics and currently, management is based on disease prevention and limiting zoonosis.

The structure and behavioral patterns of the human population affected by ixodid tick bites in Irkutsk Region, Eastern Siberia, Russia

The bites of hard ticks are the major route of transmission of tick-borne infections to humans, causing thousands of cases of diseases worldwide. However, the characteristics of the human population that is exposed to tick bites are still understudied. This work is aimed at characterizing both the structure of the population directly contacting ticks and the human behavioral features associated with tick bites. We studied 25,970 individuals who sought medical help after a tick bite at the Centre for Diagnostics and Prevention of Tick-borne Infections (CDPTBI) in Irkutsk City (Russian Federation). The demographic and behavioral characteristics of the human population were analyzed using z-tests for proportions, the Mann-Whitney U test, and the Spearman rank correlation coefficient. The majority of bitten people were urban residents (70 %), and most of them were either of active ages between 30 and 74 years old (62 %), or children between 0 and 9 years old (approximately 20%). Tick bites occurred mostly in the range of 150 km around the location of the diagnostic facility (83 %). In comparison to the general population, significant differences were revealed in the representation of different age groups among bitten people. The population affected by tick bites included fewer men and women in the ages of 10-29 and over 75 years old than would be predicted based on the demographics of the general population. Vice versa, the proportions of people in the ages of 5-9 and 60-74 increased among bitten people. Among men, such activities (in order of occurrence) as "leisure and recreation", "visiting allotments", "foraging for forest food", and "fulfilling work duties" tend to be more associated with tick bites. Among women, tick bites occurred mainly during "visiting allotments", "leisure and recreation", "visiting cemeteries" and "contact with pets and plants at home". The overall vaccination rate was 12 %; however, significantly more men than women were vaccinated against tick-borne encephalitis (up to 20 % vs. approximately 7 % respectively). The structure of the tick bite - affected population suggests that it is age-specific human behavior that mainly determines the frequency of contact between people and ticks. However, in several age groups, especially among children from 5 to 9 and people aged 30-39 years old, gender-related factors could significantly change the exposure of people to tick bites.

Ticks - public health risks in urban green spaces

BACKGROUND

Urban green spaces are important for human health, but they may expose visitors to tick-borne diseases. This not only presents a potential public health challenge but also undermines the expected public health gains from urban green spaces. The aim of this study is to assess the public health risk of tick-borne diseases in an urban green space used for recreation in Stockholm, Sweden.

METHODS

We used a mixed method approach identifying both the magnitude of the tick hazard and the extent of the human exposure to tick-borne diseases. At six entry points to an urban green space, we sampled ticks and documented microhabitat conditions from five randomly assigned 2 m × 2 m plots. Surrounding habitat data was analyzed using geographical information system (GIS). Nymphs and adult ticks were tested for Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum using TaqMan qPCR. Positive B. burgdorferi (s.l.) ticks were further analyzed by nested PCR amplification and sequence analysis. Population census data and visitor count data were used to estimate the degree of human exposure to tick-borne diseases. To further understand the degree to which visitors get in contact with infected ticks we also conducted interviews with visitors to green spaces.

RESULTS

High tick densities were commonly found in humid broadleaved forest with low field vegetation. High pathogen prevalence was significantly correlated with increasing proportions of artificial areas. Integrating the tick hazard with human exposure we found that the public health risk of tick-borne diseases was moderate to high at most of the studied entry points. Many of the visitors frequently used urban green spaces. Walking was the most common activity, but visitors also engaged in activities with higher risk for tick encounters. Individual protective measures were connected to specific recreational activities such as picking berries or mushrooms.

CONCLUSIONS

The number of visitors can be combined with tick inventory data and molecular analyses of pathogen prevalence to make crude estimations of the public health risk of tick-borne diseases in urban green spaces. The risk of encountering infected ticks is omnipresent during recreational activities in urban green spaces, highlighting the need for public health campaigns to reduce the risk of tick-borne diseases.

Describing the experience of livestock producers from Ohio, USA with ticks and associated diseases

BACKGROUND

As tick ranges expand across North America, the risk of tick bites and tick-borne diseases (TBDs, i.e. diseases or syndromes associated with ticks) rises for humans and animals, making prevention critical. Several U.S. studies have examined knowledge, attitudes, and practices regarding ticks and TBDs for various cohorts of people. However, among occupational groups with high exposure risk from ticks and TBDs are livestock producers, of which we know little about. To help address this gap, an electronic questionnaire was distributed to livestock producers in Ohio, U.S, a state with a robust agricultural sector.

METHODS

We generated descriptive statistics and conducted a multiple correspondence analysis followed by hierarchical clustering on principal components to identify producers with similar response profiles.

RESULTS

Responses from 57 producers showed that most (52.6%) think the American dog tick (Dermacentor variabilis) is found in Ohio but are unsure about other species. Although several TBDs are present in Ohio, most (> 50%) producers were unsure or unaware of their presence. Interestingly, most (54.4%) thought ticks pose major health risks for their livestock but fewer (49.1%) thought the same for humans. Regardless, most producers did employ at least one prevention method for themselves (96.5%) and their animals (82.5%). Cluster analysis (n = 48) identified three groups: the largest (n = 21) was considered "aware and cautious" consisting primarily of farm owners. The others generally practiced less prevention and consisted primarily of farm employees.

CONCLUSIONS

Our findings indicate that producers in Ohio practice prevention for themselves and their livestock, but demonstrate gaps in knowledge (e.g., TBD occurrence) and attitudes (e.g., health risks) that could be addressed via educational formats we found producers preferred (e.g., extension materials), to encourage informed prevention. This is especially important for farm employees that may practice less prevention because of lower awareness. Our study can guide others in regions faced with similar tick and TBD risks to protect occupational and livestock health.

Ecological and environmental factors affecting the risk of tick-borne encephalitis in Europe, 2017 to 2021

BackgroundTick-borne encephalitis (TBE) is a disease which can lead to severe neurological symptoms, caused by the TBE virus (TBEV). The natural transmission cycle occurs in foci and involves ticks as vectors and several key hosts that act as reservoirs and amplifiers of the infection spread. Recently, the incidence of TBE in Europe has been rising in both endemic and new regions.AimIn this study we want to provide comprehensive understanding of the main ecological and environmental factors that affect TBE spread across Europe.MethodsWe searched available literature on covariates linked with the circulation of TBEV in Europe. We then assessed the best predictors for TBE incidence in 11 European countries by means of statistical regression, using data on human infections provided by the European Surveillance System (TESSy), averaged between 2017 and 2021.ResultsWe retrieved data from 62 full-text articles and identified 31 different covariates associated with TBE occurrence. Finally, we selected eight variables from the best model, including factors linked to vegetation cover, climate, and the presence of tick hosts.DiscussionThe existing literature is heterogeneous, both in study design and covariate types. Here, we summarised and statistically validated the covariates affecting the variability of TBEV across Europe. The analysis of the factors enhancing disease emergence is a fundamental step towards the identification of potential hotspots of viral circulation. Hence, our results can support modelling efforts to estimate the risk of TBEV infections and help decision-makers implement surveillance and prevention campaigns.

Seroprevalence and risk factors of tick-borne encephalitis in Mongolia between 2016 and 2022

The tick-borne encephalitis virus (TBEV) is a zoonotic agent that causes severe encephalitis in humans and is transmitted through the bites of infected ticks. Ixodes ticks are the primary vector for TBEV in Mongolia, and approximately 3.4% carry the TBEV. The ticks are capable of not only transmitting these viruses but also serve as excellent reservoir hosts. The Dermacenter tick species may have similar properties. TBEV is a significant cause of virus-related diseases of the central nervous system in many European countries as well as in China, Russia, and Mongolia. Our objectives were to investigate TBEV seroprevalence and infection risk factors in different biogeographical zones and provinces, especially in the highly endemic areas of Mongolia. Serum samples were collected from individuals who experienced tick bites (n = 993) in Mongolia between 2016 and 2022. Enzyme-linked immunosorbent assay of the samples was performed to evaluate for TBEV-specific immunoglobulin (Ig)M and IgG. We analyzed the risk factors and seroprevalence of TBEV infection among these individuals using a cross-sectional, questionnaire-based study. Statistical analyses were performed using a multistage cluster sampling survey design, and all data were analyzed using the R software. TBEV IgM and IgG antibodies were detected in 8.1% (80/993) and 20.2% (201/993) of all serum samples, respectively. The seroprevalence was significantly higher in men (68%, 95% confidence interval [CI]: 1.63-3.13, odds ratio [OR]: 2.25) than in women (p < 0.001). Additionally, the seroprevalence was significantly higher among unemployed (35.0%, 95% CI: 0.31-0.84, OR: 0.51) than employed individuals (p < 0.001). The seroprevalence was the highest among the 25-29 and 35-39-year age groups (11%, 95% CI: 1.29-5.51, OR: 2.65 and 11%, 95% CI: 0.94-3.87, OR: 1.9, respectively), and the lowest in the 65-69-year age group (4%, 95% CI: 0.46-6.15, OR: 1.83) (p < 0.001). Furthermore, the seroprevalence was the highest in Selenge province and the capital city Ulaanbaatar (40%, 95% CI: 1.73-21.7, OR: 5.07 and 28%, 95% CI: 0.51-6.89, OR: 1.57, respectively) and the lowest in Bayan-Ulgii and Dornod provinces (0.5%, 95% CI: 0.06-12.4, OR: 1.33 and 0.5%, 95% CI: 0.03-6.24, OR: 0.72, respectively). TBEV infection incidence remained low in most regions of Mongolia but increased in endemic areas. Furthermore, in the univariate subgroup analysis, age, occupation status, and residential area were significantly associated with TBEV seroprevalence.

The Emergence and Dynamics of Tick-Borne Encephalitis Virus in a New Endemic Region in Southern Germany

Tick-borne encephalitis (TBE) is the most important viral tick-borne infection in Europe and Asia. It is emerging in new areas. The mechanisms of emergence are fairly unknown or speculative. In the Ravensburg district in southern Germany, TBE emerged, mainly over the last five years. Here, we analyzed the underlying epidemiology in humans. The resulting identified natural foci of the causal TBE virus (TBEV) were genetically characterized. We sampled 13 potential infection sites at these foci and detected TBEV in ticks (Ixodes ricinus) at eight sites. Phylogenetic analysis spurred the introduction of at least four distinct TBEV lineages of the European subtype into the Ravensburg district over the last few years. In two instances, a continuous spread of these virus strains over up to 10 km was observed.

Tick-Borne Encephalitis Risk Increases with Dog Ownership, Frequent Walks, and Gardening: A Case-Control Study in Germany 2018-2020

In Germany, tick-borne encephalitis (TBE) infections mainly occur in southern regions. Despite recent increases in incidence, TBE vaccination coverage remains low, necessitating additional preventive strategies against TBE. Our case-control study in Southern Germany from 2018 to 2020 mapped knowledge/application of tick-protective strategies and identified TBE risk factors. We calculated odds ratios (OR), with 95% confidence intervals (CI). We interviewed 581 cases and 975 matched controls. Most participants recalled lifetime tick bites, mainly while walking, gardening, or hiking. However, only 45% of cases noticed ticks during exposure time; another 12% reported unpasteurized milk intake. While tick-protection knowledge was satisfactory, application lagged behind. Risk factors included dog ownership (OR = 2.45, 95% CI: 1.85−3.24), walks ≥ 4×/week (OR = 2.11, 95% CI: 1.42−3.12), gardening ≥ 4×/week (OR = 1.83, 95% CI: 1.11−3.02), and garden proximity < 250 m of forests (OR = 2.54, 95% CI: 1.82−3.56). Applying ≥2 tick-protective strategies (OR = 0.52, 95% CI: 0.40−0.68) and keeping lawns mowed (OR = 0.63, 95% CI: 0.43−0.91) were inversely associated with TBE. In 2020 (likely pandemic-related), cases reported significantly more walks than previously, potentially explaining the record high case numbers. Our findings provide guidance on targets for TBE prevention. Persons with gardens near forests, frequent outdoor activities, or dogs could particularly benefit from targeted information, including on vaccination and preventing tick bites.

Meningitis and encephalitis in Poland in 2020

INTRODUCTION

Meningitis and/or encephalitis are one of the main infectious diseases of the nervous system. These diseases are most commonly caused by bacterial and viral etiological factors. In this publication, meningitis and/or encephalitis caused by Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae and those with a viral origin - in Poland, most often caused by tick-borne encephalitis virus - are presented in detail. In addition to epidemiological surveillance, immunoprophylaxis in the form of mandatory and recommended vaccinations is used in Poland to prevent these infections.

AIM OF THE STUDY

The aim of this study was to to assess the epidemiological situation of meningitis and encephalitis in Poland, in 2020.

MATERIAL AND METHODS

To analyse the epidemiological situation of neuroinfections in Poland were used data sent to NIPH NIH - NRI by Voivodeship Sanitary and Epidemiological Stations and published in the annual bulletins: "Infectious diseases and poisonings in Poland in 2020" and "Protective vaccination in Poland in 2020" and individual epidemiological interviews registered in the EpiBaza system.

RESULTS

In 2020, a total of 831 cases of meningitis and/or encephalitis were registered in Poland. This is a decrease in incidence of up to 62.9% compared to 2019. For infections of bacterial etiology, including cases of neuroborreliosis (incidence of 2.40 per 100,000), the number of cases decreased by 60.4% (from 931 to 369). In the viral infection group, there was a 64.9% decrease (from 1,318 to 462 cases). Of all registered cases, 56% were infections with a viral etiology. Compared to 2019, the number of cases with an S. pneumoniae etiology decreased by 61.3% and for N. meningitidis by 41.1%. It is interesting to note that, in the case of H. influenzae, we can speak of a 20% increase in cases compared to the previous year. In addition, we can see a decrease in the incidence of tick-borne encephalitis - from 265 in 2019 to 158 in 2020 (a decrease of 40.4%).

SUMMARY AND CONCLUSIONS

Overall, a downward trend in incidence was shown for both bacterial and viral meningitis and/or encephalitis. The SARS-CoV-2 pandemic and the introduction of restrictions on personto-person contact and various forms of activity, resulting in a reduction in pathogen transmission, were key to the significant reduction in the number of meningitis and/or encephalitis cases in 2020, but a reduction in the availability of medical facilities or the completeness of case reports due to the burden of anti-epidemic measures on the Sanitary Inspectorate cannot be excluded either. Only in the case of cases caused by H. influenzae was a slight increase observed compared to the previous year (12 versus 10 cases). Meningoencephalitis and/or encephalitis, due to its wide etiological range, poses a major challenge to the health care system, particularly in terms of correct clinical diagnosis.

Impact of Land Use Changes and Habitat Fragmentation on the Eco-epidemiology of Tick-Borne Diseases

The incidence of tick-borne diseases has increased in recent decades and accounts for the majority of vector-borne disease cases in temperate areas of Europe, North America, and Asia. This emergence has been attributed to multiple and interactive drivers including changes in climate, land use, abundance of key hosts, and people's behaviors affecting the probability of human exposure to infected ticks. In this forum paper, we focus on how land use changes have shaped the eco-epidemiology of Ixodes scapularis-borne pathogens, in particular the Lyme disease spirochete Borrelia burgdorferi sensu stricto in the eastern United States. We use this as a model system, addressing other tick-borne disease systems as needed to illustrate patterns or processes. We first examine how land use interacts with abiotic conditions (microclimate) and biotic factors (e.g., host community composition) to influence the enzootic hazard, measured as the density of host-seeking I. scapularis nymphs infected with B. burgdorferi s.s. We then review the evidence of how specific landscape configuration, in particular forest fragmentation, influences the enzootic hazard and disease risk across spatial scales and urbanization levels. We emphasize the need for a dynamic understanding of landscapes based on tick and pathogen host movement and habitat use in relation to human resource provisioning. We propose a coupled natural-human systems framework for tick-borne diseases that accounts for the multiple interactions, nonlinearities and feedbacks in the system and conclude with a call for standardization of methodology and terminology to help integrate studies conducted at multiple scales.

Analysis of Multiple Risk Factors for Seronegative Rate of Anti-Tick-Borne Encephalitis Virus Immunization in Human Serum

Background and objectives: Tick-borne encephalitis virus (TBEV) infections have been the cause of threatening outbreaks for many years. Apart from several physical and chemical methods to prevent tick bites, active vaccination of people highly exposed to infection is still the most important strategy of prevention. However, in some subjects, the lack of or low response to TBEV antigens is observed. The aim of the current study was to assess the prevalence of seronegative rate for anti-TBEV antibodies and the risk factors for waning immunity. Materials and Methods: 2315 at least primary vaccinated subjects from the high risk group for TBEV infections participated in this study. A commercial enzyme-linked immunosorbent assay (ELISA) test was used for the assessment of anti-TBEV IgG serum level. Results: Data showed that 86.2% of subjects who underwent vaccination were positive for anti-TBEV antibodies within 5 years. As much as 13.8% of subjects that underwent primary or primary and booster vaccination were barely protected after vaccination. Women and subjects under 60 years underwent more effective protection but sex and older age was not a risk factor for being a subject of waning immunity. A logistic regression showed that both a longer time since the vaccination and a lower number of booster doses constantly increased the chance of lost anti-TBEV antibodies. Conclusions: This study demonstrates that the vaccination schedule should be reevaluated. The extension of the interval of booster immunization is risky and all subjects should be surrounded by care consisting of more frequent monitoring of serum antibodies by personalized schedule to adjust the frequency of subsequent doses of booster vaccination.

Tick-borne encephalitis virus infections in Germany. Seasonality and in-year patterns. A retrospective analysis from 2001-2018

Background

Little is known regarding the changing seasonality of infections with the tick-borne encephalitis virus (TBEV) and the incidence of the resulting disease over the last two decades. Seasonal patterns have to our knowledge not previously been systematically investigated and are poorly understood. We investigate emerging seasonal changes in clinical aspects like potentially increasing hospitalization during the year, variations in clinical symptoms and disease severity during the season and seasonal dynamics of fatal outcomes.

Material and methods

TBEV infection became a notifiable disease in Germany in 2001. We used the national reporting dataset spanning from 2001–2018, provided by the Robert Koch-Institute (RKI). There were general epidemiological variables available, including “symptom onset”, “age” and “sex”. Furthermore, several variables documented disease severity. These included “CNS symptoms”, “myelitis”, “fatal outcome” and “hospitalization”. Potential factors influencing the occurrence of CNS symptoms, myelitis, hospitalizations and fatal outcome were analyzed using logistic regression models. Linear trends, including the “time point in year” at which TBEV infection related symptoms were detected, were tested using calendar year as a continuous covariate. In addition, seasonal trends and age and sex specific differences were exploratively tested for non-linear effects using restricted cubic splines with knot locations based on Harrell's recommended percentiles. Finally, the dynamic relationship between in-seasonal trends year of detection, sex and age was tested using interaction terms.

Results

6,073 TBEV infection cases from 2001–2018 were included in our analysis. We find that from 2001–2018 TBEV infections are reported 0.69 days earlier each year (p<0.001). There was no detectable seasonal variation regarding the occurrence of fatal outcome, CNS and myelitis. However, there was a significant changing trend regarding hospitalizations over the course of the year: The risk for hospitalization increases until August, decreases again from October on.

Conclusion

We present epidemiological evidence that the TBE season in Germany has shifted to start earlier over the last years, beginning approximately 12 days earlier in 2018 than it did in 2001. There are seasonal patterns regarding a higher risk of hospitalization during August.

Knowledge, habits and attitudes towards TBE and other tick-borne diseases in German forestry trainees

Tick-borne encephalitis (TBE) is an occupational hazard for forestry workers. We measured knowledge levels, misbeliefs, and vaccination rates in forestry trainees in order to tailor specific measures aimed at reducing occupational TBE incidence. A paper-based survey was performed at a central training site for forestry workers in the state of Baden-Wuerttemberg. The questionnaire contained items regarding vaccination status against tick-borne encephalitis virus (TBEV), self-reported tick-borne diseases, knowledge of and attitudes towards tick-borne disease, and practices in the context of ticks and tick bites. All trainees in the period June-December 2018 were surveyed. Statistical analyses were conducted using Mann-Whitney-Rank sum test and one-way ANOVA tests. Two-hundred-twenty-five trainees participated in the survey. Almost all (>99%) were aware of living in a TBE high-risk area. Eighty-three percent of respondents were vaccinated in line with current recommendations. Seventeen percent had no effective vaccination status. Twenty-seven percent believed that ticks can transmit only TBEV and Borrelia spp. Sixty-two percent knew that TBEV infections can be fatal. Only 8% of respondents use tick repellents and only 17% wear long sleeves and pants. Trainees who graduated from a six and (eight or) nine secondary school (Realschule and Abitur respectively) had more knowledge on ticks and tick-borne disease compared to graduates from a five year school (Hauptschule) (p = 0.002 and p = 0,037 respectively). Overall, the TBE vaccination rate is not high enough in this high-risk occupational group. We identified gaps in knowledge and practices that could have an impact on TBE incidence in this group if addressed. Further epidemiological research is needed on knowledge, attitudes, and practices in different high-risk populations.

The brown dog tick Rhipicephalus sanguineus sensu Roberts, 1965 across Australia: Morphological and molecular identification of R. sanguineus s.l. tropical lineage

The brown dog tick Rhipicephalus sanguineus (Latreille, 1806) is the most widely distributed tick species globally. Throughout the world there are at least two divergent lineages on dogs that are traditionally grouped into what was known as R. sanguineus. The species R. sanguineus was recently redescribed using a neotype reported from countries with a temperate climate. The second lineage distributed in countries with primarily tropical climates is currently designated R. sanguineus s.l. tropical lineage. Here, we present a comprehensive genetic evaluation of Australian brown dog ticks from across the continent that complements the morphological study of R. sanguineus sensu Roberts (1965). A total of 294 ticks were collected from dogs around Australia - including New South Wales, Queensland, the Northern Territory and Western Australia - for morphological identification. All ticks were morphologically identified as R. sanguineus sensu Roberts (1965). DNA was isolated from a single leg from morphologically characterised individuals from New South Wales (n = 14), Queensland (n = 18), Northern Territory (n = 7) and Western Australia (n = 13), together with ticks from Fiji (n = 1) and the Seychelles (n = 1) for comparison with Australian ticks. The study revealed three cox1 haplotypes clustered only with R. sanguineus s.l. tropical lineage'. An updated distribution of R. sanguineus sensu Roberts (1965) is compared to the 1965 distribution. In the Australian context, R. sanguineus s.l. has appeared in north-western New South Wales but remains absent from coastal New South Wales. Despite both temperate and tropical climates being present in Australia, only R. sanguineus s.l. tropical lineage was found. The evidence does not support the presence of the strictly defined brown dog tick, R. sanguineus by Nava et al. (2018) in Australia, because the examined ticks are genetically and morphologically distinct. We recommend using the term brown dog tick, R. sanguineus sensu Roberts (1965) for specimens from Australia.

Large-scale health disparities associated with Lyme disease and human monocytic ehrlichiosis in the United States, 2007-2013

Promoting health equity is a fundamental public health objective, yet health disparities remain largely overlooked in studies of vectorborne diseases, especially those transmitted by ticks. We sought to identify health disparities associated with Lyme disease and human monocytic ehrlichiosis, two of the most pervasive tickborne diseases within the United States. We used general linear mixed models to measure associations between county-level disease incidence and six variables representing racial/ethnic and socioeconomic characteristics of counties (percent white non-Hispanic; percent with a bachelors degree or higher; percent living below the poverty line; percent unemployed; percent of housing units vacant; per capita number of property crimes). Two ecological variables important to tick demography (percent forest cover; density of white-tailed deer) were included in secondary analyses to contextualize findings. Analyses included data from 2,695 counties in 37 states and the District of Columbia during 2007-2013. Each of the six variables was significantly associated with the incidence of one or both diseases, but the direction and magnitude of associations varied by disease. Results suggested that the incidence of Lyme disease was highest in counties with relatively higher proportions of white and more educated persons and lower poverty and crime rates; the incidence of human monocytic ehrlichiosis was highest in counties with relatively higher proportions of white and less educated persons, higher unemployment rates and lower crime rates. The percentage of housing units vacant was a strong positive predictor for both diseases with a magnitude of association comparable to those between incidence and the ecological variables. Our findings indicate that racial/ethnic and socioeconomic disparities in disease incidence appear to be epidemiologically important features of Lyme disease and human monocytic ehrlichiosis in the United States. Steps to mitigate encroachment of wild flora and fauna into areas with vacant housing might be warranted to reduce disease risk.

A Predictive Model Has Identified Tick-Borne Encephalitis High-Risk Areas in Regions Where No Cases Were Reported Previously, Poland, 1999-2012

During 1999–2012, 77% of the cases of tick-borne encephalitis (TBE) were recorded in two out of 16 Polish provinces. However, historical data, mostly from national serosurveys, suggest that the disease could be undetected in many areas. The aim of this study was to identify which routinely-measured meteorological, environmental, and socio-economic factors are associated to TBE human risk across Poland, with a particular focus on areas reporting few cases, but where serosurveys suggest higher incidence. We fitted a zero-inflated Poisson model using data on TBE incidence recorded in 108 NUTS-5 administrative units in high-risk areas over the period 1999–2012. Subsequently we applied the best fitting model to all Polish municipalities. Keeping the remaining variables constant, the predicted rate increased with the increase of air temperature over the previous 10–20 days, precipitation over the previous 20–30 days, in forestation, forest edge density, forest road density, and unemployment. The predicted rate decreased with increasing distance from forests. The map of predicted rates was consistent with the established risk areas. It predicted, however, high rates in provinces considered TBE-free. We recommend raising awareness among physicians working in the predicted high-risk areas and considering routine use of household animal surveys for risk mapping.

Borrelia burgdorferi DNA absent, multiple Rickettsia spp. DNA present in ticks collected from a teaching forest in North Central Florida

Tick-borne diseases are an emerging public health threat in the United States. In Florida, there has been public attention directed towards the possibility of locally acquired Borrelia burgdorferi sensu stricto, the causative agent of Lyme disease, in association with the lone star tick. The aim of this study was to determine the prevalence of ticks and the pathogens they carry and potentially transmit, such as B. burgdorferi, in a highly utilized teaching and research forest in North Central Florida. Ticks were collected by dragging and flagging methods over a four month period in early 2014, identified, and tested by PCR for multiple pathogens including Anaplasma, Borrelia, Rickettsia, and Ehrlichia species. During the study period the following ticks were collected: 2506 (96.5%) Amblyomma americanum L., 64 (2.5%) Ixodes scapularis Say, 19 (0.7%) Dermacentor variabilis Say, and 5 (0.2%) Ixodes affinis Neuman. Neither Borrelia spp. (0/846) nor Anaplasma spp. (0/69; Ixodes spp. only) were detected by PCR in any of the ticks tested. However, Rickettsia DNA was present in 53.7% (86/160), 62.5% (40/64), 60.0% (3/5) and 31.6% (6/19) of A. americanum, I. scapularis, I. affinis and D. variabilis, respectively. Furthermore, E. chaffeensis and E. ewingii DNA were detected in 1.3% and 4.4% of adult A. americanum specimens tested, respectively. Although receiving an A. americanum bite is likely in wooded areas in North Central Florida due to the abundance of this tick, the risk of contracting a tick-borne pathogen in this specific area during the spring season appears to be low. The potential for pathogen prevalence to be highly variable exists, even within a single geographical site and longitudinal studies are needed to assess how tick-borne pathogen prevalence is changing over time in North Central Florida.

Tick-borne encephalitis in north-east Italy: a 14-year retrospective study, January 2000 to December 2013

Italy is considered at low incidence of tick-borne encephalitis (TBE), and the occurrence of human cases of TBE appears to be geographically restricted to the north east of the country. However, most information to date derives from case series, with no systematic data collection. To estimate incidence rates (IR) and spatial distribution of TBE cases, we conducted a retrospective study in north-eastern Italy. Data were collected through the infectious disease units and public health districts of three regions (Friuli Venezia Giulia, Trentino Alto Adige and Veneto) between 2000 and 2013. Overall, 367 cases were identified (IR: 0.38/100,000). The cases' median age was 56 years and 257 (70%) were male. Central nervous system involvement was reported in 307 cases (84%). Annual fluctuations in case numbers occurred, with peaks in 2006 and in 2013, when 44 and 42 cases were respectively observed. A strong seasonality effect was noted, with the highest number of cases in July. In terms of geographical location, three main endemic foci with high TBE IR (>10/100,000) were identified in three provinces, namely Belluno (Veneto region), Udine (Friuli Venezia Giulia) and Trento (Trentino Alto-Adige). When investigating the whole study area in terms of altitude, the IR between 400 and 600 m was greater (2.41/100,000) than at other altitudes (p<0.01). In conclusion, the incidence of TBE in Italy is relatively low, even considering only the three known affected regions. However, three endemic foci at high risk were identified. In these areas, where the risk of TBEV infection is likely high, more active offer of TBE vaccination could be considered.

Hierarchical Bayesian Spatio-Temporal Analysis of Climatic and Socio-Economic Determinants of Rocky Mountain Spotted Fever

This study aims to examine the spatio-temporal dynamics of Rocky Mountain spotted fever (RMSF) prevalence in four contiguous states of Midwestern United States, and to determine the impact of environmental and socio-economic factors associated with this disease. Bayesian hierarchical models were used to quantify space and time only trends and spatio-temporal interaction effect in the case reports submitted to the state health departments in the region. Various socio-economic, environmental and climatic covariates screened a priori in a bivariate procedure were added to a main-effects Bayesian model in progressive steps to evaluate important drivers of RMSF space-time patterns in the region. Our results show a steady increase in RMSF incidence over the study period to newer geographic areas, and the posterior probabilities of county-specific trends indicate clustering of high risk counties in the central and southern parts of the study region. At the spatial scale of a county, the prevalence levels of RMSF is influenced by poverty status, average relative humidity, and average land surface temperature (>35°C) in the region, and the relevance of these factors in the context of climate-change impacts on tick-borne diseases are discussed.

Neoehrlichiosis: an emerging tick-borne zoonosis caused by Candidatus Neoehrlichia mikurensis

Candidatus Neoehrlichia mikurensis is an emerging tick-borne pathogen causing a systemic inflammatory syndrome mostly in persons with underlying hematologic or autoimmune diseases. As it is neither well-known nor well-recognized, it might be misdiagnosed as recurrence of the underlying disease or as an unrelated arteriosclerotic vascular event. The pathogen is transmitted by hard ticks of the genus Ixodes and is closely associated with rodents in which transplacental transmission occurs. Transovarial transmission in ticks has not yet been shown. Infection rates vary greatly in ticks and rodents, but the causes for its spatiotemporal variations are largely unknown. This review summarizes the current state of knowledge on the geographical distribution and clinical importance of Ca. N. mikurensis. By elucidating the life history traits of this pathogen and determining more accurately its incidence in the human population, a better assessment of its public health relevance can be made. Most urgent research needs are the in vitro-cultivation of the pathogen, the development of specific serological tests, the determination of the full genomic sequence, the routine implementation of molecular diagnosis in diseased patients with a particular panel of underlying diseases, and promoting the knowledge about neoehrlichiosis among general practitioners, hospital physicians and the risk groups such as forest workers or immune-compromised people to raise awareness about this disease that can easily be treated when correctly diagnosed.

How a multidisciplinary 'One Health' approach can combat the tick-borne pathogen threat in Europe

In Europe, ticks are the major arthropod vectors of disease agents to humans and domestic animals. They are capable of transmitting many pathogens most of which have been discovered or identified as tick-borne pathogens in the last 20 years. In recent years, unexplained syndromes occurring after a tick bite have become an increasingly important issue in public and animal health. Ticks and wildlife (the main reservoir of tick-borne pathogens) are highly susceptible to global environmental and socio-economic changes, which in turn may lead to an increased burden of tick-borne diseases. In this review, we explain the importance of a 'One Health' approach to better combat tick-borne diseases.

Prototype early warning systems for vector-borne diseases in Europe

Globalization and environmental change, social and demographic determinants and health system capacity are significant drivers of infectious diseases which can also act as epidemic precursors. Thus, monitoring changes in these drivers can help anticipate, or even forecast, an upsurge of infectious diseases. The European Environment and Epidemiology (E3) Network has been built for this purpose and applied to three early warning case studies: (1) The environmental suitability of malaria transmission in Greece was mapped in order to target epidemiological and entomological surveillance and vector control activities. Malaria transmission in these areas was interrupted in 2013 through such integrated preparedness and response activities. (2) Since 2010, recurrent West Nile fever outbreaks have ensued in South/eastern Europe. Temperature deviations from a thirty year average proved to be associated with the 2010 outbreak. Drivers of subsequent outbreaks were computed through multivariate logistic regression models and included monthly temperature anomalies for July and a normalized water index. (3) Dengue is a tropical disease but sustained transmission has recently emerged in Madeira. Autochthonous transmission has also occurred repeatedly in France and in Croatia mainly due to travel importation. The risk of dengue importation into Europe in 2010 was computed with the volume of international travelers from dengue affected areas worldwide.These prototype early warning systems indicate that monitoring drivers of infectious diseases can help predict vector-borne disease threats.

Shaping zoonosis risk: landscape ecology vs. landscape attractiveness for people, the case of tick-borne encephalitis in Sweden

BACKGROUND

In this paper, the hazard and exposure concepts from risk assessment are applied in an innovative approach to understand zoonotic disease risk. Hazard is here related to the landscape ecology determining where the hosts, vectors and pathogens are and, exposure is defined as the attractiveness and accessibility to hazardous areas. Tick-borne encephalitis in Sweden was used as a case study.

METHODS

Three boosted regression tree models are compared: a hazard model, an exposure model and a global model which combines the two approaches.

RESULTS

The global model offers the best predictive power and the most accurate modelling. The highest probabilities were found in easy-to-reach places with high landscape diversity, holiday houses, waterbodies and, well-connected forests of oak, birch or pine, with open-area in their ecotones, a complex shape, numerous clear-cuts and, a variation in tree height.

CONCLUSION

While conditions for access and use of hazardous areas are quite specific to Scandinavia, this study offers promising perspectives to improve our understanding of the distribution of zoonotic and vector-borne diseases in diverse contexts.

Monitoring human tick-borne disease risk and tick bite exposure in Europe: available tools and promising future methods

Ticks are the main vector for infectious disease pathogens in both humans and animals, and tick-borne diseases are currently spreading throughout Europe. Various surveillance methods have been developed to estimate the burden and risk of tick-borne diseases and host exposure to tick bites. The ultimate aims of these approaches are to determine the risk level of a tick-borne disease in a given area, determine its health priority, identify the at-risk population and propose specific countermeasures or complementary studies as needed. The purpose of this review is to present the current methods for monitoring the circulation of tick-borne diseases and to highlight the use of salivary antigens as original and recently developed serological tools that could be useful for tick bite risk assessment and could improve the current surveillance methods.

Expanding Integrated Vector Management to promote healthy environments

Integrated Vector Management (IVM) strategies are intended to protect communities from pathogen transmission by arthropods. These strategies target multiple vectors and different ecological and socioeconomic settings, but the aggregate benefits of IVM are limited by the narrow focus of its approach; IVM strategies aim only to control arthropod vectors. We argue that IVM should encompass environmental modifications at early stages - for instance, infrastructural development and sanitation services - to regulate not only vectors but also nuisance biting arthropods. An additional focus on nuisance biting arthropods will improve public health and quality of life and minimize social-disparity issues fostered by pests. Optimally, IVM could incorporate environmental awareness and promotion of control methods proactively to reduce threats of serious pest situations.

Bayesian spatio-temporal analysis and geospatial risk factors of human monocytic ehrlichiosis

Variations in spatio-temporal patterns of Human Monocytic Ehrlichiosis (HME) infection in the state of Kansas, USA were examined and the relationship between HME relative risk and various environmental, climatic and socio-economic variables were evaluated. HME data used in the study was reported to the Kansas Department of Health and Environment between years 2005–2012, and geospatial variables representing the physical environment [National Land cover/Land use, NASA Moderate Resolution Imaging Spectroradiometer (MODIS)], climate [NASA MODIS, Prediction of Worldwide Renewable Energy (POWER)], and socio-economic conditions (US Census Bureau) were derived from publicly available sources. Following univariate screening of candidate variables using logistic regressions, two Bayesian hierarchical models were fit; a partial spatio-temporal model with random effects and a spatio-temporal interaction term, and a second model that included additional covariate terms. The best fitting model revealed that spatio-temporal autocorrelation in Kansas increased steadily from 2005–2012, and identified poverty status, relative humidity, and an interactive factor, ‘diurnal temperature range x mixed forest area’ as significant county-level risk factors for HME. The identification of significant spatio-temporal pattern and new risk factors are important in the context of HME prevention, for future research in the areas of ecology and evolution of HME, and as well as climate change impacts on tick-borne diseases.

Survey of selected tick-borne diseases in dogs in Finland

Background

Due to climate changes during the last decades, ticks have progressively spread into higher latitudes in northern Europe. Although some tick borne diseases are known to be endemic in Finland, to date there is limited information with regard to the prevalence of these infections in companion animals. We determined the antibody and DNA prevalence of the following organisms in randomly selected client-owned and clinically healthy hunting dogs living in Finland: Ehrlichia canis (Ec), Anaplasma phagocytophilum (Ap), Borrelia burgdorferi (Bb) and Bartonella.

Methods

Anti-Ap, −Bb and –Ec antibodies were determined in 340 Finnish pet dogs and 50 healthy hunting dogs using the 4DX Snap®Test (IDEXX Laboratories). In addition, PCRs for the detection of Ap and Bartonella DNA were performed. Univariate and multivariate logistic regression analyses were used to identify risk factors associated with seropositivity to a vector borne agent.

Results

The overall seroprevalence was highest for Ap (5.3%), followed by Bb (2.9%), and Ec (0.3%). Seropositivities to Ap and Bb were significantly higher in the Åland Islands (p <0.001), with prevalence of Ap and Bb antibodies of 45 and 20%, respectively. In healthy hunting dogs, seropositivity rates of 4% (2/50) and 2% (1/50) were recorded for Ap and Bb, respectively. One client-owned dog and one hunting dog, both healthy, were infected with Ap as determined by PCR, while being seronegative. For Bartonella spp., none of the dogs tested was positive by PCR.

Conclusions

This study represents the first data of seroprevalence to tick borne diseases in the Finnish dog population. Our results indicate that dogs in Finland are exposed to vector borne diseases, with Ap being the most seroprevalent of the diseases tested, followed by Bb. Almost 50% of dogs living in Åland Islands were Ap seropositive. This finding suggests the possibility of a high incidence of Ap infection in humans in this region. Knowing the distribution of seroprevalence in dogs may help predict the pattern of a tick borne disease and may aid in diagnostic and prevention efforts.

ANTIDotE: anti-tick vaccines to prevent tick-borne diseases in Europe

Ixodes ricinus transmits bacterial, protozoal and viral pathogens, causing disease and forming an increasing health concern in Europe. ANTIDotE is an European Commission funded consortium of seven institutes, which aims to identify and characterize tick proteins involved in feeding and pathogen transmission. The knowledge gained will be used to develop and evaluate anti-tick vaccines that may prevent multiple human tick-borne diseases. Strategies encompassing anti-tick vaccines to prevent transmission of pathogens to humans, animals or wildlife will be developed with relevant stakeholders with the ultimate aim of reducing the incidence of tick-borne diseases in humans.

Ixodes ricinus abundance and its infection with the tick-borne pathogens in urban and suburban areas of Eastern Slovakia

Background

Raising abundance of ticks and tick-borne diseases in Europe is the result of multiple factors including climate changes and human activities. Herein, we investigated the presence and seasonal activity of Ixodes ricinus ticks from 10 urban and suburban sites in two different geographical areas of southeastern and northeastern Slovakia during 2008–2010. Our aim was to study the abundance of ticks in correlation with the environmental factors and their infection with Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum and Neoehrlichia mikurensis.

Methods

Questing I. ricinus ticks were collected from ten urban and suburban sites in Eastern Slovakia. A total of 670 ticks were further analysed for the presence of B. burgdorferi s.l., A. phagocytophilum and N. mikurensis by molecular methods. Tick site and environmental relations were analysed using General Linear Models (LM). The differences between the number of Lyme borreliosis cases between the Košice and Bardejov regions during a ten-year period were tested by Wilcoxon matched pairs test.

Results

In total, 2921 (1913 nymphs, 1008 adults) I. ricinus ticks were collected from 10 study sites during the main questing season. Tick activity and relative abundance differed between locations and months. Temperature and humidity were the main factors affecting the tick abundance and questing activity. Out of 670 examined ticks, 10.15% were infected with spirochetes from B. burgdorferi s.l. complex (represented by B. afzelii, B. garinii, B.valaisiana and B. burgdorferi s.s.), 2.69% with the A. phagocytophilum and 2.39% with N. mikurensis. The number of Lyme borreliosis cases per 100,000 inhabitants in the Bardejov region was significantly higher than in the Košice region.

Conclusions

Our data indicate that the risk of infection with tick-borne pathogens in Eastern Slovakia is common since 15.2% of ticks were infected at least with one of the tested microorganisms. Even though the abundance of ticks was affected by the microclimatic conditions and the prevalence of pathogens differed between the habitats, the infection risk for humans is also affected by human activities leading to an increased contact with infected ticks.

New endemic foci of tick-borne encephalitis (TBE) identified in districts where testing for TBE was not available before 2009 in Poland

BACKGROUND

Tick-borne encephalitis (TBE) is found in limited endemic foci in Poland. Lack of diagnosis limits disease detection in non-endemic provinces.

METHODS

In 2009, we enhanced TBE surveillance to confirm the location of endemic foci and inform vaccination policy. In 105 hospitals located in 11/16 provinces, we identified suspected TBE cases through admission ICD-10 codes indicating aseptic meningo-encephalitis or from specimens tested for TBE. The National Reference Laboratory confirmed cases at no cost, by testing serum and/or cerebrospinal fluid using ELISA method. We calculated TBE reported rates as the number of confirmed TBE cases per 100,000 inhabitants. Adjusting to neighbouring districts, we classified districts as non-endemic (<0.1 cases per 100,000 inhabitants), low endemic (> = 0.1 to <1), moderately endemic (> = 1 to <5) and highly endemic (> = 5). We compared surveillance data obtained in 2009 with 2004-2008 baseline data.

RESULTS

Among 166,099 admissions, we identified 1,585 suspected TBE cases of which 256 were confirmed. Physicians reported more suspected cases among patients <40 years old (12 cases per 1,000 admissions) than among older patients (8 cases per 1,000 admissions). However, patients <40 years of age were confirmed less frequently (16%), than older patients (35%). Physicians reported more suspected cases in districts classed as endemic during 2004-2008 (12 cases per 1,000 admissions, 77% tested for TBE) than in districts classed as non-endemic (7 cases per 1,000 admissions, 59% tested). Of the 38 newly identified endemic districts, 31 were adjacent to 2004-2008 endemic districts and 7 were isolated.

CONCLUSIONS

Enhanced surveillance detected 38 new endemic districts to be considered for TBE vaccination. However, lack of consistent testing in districts believed to be TBE-free remained an obstacle for mapping TBE risk. Although the disease affects mostly older adults and the elderly, more attention is given to the diagnosis of TBE in young patients. Solutions need to be identified to sustain sensitive, acceptable and affordable TBE surveillance in all districts of Poland. Also, higher attention should be given to the diagnosis of TBE in the elderly.

Circumstantial evidence for an increase in the total number and activity of Borrelia-infected Ixodes ricinus in the Netherlands

Background

Between 1994 and 2009, a threefold increase has been observed in consultations of general practitioners for tick bites and Lyme disease in The Netherlands. The objective of this study was to determine whether an increase in the number of questing ticks infected with B. burgdorferi sensu lato is a potential cause of the rise in Lyme disease incidence.

Methods

Historic data on land usage, temperature and wildlife populations were collected and analyzed together with data from two longitudinal field studies on density of questing ticks. Effective population sizes of Borrelia burgdorferi s.l. were calculated.

Results

Long-term trend analyses indicated that the length of the annual tick questing season increased as well as the surface area of tick-suitable habitats in The Netherlands. The overall abundances of feeding and reproductive hosts also increased. Mathematical analysis of the data from the field studies demonstrated an increase in mean densities/activities of questing ticks, particularly of larvae between 2006 and 2009. No increase in infection rate of ticks with Borrelia burgdorferi sensu lato was found. Population genetic analysis of the collected Borrelia species points to an increase in B. afzelii and B. garinii populations.

Conclusions

Together, these findings indicate an increase in the total number of Borrelia-infected ticks, providing circumstantial evidence for an increase in the risk of acquiring a bite of a tick infected with B. burgdorferi s.l. Due to the high spatiotemporal variation of tick densities/activities, long-term longitudinal studies on population dynamics of I. ricinus are necessary to observe significant trends.