a clear and present danger tick-borne diseases in europe pdf

A Clear And Present Danger Tick-borne Diseases In Europe Pdf

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In Europe, tick-borne diseases are the most important group of vector-borne diseases Heyman et al. Research focus has long been on Lyme borreliosis and tick-borne encephalitis TBE , because of their prevalence and public health impact. However, recently, new pathogens have emerged or re-emerged and geographical distributions of pathogens are changing. Also new techniques and developments in statistical and mathematical modelling have become available which allow for more accurate identification of risk areas as well as for conducting scenario studies.

This special issue aims at bringing together some of the latest results on re emerging tick-borne diseases and putting them in the perspective of the trends and developments in the ever-changing research field of tick-borne pathogens, with emphasis on the European continent. We see that for some disease systems, such as louping ill, TBE and Lyme disease, intensive studies over the last decades have increased our understanding of the relationship between population dynamics of the various tick-host species, tick populations and pathogen transmission.

This is much less the case for other pathogens, including many emerging pathogens, and these knowledge gaps still have to be filled in order to obtain a true understanding of the role of population dynamics, land use, changes in climate, etc. Knowledge and understanding of the underlying mechanisms driving the dynamics of these complex disease systems are of vital importance if we want to minimize the burden of tick-borne diseases now and in the future.

The population dynamics of ticks, their hosts and tick-borne pathogens are naturally closely intertwined. Ticks depend on vertebrate hosts for their blood meals, and tick-borne pathogens are maintained in a cycle between ticks and hosts.

The probability of a tick to find a host for a blood meal, and hence tick survival, will depend on local host density van Duijvendijk et al.

Also, not all host species are equally competent for transmission of each type of pathogen, which means that the composition of the local host population will also affect the transmission opportunities. At least theoretically, a larger proportion of non-competent hosts will reduce the number of bites on infectious hosts and thereby the number of infected ticks. However, as non-competent hosts e. Recent work by Mannelli et al. On the other hand, above certain threshold densities, or in the presence of competition with primary reservoir hosts or low attachment rate of ticks to reservoir hosts, incompetent or less competent hosts may reduce transmission through dilution.

Tick population dynamics and pathogen transmission dynamics are also determined by abiotic factors, such as temperature and humidity. Not only do these factors determine the vegetation type and the associated host population, but they also affect the survival and questing activity of ticks Gassner ; Randolph and Storey This may, for instance, determine the onset of the transmission season, or the degree of synchrony in activity of the tick life stages, which determines the co-feeding opportunities between nymphs and larva, an important factor in TBE epidemiology Randolph et al.

Altogether, population dynamics of ticks and their hosts and the resulting pathogen transmission dynamics form a highly complex system, determined by a combination of biotic and abiotic factors. Land use changes and climate are known to have impact on tick ecology and therefore also on tick-borne pathogen dynamics, but due to the complex interactions and feedback loops, effects may be different for each pathogen. A recent review paper describes the drivers of latitudinal and altitudinal spread of the important tick vector I.

It discusses the many climatic, ecological, landscape and anthropogenic drivers, based on published literature and unpublished expert opinion from the VBORNET network Medlock et al. Management of habitats on a landscape scale, and changes in the distribution and abundance of tick hosts are important considerations for management of public health risks associated with ticks and tick-borne disease issues in the future.

The authors state that a better understanding and mapping of the spread of I. Another trend in the research of the distribution of ticks is that more attention is being paid to habitats other than forested areas, the classic habitat. Conditions of modern urban and especially suburban environment in developed European countries adequately meet tick requirements Uspensky A review by Rizzoli et al.

Emerging pathogens, including bacteria of the order Rickettsiales Anaplasma phagocytophilum , Candidatus Neoehrlichia mikurensis , Rickettsia helvetica , and R. Understanding the ecology of ticks and their associations with blood hosts in a European urbanized environment is important for risk assessment and identification of public health strategies for control and prevention of tick-borne diseases Rizzoli et al.

Concrete control measures in urban areas could include better risk communication to the urban population, control of reservoir populations and changing other environmental conditions in parks and green areas to make them less suitable for ticks Uspensky Previous studies have investigated ticks and rickettsiae prevalence in mountain forest, recreational areas and urban areas in Slovakia, but this is the first study to report the prevalence of Rickettsia species in ticks 7.

Human-induced changes are of course also important. Besides the obvious effect of human activities on tick-borne disease risk via human exposure e. For instance, land abandonment may lead to more bushes, which provide good habitat for ticks and their hosts. For example, it was recently reported that the increase in I. The effect of bush encroachment on tick density is the topic of the study of Vanwambeke and co-authors in this issue Vanwambeke et al.

Of the many tick-borne pathogens in Europe, B. Other pathogens include Babesia spp. Although many of these pathogens have been known to circulate in European ecosystems for a long time, they appear to have become more prevalent in recent years, and their geographical distribution is expanding.

On the eco-epidemiology of Lyme borreliosis and its causative agent, B. In Europe, several of the at least 18 genospecies of the B. For other genospecies, such as B. Lyme borreliosis has been present in Europe for a long time, and is not an emerging pathogen in the sense of having emerged in Europe recently. However, a review by Rizzoli et al.

Also, Lyme borreliosis incidence has increased significantly in recent decades in specific areas, such as The Netherlands and Belgium Gassner and Overbeek ; Hofhuis et al. A particular reason for concern is the high prevalence of B. Due to the high human population density in these areas, the risk of people being exposed to infected tick bites is high. The dynamics of TBE has been studied extensively in the last decades Amicizia et al.

The importance of co-feeding for the transmission cycle has been highlighted Labuda et al. Climatic factors, such as rapid spring warming has been linked to the distribution of TBE Randolph et al. Still, the spotty distribution and the fact that TBE does not occur everywhere where I.

Crimean—Congo haemorrhagic fever virus is an emerging tick-borne virus, with a high case-fatality rate in humans. Even though in the last decade immense progress has been made on knowledge of the biology of the virus, the clinical aspects of the disease, and the establishment of rapid and sensitive diagnostics, there are still many gaps to be filled Papa et al. One of these is the lacking knowledge of the exact distribution of CCHFV in Southeastern Europe, and this is partly a result of a lack of proper tests.

The work by Schuster and co-authors , this issue aims at investigating which ruminant species is best suited as indicator for the detection of a CCHFV circulation in an area. As there are no commercial tests available for the detection of CCHFV-specific antibodies in animals, two commercial tests for testing human sera were adapted for the investigation of sera from sheep and goats, and new in-house enzyme-linked immunosorbent assays ELISAs were developed.

As sero-prevalence rates were significantly lower for cattle than for small ruminants, the latter are considered to be more suitable indicator animals for CCHFV infections and should therefore be tested preferentially, when risk areas are to be identified. Much crucial information on the eco-epidemiology of CCHFV is not yet available, but considerable progress has been made Papa et al. For Louping ill, another tick-borne virus, much research and modelling has been done on the system in the UK, where the pathogen is endemic.

In this issue, the current knowledge on the reservoir hosts, their effect on the dynamics of tick populations and on pathogen transmission has been reviewed by Gilbert , this issue. Louping ill virus LIV is part of the tick-borne encephalitis complex of viruses, but differs from TBE in terms of eco-epidemiological aspects. Whereas western TBEV is found primarily in woodlands, in small rodents as reservoir, LIV is generally circulating between sheep, red grouse and mountain hares and, therefore, associated with upland heather moorland and rough grazing land.

This overview also highlights the usefulness of mathematical modelling for scenario studies, assessing the effect of control measures. This issue features a review of the emerging pathogen Candidatus Neoerhlichi mikurensis Silaghi et al.

It summarizes the current state of knowledge on its geographical distribution and clinical importance. 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, and the routine implementation of molecular diagnosis in diseased patients with a particular panel of underlying diseases. The authors also advocate 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.

They studied the natural infection of birds and mostly immature I. Sixteen out of 43 caught bird species were infested by ticks and some birds carried more than one tick. Of the birds, C. Of the in total specimens of bird-attached ticks larvae, nymphs, 1 adult female , 6.

The study is a first step towards a better understanding of the circulation of rickettsiae and C. Babesia spp. In the study of Capligina and co-authors , this issue , Babesia spp. Babesia microti , B. The results suggest that both I.

It is clear that for many emerging tick-borne pathogens, knowledge on the exact geographic distribution, the reservoir hosts and their relative importance in the transmission cycles, and on many other aspects of the eco-epidemiology is still lacking. Information on tick population dynamics and its influence on tick-borne pathogen transmission can only be acquired via long-term systematic field work. Standardized methods, such as the standard sampling method for questing ticks that has been used within the framework of EDEN and EDENext, ensure that all tick collections are conducted in a similar way, with similar cloth and over the same distance.

This is essential in obtaining comparable field work outcomes — only then can results be compared among countries and regions, so that patterns on a larger geographic scale can be assessed and local outliers be studied in more detail. Of course, reliable tests for detection of pathogens in ticks and hosts are crucial, and for some pathogens, such as CCHFV, the development of tests in still work in progress see also Schuster et al.

Whereas the spatial geographic distribution of pathogens like babesia, rickettsia and anaplasma is still under study, as can be seen from the contributions to this special issue, the temporal dynamics are often even less well known.

Also, the pathogenicity to humans is often not known. For example, in The Netherlands prevalence of rickettsia in ticks appears to be high, but no clinical cases have been reported.

Furthermore, the notion that ticks and their hosts may carry more than one pathogen at the same time should be incorporated in our thinking about tick-borne diseases. The pathobioma paradigm entails considering the pathogenic agent integrated within its abiotic and biotic environments and taking into account the complexity of the tick microbiome, which may affect its vectorial capacity Vayssier-Taussat et al.

The use of models in research on tick-borne pathogens has become increasingly popular. Mathematical models have been developed to describe the dynamics of tick populations and of tick-borne pathogens. These models are often very complex, because the population dynamics of the ticks, their hosts and the tick-borne pathogens are closely intertwined.

Abiotic as well as biotic factors are known to play a role and need to be taken into account in order to capture the essential mechanisms driving the dynamics. Mechanistic mathematical models are an important tool for scenario studies; that is, assessing the potential effect of control measures, or of changes in land use or environmental conditions.

This has, for instance, been demonstrated by the work of Dobson and Randolph , who modelled the effect of changes in climate, host densities and acaricide treatments on I. In this issue, the paper by Hoch et al. The R 0 model is based on a tick population dynamics model and also considers the influence of abiotic meteorological variables and biotic factors host densities.

The model was used to test control strategies and especially the effect of acaricide treatment. The paper is a typical example of how modelling can help to get insight into the ability of a variety of strategies to prevent and control disease spread.

Modelling has also been particularly useful in unraveling the dynamics of LIV, as was demonstrated in the paper by Gilbert , this issue. The use of species distribution models or environmental niche models for the prediction of suitable habitat for ticks, or for tick-borne pathogens, is now one of the standard tools in tick-borne disease eco-epidemiology Randolph

Mosquito-borne diseases in Europe: an emerging public health threat

Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. The objective of our study was to estimate the seroprevalence of six pathogens transmitted by ticks in HIV-infected persons and blood donors in Poland B. Bartonella henselae to assess the frequency of exposure to such microorganisms in immunocompetent and immunocompromised individuals in endemic regions for I.

In Europe, tick-borne diseases are the most important group of vector-borne diseases Heyman et al. Research focus has long been on Lyme borreliosis and tick-borne encephalitis TBE , because of their prevalence and public health impact. However, recently, new pathogens have emerged or re-emerged and geographical distributions of pathogens are changing. Also new techniques and developments in statistical and mathematical modelling have become available which allow for more accurate identification of risk areas as well as for conducting scenario studies. This special issue aims at bringing together some of the latest results on re emerging tick-borne diseases and putting them in the perspective of the trends and developments in the ever-changing research field of tick-borne pathogens, with emphasis on the European continent.

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Vector-borne diseases are infections transmitted by the bite of infected arthropod species, such as mosquitoes, ticks, triatomine bugs, sandflies, and blackflies. Arthropod vectors are cold-blooded ectothermic and thus especially sensitive to climatic factors. Weather influences survival and reproduction rates of vectors, in turn influencing habitat suitability, distribution and abundance; intensity and temporal pattern of vector activity particularly biting rates throughout the year; and rates of development, survival and reproduction of pathogens within vectors. However, climate is only one of many factors influencing vector distribution, such as habitat destruction, land use, pesticide application, and host density. Vector-borne diseases are widespread in Europe and are the best studied diseases associated with climate change, which is reflected in this Review.

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Vector-Borne Diseases

CCHF is a tick-borne disease that is predominantly associated with Hyalomma ticks and have a widespread distribution in Africa, Asia and Europe. CCHF usually presents as a subclinical disease, but in some cases, it may present as a hemorrhagic fever with a high mortality rate. This systematic review of the literature was performed to identify the available evidence on the prevalence of CCHF in the European Region of the World Health Organization, based on seroprevalence IgG antibodies.

To the Editor: Borrelia miyamotoi is a relatively novel tickborne relapsing fever spirochete, and is a different species than B. Recently, the first patient infected with B. Conditions reported to be associated with B. Because of the nature of these manifestations and because regular diagnostic tests for B. Nevertheless, the relationship between B. The extent to which B. As a first step to indicate the population at risk for infection, we investigated human exposure to B.

Climate change is expected to alter the geographic and seasonal distributions of existing vectors and vector-borne diseases [Likely, High Confidence]. Ticks capable of carrying the bacteria that cause Lyme disease and other pathogens will show earlier seasonal activity and a generally northward expansion in response to increasing temperatures associated with climate change [Likely, High Confidence]. Longer seasonal activity and expanding geographic range of these ticks will increase the risk of human exposure to ticks [Likely, Medium Confidence]. Rising temperatures, changing precipitation patterns, and a higher frequency of some extreme weather events associated with climate change will influence the distribution, abundance, and prevalence of infection in the mosquitoes that transmit West Nile virus and other pathogens by altering habitat availability and mosquito and viral reproduction rates [Very Likely, High Confidence]. Alterations in the distribution, abundance, and infection rate of mosquitoes will influence human exposure to bites from infected mosquitoes, which is expected to alter risk for human disease [Very Likely, Medium Confidence]. Vector-borne pathogens are expected to emerge or reemerge due to the interactions of climate factors with many other drivers, such as changing land-use patterns [Likely, High Confidence]. The impacts to human disease, however, will be limited by the adaptive capacity of human populations, such as vector control practices or personal protective measures [Likely, High Confidence].

3 comments

Evan D.

This review will focus on the most important circulating tick-transmitted pathogens in Europe (Borrelia spp., Anaplasma phagocytophilum.

REPLY

Elita B.

This review will focus on the most important circulating tick-transmitted pathogens in Europe (Borrelia spp., Anaplasma phagocytophilum, Babesia spp., tick-borne.

REPLY

Ambra D.

Lyme disease , also known as Lyme borreliosis , is an infectious disease caused by the Borrelia bacterium which is spread by ticks.

REPLY

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