CiteULike: Tag tick-borne

Tick-borne rickettsial diseases: emerging risks in Europe.

P Parola — 2005-11-05T08:35:24-00:00

Comp Immunol Microbiol Infect Dis, Vol. 27, No. 5. (September 2004), pp. 297-304.

Ticks are currently considered the main vectors of human infectious diseases in Europe, particularly since their role in the transmission of the agent of Lyme borreliosis was demonstrated in the 1980s. In the recent years, ticks have also been shown to be the vectors of numerous emerging rickettsial diseases. Although Mediterranean spotted fever (MSF) due to Rickettsia conorii was thought for a long time to be the only tick-borne rickettsial disease prevalent in Europe, five more spotted fever rickettsiae have been described as emerging pathogens in the last decade. Further, cases of infection due to Anaplasma phagocytophilum, the agent of human anaplasmosis (previously known as human granulocytic ehrlichiosis), have been reported throughout Europe. We present here these emerging diseases and discuss other potential threat for the future.

Tick-borne encephalitis in Friuli Venezia Giulia, northeastern Italy.

A Beltrame — 2005-08-08T20:05:23-00:00

Infection, Vol. 33, No. 3. (June 2005), pp. 158-159.

Fragile transmission cycles of tick-borne encephalitis virus may be disrupted by predicted climate change.

SE Randolph — 2005-08-08T19:09:34-00:00

Proc Biol Sci, Vol. 267, No. 1454. (7 September 2000), pp. 1741-1744.

Repeated predictions that vector-borne disease prevalence will increase with global warming are usually based on univariate models. To accommodate the full range of constraints, the present-day distribution of tick-borne encephalitis virus (TBEv) was matched statistically to current climatic variables, to provide a multivariate description of present-day areas of disease risk. This was then applied to outputs of a general circulation model that predicts how climatic variables may change in the future, and future distributions of TBEv were predicted for them. The expected summer rise in temperature and decrease in moisture appears to drive the distribution of TBEv into higher-latitude and higher-altitude regions progressively through the 2020s, 2050s and 2080s. The final toe-hold in the 2080s may be confined to a small part of Scandinavia, including new foci in southern Finland. The reason for this apparent contraction of the range of TBEv is that its transmission cycles depend on a particular pattern of tick seasonal dynamics, which may be disrupted by climate change. The observed marked increase in incidence of tick-borne encephalitis in most parts of Europe since 1993 may be due to non-biological causes, such as political and sociological changes.

Prevalence of Borrelia burgdorferi s.l. and Anaplasma phagocytophilum in the wood tick Ixodes ricinus in the Province of Trento, Italy

B Mantelli — 2006-10-27T13:52:29-00:00

European Journal of Clinical Microbiology & Infectious Diseases

In Europe, lyme borreliosis (LB) and human granulocytic anaplasmosis (HGA) are emerging tick-borne zoonoses. Both are transmitted by the hard tick Ixodes ricinus, which is widespread in the Province of Trento in northeastern Italy [1]. The risk of infection with the agents of LB and HGA is dependent on local tick distribution and abundance, and the proportion of infected ticks, which are in turn correlated with the type of habitat and the density of vertebrate reservoir hosts. The etiological agent of LB, the spirochete Borrelia burgdorferi s.l., causes a wide range of clinical symptoms, and levels of pathogenicity are associated with different genospecies. In Italy, reports of LB infection have been increasing, especially in the northeastern regions of the country [2, 3].

Socio-economic factors in the differential upsurge of tick-borne encephalitis in central and Eastern Europe

Dana Sumilo — 2008-01-29T15:29:30-00:00

Reviews in Medical Virology, Vol. 9999, No. 9999. (2008), n/a.

Tick-borne encephalitis (TBE), the most serious widespread vector-borne disease of humans in Europe, increased from 2- to 30-fold in many Central and Eastern European countries from 1992 to 1993, coinciding with independence from Soviet rule. Unemployment and low income have been shown in Latvia to be statistically associated with high-risk behaviour involving harvest of wild foods from tick-infested forests, and also with not being vaccinated against TBE. Archival data for 1970--2005 record major changes in the agricultural and industrial sectors, and consequent changes in the abiotic and biotic environment and socio-economic conditions, which could have increased the abundance of infected ticks and the contact of humans with those ticks. For example, abandoned agricultural fields became suitable for rodent transmission hosts; use of pesticides and emissions of atmospheric industrial pollutants plummeted; wildlife hosts for ticks increased; tick populations appear to have responded; unemployment and inequality increased in all countries. These factors, by acting synergistically but differentially between and within each country, can explain the marked spatio-temporal heterogeneities in TBE epidemiology better than can climate change alone, which is too uniform across wide areas. Different degrees of socio-economic upheaval caused by political transition in Estonia, Latvia, Lithuania, Slovenia and the Czech Republic can apparently explain the marked variation in TBE upsurge. Causal linkage between national socio-economic conditions and epidemiology is strongly indicated by striking correlations across eight countries between the degree of upsurge of TBE and both poverty and household expenditure on food (R2 = 0.533 and 0.716, respectively).

Globalisation of Lyme borreliosis

Stephen Barthold — 2008-01-11T13:58:28-00:00

The Lancet, Vol. 348, No. 9042. (14 December 1996), pp. 1603-1604.

Ticks and tick-borne disease systems in space and from space.

SE Randolph — 2005-08-08T19:28:22-00:00

Advances in Parasitology, Vol. 47 (2000), pp. 217-243.

Analyses within geographical information systems (GISs) indicate that small- and large-scale ranges of hard tick species (Ixodidae) are determined more by climate and vegetation than by host-related factors. Spatial distributions of ticks may therefore be analysed by statistical methods that seek correlations between known tick presence/absence and ground- or remotely-sensed (RS) environmental factors. In this way, local habitats of Amblyomma variegatum in the Caribbean and Ixodes ricinus in Europe have been mapped using Landsat RS imagery, while regional and continental distributions of African and temperate tick species have been predicted using multi-temporal information from the National Oceanic and Atmospheric Administration-Advanced Very High Resolution Radiometer (NOAA-AVHRR) imagery. These studies illustrate ways of maximizing statistical accuracy, whose interpretation is then discussed in a biological framework. Methods such as discriminant analysis are biologically transparent and interpretable, while others, such as logistic regression and tree-based classifications, are less so. Furthermore, the most consistently significant variable for predicting tick distributions, the RS Normalized Difference Vegetation Index (NDVI), has a sound biological basis in that it is related to moisture availability to free-living ticks and correlated with tick mortality rates. The development of biological process-based models for predicting the spatial dynamics of ticks is a top priority, especially as the risk of tick-borne infections is commonly related not simply to the vector's density, but to its seasonal population dynamics. Nevertheless, using statistical pattern-matching, the combination of RS temperature indices and NDVI successfully predicts certain temporal features essential for the transmission of tick-borne encephalitis virus, which translate into a spatial pattern of disease foci on a continental scale.

First detection of TBE virus sequences in Ixodes ricinus from Friuli Venezia Giulia (Italy).

R Floris — 2007-02-20T21:55:10-00:00

New Microbiol, Vol. 29, No. 2. (April 2006), pp. 147-150.

We report, for the first time, the presence of tick-borne encephalitis (TBE) virus in the tick Ixodes ricinus collected in the Friuli Venezia Giulia region of north-eastern Italy. Using molecular methods, we demonstrate that the TBE virus carried by ticks from FVG is a western European strain. Sequence analysis of the 5' NCR showed 98.4% identity to the Neudoerfl strain.

Tick-borne encephalitis in Southwestern Germany

R Kaiser — 2008-04-16T08:45:00-00:00

Infection, Vol. 24, No. 5. (1996), pp. 398-399.

Summary In Baden-Württemberg in 1994 and 1995 approximately 390 persons fell ill after infection with the tick-borne encephalitis (TBE) virus. Detailed clinical data were available from 300 patients for further analysis. TBE mostly manifested as meningitis (50%) or meningoencephalitis (38%) and more rarely as encephalomyelitis and/or radiculitis (12%). Four patients with encephalomyelitis died.

Risk assessment and prediction of Ixodes ricinus tick questing activity and human tick-borne encephalitis infection in space and time in the Czech Republic

Milan Daniel — 2006-07-23T11:58:07-00:00

International Journal of Medical Microbiology, Vol. 296, No. Supplement 1. (22 May 2006), pp. 41-47.

Present risk assessment and prediction of future risk of humans exposed to Ixodes (I.) ricinus tick attacks and, consequently, to tick-borne encephalitis (TBE) virus infection as one of the basic preconditions for successful TBE prevention has been intensively studied in the Czech Republic. An atlas of TBE in the Czech Republic containing predictive maps of I. ricinus high-incidence habitats and TBE risk sites identified by satellite data (Landsat 5 TM with spatial resolution 30 m) at a scale of 1:200,000 over a territory of 52,000 km2 and maps of human TBE case distribution (1971-2000) has been prepared using remote sensing and geographical information systems technologies. The influence of climate changes on a forest ecosystem inhabited by I. ricinus has been studied in the southern region of the Czech Republic. The analysis of long-term series (1931-2000) of climatologic and phenological characteristics has been carried out. The results are compared with the long-term series of TBE incidence. The influence of weather condition on day-to-day changes of I. ricinus host-seeking activities was studied in 2001-2004. Field observations were realized in the south-eastern periphery of Prague where the experimental plots for tick monitoring were established in a relevant type of forest growth (Querceto-carpinetum). I. ricinus activities were investigated by the flagging method on three plots (200 m2 each) in weekly intervals (March to November) during 2001-2004. The instruments for micrometeorological observations were installed between the experimental plots. Macrometeorological data were used from the nearby Czech Hydrometeorological Institute first class meteorological observatory. Simple and multiple linear regression and quadratic regression were used to test the relation between weather modification and I. ricinus host-seeking activity. Two preliminary most suitable 'models' are demonstrated.

Extension of Ixodes ricinus ticks and agents of tick-borne diseases to mountain areas in the Czech Republic

Vlasta Danielova — 2006-07-23T11:52:25-00:00

International Journal of Medical Microbiology, Vol. 296, No. Supplement 1. (22 May 2006), pp. 48-53.

Along with the shift of the hard tick Ixodes ricinus to higher altitudes observed in the Czech Republic a corresponding shift of tick-borne infections to higher altitudes has been expected. Therefore, I. ricinus ticks, mainly nymphs, were investigated for the presence of tick-borne viruses, tick-borne encephalitis (TBE), Tribec and Eyach, and the spirochaete Borrelia burgdorferi sensu lato in the Sumava and Krkonose Mountains (Czech Republic). The TBE virus and different genospecies of B. burgdorferi s.l. were detected by RT-PCR and PCR, respectively. TBE virus was detected in ticks at 620 and 720 m above sea level (a.s.l.), B. burgdorferi s.l. was detected in ticks up to 1065 m a.s.l. Four genospecies of B. burgdorferi s.l. were identified, B. afzelii, B. garinii, B. burgdorferi sensu stricto, and B. valaisiana. Some nymphs carried multiple Borrelia infections. The conditions of tick-borne agents' distribution and potential epidemiological consequences are discussed.

Ixodes ricinus (Acari: Ixodidae) infestation on roe deer (Capreolus capreolus) in Trentino, Italian Alps.

C Chemini — 2006-08-02T15:34:06-00:00

Parassitologia, Vol. 39, No. 1. (March 1997), pp. 59-63.

The most important tick-deer system potentially supporting the epidemiology of Lyme disease in the Italian Alps is that regarding Ixodes ricinus (L.) and roe deer (Capreolus capreolus L.). In this study, the pattern of tick infestation on 562 male roe deer harvested in September 1994 in 56 game districts of Trentino, Northern Italy, was assessed. The prevalence and density of infestation by I. ricinus were analyzed by a model based on classification and regression trees (CART), using both discrete and continuous variables concerning environmental and host parameters. The model discriminated attitude and host density as the 2 variables having the greatest effect on the prevalence and density of infestation of deer; the levels of infestation were higher at an altitude below 1125 m or at roe deer densities over 8.5 head per 100 ha. The density of tick infestation tended to be higher in older roe deer.

Tickborne encephalitis virus, northeastern Italy.

A Beltrame — 2007-02-20T21:51:30-00:00

Emerg Infect Dis, Vol. 12, No. 10. (October 2006), pp. 1617-1619.

Incidence from coincidence: patterns of tick infestations on rodents facilitate transmission of tick-borne encephalitis virus.

SE Randolph — 2006-04-30T22:02:03-00:00

Parasitology, Vol. 118 (February 1999), pp. 177-186.

Tick-borne encephalitis (TBE) virus has a highly focal distribution through Eurasia. Endemic cycles appear to depend on the transmission of non-systemic infections between ticks co-feeding on the same rodent hosts. The particular features of seasonal dynamics and infestation patterns of larval and nymphal Ixodes ricinus, but not Dermacentor reticulatus, from 4 regions within TBE foci in Slovakia, are such as to promote TBE virus transmission. The distributions of larvae and nymphs on their principal rodent hosts are highly aggregated and, rather than being independent, the distributions of each stage are coincident so that the same ca. 20% of hosts feed about three-quarters of both larvae and nymphs. This results in twice the number of infectible larvae feeding alongside potentially infected nymphs compared with the null hypothesis of independent distributions. Overall, co-feeding transmission under these circumstances brings the reproductive number (R0) for TBE virus to a level that accounts quantitatively for maintained endemic cycles. Essential for coincident aggregated distributions of larvae and nymphs is their synchronous seasonal activity. Preliminary comparisons support the prediction of a greater degree of coincident seasonality within recorded TBE foci than outside. This identifies the particular climatic factors that permit such patterns of tick seasonal dynamics as the primary predictors for the focal distribution of TBE.

A simple spatial model to explain the distribution of human tick-borne encephalitis cases in hungary.

GR Rácz — 2007-01-22T16:18:42-00:00

Vector-Borne and Zoonotic Diseases, Vol. 6, No. 4. (2006), pp. 369-378.

Tick-borne encephalitis (TBE) is a common medical problem in Hungary and throughout much of Europe and Asia. This paper develops a geographic model that helps to predict the distribution of human tick-borne encephalitis cases in Hungary. The model is tested on a dataset of serologically confirmed TBE cases mapped by patients' residences. Case densities (incidence rates) are compared to predicted distributions of TBE derived from digital land-cover data. Maps are analyzed at the county level and on a smaller spatial scale. The analyses identified three major factors that shape the geographic distribution of human TBE cases in Hungary. The most important component is the distribution of forest habitat. TBE incidence correlates positively with the amount of forested habitat in each county. On a finer scale, the amount of forests within a 2500-meter radius of each town and village correlated significantly with TBE incidence rate. Based on these data, about 30% of the variation in TBE incidence is accounted for by the specific distribution of forest habitats in Hungary. Besides the distribution of forests, differences in human land-use practices among regions also affect the distribution of TBE cases. Additionally, because of the low transmission rate of the virus to humans, the perceived distribution of TBE cases is affected by random stochastic events. As a consequence of stochastic variation, meaningful patterns in the distribution of TBE cases can be only recognized when data are analyzed over broader temporal and spatial scales.

Ticks and tickborne bacterial diseases in humans: an emerging infectious threat.

P Parola — 2007-01-15T22:20:49-00:00

Clinical Infectious Diseases, Vol. 32, No. 6. (15 March 2001), pp. 897-928.

Ticks are currently considered to be second only to mosquitoes as vectors of human infectious diseases in the world. Each tick species has preferred environmental conditions and biotopes that determine the geographic distribution of the ticks and, consequently, the risk areas for tickborne diseases. This is particularly the case when ticks are vectors and reservoirs of the pathogens. Since the identification of Borrelia burgdorferi as the agent of Lyme disease in 1982, 15 ixodid-borne bacterial pathogens have been described throughout the world, including 8 rickettsiae, 3 ehrlichiae, and 4 species of the Borrelia burgdorferi complex. This article reviews and illustrate various aspects of the biology of ticks and the tickborne bacterial diseases (rickettsioses, ehrlichioses, Lyme disease, relapsing fever borrelioses, tularemia, Q fever), particularly those regarded as emerging diseases. Methods are described for the detection and isolation of bacteria from ticks and advice is given on how tick bites may be prevented and how clinicians should deal with patients who have been bitten by ticks.

Methods for evaluating Lyme disease risks using geographic information systems and geospatial analysis.

MC Nicholson — 2006-08-02T15:00:34-00:00

J Med Entomol, Vol. 33, No. 5. (September 1996), pp. 711-720.

Lyme disease is a tick-transmitted borreliosis of humans and domestic animals emerging as one of the most significant threats to public health in north temperate regions of the world. However, despite a myriad of studies into symptomology, causes, and treatment of the disease, few researchers have addressed the spatial aspects of Lyme disease transmission. Using statewide data collected in Rhode Island (United States) as a test case, we demonstrated that exposure to deer ticks and the risk of contracting Lyme disease occurs mostly in the peridomestic environment. A Geographic Information System model was developed indicating a strong association among Lyme disease in humans, the degree of nymphal blacklegged tick, Ixodes scapularis Say, abundance in the environment, and prevalence of Borrelia burgdorferi infection in ticks. In contrast, occurrence of plant communities suitable for sustaining I. scapularis populations (forests) was not predictive of Lyme disease risk. Instead, we observed a highly significant spatial trend for decreasing number of ticks and incident cases of Lyme disease with increasing latitude. Geostatistics were employed for modeling spatial autocorrelation of tick densities. These findings were combined to create a model that predicts Lyme disease transmission risk, thereby demonstrating the utility of incorporating geospatial modeling techniques in studying the epidemiology of Lyme disease.

Environmental risk factors for Lyme disease identified with geographic information systems.

GE Glass — 2006-08-02T14:56:10-00:00

Americal Journal of Public Health, Vol. 85, No. 7. (July 1995), pp. 944-948.

OBJECTIVES. A geographic information system was used to identify and locate residential environmental risk factors for Lyme disease. METHODS. Data were obtained for 53 environmental variables at the residences of Lyme disease case patients in Baltimore County from 1989 through 1990 and compared with data for randomly selected addresses. A risk model was generated combining the geographic information system with logistic regression analysis. The model was validated by comparing the distribution of cases in 1991 with another group of randomly selected addresses. RESULTS. In crude analyses, 11 environmental variables were associated with Lyme disease. In adjusted analyses, residence in forested areas (odds ratio [OR] = 3.7, 95% confidence interval [CI] = 1.2, 11.8), on specific soils (OR = 2.1, 95% CI = 1.0, 4.4), and in two regions of the county (OR = 3.5, 95% CI = 1.6, 7.4) (OR = 2.8, 95% CI = 1.0, 7.7) was associated with elevated risk of getting Lyme disease. Residence in highly developed regions was protective (OR = 0.3, 95% CI = 0.1, 1.0). The risk of Lyme disease in 1991 increased with risk categories defined from the 1989 through 1990 data. CONCLUSIONS. Combining a geographic information system with epidemiologic methods can be used to rapidly identify risk factors of zoonotic disease over large areas.

GIS tools for tick and tick-borne disease occurrence.

M Daniel — 2005-07-24T22:32:25-00:00

Parasitology, Vol. 129 Suppl (2004)

Geographic information systems (GIS), their fundamental components and technologies are described. GIS is a computer-based system enabling the storage, integration, query, display and analysis of data using information on data location. Further, remote sensing (RS) methods and their application in landscape characterization are described. Landscape pattern analysis, combined with statistical analysis, allows the determination of landscape predictors of disease risk. This makes RS/GIS a powerful set of tools for disease surveillance, enabling the prediction of potential disease outbreaks and targeting intervention programs. The 'pre-GIS era' is briefly described including the early mapping of tick distribution, analyses and the display of biogeographical and medical data. The theory of natural focality of diseases (NFD) is explained and its significance in tick-borne diseases (TBD) research is discussed. Many problems of tick ecology and TBD epidemiology and epizootology have been addressed by means of GIS and examples of these studies are presented and discussed.

Tick-borne encephalitis virus foci in Slovakia.

M Labuda — 2007-09-19T19:10:17-00:00

Int J Med Microbiol, Vol. 291 Suppl 33 (June 2002), pp. 43-47.

Tick-borne encephalitis (TBE) virus as a typical arbovirus relies on two types of hosts for its survival: ticks act both as virus vectors and reservoir hosts, and vertebrates amplify the virus infection by acting as a source of infection for feeding ticks. Longitudinal monitoring of TBE virus in ticks and vertebrate hosts including humans over a period of 40 years resulted in the identification of the areas of Slovakia where TBE virus is endemic. These are concentrated to the western, southern, and eastern parts of the country. Even with recently identified foci there is no evidence that the size and location of the natural TBE foci have changed significantly during the last decades. Numbers of diagnosed hospitalised cases of TBE in Slovakia vary from less than 20 to almost 100 cases annually with 54-89 cases in recent years. A part of these cases (33 cases during the last 5 years) are alimentary infections after drinking of raw goat and sheep milk.

Climate change cannot explain the upsurge of tick-borne encephalitis in the baltics.

D Sumilo — 2007-07-27T13:33:40-00:00

PLoS ONE, Vol. 2 (2007)

BACKGROUND: Pathogens transmitted by ticks cause human disease on a greater scale than any other vector-borne infections in Europe, and have increased dramatically over the past 2-3 decades. Reliable records of tick-borne encephalitis (TBE) since 1970 show an especially sharp upsurge in cases in Eastern Europe coincident with the end of Soviet rule, including the three Baltic countries, Estonia, Latvia and Lithuania, where national incidence increased from 1992 to 1993 by 64, 175 and 1,065%, respectively. At the county level within each country, however, the timing and degree of increase showed marked heterogeneity. Climate has also changed over this period, prompting an almost universal assumption of causality. For the first time, we analyse climate and TBE epidemiology at sufficiently fine spatial and temporal resolution to question this assumption. METHODOLOGY/PRINCIPAL FINDING: Detailed analysis of instrumental records of climate has revealed a significant step increase in spring-time daily maximum temperatures in 1989. The seasonal timing and precise level of this warming were indeed such as could promote the transmission of TBE virus between larval and nymphal ticks co-feeding on rodents. These changes in climate, however, are virtually uniform across the Baltic region and cannot therefore explain the marked spatio-temporal heterogeneity in TBE epidemiology. CONCLUSIONS/SIGNIFICANCE: Instead, it is proposed that climate is just one of many different types of factors, many arising from the socio-economic transition associated with the end of Soviet rule, that have acted synergistically to increase both the abundance of infected ticks and the exposure of humans to these ticks. Understanding the precise differential contribution of each factor as a cause of the observed epidemiological heterogeneity will help direct control strategies.

Tick-borne viruses.

M Labuda — 2005-07-24T22:26:50-00:00

Parasitology, Vol. 129 Suppl (2004)

At least 38 viral species are transmitted by ticks. Virus-tick-vertebrate host relationships are highly specific and less than 10% of all tick species (Argasidae and Ixodidae) are known to play a role as vectors of arboviruses. However, a few tick species transmit several (e.g. Ixodes ricinus, Amblyomma variegatum) or many (I. uriae) tick-borne viruses. Tick-borne viruses are found in six different virus families (Asfarviridae, Reoviridae, Rhabdoviridae, Orthomyxoviridae, Bunyaviridae, Flaviviridae) and at least 9 genera. Some as yet unassigned tick-borne viruses may belong to a seventh family, the Arenaviridae. With only one exception (African swine fever virus, family Asfarviridae) all tick-borne viruses (as well as all other arboviruses) are RNA viruses. Tick-borne viruses are found in all the RNA virus families in which insect-borne members are found, with the exception of the family Togaviridae. Some tick-borne viruses pose a significant threat to the health of humans (Tick-borne encephalitis virus, Crimean-Congo haemorrhagic fever virus) or livestock (African swine fever virus, Nairobi sheep disease virus). Key challenges are to determine the molecular adaptations that allow tick-borne viruses to infect and replicate in both tick and vertebrate cells, and to identify the principal ecological determinants of tick-borne virus survival.

The ecology of ticks transmitting Lyme borreliosis

JS Gray — 2008-01-02T14:34:44-00:00

Experimental and Applied Acarology, Vol. 22, No. 5. (May 1998), pp. 249-258.

The main vectors of Borrelia burgdorferi sensu lato, the cause of Lyme borreliosis, are ixodid ticks of the Ixodes persulcatus species complex. These ticks, which occur throughout the northern temperate zone, have very similar life cycles and ecological requirements. All are three-host ticks, with the immature stages mainly parasitizing small to medium-sized mammals and birds and the adult females parasitizing large mammals such as deer, cattle, sheep and hares. The host-seeking stages show a distinct seasonality, which is regulated by diapause mechanisms and there appear to be major differences in this respect between the Old World and New World species. Most cases of human borreliosis are transmitted in the summer by the nymphal stages, with the exception of the Eurasian species, I. persulcatus, in which the adult females are mainly responsible. The ticks acquire the spirochaetes from a wide variety of mammals and birds but large mammals do not seem to be infective, so that ticks that feed almost exclusively on large mammals, for example in some agricultural habitats, are rarely infected. The greatest tick infection prevalences occur in deciduous woodland harbouring a diverse mix of host species and the diversity of the different genospecies of B. burgdorferi s.l. is also greatest in such habitats. There is evidence that these genospecies have different host predilections but, apart from the fact that I. persulcatus does not seem to be infected by B. burgdorferi sensu stricto, they do not seem to be adapted to different tick strains or species.

[Fauna, climate and politics: possible causes for the recent increases in tick-borne zoonoses]

SE Randolph — 2005-07-24T22:09:35-00:00

Arch Pediatr, Vol. 11, No. 10. (October 2004), pp. 1282-1285.

Le climat exerce assurément une influence forte sur la dynamique des systèmes des maladies vectorielles. Son effet, cependant, n'est pas unidirectionnel, si bien que les changements climatiques passés et futurs peuvent donner lieu à des schémas géographiquement variables de croissance, ou de décroissance, de l'incidence des infections. Le climat n'est pas non plus le seul facteur à avoir changé. Les importants changements observés, au cours des récentes décennies, de l'incidence des maladies à tiques, peuvent être dus à un meilleur dépistage ainsi qu'à une augmentation du contact homme-tiques infectées. Dans ce dernier cas, les raisons peuvent en être non biologiques (sociopolitiques) ou biologiques, notamment l'influence de l'homme sur les habitats des tiques et sur les hôtes sauvages ou encore des changements de climat. L'accroissement des effectifs des espèces hôtes des tiques, comme le chevreuil, est favorable aux populations de tiques. L'influence biotique est tout à fait évidente sur les espèces d'lxodes responsables de la transmission de la maladie de Lyme et de l'encéphalite à tiques (TBE, tick-borne encephalitis), alors qu'au contraire il y a peu d'évidence directe quant au rôle du changement climatique sur l'augmentation de ces maladies. Dans de nombreux pays de l'est de l'Europe, une plus forte exposition des hommes aux tiques infectées, résultant des changements de pratique agricole et sociologiques de l'après-communisme, peut avoir joué un rôle important dans la brutale augmentation des cas de TBE au cours des années 1990. Les interactions géographiquement variables de la faune, du climat et des pratiques politiques, contribuent à la variété des profils des zoonoses émergentes.

Tick infestation on roe deer in relation to geographic and remotely sensed climatic variables in a tick-borne encephalitis endemic area.

G Carpi — 2008-01-02T09:47:23-00:00

Epidemiology and Infection (17 December 2007), pp. 1-9.

Roe deer Capreolus capreolus are among the most important feeding hosts for the sheep tick Ixodes ricinus, thus contributing to the occurrence of tick-borne diseases in Europe. Tick-borne encephalitis (TBE), which is transmitted by co-feeding of larvae and nymphs on rodents, requires precise climatic conditions to occur. We used roe deer as sentinels for potential circulation of TBE virus in Northern Italy, by examining the association between tick infestation, occurrence of TBE human cases, geographical and climatic parameters. Tick infestation on roe deer, and particularly frequency of co-feeding, was clearly associated with the geographic location and the autumnal cooling rate. Consistently, TBE occurrence in humans was geographically related to co-feeding tick abundance. The surveillance of tick infestation on roe deer, combined with remotely sensed climatic data, could therefore be used as an inexpensive early risk assessment tool of favourable conditions for TBE emergence and persistence in humans.

Tick-borne Disease Systems: Mapping Geographic and Phylogenetic Space.

SE Randolph — 2007-05-07T13:26:01-00:00

Adv Parasitol, Vol. 62 (2006), pp. 263-291.

Evidence is presented that the evolution of the tick-borne flaviviruses is driven by biotic factors, principally the exploitation of new hosts as transmission routes. Because vector-borne diseases are limited by climatic conditions, however, abiotic factors have the potential to direct and constrain the evolutionary pathways. This idea is explored by testing the hypothesis that closely related viruses occupy more similar eco-climatic spaces than do more distantly related viruses. A statistical comparison of the conventional phylogenetic tree derived from molecular distances and a novel phenetic tree derived from distances between the climatic spaces within which each virus circulates, indicates that these trees match each other more closely than would be expected at random. This suggests that these viruses are indeed limited in the degree to which they can evolve into new environmental conditions.

Climate change and vector-borne diseases.

DJ Rogers — 2007-05-07T12:23:58-00:00

Adv Parasitol, Vol. 62 (2006), pp. 345-381.

In this review we examine formally the conditions under which vector-borne diseases are likely to change, and the directions of those changes, under various scenarios of climate change. We specify the criteria that must be met in order to conclude that climate change is having an effect on vector-borne diseases. We then take several examples from the literature and show how some of them meet these criteria, while others do not. For those that do not, there are alternative explanations that involve much more plausible drivers of the recorded changes in the diseases concerned.

Wildlife, environment and (re)-emerging zoonoses, with special reference to sylvatic tick-borne zoonoses in North-Western Italy.

D De Meneghi — 2008-01-11T09:34:43-00:00

Ann Ist Super Sanita, Vol. 42, No. 4. (2006), pp. 405-409.

Over the last century, changes in land-use, modification of agriculture-livestock production systems, disruption of wildlife habitats, increase of human activities, higher frequency of international and intercontinental travels, wider circulation of animals and animal products have contributed to alter the distribution, presence and density of hosts and vectors. As a result, the number of emerging and reemerging diseases, including zoonoses, have greatly increased. Some infectious pathogens, originated in wild animals and/or maintained in sylvatic environments, have become increasingly important worldwide for their impact on wildlife, human health, livestock and agricultural production systems. In this paper, a synthesis of the information available on selected zoonoses of wildlife origin is given, with special reference to sylvatic tick-borne zoonoses in North-western Italy.

Reported distribution of Ixodes scapularis and Ixodes pacificus (Acari: Ixodidae) in the United States.

DT Dennis — 2008-01-09T13:28:50-00:00

Journal of Medical Entomology, Vol. 35, No. 5. (September 1998), pp. 629-638.

Lyme disease, caused by infection with Borrelia burgdorferi, is the most frequently reported arthropod-borne disease in the United States. To develop a national map of the distribution of the vectors of B. burgdorferi to humans (Ixodes scapularis Say and Ixodes pacificus Cooley & Kohls ticks), we sent questionnaires to acarologists, health officials, and Lyme disease researchers; surveyed the 1966-1996 MEDLINE data base; and reviewed 1907-1995 National Tick Collection data. Tick collection methods cited included flagging and dragging, deer surveys, small- and medium-sized mammal surveys, CO2 baiting, and receipt of tick submissions. A total of 1,058 unique, county-specific I. scapularis and I. pacificus records was obtained. Tick populations were classified as "reported" (< 6 ticks and 1 life stage identified) or "established" (> or = 6 ticks or > 1 life stage identified). Established populations of I. scapularis were identified in 396 counties in 32 states in the eastern and central United States, whereas established populations of I. pacificus were found in 90 counties in 5 western states. Counties with established populations were most concentrated in the northeastern, upper northcentral, and west-coastal states but were also clustered in southeastern and Gulf-coastal states. A less concentrated distribution was found in the south-central states. Reports were notably missing from all but a few counties in Ohio, West Virginia, western Virginia and North Carolina, Kentucky, and Tennessee. They were absent in the Great Plains and Rocky Mountain regions and from large areas of western states east of the Cascade and Sierra Nevada cordilleras. These data are useful for identifying areas of Lyme disease risk, for targeting Lyme disease prevention strategies, and for monitoring trends in spatial distribution of Lyme disease vector ticks.

Detection, characterization, and prediction of tick-borne disease foci.

MR Cortinas — 2005-07-24T21:44:02-00:00

Int J Med Microbiol, Vol. 291 Suppl 33 (June 2002), pp. 11-20.

Tick-borne disease (TBD) transmission foci need to be characterized in space and time, and are often discontinuous on both scales. An active TBD focus is dependent on the fulfillment of three conditions: tick survival, pathogen survival and opportunities for human exposure. The essentials for tick survival include food sources, reproduction, and protection from environmental extremes. The pathogen survival kit includes sufficient densities of ticks and suitable reservoir hosts, and opportunities for transmission between them in order to maintain infection. Opportunities for human exposure depend on sufficient number of encounters between ticks and humans. Because tick foci need to be described on a range of spatial and temporal resolutions, data for such characterization include a variety of surveillance data, field and laboratory experimental data, as well as results of statistical and mathematical analysis and modeling. The application of new tools from molecular biology, geographic information systems (GIS), and satellite imagery, in conjunction with appropriate analytical methods allow for detection of unknown foci and prediction of new ones. A long-term multi-scale study of Ixodes scapularis and Lyme disease in the north-central U. S. is reviewed. Diverse surveillance methods of ticks, rodents, deer, canids and humans were coupled with environmental characterization in situ to create a habitat profile for Lyme disease ticks. Incorporating various digitized databases, a statistical model was used to develop a risk map for tick distribution in the region. The process of introduction and establishment of new tick foci along the Illinois River is described in relation to the known tick distribution and predictions of invasion based on the risk model.

Tick-borne encephalitis in Europe (Comment).

S Randolph — 2007-05-10T14:02:31-00:00

Lancet, Vol. 358, No. 9294. (17 November 2001), pp. 1731-1732.

Fall and rise of Lyme disease and other Ixodes tick-borne infections in North America and Europe.

AG Barbour — 2005-07-24T21:12:54-00:00

Br Med Bull, Vol. 54, No. 3. (1998), pp. 647-658.

Lyme disease is a spirochaetal infection with acute and chronic manifestations. Lyme disease and other infections transmitted by Ixodes species ticks are increasing in temperate and Holarctic regions of the Northern hemisphere. These zoonotic infections are most commonly acquired in suburban residential areas and outdoor recreation areas close to cities. Different enzootic cycles, which include a variety of large and small mammals as well as migratory birds, maintain and distribute in nature the Borrelia species that cause Lyme disease. The rise in cases of Lyme disease and the other Ixodes tick-borne infections is, in part, the consequence of reforestation and the increase in deer populations in developed countries.

Remote Sensing and Geographical Information Systems in Epidemiology (Advances in Parasitology)

SI Hay — 2006-07-31T08:02:58-00:00

(15 September 2000)

Global problems require global information, which satellites can now provide. With ever more sophisticated control methods being developed for infectious diseases, our ability to map spatial and temporal variation in risk is more important than ever. Only then may we plan control campaigns and deliver novel interventions and remedies where the need is greatest, and sustainable success is most likely. This book presents a comprehensive guide to using the very latest methods of surveillance from satellites, including analysing spatial data within geographical information systems, interpreting complex biological patterns, and predicting risk both today and as it may change in the future. Of all infectious disease systems, those that involve free-living invertebrate vectors or intermediate hosts are most susceptible to changing environmental conditions, and have hitherto received most attention from the marriage of analytical biology with this new space technology. Accordingly, this volume presents detailed case studies on malaria, African trypanosomiasis (sleeping sickness), tick-borne infections and helminths (worms). For those who are unfamiliar with this science, and unsure how to start, the book ends with a chapter of practical advice on where to seek hands-on instruction. The lessons to be learned from these studies are applicable to many other epidemiological and ecological problems that face us today, most significantly the preservation of the world's biodiversity. Key Features * Only book to provide a synthesis of complex biology, quantitative analysis, space technology and practical applications, focused on solving real epidemiological problems on a global scale * Broad scope, with methods relevant to subjects ranging from biodiversity to public health * Practical advice on relevant courses * 24 pages of colour plates

Anaplasma phagocytophilum - the most widespread tick-borne infection in animals in Europe.

S Stuen — 2007-12-27T11:19:32-00:00

Vet Res Commun, Vol. 31 Suppl 1 (August 2007), pp. 79-84.

The bacterium Anaplasma phagocytophilum (formerly Ehrlichia phagocytophila) may cause infection in several animal species including human. The disease in domestic ruminants is also called tick-borne fever (TBF), and has been known for at least 200 years. In Europe, clinical manifestations due to A. phagocytophilum have been recorded in sheep, goat, cattle, horse, dog, cat, roe deer, reindeer and human. However, seropositive and PCR-positive mammalian have been detected in several other species. Investigations indicate that the infection is prevalent in Ixodes ricinus areas in most countries in Europe. A. phagocytophilum infection may cause high fever, cytoplasmatic inclusions in phagocytes and severe neutropenia, but is seldom fatal unless complicated by other infections. Complications may include abortions, and impaired spermatogenesis for several months. However, the most important aspect of the infection at least in sheep is its implication as a predisposing factor for other infections. Factors such as climate, management, other infections, individual conditions etc. are important for the outcome of the infection. A. phagocytophilum may cause persistent infection in several species. Based on the 16S rRNA gene sequences several variants exist. Different variants may exist within the same herd and even simultaneously in the same animal. Variants may behave differently and interact in the mammalian host.

Tick- and flea-borne rickettsial emerging zoonoses.

P Parola — 2006-07-20T21:09:30-00:00

Veterinary Research, Vol. 36, No. 3. (n 2005), pp. 469-492.

Between 1984 and 2004, nine more species or subspecies of spotted fever rickettsiae were identified as emerging agents of tick-borne rickettsioses throughout the world. Six of these species had first been isolated from ticks and later found to be pathogenic to humans. The most recent example is Rickettsia parkeri, recognized as a human pathogen more than 60 years after its initial isolation from ticks. A new spotted fever rickettsia, R. felis was also found to be associated with fleas and to be a human pathogen. Similarly, bacteria within the family Anaplasmataceae have been considered to be of veterinary importance only, yet three species have been implicated in human diseases in recent years, including Ehrlichia chaffeensis, the agent of human monocytic ehrlichiosis, Anaplasma phagocytophilum, the agent of human anaplasmosis (formerly known as "human granulocytic ehrlichiosis agent", E. equi and E. phagocytophila), and finally Ehrlichia ewingii, which causes granulocytic ehrlichiosis in humans. We present here an overview of the various tick- and flea-borne rickettsial zoonoses described in the last 20 years, focusing on the ecological, epidemiological and clinical aspects.

Habitat factors influencing distributions of Anaplasma phagocytophilum and Ehrlichia chaffeensis in the Mississippi Alluvial Valley.

JS Manangan — 2008-04-19T06:03:05-00:00

Vector borne and zoonotic diseases (Larchmont, N.Y.), Vol. 7, No. 4. (2007), pp. 563-573.

Human monocytotropic ehrlichiosis (HME), caused by the bacterium Ehrlichia chaffeensis, and human granulocytic anaplasmosis (HGA), caused by the bacterium Anaplasma phagocytophilum, are two emerging tick-borne zoonoses of concern. Factors influencing geographic distributions of these pathogens are not fully understood, especially at varying spatial extents (regional versus landscape) and resolutions (counties versus smaller land units). We used logistic regression to compare influences of physical environment, land cover composition, and landscape heterogeneity on distributions of A. phagocytophilum and E. chaffeensis at multiple spatial extents. Pathogen presence or absence was determined from white-tailed deer (Odocoileus virginianus) serum samples collected from 1981 to 2005. Ecological predictor variables were derived from spatial datasets that represented deer density, elevation, land cover, normalized difference vegetation index (NDVI), hydrology, and soil moisture. We used three strategies (a priori, exploratory, and spatial extent) to develop models. Best fitting models were applied within a geographic information system to create predictive probability surfaces for each bacterium. Ecological predictor variables generally resulted in better fitting models for E. chaffeensis than A. phagocytophilum (90.5% and 68% sensitivity, respectively), possibly as a result of differences in the natural histories of tick vectors. Although alternative model development strategies produced different models, in all cases bacteria presence or absence was affected by a combination of soil moisture or flooding variables (thought to affect primarily tick vectors) and forest cover or NDVI variables (thought to affect primarily mammalian hosts). This research demonstrates the potential for modeling the distributions of microscopic tick-borne pathogens using coarse regional datasets and emphasizes the importance of forest cover and flooding as environmental constraints, as well as the importance of considering ecological variables at multiple spatial extents.

Enhanced spatial models for predicting the geographic distributions of tick-borne pathogens

Michael Wimberly — 2008-04-17T06:06:36-00:00

International Journal of Health Geographics, Vol. 7 (15 April 2008), 15.

Threats to international travellers posed by tick-borne diseases.

M Jensenius — 2008-01-10T16:59:34-00:00

Travel Med Infect Dis, Vol. 4, No. 1. (January 2006), pp. 4-13.

To date, 14 tick-borne diseases have been reported in international travellers, the majority of cases being Lyme borreliosis caused by Borrelia burgdorferi sensu lato in North America and Eurasia, African tick bite fever caused by Rickettsia africae in sub-Saharan Africa and eastern Caribbean, and Central European encephalitis caused by tick-borne encephalitis virus in Europe. The clinical presentation is frequently non-specific, and tick-borne diseases should always, in the absence of other likely diagnoses, be suspected in travellers with flu-like symptoms following a recent visit to tick-infested areas. Feasible microbiological diagnostic tests are widely unavailable, at least outside areas of endemicity where many infected travellers present. Empiric treatment with doxycycline should be considered in suspected cases of tick-borne bacterial diseases. Since ecotourism and adventure travel are increasingly popular worldwide, the incidence of travel-associated tick-borne diseases is likely to increase in the future.

Tick-borne encephalitis in Sweden and climate change.

E Lindgren — 2005-07-22T15:33:02-00:00

Lancet, Vol. 358, No. 9275. (7 July 2001), pp. 16-18.

BACKGROUND: The incidence of tick-borne encephalitis (TBE) in Sweden has substantially increased since the mid-1980s. During the same period the climate has become milder and ticks have become more abundant. We investigated whether there is a link between the change in climate and the increase in incidence of TBE. METHODS: Since the late 1950s all cases of encephalitis admitted in Stockholm County have been serologically tested for TBE. We analysed the period 1960-98 with multiple regressions. The number of days per season with temperatures of known importance for tick prevalence and pathogen transmission were studied. 2 years of temperature data were related to each TBE incidence rate to account for the tick's long life-span. FINDINGS: Increases in disease incidence was significantly related (R(2)=0.58; p<0.0001) to a combination of two consecutive mild winters, temperatures favouring spring development (8-10 degrees C) and extended autumn activity (5-8 degrees C) in the year prior to the incidence year, and temperatures allowing tick activity (5-8 degrees C) early in the incidence year. INTERPRETATIONS: The findings indicate that the increase in TBE incidence since the mid-1980s is related to the period's change towards milder winters and early arrival of spring. Other factors may have influenced TBE incidence such as more people in endemic locations, and increases in host animal populations; factors which are partly climate related. Access to TBE vaccination since 1986 and increased awareness of ticks might have caused an underestimation of the links found. Our findings also suggest that the incidence of other tick-borne zoonoses might have been affected by the milder climate.

Tick-borne encephalitis virus expansion to higher altitudes correlated with climate warming.

Vlasta Danielová — 2008-04-28T15:35:33-00:00

International journal of medical microbiology : IJMM (21 April 2008)

Since 2002, the expansion of Ixodes ricinus ticks and tick-borne infection agents have been studied in the Krkonose Mts., Czech Republic. Tick-borne encephalitis virus was detected by means of RT-PCR. In 2003, it was detected in 2 out of 491 ticks at 620 and 710-720m a.s.l., respectively, and in 3 out of 939 ticks at 600m a.s.l. at the same locality in 2004. In 2005, tick-borne encephalitis virus was detected in 5 out of 295 ticks at 900-1100m a.s.l., which is above the formerly known altitudinal limit of I. ricinus distribution. The reason for that could be found in the changing climate. Based on the meteorological data collected in the Krkonose Mts., 1961-2005, there was a significant increase in the mean annual temperature (1.3-1.4 degrees C) over that period, namely by 2-3.5 degrees C in May through August. Thus, with respect to the average vertical temperature gradient in summer of about 0.6 degrees C/100m, 2 degrees C correspond to 300-350m in altitude, and accordingly 3.5 degrees C correspond to a shift in altitude of approximately 550-600m, that being in accordance with environmental conditions of the former I. ricinus altitudinal limit confirmed in the Krkonose Mts. 20 years ago.

Anaplasmosis in Cattle in Italy

A Torina — 2008-04-14T14:52:43-00:00

Veterinary Research Communications, Vol. 31, No. 0. (2007), pp. 73-78.

Torina, A. and Caracappa, S., 2007. Anaplasmosis in cattle in Italy. Veterinary Research Communications, 31(Suppl. 1), 73–78

Fundamental processes in the evolutionary ecology of Lyme borreliosis

Klaus Kurtenbach — 2006-08-19T00:40:25-00:00

Nature Reviews Microbiology, Vol. 4, No. 9. (07 August 2006), pp. 660-669.

Biology of Ixodes species ticks in relation to tick-borne zoonoses.

JS Gray — 2005-07-24T20:19:03-00:00

Wien Klin Wochenschr, Vol. 114, No. 13-14. (31 July 2002), pp. 473-478.

At least six tick-borne zoonoses are transmitted by members of the Ixodes ricinus species complex in northern hemisphere temperate regions, and include the relatively recently emerged diseases, Lyme borreliosis and ehrlichiosis. An understanding of the biology of these ticks is essential for the prevention and control of the zoonoses they transmit and this review summarises established knowledge in addition to addressing recent work on host specificity of ticks, inter- and intra-specific biological variation and factors affecting tick distribution and abundance.

Empirical evidence for key hosts in persistence of a tick-borne disease.

SE Perkins — 2006-07-11T07:43:18-00:00

Int J Parasitol, Vol. 33, No. 9. (August 2003), pp. 909-917.

An important epidemiological consequence of aggregated host-parasite associations occurs when parasites are vectors of pathogens. Those hosts that attract many vectors will tend to be the focus of transmission. But to what extent, and can we identify characteristics of these key hosts? We investigated these questions with respect to the host-tick relationship of the yellow-necked mouse, Apodemus flavicollis, a critical host in the maintenance of the zoonotic disease, tick-borne encephalitis. Transmission of the virus occurs when ticks feed in a 'co-feeding' aggregation. Thus, the number and frequency of co-feeding groups provides an estimate of the potential rate of virus transmission. We recorded the spatio-temporal variations in co-feeding on a population of rodents in conjunction with recording individual host characteristics. Using Lorenz curves, we revealed conformation of tick-borne encephalitis transmission potential to the 20/80 Rule, where the 20% of hosts most infested with ticks were accountable for 80% of transmission potential. Hosts in the transmission cohort were identified as the sexually mature males of high body mass. Therefore control efforts targeted at this group would substantially reduce transmission potential compared to non-targeted control of the population, which resulted in a linear reduction in transmission potential. Focusing on the 'wrong' functional group would have little impact upon transmission potential until a considerable proportion of the population had been subject to control. However, individuals can change their functional status over time making it difficult to predict the contribution of these individuals to future transmission.

Tick-borne encephalitis virus transmission between ticks cofeeding on specific immune natural rodent hosts.

M Labuda — 2006-07-11T07:33:07-00:00

Virology, Vol. 235, No. 1. (18 August 1997), pp. 138-143.

To determine whether the portion of a vertebrate host population having specific immunity to tick-borne encephalitis (TBE) virus can participate in the TBE virus transmission cycle, natural hosts immunized against TBE virus were challenged with infected and uninfected ticks. Yellow-necked field mice (Apodemus flavicollis) and bank voles (Clethrionomys glareolus) were either immunized with TBE virus by subcutaneous inoculation of the virus, or they were exposed to virus-infected Ixodes ricinus ticks. One month later, when serum neutralizing antibody was detectable, the animals were infested with infected (donor) adult female ticks and uninfected (recipient) nymphal ticks; recipients were allowed to feed either in close contact (chamber 1) or physically separated (chamber 2) from the infected donor ticks. Following challenge with infected (and uninfected) ticks, viremia developed in all the control, nonimmune animals, whereas viremia was undetectable in all those animals naturally immunized by previous exposure to infected ticks. Despite the presence of neutralizing antibodies in all the immunized animals, 89% (24/ 27) immune animals supported virus transmission between infected and uninfected cofeeding ticks. Most transmission was localized, occurring within chamber 1; disseminated transmission from chamber 1 to chamber 2 was reduced. Immunization by tick bite was more effective than immunization by syringe inoculation in blocking cofeeding virus transmission. Nevertheless 76% (9/12) animals with "natural" immunity still supported transmission. The results demonstrate that natural hosts having neutralizing antibodies to TBE virus (and no detectable viremia) can still support virus transmission between infected and uninfected ticks feeding closely together on the same animal. These observations have important epidemiological implications relating to the survival of TBE virus in Nature.

Epidemiology and ecology of TBE relevant to the production of effective vaccines.

J Süss — 2006-07-11T07:24:24-00:00

Vaccine, Vol. 21 Suppl 1 (1 April 2003)

This review focuses on the epidemiology and ecology of the tick-borne encephalitis (TBE) virus including all the factors influencing the ecology of the TBE virus, environmental and climatic conditions, the vectors and reservoir hosts and their interactions. Consequently, the structure and the conditions of natural foci of TBE are described, as well. Special emphasis is given on data regarding the virus prevalence in ticks in the field. In the second part of this review all the epidemiological and surveillance data of TBE in the 27 European countries and in the Far East with risk areas of TBE and in China and Japan are summarised. Therefore the review is a basis for travellers and inhabitants to get background information for their personal risk assessment.

Wildlife as source of zoonotic infections.

H Kruse — 2008-05-09T20:47:13-00:00

Emerging infectious diseases, Vol. 10, No. 12. (December 2004), pp. 2067-2072.

Zoonoses with a wildlife reservoir represent a major public health problem, affecting all continents. Hundreds of pathogens and many different transmission modes are involved, and many factors influence the epidemiology of the various zoonoses. The importance and recognition of wildlife as a reservoir of zoonoses are increasing. Cost-effective prevention and control of these zoonoses necessitate an interdisciplinary and holistic approach and international cooperation. Surveillance, laboratory capability, research, training and education, and communication are key elements.

Prevalence and incidence of antibodies to Borrelia burgdorferi and to tick-borne encephalitis virus in agricultural and forestry workers from Tuscany, Italy.

P Tomao — 2005-08-08T20:02:04-00:00

Eur J Clin Microbiol Infect Dis, Vol. 24, No. 7. (July 2005), pp. 457-463.

The ticks Ixodes persulcatus and Ixodes ricinus are the main vectors of both Borrelia burgdorferi sensu lato and tick-borne encephalitis (TBE) virus in Eurasia. Borrelia burgdorferi is the cause of Lyme borreliosis, and TBE is a biphasic meningoencephalitis induced by an arbovirus belonging to the flavivirus family. The principal aims of the current investigation were (i) to determine the frequency of serological evidence of Borrelia burgdorferi sensu lato and TBE infections in healthy agricultural and forestry workers, (ii) to determine the incidence of seroconversion for antibodies against Borrelia burgdorferi sensu lato and TBE virus in Tuscan workers during a 1-year survey; and (iii) to assess the occupational risk for agricultural and forestry activities in a defined area (Tuscany, Italy). A total of 412 blood samples were taken from agricultural and forestry workers, and information on age, duration of employment, and history of tick bites was collected in a questionnaire to establish the risk factors for the diseases. Three hundred sixty-five blood donors from the same region served as controls. To estimate the rate of seroconversion, 176 of the agricultural and forestry workers were tested 1 year later. IgG and IgM antibodies against Borrelia burgdorferi sensu lato and TBE virus were detected in serum by an enzyme-linked immunosorbent assay and confirmed by Western blot analysis for Borrelia burgdorferi and by a test for inhibition of hemagglutination for TBE. Antibodies against Borrelia burgdorferi were more frequent among the workers than in the control group (7.8% vs. 4.9% in the IgG-IgM enzyme-linked immunosorbent assay and 7.03% vs. 3.56% in the confirmatory test). No seropositivity was observed for TBE virus. Eighteen of 176 subjects who underwent a second blood test developed specific antibodies against Borrelia burgdorferi within 1 year.

Quantitative ecology of ticks as a basis for transmission models of tick-borne pathogens.

S Randolph — 2005-07-22T08:50:49-00:00

Vector Borne Zoonotic Dis, Vol. 2, No. 4. (2002), pp. 209-215.

Tick population ecology is the basis of spatiotemporal variation in the risk of infection by tick-borne pathogens. The continental distribution of tick-borne encephalitis (TBE) in Europe is statistically associated with a specific pattern of the seasonal dynamics of Ixodes ricinus, and a particular characteristic of the seasonal land surface temperature profile. A tick population model would allow us to move from this statistical analysis to a biological, process-based model for TBE virus and the many other pathogens vectored by Ixodes spp. ticks in Europe and the United States. Long-term field data on I. ricinus are analyzed to provide empirical estimates of rates of the major demographic processes, development, questing, attachment to hosts, and mortality.

Detection and identification of pathogens and host DNA in unfed host-seeking Ixodes ricinus L. (Acari: Ixodidae).

B Pichon — 2008-04-24T19:44:46-00:00

Journal of medical entomology, Vol. 40, No. 5. (September 2003), pp. 723-731.

In this study, we have developed molecular methods for the identification of reservoir hosts of sylvatic tick-borne zoonoses. The methods are based on the analysis of the blood meal remnant in the tick gut and include detection of pathogens and identification of the host origin of the blood meal. For host identification, a universal primer pair was used to amplify part of the vertebrate 18S rRNA gene followed by reverse line blot hybridization using subgroup-specific probes. Analyses of DNA from whole blood of vertebrates identified the correct subgroup of a broad range of vertebrate species (e.g., Ruminantia, Leporidea, Canidae, Murinae, Arvicolinae, Insectivora, Galliformes, Passeriformes) using probes based on the 18S rDNA sequences. Host DNA in the remnants of larval blood meals was detected in the gut of Ixodes ricinus nymphs maintained under natural conditions up to 9 mo after molting. For pathogen identification, a multiplex polymerase chain reaction was used that targeted parts of the 18S rRNA gene of piroplasm protozoa, the 16S rRNA gene of bacteria, and the intergenic spacer of the Borrelia burgdorferi genospecies complex. The utility of both methods was demonstrated under laboratory conditions by detecting Babesia microti (Franca) and gerbil DNA in 3-mo-old I. ricinus nymphs that had fed on B. microti-infected gerbils as larvae, and under field conditions by analyzing unfed ticks that were collected in a forest. The field study showed that the majority of ticks had fed on ruminants or birds and few on rodents, which is in accord with our knowledge of the fauna in this forest. Few pathogens were detected but the discovery of Borrelia valaisiana and B. burgdorferi s.s. in ticks that had fed on deer and Borrelia afzelii in a tick that had fed on a bird raises questions about the mode of transmission of these spirochetes and possibly about their host specificity.