CiteULike: neteler's disease

Predicting the emergence of human hantavirus disease using a combination of viral dynamics and rodent demographic patterns.

F Sauvage — 2008-03-18T11:44:46-00:00

Epidemiol Infect, Vol. 135, No. 1. (January 2007), pp. 46-56.

The paper proposes a model explaining the spatial variation in incidence of nephropathia epidemica in Europe. We take into account the rodent dynamic features and the replicative dynamics of the virus in animals, high in the acute phase of newly infected animals and low in the subsequent chronic phase. The model revealed that only vole populations with multi-annual fluctuations allow for simultaneously high numbers of infected rodents and high proportions of those rodents in the acute excretion phase during the culminating phase of population build-up. This leads to a brief peak in exceptionally high concentrations of virus in the environment, and thereby, to human exposure. Such a mechanism suggests that a slight ecological disturbance in animal-parasite systems could result in the emergence of human diseases. Thus, the potential risk for public health due to several zoonotic diseases may be greater than previously believed, based solely on the distribution of human cases.

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.

Spatial epidemiology: an emerging (or re-emerging) discipline

Richard Ostfeld — 2008-05-09T20:21:42-00:00

Trends in Ecology & Evolution, Vol. 20, No. 6. (June 2005), pp. 328-336.

Spatial epidemiology is the study of spatial variation in disease risk or incidence. Several ecological processes can result in strong spatial patterns of such risk or incidence: for example, pathogen dispersal might be highly localized, vectors or reservoirs for pathogens might be spatially restricted, or susceptible hosts might be clumped. Here, we briefly describe approaches to spatial epidemiology that are spatially implicit, such as metapopulation models of disease transmission, and then focus on research in spatial epidemiology that is spatially explicit, such as the creation of risk maps for particular geographical areas. Although the spatial dynamics of infectious diseases are the subject of intensive study, the impacts of landscape structure on epidemiological processes have so far been neglected. The few studies that demonstrate how landscape composition (types of elements) and configuration (spatial positions of those elements) influence disease risk or incidence suggest that a true integration of landscape ecology with epidemiology will be fruitful.

Global trends in emerging infectious diseases

Kate Jones — 2008-02-21T13:23:19-00:00

Nature, Vol. 451, No. 7181., pp. 990-993.

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.

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.

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.

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

Influence of some climatic factors on Ixodes ricinus ticks studied along altitudinal gradients in two geographic regions in Switzerland.

Lise Gern — 2008-04-10T08:01:37-00:00

International journal of medical microbiology : IJMM (14 March 2008)

In the context of climate change, the seasonal activity of questing Ixodes ricinus and their infection with Borrelia burgdorferi sensu lato (s.l.) were examined in relation to some climatic data along altitudinal gradients in Switzerland. The first study took place in an Alpine area (Valais) from 750 to 1020m above sea level. The other gradient was located on a mountain in the foothills of the Jura chain (Neuchâtel) from 620 to 1070m above sea level. In the Alpine area, the highest questing tick density was observed at the highest altitude. At the lowest altitudes (750 and 880m), very high saturation deficits, >10mmHg, were present during most of the tick activity season and they seem to have impaired the thriving of tick populations. The second study in Neuchâtel (2003-2005) was a follow-up of a previous study (1999-2001) in which it was observed that tick density decreased with increasing altitude. During the follow-up study, substantial differences in questing tick density and phenology of ticks were observed: At high elevations, questing tick densities were 2.25 and 3.5 times higher for nymphs and adults, respectively, than during 1999-2001. As observed during 1999-2001, questing tick density decreased with increasing altitude in this site in 2003-2005. Tick questing density remained higher at the lowest altitude. Increased temperatures during summer months, more favorable for ticks, reaching values similar to those registered in the first study at the lowest elevations are probably responsible for the higher tick questing density at high altitudes. B. burgdorferi s.l. infection prevalence in ticks decreased with increasing altitudes along both altitudinal gradients. Long-lasting high saturation deficit values may limit the development of tick populations as too high a moisture stress has a negative effect on tick survival. This factor may have a permanent impact, as it is probably the case at the lowest altitudes in the Alpine area or a more transient effect like in the Neuchâtel gradient.

Ixodes ricinus density and infection prevalence of Borrelia burgdorferi sensu lato along a North-facing altitudinal gradient in the Rhône Valley (Switzerland).

C Burri — 2008-01-11T09:28:45-00:00

Vector Borne Zoonotic Dis, Vol. 7, No. 1. (2007), pp. 50-58.

Questing Ixodes ricinus ticks were sampled monthly along a north-facing altitudinal gradient in the canton of Valais, Switzerland, from March 2004 to February 2005. Tick density and infection with Borrelia burgdorferi sensu lato were monitored. Ticks were collected by flagging vegetation at three different altitudes (750 m, 880 m, and 1020 m above sea level). Ticks were examined for Borrelia by polymerase chain reaction (PCR) followed by reverse line blot. At the three altitudes, questing tick activity was not observed under 10 degrees C and was reduced when saturation deficit was higher than 5 mm Hg, most questing tick activity was occurred between 2 mm Hg and 7 mm Hg. Tick density and peak tick density were highest at 1020 m. High saturation deficits at the lowest altitudes appear to impair the tick population. The prevalence of B. burgdorferi infection in nymphs and adults decreased with altitude. The prevalence of infection was higher in adult ticks (47%) than in nymphs (29%). Four B. burgdorferi sensu lato genospecies were detected: B. afzelii (40%), B. garinii (22%), B. valaisiana (12%) and B. burgdorferi sensu stricto (6%). Mixed infections were detected in 13% of infected ticks.

Human ehrlichiosis in central Europe.

S Lotric-Furlan — 2008-03-09T18:11:28-00:00

Wien Klin Wochenschr, Vol. 110, No. 24. (23 December 1998), pp. 894-897.

Ehrlichioses are tick-transmitted diseases associated with illnesses of animals for decades, but recently recognised to be emerging human diseases. In the last ten years increasing number of cases of human infections caused by Ehrlichia chaffeensis and granulo-cytic ehrlichia were described in the United States. Several reports also indicate the presence of infection with the human granulocytic ehrlichiosis (HGE) agent in Europe. The first confirmed acute human disease caused by HGE agent was reported from Slovenia. Until 1997, five patients have been discovered in a prospective study on the etiology of febrile illnesses occurring within six weeks following a tick bite, conducted at the Department of Infectious Diseases, University Medical Centre, Ljubljana, Slovenia. The diagnosis of acute HGE was established by seroconversion to the HGE agent and/or molecular identification of ehrlichial organisms. None of the patients had detectable morulae on blood smear examination. Clinical characteristics and laboratory findings were similar to those reported from the United States, although the disease course was relatively mild in the Slovenian cases. All patients recovered rapidly and without sequelae, although only three patients received antibiotic therapy (of whom only two were treated with doxycycline). Many ehrlichiosis cases could go undetected due to a lack of physician awareness, lack of public knowledge, or limited investigation. HGE should now be also included in the differential diagnosis of febrile illnesses occurring after a tick bite in Europe.

Reflections on an evaluation of the Dutch infectious diseases surveillance information system

BHB van Benthem — 2008-03-17T10:28:49-00:00

Eurosurveillance, Vol. 13, No. 11. (March 2008)

The Netherlands’ Infectious diseases Surveillance Information System (ISIS) was developed 12 years ago as an early warning system for the country. The initial objective was to establish a surveillance system that gathered the test results of all micro-organisms from all medical microbiology laboratories (MMLs) in the Netherlands on a daily basis in order to create an early warning system. This paper analyses the most important results of a recent evaluation of the system. The evaluation was based on an analysis of early warning signals to detect outbreaks, number of visits to the ISIS website, and interviews with stakeholders, documentation on the ISIS system, and analyses of the ISIS MML database. While the daily collection of data on all micro-organisms for early warning has been achieved, the connection of all 85 MMLs in the Netherlands to the central ISIS MML database has not been achieved – only 18 MMLs have been connected. This has resulted in a low coverage and non-representative selection of MMLs for the Netherlands and therefore national outbreaks were missed. Data were used to determine trends in antimicrobial resistance over time. The ISIS system was not found suitable for early warning since outbreaks were detected via other systems. However, with some adaptations the ISIS system could be suitable for the surveillance of antimicrobial resistance. Furthermore, the discontinuation of this network would cause the loss of the most important data system for antimicrobial resistance in the Netherlands, since there is no other national system that gathers data on this topic. This evaluation resulted in a restart of the network.

Online GIS services for mapping and sharing disease information

Sheng Gao — 2008-02-26T01:53:02-00:00

International Journal of Health Geographics, Vol. 7 (25 February 2008), 8.

Vorkommen und Verhütung vektorassoziierter Erkrankungen des Menschen in Deutschland unter Berücksichtigung zoonotischer Aspekte

M Faulde — 2008-01-29T16:09:49-00:00

Bundesgesundheitsblatt - Gesundheitsforschung - Gesundheitsschutz, Vol. 44, No. 2. (5 February 2001), pp. 116-136.

Zusammenfassung Derzeit sind in Deutschland 24 von Arthropoden oder Nagetieren übertragene Infektionserkrankungen endemisch, von denen 13 durch Schildzecken, fünf durch Ratten und Mäuse, drei durch Stechmücken und eine durch Kleiderläuse übertragen werden. Das Auftreten weiterer neun Infektionserkrankungen kann vermutet werden, von denen vier durch Schildzecken, vier durch Stechmücken und eine durch Flöhe übertragen werden. Von den durch heimische Arthropoden übertragenen Infektionserregern werden 72% (13 von 18) durch Schildzecken übertragen. Die bei weitem häufigste von Vektoren übertragene Erkrankung in Deutschland ist die Lyme-Borreliose mit einer angenommenen jährlichen Inzidenzrate von 20.000 bis 60.000 Fällen, weshalb Schildzecken im Vergleich mit anderen Vektorenfamilien qualitativ und quantitativ das größte Gefährdungspotential darstellen. Das Auftreten sowie die Ausbreitung neuer humanpathogener Infektionserreger ist in Mitteleuropa grundsätzlich immer möglich. Bei kürzlich durchgeführten serologischen Studien konnten bei Menschen erstmals anti-Ehrlichia- und anti-Babesia-Antikörper nachgewiesen werden. Dies deutet darauf hin, dass auch in Deutschland bislang nicht nachgewiesene Infektionserreger vorkommen und die Gefährdung durch von Zecken übertragene Infektionserkrankungen vermutlich erheblich unterschätzt wird. Zugleich breiten sich in Europa die FSME, das Mittelmeerfleckfieber, das West-Nil-Fieber sowie das Mäusefleckfieber weiter aus. Verfügbare Schutzmaßnahmen zur Verhinderung von vektorassoziierten Infektionserkrankungen basieren hauptsächlich auf persönlichen Schutz- und Schädlingsbekämpfungsmaßnahmen, die im Folgenden näher vorgestellt werden. Die im weltweiten Vergleich geringen und schlecht koordinierten Anstrengungen auf medizinisch-zoologischem Fachgebiet in Deutschland müssen dem internationalen Niveau sowie der globalen Situation angepasst werden. Abstract Overall, 24 known or potentially human-pathogenic vector-borne disease agents are transmitted in Germany, 13 of them by hard ticks, 5 by commensal rodents (rats and mice), 3 by mosquitoes, and one by body lice, respectively. Regarding vector-borne disease agents that are suspected to be present or hypothetically are transmissible in Germany, additionally 4 disease agents are vectored by hard ticks, 4 by mosquitoes, and one by fleas, and possibly sandflies, respectively. Among vector-borne diseases proven to be endemic in Germany, tick-borne diseases prevail significantly, both in the number of disease agents transmitted as well as in the resulting annual case-load of human diseases. Lyme-borreliosis is by far the most frequent vector-borne disease showing an estimated incidence between 20.000 and 60.000 cases annually. Serologic studies conducted recently for the determination of anti-Ehrlichia- and anti-Babesia-antibodies in human populations indicate that these newly detected disease agents are present and thus the burden of tick-borne diseases may be underestimated in Germany. Currently, Central European tick-borne encephalitis, Mediterranean spotted fever, West Nile fever, and Murine typhus are reportedly spreading across Europe. Available measures for disease prevention mainly base on different principles of personal protection and vector control further discussed herein. Strong efforts in the field of medical entomology must be taken in Germany to improve the health support required to deal with the global disease threat and reach an international standard in this area.

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).

Environmental conditions and Puumala virus transmission in Belgium

Catherine Linard — 2007-12-14T10:49:42-00:00

International Journal of Health Geographics, Vol. 6 (14 December 2007), 55.

Habitat Factors Associated with Bank Voles (Clethrionomys glareolus) and Concomitant Hantavirus in Northern Sweden

Gert Olsson — 2008-01-16T14:12:48-00:00

Vector-Borne and Zoonotic Diseases, Vol. 5, No. 4. (2005), pp. 315-323.

Puumala virus (PUUV), genus hantavirus, causes nephropathia epidemica, a mild form of hemorrhagic fever with renal syndrome in humans. In this study, bank voles, the natural reservoir of PUUV, were captured at locations of previous human PUUV exposure and paired controls within a region of high incidence in northern Sweden. The aim of the study was to evaluate the influence of environmental factors on the abundance of bank voles and the occurrence of PUUV. The total number of voles and the number of PUUV-infected voles did not differ between locations of previous human PUUV exposure and paired controls. The number of bank voles expressing antibodies to PUUV infection increased linearly with total bank vole abundance implying density independent transmission. Using principal component and partial correlation analysis, we found that particular environmental characteristics associated with old-growth moist forests (i.e., those dominated by Alectoria spp., Picea abies, fallen wood, and Vaccinium myrtillus) were also associated with increased abundance of bank vole and hence the number of PUUV-infected bank voles, whereas there were no correlations with factors associated with dry environments (i.e., Pinus sylvestris and V. vitis-idea). This suggests that circulation and persistence of PUUV within bank vole populations was influenced by habitat factors. Future modeling of risk of exposure to hantavirus and transmission of PUUV within vole populations should include the influence of these factors. Vector-Borne Zoonotic Dis. 5, 315-323.

Emerging infectious diseases in wildlife.

ES Williams — 2007-12-17T21:39:14-00:00

Rev Sci Tech, Vol. 21, No. 1. (April 2002), pp. 139-157.

The processes which give rise to emerging infectious diseases of wildlife can be categorised as follows: ecosystem alterations of anthropogenic or natural origin; movement of pathogens or vectors, via human or natural agency; and changes in microbes or in the recognition of emerging pathogens due to advances in the techniques of epidemiology. These are simplistic divisions because factors influencing the emergence of diseases of wild animals generally fall into more than one category. Mycoplasmosis among passerines is related to habitat changes and artificial feeding resulting in increased bird densities and subsequent disease transmission. The origin of this strain of Mycoplasma gallisepticum is not known. Hantavirus infections in rodents have emerged due to human-induced landscape alterations and/or climatic changes influencing population dynamics of hantavirus reservoir hosts, with disease consequences for humans. Movement of pathogens or vectors is a very important process by which diseases of wildlife expand geographic range. Although the origin of caliciviruses of rabbits and hares is somewhat obscure, their movement by humans, either deliberately or accidentally, has greatly expanded the distribution of these viruses. Rabies is an ancient disease, but geographic expansion has occurred by both natural and anthropogenic movements of wild animals. Human movement of amphibians may explain the distribution of the highly pathogenic chytrid fungus around the world. Newly recognised paramyxoviruses may reflect both changes in these pathogens and the development of techniques of identification and classification. Many more such examples of emerging diseases will arise in the future, given the extensive alterations in landscapes world-wide and movements of animals, vectors and pathogens. Those who study and diagnose diseases of wildlife must be alert for emerging diseases so that the impact of such diseases on wild animals, domestic animals and humans can be minimised.

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.

Human babesiosis in Germany: Just overlooked or truly new

Anke Hildebrandt — 2008-01-11T14:07:52-00:00

International Journal of Medical Microbiology, Vol. In Press, Corrected Proof

Tick-borne infections are among the more important vector-borne infections in the northern hemisphere. However, many facts pertaining to the epidemiology and pathogenesis of such diseases in Europe remain unclear. Human babesiosis in particular may have previously been overlooked in many parts of the world due to a lack of medical awareness and microbiological detection methods. Recently, the first two cases of human babesiosis were reported in Germany, occurring in vicinities where the presence of Babesia spp. in enzootic cycles was obvious for decades but where the risk of acquiring Babesia spp. either from ticks or from human blood products was not known before. It is important to note, though, that as with other tick-borne diseases, Babesia infections may arise in geographic areas where they have not been recorded in the past. Better molecular detection methods and strain typing of parasites are necessary to investigate the epidemiological distribution of zoonotic Babesia spp. in Europe and to clarify whether their virulence or transmissibility is strain-dependent. Therefore, further seroepidemiological and molecular epidemiological studies are urgently needed to learn more about the distribution and medical relevance of these pathogens in various parts of Europe in general and in Germany in particular.

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.

Globalization and infectious diseases: A review of the linkages

Lee Saker — 2008-01-11T13:55:00-00:00

(2004)

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.

A serologic survey for some bacterial and viral zoonoses in game animals in the Czech Republic

Z Hubalek — 2008-01-06T18:26:42-00:00

J Wildl Dis, Vol. 29, No. 4. (1 October 1993), pp. 604-607.

Between 1986 and 1991, sera were collected from 33 roe deer (Capreolus capreolus), 24 red deer (Cervus elaphus), four fallow deer (Dama dama), two mouflon (Ovis musimon), 34 wild boars (Sus scrofa), and 48 hares (Lepus europaeus) shot in two areas of the Czech Republic. Collectively, the sera contained antibodies to Coxiella burnetii (prevalence of 12%), Francisella tularensis (4%), Brucella spp. (2%), Central European tick-borne encephalitis virus (8%), Tahyna (California serogroup) virus (36%), and Calovo (= Batai) virus (23%). We propose that these mammals may play a role in maintaining natural foci of Q-fever, Tahyna fever and Calovo virus infection.

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.

The vector-borne human infections of Europe : their distribution and burden on public health

World Organization — 2008-01-10T14:57:18-00:00

(2004)

While the number of vector-borne diseases and their incidence in Europe is much less than that of the tropical, developing countries, there are, nevertheless, a substantial number of such infections in Europe. Furthermore, the incidence of many of these diseases has been on the rise, and their distribution is spreading. This publication reviews the distribution of all of the vector-borne diseases of public health importance in Europe, their principal vectors, and the extent of their public health burden. Such an overall review is necessary to understand the importance of this group of infections and the resources that must be allocated to their control by public health authorities. Medical personnel must be aware of these infections and their distribution to ensure their timely diagnosis and treatment. New combinations of diseases have also been noted, such as the appearance and spread of co-infections of HIV virus and leishmaniasis. The effect of global warming may lead to the resurgence of some diseases or the establishment of others never before transmitted on the continent. Tropical infections are constantly being introduced into Europe by returning tourists and immigrants and local transmission of some of these, such as malaria, has already taken place as a result.

Geographical incidence of infection with Borrelia burgdorferi in Europe.

I Santino — 2008-01-10T13:41:03-00:00

Panminerva Medica, Vol. 39, No. 3. (September 1997), pp. 208-214.

During recent years many seroepidemiological studies have been published about Lyme borreliosis in various European countries. This paper presents a review of these studies to clarify the geographical incidence of the infection by B. burgdorferi in Europe and particularly in Italy. Data of Lyme disease seroprevalence has been established in European patients or at-risk populations and in blood donors or control subjects. In Northern Europe the sero-prevalence of antibodies to B. burgdorferi in patients or in at-risk subjects is higher in Sweden, 19% and lower in Estonia, 2.7%. In Central Europe the incidence of antibodies to B. burgdorferi in patients or in at-risk subjects is higher in The Netherlands, 28% and Switzerland, about 26%, and lower in Poland, 15%. The range of antibodies to B. burgdorferi in blood donors or control subjects shows the highest spikes in Ireland 15% and the lowest in Austria 7.7% and in Germany 5.5%. In Southern Europe we have the highest incidence in Croatia, 43%, while we have the lowest incidence in Greece, 1.1%. In Italy the seroprevalence of antibodies to B. burgdorferi in patients or in at-risk subjects seems to vary, in Northern Italy, from the lowest incidence in Lombardia 3.2% to the highest in Friuli 22.3%; in Central Italy, from the lowest incidence in Emilia (Parma) 0.2% to the highest in Toscana 18.3%. The range of antibodies to B. burgdorferi in blood donors or control subjects shows the lowest spikes in Lazio 1.5%, while the highest are in Sicilia 10.9%. Although the amount of works on infection diffusion by B. burgdorferi is increasing, the statistical evaluations, comparisons and the drawing of acceptable conclusions continue to be difficult. In fact data, obtained from various European laboratories, are often not directly comparable, because of different serological tests used to detect antibodies to B. burgdorferi. Consequently it seems very important the work that could be performed by a multicenter study on the standardization of the criteria to be used in WB interpretation, presently in progress among several different European laboratories, and the necessary consequent efforts to elaborate a common panel of criteria about the comparison of the data.

Hantavirus Infections in Europe

Olli Vapalahti — 2008-01-10T07:58:41-00:00

The Lancet Infectious Diseases, Vol. 3, No. 10. (October 2003), pp. 653-661.

Summary Hantaviruses are enveloped RNA viruses each carried by a specific rodent species. Three hantaviruses, Puumala, Dobrava, and Saaremaa viruses, are known to cause haemorrhagic fever with renal syndrome. In Europe, Puumala causes a generally mild disease, nephropathia epidemica, which presents most commonly with fever, headache, gastrointestinal symptoms, impaired renal function, and blurred vision, whereas Dobrava infections often also have haemorrhagic complications. There are few available data about the clinical picture of confirmed Saaremaa infections, but epidemiological evidence suggests that it is less pathogenic than Dobrava, and that Saaremaa infections are more similar to nephropathia epidemica caused by Puumala. Along with its rodent host, the bank vole (Clethrionomys glareolus), Puumala is reported throughout most of Europe (excluding the Mediterranean region), whereas Dobrava, carried by the yellow-necked mouse (Apodemus flavicollis), and Saaremaa, carried by the striped field mouse (Apodemus agrarius), are reported mainly in eastern and central Europe. The diagnosis of acute hantavirus infection is based on the detection of virusspecific IgM. Whereas Puumala is distinct, Dobrava and Saaremaa are genetically and antigenically very closely related and were previously thought to be variants of the same virus. Typing of a specific hantavirus infection requires neutralisation antibody assays or reverse transcriptase PCR and sequencing.

Climate variability and change in the United States: potential impacts on vector- and rodent-borne diseases.

DJ Gubler — 2008-01-09T16:34:53-00:00

Environ Health Perspect, Vol. 109 Suppl 2 (May 2001), pp. 223-233.

Diseases such as plague, typhus, malaria, yellow fever, and dengue fever, transmitted between humans by blood-feeding arthropods, were once common in the United States. Many of these diseases are no longer present, mainly because of changes in land use, agricultural methods, residential patterns, human behavior, and vector control. However, diseases that may be transmitted to humans from wild birds or mammals (zoonoses) continue to circulate in nature in many parts of the country. Most vector-borne diseases exhibit a distinct seasonal pattern, which clearly suggests that they are weather sensitive. Rainfall, temperature, and other weather variables affect in many ways both the vectors and the pathogens they transmit. For example, high temperatures can increase or reduce survival rate, depending on the vector, its behavior, ecology, and many other factors. Thus, the probability of transmission may or may not be increased by higher temperatures. The tremendous growth in international travel increases the risk of importation of vector-borne diseases, some of which can be transmitted locally under suitable circumstances at the right time of the year. But demographic and sociologic factors also play a critical role in determining disease incidence, and it is unlikely that these diseases will cause major epidemics in the United States if the public health infrastructure is maintained and improved.

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.

Surveillance and monitoring of wildlife diseases.

T Mörner — 2008-01-04T12:31:30-00:00

Rev Sci Tech, Vol. 21, No. 1. (April 2002), pp. 67-76.

It is now recognised that those countries which conduct disease surveillance of their wild animal populations are more likely to detect the presence of infectious and zoonotic diseases and to swiftly adopt counter measures. The surveillance and monitoring of disease outbreaks in wildlife populations are particularly relevant in these days of rapid human and animal translocation, when the contact between wild and domestic animals is close and the threat of a bioterrorist attack is very real. The authors describe the problems inherent in wildlife disease surveillance and stress the importance of the establishment of national strategies for disease detection. The various sampling methods employed for monitoring outbreaks of disease and mortality in wildlife populations are discussed and their strengths and weaknesses described. A major advantage of an efficient disease monitoring programme for wildlife is the early detection of new and 'emerging' diseases, some of which may have serious zoonotic and economic implications. The authors conclude that wildlife disease monitoring programmes that are integrated within national animal health surveillance infrastructures should have the capacity to respond promptly to the detection of unusual wildlife mortality and to institute epizootiological research into new and emerging wildlife diseases.

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.

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.

Lyme borreliosis in Europe. Influences of climate and climate change, epidemiology, ecology and adaptation measures

Elisabet Lindgren — 2008-01-02T11:20:08-00:00

(2006)

Stockholm University and WHO, within a project funded by the European Commission (EVK2-2000-00070), reviewed the impacts of climate change and adaptation on Lyme borreliosis (LB) in Europe. LB is the most common vector-borne disease in Europe. The highest incidence is reported from Austria, the Czech Republic, Germany, and Slovenia, as well as from the northern countries bordering the Baltic Sea. LB is a multi-system disorder that is treatable with antibiotics, but may lead to severe complications of the neurological system, the heart, and the joints. LB is caused by a spirochete (Borrelia burgdorferi s.l.), which is transmitted to humans by ticks, in Europe mainly the species Ixodes ricinus. Reservoir animals are small rodents, insectivores, hares and birds. Ticks may live for more than three years and are highly sensitive to changes in seasonal climate. Daily seasonal climatic conditions directly impact tick survival and activity. Indirectly, climate affects both tick and pathogen occurrence through effects on habitat conditions and reservoir animal density. In addition, climate-induced changes in land use and in recreational behaviour influence human exposure to infected ticks and thus disease prevalence. Since the 1980s, tick vectors have increased in density and spread into higher latitudes and altitudes in Europe. It can be concluded that future climate change in Europe will facilitate a spread of LB into higher latitudes and altitudes, and contribute to increased disease occurrence in endemic areas. In some locations, where climate conditions will become too hot and dry for tick survival, LB will disappear. There is a need to strengthen preventive measures such as information to the general public, surveillance activities within a pan-European network and to use standardized methods to provide data for future research activities.

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.

Emerging infectious diseases in wildlife

ES Williams — 2007-12-17T21:25:08-00:00

Revue Scientifique et Technique de l'Office International des Epizooties, Vol. 21, No. 1. (April 2002), pp. 139-157.

The processes which give rise to emerging infectious diseases of wildlife can be categorised as follows: ecosystem alterations of anthropogenic or natural origin; movement of pathogens or vectors, via human or natural agency; and changes in microbes or in the recognition of emerging pathogens due to advances in the techniques of epidemiology. These are simplistic divisions because factors influencing the emergence of diseases of wild animals generally fall into more than one category. Mycoplasmosis among passerines is related to habitat changes and artificial feeding resulting in increased bird densities and subsequent disease transmission. The origin of this strain of Mycoplasma gallisepticum is not known. Hantavirus infections in rodents have emerged due to human-induced landscape alterations and/or climatic changes influencing population dynamics of hantavirus reservoir hosts, with disease consequences for humans. Movement of pathogens or vectors is a very important process by which diseases of wildlife expand geographic range. Although the origin of caliciviruses of rabbits and hares is somewhat obscure, their movement by humans, either deliberately or accidentally, has greatly expanded the distribution of these viruses. Rabies is an ancient disease, but geographic expansion has occurred by both natural and anthropogenic movements of wild animals. Human movement of amphibians may explain the distribution of the highly pathogenic chytrid fungus around the world. Newly recognised paramyxoviruses may reflect both changes in these pathogens and the development of techniques of identification and classification. Many more such examples of emerging diseases will arise in the future, given the extensive alterations in landscapes world-wide and movements of animals, vectors and pathogens. Those who study and diagnose diseases of wildlife must be alert for emerging diseases so that the impact of such diseases on wild animals, domestic animals and humans can be minimised.

Tick-borne diseases in Switzerland and climate change

A Huss — 2007-11-25T20:37:05-00:00

(April 2007), pp. 1-18.

Tick-borne diseases are the most common vector-borne diseases in Europe. In Central Europe, the tick Ixodes ricinus is responsible for most tick bites. Next to tick borne encephalitis (TBE or in German "FSME" Frühsommer-Meningoenzephalitis), ticks transmit a range of other diseases, such as Lyme Borreliosis. In the last decades, Switzerland has witnessed a marked increase of cases of TBE. Climate directly and indirectly influences ticks, ticks' habitat, hosts and reservoir animals. Our climate is changing and it seems plausible that this change might be related to the changes in tick-borne disease observed in humans. Climate change, in particular a decrease in minimum temperatures, has been linked to an expansion of the vector's distribution to higher latitudes and altitudes in European regions. Longitudinal data on spatial distribution of ticks in high altitudes, however, are missing in Switzerland. The exact influences that account for the observed increase and the spatial differences in TBE occurrence, however, remain unclear. Overall, there seem to be factors that have enhanced the frequency of contact between humans and infected ticks, which is expressed in the observed higher infection rate in humans. To help forecast risk more precisely and, if possible, to initiate first steps in pest control, more data on a sufficiently detailed spatio-temporal resolution are necessary. From a public health perspective, the adapted Swiss vaccination plan is a first step to reduce numbers of patients with TBE.

Climate change and vector-borne diseases: a regional analysis.

AK Githeko — 2007-10-02T13:57:48-00:00

Bull World Health Organ, Vol. 78, No. 9. (2000), pp. 1136-1147.

Current evidence suggests that inter-annual and inter-decadal climate variability have a direct influence on the epidemiology of vector-borne diseases. This evidence has been assessed at the continental level in order to determine the possible consequences of the expected future climate change. By 2100 it is estimated that average global temperatures will have risen by 1.0-3.5 degrees C, increasing the likelihood of many vector-borne diseases in new areas. The greatest effect of climate change on transmission is likely to be observed at the extremes of the range of temperatures at which transmission occurs. For many diseases these lie in the range 14-18 degrees C at the lower end and about 35-40 degrees C at the upper end. Malaria and dengue fever are among the most important vector-borne diseases in the tropics and subtropics; Lyme disease is the most common vector-borne disease in the USA and Europe. Encephalitis is also becoming a public health concern. Health risks due to climatic changes will differ between countries that have developed health infrastructures and those that do not. Human settlement patterns in the different regions will influence disease trends. While 70% of the population in South America is urbanized, the proportion in sub-Saharan Africa is less than 45%. Climatic anomalies associated with the El Niño-Southern Oscillation phenomenon and resulting in drought and floods are expected to increase in frequency and intensity. They have been linked to outbreaks of malaria in Africa, Asia and South America. Climate change has far-reaching consequences and touches on all life-support systems. It is therefore a factor that should be placed high among those that affect human health and survival.

Seasonality and the dynamics of infectious diseases

Sonia Altizer — 2006-03-30T14:33:32-00:00

Ecology Letters, Vol. 9, No. 4. (April 2006), pp. 467-484.

West Nile Virus Circulation Detected in Northern Italy in Sentinel Chickens.

Annapaola Rizzoli — 2007-09-13T14:31:42-00:00

Vector Borne Zoonotic Dis (3 September 2007)

Ninety percent (56/62) of sentinel chickens introduced to two regions within the Italian Alps seroconverted to West Nile virus (WNV) during the summer of 2005, showing a range of antibody titres from 1/20 to 1/320 in a virus neutralization test. Neutralization specificity for WNV antibodies was confirmed on an additional 34 sera that were tested in parallel against WNV (16/34 seropositivity), Usutu virus (3/34 seropositivity) and Koutango virus. The geometric mean neutralizing titre (GMT) calculated for WN-specific antibodies was 33.68 and did not differ significantly amongst sample sites, although the overall results indicate more active circulation of WNV at the higher elevations. Such high levels of seroconversion raise the possibility that many chickens may have been exposed to virus via routes other than mosquito transmission. No chickens or any other local animals were associated with illness due to WNV implying that WNV, and to a much lower extent Usutu virus, circulate harmlessly amongst wildlife species in northern Italy from late May onwards until early autumn.

Climate and Tickborne Encephalitis

E Lindgren — 2007-07-18T12:46:17-00:00

Conservation Ecology [online], Vol. 2, No. 1. (1998)

Climatic changes are projected to alter the abundance, dynamics, and geographical distribution of many vector-borne diseases in human populations. Tick-borne diseases such as Lyme disease and tick-borne encephalitis (TBE) are a growing concern in northern Europe and the United States. The impact of a future climate change on the transmission of tick-borne diseases is not known. To make such assumptions, more empirical data are needed on the relations between short-term fluctuations in contemporary weather and disease incidence. This paper analyzes relations between daily minimum and maximum temperatures, monthly precipitation, and TBE incidence during a 36-yr period in Stockholm County, a high-endemic region for TBE in Sweden. Multiple regression analyses were performed, with temperature variables expressed as number of days per winter or spring - summer - fall season with temperatures above, below, or in the interval between different temperature limits. The limits used for daily minimum temperatures represent bioclimatic thresholds of importance for pathogen transmission. To adjust for the length of the tick's life cycle, each TBE incidence rate was related to meteorological data over two consecutive years. Results reveal that increased incidence of tick-borne encephalitis is related to a combination of two successive years of more days with temperatures permitting prolonged seasonal tick activity and, hence, pathogen transmission (i.e., daily minimum temperatures above 5°-10°C), and a mild winter preceding the year before the incidence year (i.e., fewer winter days with minimum temperatures below -7°C). Alternative explanations of the results are discussed. Findings of this study suggest that a climate change may extend the seasonal range and intensify the endemicity of tick-borne diseases, in particular, at northern latitudes.

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.

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.

Early detection of TBEv spatial distribution and activity in the Province of Trento assessed using serological and remotely-sensed climatic data

A Rizzoli — 2007-05-05T20:13:14-00:00

Geospatial Health, Vol. 1, No. 2. (May 2007), pp. 169-176.

New human cases of tick borne encephalitis (TBE) have recently been recorded outside the recognized foci of this disease, i.e. in the province of Trento in northern Italy. In order to predict the highest risk areas for increased tick-borne encephalitis virus activity, we have combined cross-sectional serological data, obtained from 459 domestic goats, with analysis of the autumnal cooling rate based on Moderate Resolution Imaging Spectroradiometer (MODIS) Land Surface Temperature (LST) data. A significant relationship between finding antibodies against the virus in serum (seroprevalence) in goats and the autumnal cooling rate was detected, indicating that the transmission intensity of the virus does not only vary spatially, but also in relation to climatic factors. Virus seroprevalence in goats was correlated with the occurrence of tick-borne encephalitis in humans and also with the average number of forestry workers' tick bites, demonstrating that serological screening of domestic animals, combined with an analysis of the autumnal cooling rate, can be used as early-warning predictors of tick-borne encephalitis risk in humans.

Determinants of the geographic distribution of Puumala virus and Lyme borreliosis infections in Belgium

Catherine Linard — 2007-05-02T13:31:23-00:00

International Journal of Health Geographics, Vol. 6 (02 May 2007), 15.

Background Vector-borne and zoonotic diseases generally display clear spatial patterns due to different space-dependent factors. Land cover and land use influence disease transmission by controlling both the spatial distribution of vectors or hosts, and the probability of contact with susceptible human populations. The objective of this study was to combine environmental and socio-economic factors to explain the spatial distribution of two emerging human diseases in Belgium, Puumala virus (PUUV) and Lyme borreliosis. Municipalities were taken as units of analysis. Results Negative binomial regressions including a correction for spatial endogeneity show that the spatial distribution of PUUV and Lyme borreliosis infections are associated with a combination of factors linked to the vector and host populations, to human behaviours, and to landscape attributes. Both diseases are associated with the presence of forests, which are the preferred habitat for vector or host populations. The PUUV infection risk is higher in remote forest areas, where the level of urbanisation is low, and among low-income populations. The Lyme borreliosis transmission risk is higher in mixed landscapes with forests and spatially dispersed houses, mostly in wealthy peri-urban areas. The spatial dependence resulting from a combination of endogenous and exogenous processes could be accounted for in the model on PUUV but not for Lyme borreliosis. Conclusions A large part of the spatial variation in disease risk can be explained by environmental and socio-economic factors. The two diseases not only are most prevalent in different regions but also affect different groups of people. Combining these two criteria may increase the efficiency of information campaigns through appropriate targeting.

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.

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.

Spatial aspects of disease dynamics

G Hess — 2007-01-24T17:34:47-00:00

(2002), pp. 102-118.

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.