The importance of wildlife in the ecology and epidemiology of the TBE virus in Sweden: incidence of human TBE correlates with abundance of deer and hares
Abstract Background Tick-borne encephalitis (TBE) is one tick-transmitted disease where the human incidence has increased in some European regions during the last two decades. We aim to find the most important factors causing the increasing incidence of human TBE in Sweden. Based on a review of publ...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
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BMC
2018-08-01
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| Series: | Parasites & Vectors |
| Subjects: | |
| Online Access: | http://link.springer.com/article/10.1186/s13071-018-3057-4 |
| _version_ | 1818609605502042112 |
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| author | Thomas G. T. Jaenson Erik H. Petersson David G. E. Jaenson Jonas Kindberg John H.-O. Pettersson Marika Hjertqvist Jolyon M. Medlock Hans Bengtsson |
| author_facet | Thomas G. T. Jaenson Erik H. Petersson David G. E. Jaenson Jonas Kindberg John H.-O. Pettersson Marika Hjertqvist Jolyon M. Medlock Hans Bengtsson |
| author_sort | Thomas G. T. Jaenson |
| collection | DOAJ |
| description | Abstract Background Tick-borne encephalitis (TBE) is one tick-transmitted disease where the human incidence has increased in some European regions during the last two decades. We aim to find the most important factors causing the increasing incidence of human TBE in Sweden. Based on a review of published data we presume that certain temperature-related variables and the population densities of transmission hosts, i.e. small mammals, and of primary tick maintenance hosts, i.e. cervids and lagomorphs, of the TBE virus vector Ixodes ricinus, are among the potentially most important factors affecting the TBE incidence. Therefore, we compare hunting data of the major tick maintenance hosts and two of their important predators, and four climatic variables with the annual numbers of human cases of neuroinvasive TBE. Data for six Swedish regions where human TBE incidence is high or has recently increased are examined by a time-series analysis. Results from the six regions are combined using a meta-analytical method. Results With a one-year time lag, the roe deer (Capreolus capreolus), red deer (Cervus elaphus), mountain hare (Lepus timidus) and European hare (Lepus europaeus) showed positive covariance; the Eurasian elk (moose, Alces alces) and fallow deer (Dama dama) negative covariance; whereas the wild boar (Sus scrofa), lynx (Lynx lynx), red fox (Vulpes vulpes) and the four climate parameters showed no significant covariance with TBE incidence. All game species combined showed positive covariance. Conclusions The epidemiology of TBE varies with time and geography and depends on numerous factors, i.a. climate, virus genotypes, and densities of vectors, tick maintenance hosts and transmission hosts. This study suggests that the increased availability of deer to I. ricinus over large areas of potential tick habitats in southern Sweden increased the density and range of I. ricinus and created new TBEV foci, which resulted in increased incidence of human TBE. New foci may be established by TBE virus-infected birds, or by birds or migrating mammals infested with TBEV-infected ticks. Generally, persistence of TBE virus foci appears to require presence of transmission-competent small mammals, especially mice (Apodemus spp.) or bank voles (Myodes glareolus). |
| first_indexed | 2024-12-16T15:01:12Z |
| format | Article |
| id | doaj.art-88644c4c270f4c5b966ec542f3161909 |
| institution | Directory Open Access Journal |
| issn | 1756-3305 |
| language | English |
| last_indexed | 2024-12-16T15:01:12Z |
| publishDate | 2018-08-01 |
| publisher | BMC |
| record_format | Article |
| series | Parasites & Vectors |
| spelling | doaj.art-88644c4c270f4c5b966ec542f31619092022-12-21T22:27:17ZengBMCParasites & Vectors1756-33052018-08-0111111810.1186/s13071-018-3057-4The importance of wildlife in the ecology and epidemiology of the TBE virus in Sweden: incidence of human TBE correlates with abundance of deer and haresThomas G. T. Jaenson0Erik H. Petersson1David G. E. Jaenson2Jonas Kindberg3John H.-O. Pettersson4Marika Hjertqvist5Jolyon M. Medlock6Hans Bengtsson7Department of Organismal Biology, Uppsala UniversityDepartment of Aquatic Resources, Division of Freshwater Research, Swedish University of Agricultural SciencesDepartment of Automatic Control, Lund UniversityDepartment of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural SciencesDepartment of Infectious Disease Epidemiology and Modelling, Norwegian Institute of Public HealthPublic Health Agency of SwedenMedical Entomology Group, Emergency Response Department, Public Health EnglandSwedish Meteorological and Hydrological Institute (SMHI)Abstract Background Tick-borne encephalitis (TBE) is one tick-transmitted disease where the human incidence has increased in some European regions during the last two decades. We aim to find the most important factors causing the increasing incidence of human TBE in Sweden. Based on a review of published data we presume that certain temperature-related variables and the population densities of transmission hosts, i.e. small mammals, and of primary tick maintenance hosts, i.e. cervids and lagomorphs, of the TBE virus vector Ixodes ricinus, are among the potentially most important factors affecting the TBE incidence. Therefore, we compare hunting data of the major tick maintenance hosts and two of their important predators, and four climatic variables with the annual numbers of human cases of neuroinvasive TBE. Data for six Swedish regions where human TBE incidence is high or has recently increased are examined by a time-series analysis. Results from the six regions are combined using a meta-analytical method. Results With a one-year time lag, the roe deer (Capreolus capreolus), red deer (Cervus elaphus), mountain hare (Lepus timidus) and European hare (Lepus europaeus) showed positive covariance; the Eurasian elk (moose, Alces alces) and fallow deer (Dama dama) negative covariance; whereas the wild boar (Sus scrofa), lynx (Lynx lynx), red fox (Vulpes vulpes) and the four climate parameters showed no significant covariance with TBE incidence. All game species combined showed positive covariance. Conclusions The epidemiology of TBE varies with time and geography and depends on numerous factors, i.a. climate, virus genotypes, and densities of vectors, tick maintenance hosts and transmission hosts. This study suggests that the increased availability of deer to I. ricinus over large areas of potential tick habitats in southern Sweden increased the density and range of I. ricinus and created new TBEV foci, which resulted in increased incidence of human TBE. New foci may be established by TBE virus-infected birds, or by birds or migrating mammals infested with TBEV-infected ticks. Generally, persistence of TBE virus foci appears to require presence of transmission-competent small mammals, especially mice (Apodemus spp.) or bank voles (Myodes glareolus).http://link.springer.com/article/10.1186/s13071-018-3057-4Ixodes ricinusCapreolus capreolusCervus elaphusLepusHareRed deer |
| spellingShingle | Thomas G. T. Jaenson Erik H. Petersson David G. E. Jaenson Jonas Kindberg John H.-O. Pettersson Marika Hjertqvist Jolyon M. Medlock Hans Bengtsson The importance of wildlife in the ecology and epidemiology of the TBE virus in Sweden: incidence of human TBE correlates with abundance of deer and hares Parasites & Vectors Ixodes ricinus Capreolus capreolus Cervus elaphus Lepus Hare Red deer |
| title | The importance of wildlife in the ecology and epidemiology of the TBE virus in Sweden: incidence of human TBE correlates with abundance of deer and hares |
| title_full | The importance of wildlife in the ecology and epidemiology of the TBE virus in Sweden: incidence of human TBE correlates with abundance of deer and hares |
| title_fullStr | The importance of wildlife in the ecology and epidemiology of the TBE virus in Sweden: incidence of human TBE correlates with abundance of deer and hares |
| title_full_unstemmed | The importance of wildlife in the ecology and epidemiology of the TBE virus in Sweden: incidence of human TBE correlates with abundance of deer and hares |
| title_short | The importance of wildlife in the ecology and epidemiology of the TBE virus in Sweden: incidence of human TBE correlates with abundance of deer and hares |
| title_sort | importance of wildlife in the ecology and epidemiology of the tbe virus in sweden incidence of human tbe correlates with abundance of deer and hares |
| topic | Ixodes ricinus Capreolus capreolus Cervus elaphus Lepus Hare Red deer |
| url | http://link.springer.com/article/10.1186/s13071-018-3057-4 |
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