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Investigating the spatial patterns and climate dependency of Tick-Borne Encephalitis in Sweden

Farrington, Elisabeth LU (2017) In Student thesis series INES NGEM01 20171
Dept of Physical Geography and Ecosystem Science
Abstract
The increasing prevalence of Tick-Borne Encephalitis (TBE) in Sweden is a cause of concern to both individuals and the public health service. The disease is spread via bites from the vector Ixodes ricinus and causes long-term neurological damage in 46% of cases. To date, research in this field has focussed on the relationship between climate and TBE incidence and there is little to no available research regarding the spatial distribution of TBE in Sweden. The aim of this study was to determine whether the relationship between TBE and climate factors is statistically significant and to detect spatial patterns of TBE both nationally and in the endemic Stockholm-Mälaren region in eastern Sweden. The data includes annual TBE incidence from... (More)
The increasing prevalence of Tick-Borne Encephalitis (TBE) in Sweden is a cause of concern to both individuals and the public health service. The disease is spread via bites from the vector Ixodes ricinus and causes long-term neurological damage in 46% of cases. To date, research in this field has focussed on the relationship between climate and TBE incidence and there is little to no available research regarding the spatial distribution of TBE in Sweden. The aim of this study was to determine whether the relationship between TBE and climate factors is statistically significant and to detect spatial patterns of TBE both nationally and in the endemic Stockholm-Mälaren region in eastern Sweden. The data includes annual TBE incidence from 1986 to 2016. Monthly data was not available.

Multiple linear regressions were used to determine the dependency of TBE on climate variables (temperature and precipitation). Many of the explored years show a statistically significant relationship between TBE and at least one climate variable, though using data at a finer temporal scale would produce results with more years showing statistical significance. Getis-Ord Gi* and Local Moran’s I were used in order to detect spatial autocorrelation between TBE incidence points in the Stockholm-Mälaren region. Significant clustering (p < 0.1) was detected in the majority of years in the temporal dataset, with high levels of clustering occurring in southern Stockholm County and along the shores of Lake Mälaren.

Climate change increases the risk of ticks and, as a result, TBE spreading further north in Sweden. This study recommends further spatial analysis and modelling of the spread of TBE in relation to climate factors. This will in turn allow policy makers within the public health sector to make informed decisions regarding preventative schemes and rehabilitation programmes. However, it requires that the reporting of TBE incidents takes place on a monthly basis. (Less)
Popular Abstract (Swedish)
Fästingburen hjärnhinneinflammation (TBE) är en allvarlig virussjukdom som i värsta fall kan leda till långvarig neurologiska skador (46% av fallen), och i enstaka fall, döden. Mer rumslig analys av TBE förekomst och modellering av baserat på infektioner och faktorer som temperatur och nederbörd kan bidra till att identifiera nya riskområden så att beslutsfattare inom folkhälsovården kan implementera förebyggande eller mer målinriktade insatser, som t.ex. vaccinering. Denna forskning fordrar dock att rapportering av TBE incidenter från hälsocentraler sker på månatlig basis och inte som nu årsvis.

TBE som sprids genom fästingbett har ökad kraftigt i Sverige under de senaste 30 åren, med 268 fall rapporterade under 2016. En av 600... (More)
Fästingburen hjärnhinneinflammation (TBE) är en allvarlig virussjukdom som i värsta fall kan leda till långvarig neurologiska skador (46% av fallen), och i enstaka fall, döden. Mer rumslig analys av TBE förekomst och modellering av baserat på infektioner och faktorer som temperatur och nederbörd kan bidra till att identifiera nya riskområden så att beslutsfattare inom folkhälsovården kan implementera förebyggande eller mer målinriktade insatser, som t.ex. vaccinering. Denna forskning fordrar dock att rapportering av TBE incidenter från hälsocentraler sker på månatlig basis och inte som nu årsvis.

TBE som sprids genom fästingbett har ökad kraftigt i Sverige under de senaste 30 åren, med 268 fall rapporterade under 2016. En av 600 fästingbett orsakar TBE smittan. Smittrisken är för närvarande störst i södra Stockholms län, nära Nynäshamn, och runt Mälaren, men infektionsfall har rapporterats ända från Löderup i södra Skåne till Örnsköldsvik i Västernorrlands län. Detta kan bero på optimala klimatförhållanden, habitat och tillgång till mat.

Tidigare forskning har påvisat ett samband mellan fästingförekomst och temperatur. Min studie visar korrelation mellan TBE och åtminstone en av klimatvariablerna temperatur och nederbörd under perioden 1986 till 2016. Klimatförändringar medför därför risk att fästingar och därmed risken för TBE kan sprida sig till nya delar av Sverige i framtiden.

TBE incidenter rapporterade idag bara årsvis från svenska folkhälsomyndigheten. Det gör det idag svårt att exakt analysera förhållandet mellan TBE och klimat och dra några säkra slutsatser om spridningsrisk, trender och potentiella framtida högriskområden. Eftersom TBE är en sådan allvarlig sjukdom, och förebyggande vaccineringsprogram dyra och inte alltid effektiva behöver vi mer forskning inom rumslig analys och modellering av TBE och dess påverkande faktorer för att stärka hälsomyndighetens underlag för beslutsfattning vad gäller preventiva åtgärder. Det fordrar dock att rapportering av TBE incidenter från hälsomyndigheten presenteras på månatlig basis och inte som nu årsvis. (Less)
Please use this url to cite or link to this publication:
author
Farrington, Elisabeth LU
supervisor
organization
alternative title
En undersökning av rumsliga mönster och klimatberoende av fästingburen encefalit (TBE) i Sverige
course
NGEM01 20171
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Physical Geography and Ecosystem Science, Tick-Borne Encephalitis, TBE, Sweden, Climate Change, Spatial Patterns
publication/series
Student thesis series INES
report number
429
language
English
id
8915624
date added to LUP
2017-06-15 15:20:28
date last changed
2017-06-15 15:20:28
@misc{8915624,
  abstract     = {The increasing prevalence of Tick-Borne Encephalitis (TBE) in Sweden is a cause of concern to both individuals and the public health service. The disease is spread via bites from the vector Ixodes ricinus and causes long-term neurological damage in 46% of cases. To date, research in this field has focussed on the relationship between climate and TBE incidence and there is little to no available research regarding the spatial distribution of TBE in Sweden. The aim of this study was to determine whether the relationship between TBE and climate factors is statistically significant and to detect spatial patterns of TBE both nationally and in the endemic Stockholm-Mälaren region in eastern Sweden. The data includes annual TBE incidence from 1986 to 2016. Monthly data was not available.

Multiple linear regressions were used to determine the dependency of TBE on climate variables (temperature and precipitation). Many of the explored years show a statistically significant relationship between TBE and at least one climate variable, though using data at a finer temporal scale would produce results with more years showing statistical significance. Getis-Ord Gi* and Local Moran’s I were used in order to detect spatial autocorrelation between TBE incidence points in the Stockholm-Mälaren region. Significant clustering (p < 0.1) was detected in the majority of years in the temporal dataset, with high levels of clustering occurring in southern Stockholm County and along the shores of Lake Mälaren. 

Climate change increases the risk of ticks and, as a result, TBE spreading further north in Sweden. This study recommends further spatial analysis and modelling of the spread of TBE in relation to climate factors. This will in turn allow policy makers within the public health sector to make informed decisions regarding preventative schemes and rehabilitation programmes. However, it requires that the reporting of TBE incidents takes place on a monthly basis.},
  author       = {Farrington, Elisabeth},
  keyword      = {Physical Geography and Ecosystem Science,Tick-Borne Encephalitis,TBE,Sweden,Climate Change,Spatial Patterns},
  language     = {eng},
  note         = {Student Paper},
  series       = {Student thesis series INES},
  title        = {Investigating the spatial patterns and climate dependency of Tick-Borne Encephalitis in Sweden},
  year         = {2017},
}