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Tularemia in northern Sweden - sero-prevalence and a case-control study of risk factors
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Infectious Diseases.
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(English)Article in journal (Refereed) Submitted
National Category
Infectious Medicine Public Health, Global Health, Social Medicine and Epidemiology
Identifiers
URN: urn:nbn:se:umu:diva-126960OAI: oai:DiVA.org:umu-126960DiVA: diva2:1039526
Available from: 2016-10-24 Created: 2016-10-24 Last updated: 2016-10-24
In thesis
1. Towards the Limits – Climate Change Aspects of Life and Health in Northern Sweden: studies of tularemia and regional experiences of changes in the environment
Open this publication in new window or tab >>Towards the Limits – Climate Change Aspects of Life and Health in Northern Sweden: studies of tularemia and regional experiences of changes in the environment
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background

Indigenous peoples with traditional lifestyles worldwide are considered particularly vulnerable to climate change effects. Large climate change impacts on the spread of infectious vector-borne diseases are expected as a health outcome. The most rapid climate changes are occurring in the Arctic regions, and as a part of this region northernmost Sweden might experience early effects. In this thesis, climate change effects on the lives of Sami reindeer herders are described and 30 years of weather changes are quantified. Epidemiology of the climate sensitive human infection tularemia is assessed, baseline serologic prevalence of tularemia is investigated and the disease burden is quantified across inhabitants in the region.

Methods

Perceptions and experiences of climate change effects among the indigenous Sami reindeer herders of northern Sweden were investigated through qualitative analyses of fourteen interviews. The results were then combined with instrumental weather data from ten meteorological stations in a mixed-methods design to further illustrate climate change effects in this region. In two following studies, tularemia ecology and epidemiology were investigated. A total of 4,792 reported cases of tularemia between 1984 and 2012 were analysed and correlated to ecological regions and presence of inland water using geographical mapping. The status of tularemia in the Swedish Arctic region was further investigated through risk factor analyses of a 2012 regional outbreak and a cross-sectional serological survey to estimate the burden of disease including unreported cases.

Results

The reindeer herders described how the winters of northern Sweden have changed since the 1970s – warmer winters with shorter snow season and cold periods, and earlier spring. The adverse effects on the reindeer herders through the obstruction of their work, the stress induced and the threat to their lifestyle was demonstrated, forcing the reindeer herders towards the limit of resilience. Weather data supported the observations of winter changes; some stations displayed a more than two full months shorter snow cover season and winter temperatures increased significantly, most pronounced in the lowest temperatures. During the same time period a near tenfold increase in national incidence of tularemia was observed in Sweden (from 0.26 to 2.47/100,000 p<0.001) with a clear overrepresentation of cases in the north versus the south (4.52 vs. 0.56/100,000 p<0.001). The incidence was positively correlated with the presence of inland water (p<0.001) and higher than expected in the alpine and boreal ecologic regions (p<0.001). In the outbreak investigation a dose-response relationship to water was identified; distance from residence to water – less than 100 m, mOR 2.86 (95% CI 1.79–4.57) and 100 to 500 m, mOR 1.63 (95% CI 1.08–2.46). The prevalence of tularemia antibodies in the two northernmost counties was 2.9% corresponding to a 16 times higher number of cases than reported indicating that the reported numbers represent only a minute fraction of the true tularemia.

Conclusions

The extensive winter changes pose a threat to reindeer herding in this region. Tularemia is increasing in Sweden, it has a strong correlation to water and northern ecoregions, and unreported tularemia cases are quite common.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2016. 50 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1840
Keyword
Climate change, public health, Indigenous peoples, Sami, reindeer herding, resilience, tularemia, mixed-methods, infectious disease, seroprevalence, ELISA, outbreak investigation, risk factor, ecology, Francisella tularensis
National Category
Medical and Health Sciences
Research subject
Epidemiology; Public health
Identifiers
urn:nbn:se:umu:diva-126949 (URN)978-91-7601-552-0 (ISBN)
Public defence
2016-11-18, Sal A, 9tr, by 1D,, Norrlands universitetssjukhus, Umeå, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2016-10-26 Created: 2016-10-24 Last updated: 2016-11-10Bibliographically approved

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