Outbreaks of Tularemia in a Boreal Forest Region Depends on Mosquito Prevalence

Background. We aimed to evaluate the potential association of mosquito prevalence in a boreal forest area with transmission of the bacterial disease tularemia to humans, and model the annual variation of disease using local weather data. Methods. A prediction model for mosquito abundance was built u...

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Bibliographic Details
Published in:The Journal of infectious diseases 2012-01, Vol.205 (2), p.297-304
Main Authors: Rydén, Patrik, Björk, Rafael, Schäfer, Martina L., Lundström, Jan O., Petersén, Bodil, Lindblom, Anders, Forsman, Mats, Sjöstedt, Anders, Johansson, Anders
Format: Article
Language:English
Subjects:
Adolescent
Adult
Aged
Aged, 80 and over
Animals
BACTERIA
Biological and medical sciences
Boreal forests
Child
Child, Preschool
Culicidae
Disease models
Disease Outbreaks
Disease transmission
Disease Vectors
Epidemiology
Francisella tularensis
Fundamental and applied biological sciences. Psychology
Geography
Humans
Incidence
Infant
Infectious diseases
Major and Brief Reports
Medical sciences
Microbiology
Middle Aged
Modeling
Mosquitos
Older adults
Seasons
Sweden - epidemiology
Trees
Tularemia
Tularemia - epidemiology
Tularemia - transmission
Weather
Young Adult
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Summary:Background. We aimed to evaluate the potential association of mosquito prevalence in a boreal forest area with transmission of the bacterial disease tularemia to humans, and model the annual variation of disease using local weather data. Methods. A prediction model for mosquito abundance was built using weather and mosquito catch data. Then a negative binomial regression model based on the predicted mosquito abundance and local weather data was built to predict annual numbers of humans contracting tularemia in Dalarna County, Sweden. Results. Three hundred seventy humans were diagnosed with tularemia between 1981 and 2007, 94% of them during 7 summer outbreaks. Disease transmission was concentrated along rivers in the area. The predicted mosquito abundance was correlated (0.41, P < .05) with the annual number of human cases. The predicted mosquito peaks consistently preceded the median onset time of human tularemia (temporal correlation, 0.76; P < .05). Our final predictive model included 5 environmental variables and identified 6 of the 7 outbreaks. Conclusions. This work suggests that a high prevalence of mosquitoes in late summer is a prerequisite for outbreaks of tularemia in a tularemia-endemie boreal forest area of Sweden and that environmental variables can be used as risk indicators.
ISSN:0022-1899
1537-6613
1537-6613
DOI:10.1093/infdis/jir732