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Tularemia Outbreaks and Common Vole (Microtus arvalis) Irruptive Population Dynamics in Northwestern Spain, 1997-2014
Juan José Luque-Larena1,2, François Mougeot3, Dolors Vidal Roig4
11 Departamento de Ciencias Agroforestales, Escuela Técnica Superior de Ingenierías Agrarias, Universidad de Valladolid , Palencia, Spain .
Abstract:
During the last decades, large tularemia outbreaks in humans have coincided in time and space with population outbreaks of common voles in northwestern Spain, leading us to hypothesize that this rodent species acts as a key spillover agent of Francisella tularensis in the region. Here, we evaluate for the first time a potential link between irruptive vole numbers and human tularemia outbreaks in Spain. We compiled vole abundance estimates obtained through live-trapping monitoring studies and official reports of human tularemia cases during the period 1997-2014. We confirm a significant positive association between yearly cases of tularemia infection in humans and vole abundance. High vole densities during outbreaks (up to 1000 voles/hectare) may therefore enhance disease transmission and spillover contamination in the environment. If this ecological link is further confirmed, the apparent multiannual cyclicity of common vole outbreaks might provide a basis for forecasting the risk of tularemia outbreaks in northwestern Spain.
Insights
Large outbreaks of tularemia in humans in Spain are linked to population booms in common voles. This suggests voles may be a key factor in disease transmission and could help predict future tularemia risks.
Area of Science:
- Zoonotic disease ecology
- Epidemiology
- Mammalian population dynamics
Background:
- Tularemia outbreaks in humans in northwestern Spain have historically coincided with common vole population surges.
- The common vole (Microtus arvalis) is suspected as a potential reservoir and spillover agent for Francisella tularensis.
Purpose of the Study:
- To investigate the ecological association between common vole abundance and human tularemia incidence in Spain.
- To evaluate the common vole as a key factor in the epidemiology of tularemia in the region.
Main Methods:
- Compilation of data on vole abundance estimates from live-trapping and monitoring studies (1997-2014).
- Analysis of official reports of human tularemia cases during the same period.
- Statistical assessment of the correlation between vole population density and human tularemia cases.
Main Results:
- A significant positive association was confirmed between annual human tularemia cases and common vole abundance.
- High vole densities, reaching up to 1000 voles/hectare during outbreaks, were observed.
- Findings suggest increased disease transmission and environmental contamination due to high vole populations.
Conclusions:
- The common vole population irruptions are strongly linked to human tularemia outbreaks in Spain.
- This ecological relationship highlights the role of voles in tularemia spillover.
- The cyclical nature of vole outbreaks may offer a predictive tool for future tularemia risk assessment.
