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Publication type: Journal Article
Document type: Full Paper

Year: 2013

Author(s): Brugger, K; Rubel, F

Title: Bluetongue disease risk assessment based on observed and projected Culicoides obsoletus spp. vector densities.

Source: PLoS One. 2013; 8(4):e60330



Authors Vetmeduni Vienna:

Brugger Katharina
Rubel Franz

Vetmed Research Units
Unit of Veterinary Public Health and Epidemiology


Abstract:
Bluetongue is an arboviral disease of ruminants causing significant economic losses. Our risk assessment is based on the epidemiological key parameter, the basic reproduction number. It is defined as the number of secondary cases caused by one primary case in a fully susceptible host population, in which values greater than one indicate the possibility, i.e., the risk, for a major disease outbreak. In the course of the Bluetongue virus serotype 8 (BTV-8) outbreak in Europe in 2006 we developed such a risk assessment for the University of Veterinary Medicine Vienna, Austria. Basic reproduction numbers were calculated using a well-known formula for vector-borne diseases considering the population densities of hosts (cattle and small ruminants) and vectors (biting midges of the Culicoides obsoletus spp.) as well as temperature dependent rates. The latter comprise the biting and mortality rate of midges as well as the reciprocal of the extrinsic incubation period. Most important, but generally unknown, is the spatio-temporal distribution of the vector density. Therefore, we established a continuously operating daily monitoring to quantify the seasonal cycle of the vector population by a statistical model. We used cross-correlation maps and Poisson regression to describe vector densities by environmental temperature and precipitation. Our results comprise time series of observed and simulated Culicoides obsoletus spp. counts as well as basic reproduction numbers for the period 2009-2011. For a spatio-temporal risk assessment we projected our results from the location of Vienna to the entire region of Austria. We compiled both daily maps of vector densities and the basic reproduction numbers, respectively. Basic reproduction numbers above one were generally found between June and August except in the mountainous regions of the Alps. The highest values coincide with the locations of confirmed BTV cases.

Keywords Pubmed: Animals
Austria/epidemiology
Basic Reproduction Number
Bluetongue/epidemiology*
Bluetongue/transmission
Bluetongue/virology
Bluetongue virus/physiology
Cattle
Ceratopogonidae/physiology*
Ceratopogonidae/virology
Disease Outbreaks/prevention & control
Disease Outbreaks/veterinary*
Forecasting
Humans
Insect Vectors/physiology*
Insect Vectors/virology
Likelihood Functions
Population Dynamics/statistics & numerical data
Risk Assessment
Seasons
Sheep


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