Spatial-temporal Variations of Bovine Tuberculosis Incidence in France between 1965 and 2000

Abstract

We analysed the spatiotemporal variations of bovine tuberculosis (bTB) incidence between 1965 and 2000 in France at the department level (95 areas). Using a Bayesian space-time model, we studied the association between the evolution of bTB incidence and changes of cattle population structure and of herd management practices. Several spatiotemporal hierarchical Bayesian models were compared, and the deviance information criterion was used to select the best of them. Southern France remained a high-risk area over the analysed period, whereas central and western regions were low-risk areas. Besides the frequency of tuberculin skin testing (fixed according to bTB incidence in the preceding years), four factors were associated with an increased risk of bTB: the average herd density and size, the percentage of dairy cows in the cattle population, and the percentage of permanent grassland in cultivated surfaces area. These four factors are linked to the progressive professionalization and specialization of cattle farming, with the disappearance of family farms and of the intensification of breeding systems (especially in dairy farms after the application of the milk quota system in the 1980s). Both trends probably played a significant role in reducing the risk of bTB in France between 1965 and 2000, besides mandatory detection and control procedures.

Keywords: bovine tuberculosis; professionalization; spatiotemporal; specialization.

Fig. 1

Evolution of the incidence and prevalence rates of bovine tuberculosis in France, from 1965 to 2000.

Fig. 2

Evolution of the incidence rate for each region in France between 1965 and 2000; (a) definition of six homogeneous zones for the characteristics of the cattle (adapted from Pluvinage, 1971); (b) evolution of incidence rate.

Fig. 3

Evolution, from 1965 to 2000, of (a) herd density per km²; (b) the percentage dairy cows in the total cattle population; (c) the average herd size; (d) the percentage of permanent grassland in the cultivated area.

Fig. 4

Number of periods for which departments-specific predicted standardized incidence ratios were >1.

Fig. 5

Posterior means of relative risks between 1965 and 2000. (a)1965–1970; (b) 1971–1974; (c) 1975–1978; (d) 1979–1984; (e) 1985–1990; (f) 1991–1995; (g) 1996–2000.

Fig. 6

Spatiotemporal distribution of model residuals. (a)1965–1970; (b) 1971–1974; (c) 1975–1978; (d) 1979–1984; (e) 1985–1990; (f) 1991–1995; (g) 1996–2000.

Fig. 7

Geographical variations of the non-professional cattle herds (<20 animals) in 2000 (34.6% is the national-level percentage).