Prevalence of BSE in western France by screening cattle at risk: preliminary results of a pilot study

Calavas, Didier; Baron, Thierry; Morignat, Eric; Vinard, J. L.; Biacabe, A-G.; Madec, J.; Bencsik, Anna; Debeer, Sabine; Ducrot, Christian; Eliazsewicz, M.

doi:10.1136/vr.149.2.55

Cited by 20 publications

(14 citation statements)

References 4 publications

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“…The analysis was restricted to a time period of surveillance -between July 1st, 2001 and December 31, 2003 in order to get precise and comparable data on BSE incidence. During this period, the detection of BSE was based both on the Mandatory Reporting System of clinical suspicions and the comprehensive active surveillance programme based on rapid tests, carried out on every cattle aged 24 months and over, dead or slaughtered 3 [8]. These two systems were complementary since they 1 allowed the screening of every cattle aged 24 months and over, dead or slaughtered.…”

Section: Bse Casesmentioning

confidence: 99%

“…In particular, four areas located in the west, south-west, centre and east of France (highlighted with the two darkest colours on the map) presented a significant RR. Table II illustrates the set of models carried out with the covariates poultry and/or pigs, each of them was used either as a common effect for all hexagons (models 4, 5, 6) or as a specific effect for each hexagon (models 7,8,9). From these results we deduced that the "best" models (lowest DIC value) are those with covariate pigs (model 5 with a unique regression parameter, and 9 with an individual regression parameter).…”

Section: Spatial Effectmentioning

confidence: 99%

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Poultry, pig and the risk of BSE following the feed ban in France – A spatial analysis

Abrial¹,

Calavas²,

Jarrige³

et al. 2005

Vet. Res.

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-A spatial analysis was carried out in order to analyse the reason why the risk of Bovine Spongiform Encephalopathy (BSE) was spatially heterogeneous in France, during the period following the feed ban of Meat and Bone Meal to cattle. The hypothesis of cross-contamination between cattle feedstuff and monogastric feedstuff, which was strongly suggested from previous investigations, was assessed, with the assumption that the higher the pig or poultry density is in a given area, the higher the risk of cross-contamination and cattle infection might be. The data concerned the 467 BSE cases born in France after the ban of meat and bone meal (July 1990) and detected between July 1st, 2001 and December 31, 2003, when the surveillance system was optimal and not spatially biased. The disease mapping models were elaborated with the Bayesian graphical modelling methods and based on a Poisson distribution with spatial smoothing (hierarchical approach) and covariates. The parameters were estimated by a Markov Chain Monte Carlo simulation method. The main result was that the poultry density did not significantly influence the risk of BSE whereas the pig density was significantly associated with an increase in the risk of 2.4% per 10 000 pigs. The areas with a significant pig effect were located in regions with a high pig density as well as a high ratio of pigs to cattle. Despite the absence of a global effect of poultry density on the BSE risk, some areas had a significant poultry effect and the risk was better explained in some others when considering both pig and poultry densities. These findings were in agreement with the hypothesis of cross-contamination, which could take place at the feedstuff factory, during the shipment of food or on the farm. Further studies are needed to more precisely explore how the cross-contamination happened.

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Section: Bse Casesmentioning

confidence: 99%

Section: Spatial Effectmentioning

confidence: 99%

Poultry, pig and the risk of BSE following the feed ban in France – A spatial analysis

Abrial¹,

Calavas²,

Jarrige³

et al. 2005

Vet. Res.

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“…In this context, TS systems based on rapid tests [12] have proven to be a complementary tool for BSE detection [3,6]. Pooling together MRS and TS cases seems reasonable since we defined the cases as positive testing animals among the dead population; it includes clinical cases as well as preclinical cases that reached the end of the incubation period -on the basis of pathogenesis trials [15].…”

Section: Discussionmentioning

confidence: 99%

“…With the same background as the TS program, started in 1999 in Switzerland using the Prionics test ® [5,6], a TS program was carried out exhaustively in France in 2000 and during six months on cattle at risk for BSE (found dead on the farm, subjected to euthanasia or emergency slaughtered), in three contiguous regions of western France [3]. The results showed that the MRS did not detect all the clinical cases of BSE; several escaped identification, although at the clinical stage of the disease, and were only detected thanks to the TS program.…”

Section: Introductionmentioning

confidence: 99%

How the surveillance system may bias the results of analytical epidemiological studies on BSE: prevalence among dairy versus beef suckler cattle breeds in France

Ducrot¹,

Roy²,

Morignat³

et al. 2003

Vet. Res.

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-Until recently, epidemiological studies on Bovine Spongiform Encephalopathy (BSE) were based on Mandatory Reporting Systems (MRS) of clinically suspect bovines only, but rapid diagnostic tests were validated in 1999 and are used for targeted surveillance in Switzerland, France and other countries, as a complementary and secondary tool. Data on 30491 cattle issued from a French pilot program targeted at cattle having died on the farm, subjected to euthanasia or sent for emergency slaughter, did not show any significant difference in BSE risk between dairy and beef suckler breeds. The data also revealed that part of the clinical cases of BSE escaped the MRS, which permitted to detect more dairy than beef suckler affected cattle compared to the targeted surveillance in the same period (from August to December 2000) and region (Bretagne, Pays de la Loire and Basse Normandie regions). Analyzing together the data of the targeted surveillance and mandatory reporting system programs with a non-conditional logistic regression, we found that the odds of a dead cow being a BSE case among all dead cattle was 3.2 times higher for dairy breeds compared to beef suckler breeds. This confirmed British findings but points out to the fact that considering either MRS or targeted surveillance data alone may possibly create biases in epidemiological studies on BSE. BSE / epidemiology / bias / logistic regression / breed

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“…Additionally, approximately 3% of the total number of adult cattle sent to routine slaughter were randomly sampled and tested, to minimise diversion of suspected BSE cases to routine slaughter. In spring 2000, France initiated also the testing of the risk population in several regions considered at higher risk of BSE given the results of passive surveillance [15]. Based on these results, the EU introduced active screening in risk populations for BSE in January 2001, and expanded the surveillance to all cattle subject to routine slaughter over 30 months of age (in some countries also younger animals) to be implemented at latest in July 2001 1 .…”

Section: Active Surveillancementioning

confidence: 99%

Review on the epidemiology and dynamics of BSE epidemics

Ducrot¹,

et al. 2008

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-The paper describes how the comprehensive surveillance of bovine spongiform encephalopathy (BSE) and studies carried out on these data has enhanced our knowledge of the epidemiology of BSE. Around 7 000 BSE cases were detected through the screening of about 50 million cattle with rapid tests in Europe. It confirmed that the clinical surveillance had a poor capacity to detect cases, and also showed the discrepancy of this passive surveillance efficiency between regions and production types (dairy/beef). Other risk factors for BSE were being in a dairy herd (three times more than beef), having a young age at first calving (for dairy cattle), being autumn-born (dairy and beef), and being in a herd with a very high milk yield. These findings focus the risk on the feeding regimen of calves/heifers. Several epidemiological studies across countries suggest that the feedborne source related to meat and bone meal (MBM) is the only substantiated route of infection -even after the feed ban -, while it is not possible to exclude maternal transmission or milk replacers as a source of some infections. In most European countries, the average age of the cases is increasing over time and the prevalence decreasing, which reflects the effectiveness of control measures. Consistent results on the trend of the epidemic were obtained using back-calculation modelling, the R 0 approach and Age-Period-Cohort models. Furthermore, active surveillance also resulted in the finding of atypical cases. These are distinct from previously found BSE and classified in two different forms based on biochemical characteristics; their prevalence is very low (36 cases up to 1st September 2007), affected animals were old and some of them displayed clinical signs. The origin and possibility of natural transmission is unknown.

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Prevalence of BSE in western France by screening cattle at risk: preliminary results of a pilot study

Cited by 20 publications

References 4 publications

Poultry, pig and the risk of BSE following the feed ban in France – A spatial analysis

Poultry, pig and the risk of BSE following the feed ban in France – A spatial analysis

How the surveillance system may bias the results of analytical epidemiological studies on BSE: prevalence among dairy versus beef suckler cattle breeds in France

Review on the epidemiology and dynamics of BSE epidemics

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