Trends in antimicrobial resistance among Escherichia coli from defined infections in humans and animals.

OBJECTIVES: To characterize and compare resistance trends in clinical Escherichia coli isolates from humans, food-producing animals (poultry, cattle and swine) and pets (dogs and cats). METHODS: Antibiogram results collected between January 2014 and December 2017 by MedQual [the French surveillance network for antimicrobial resistance (AMR) in bacteria isolated from the community] and RESAPATH (the French surveillance network for AMR in bacteria from diseased animals) were analysed, focusing on resistance to antibiotics of common interest to human and veterinary medicine. Resistance dynamics were investigated using generalized additive models. RESULTS: In total, 743 637 antibiograms from humans, 48 170 from food-producing animals and 7750 from pets were analysed. For each antibiotic investigated, the resistance proportions of isolates collected from humans were of the same order of magnitude as those from food-producing animals or pets. However, resistance trends in humans differed from those observed in pets and food-producing animals over the period studied. For example, resistance to third-generation cephalosporins and fluoroquinolones was almost always below 10% for both humans and animals. However, in contrast to the notable decreases in resistance observed in both food-producing animals and pets, resistance in humans decreased only slightly. CONCLUSIONS: Despite several potential biases in the data, the resistance trends remain meaningful. The strength of the parallel is based on similar data collection in humans and animals and on a similar statistical methodology. Resistance dynamics seemed specific to each species, reflecting different antibiotic-use practices. These results advocate applying the efforts already being made to reduce antibiotic use to all sectors and all species, both in human and veterinary medicine.

Antimicrobial resistance in bacteria isolated from mastitis in dairy cattle in France, 2006-2016.

In dairy cattle, mastitis is the most frequent bacterial disease, and the routine use of antibiotics for treatment and prevention can drive antimicrobial resistance (AMR). The aim of our study was to estimate the levels of AMR of the 3 main bacteria isolated from dairy cattle with mastitis in France (Streptococcus uberis, Escherichia coli, and coagulase-positive staphylococci) and to investigate their changes over time. Data collected between 2006 and 2016 by the French surveillance network for AMR in pathogenic bacteria of animal origin (called RESAPATH) were analyzed. The proportions of mono- and multidrug resistance were calculated and the trends were investigated using nonlinear analyses applied to time series. Over the whole period, the lowest proportions of resistance in S. uberis isolates were observed for oxacillin (2.2%) and gentamicin (2.4%) and most resistance levels were below 20%. The trends in resistance showed some significant variation, mainly for S. uberis, but without a common pattern across the various antibiotics examined. For only 2 combinations of bacteria-antibiotic the trend in resistance showed a continuous increase from 2006 to 2016: tetracycline resistance in S. uberis isolates and third-generation cephalosporin resistance in E. coli isolates. In E. coli, the highest proportions of resistance were observed for amoxicillin (28.1%) and tetracycline (23.1%). Resistance to third-generation cephalosporins in E. coli from dairy cattle was almost nil in 2006, but reached 2.4% in December 2016. This increase is particularly concerning because these antibiotics constitute one of the latest therapeutic alternatives to fight severe infectious diseases in humans. Except for penicillin (33.9%), the proportions of resistance in coagulase-positive staphylococci were below 11% during the whole study period. Multidrug resistance (isolates with acquired resistance to at least one antibiotic in 3 or more antibiotic classes) ranged from 2.4% for coagulase-positive staphylococci to 9.9% for S. uberis. These findings can serve as guidelines for practitioners in the choice of the most appropriate antibiotic according to the prevailing epidemiological context. Ultimately, our results contribute to risk assessment of AMR and provide a baseline for setting up and evaluating control measures and designing strategies to limit AMR.

Evolution of the proportion of colistin-resistant isolates in animal clinical Escherichia coli over time - A hierarchical mixture model approach.

Colistin resistance has been the subject of much attention since mcr genes encoding plasmid-mediated colistin resistance description in 2015. To date, surveillance data about resistance levels encountered in food-producing animals are scarce. In France, the Resapath dataset, consisting in a large collection of disk diffusion antibiogram results transmitted by a network of laboratories. It offers a unique opportunity to study the evolution of resistance towards colistin over the past 15 years in Escherichia coli isolated from diseased food-producing animals. This study used a Bayesian hierarchical Gaussian mixture model to estimate the resistant proportions from those data. This non-classical approach deals with the colistin-specific problem of overlapping distributions of diameters measured for susceptible and resistant isolates that makes the definition of epidemiological cut-off very hard. This model also considers the variability observed between the measurements performed by different laboratories. Proportion of resistant isolates has been calculated for several food-producing animals and most encountered diseases. From those estimations, a marked evolution of the proportions of resistant isolates is noticeable, for swine suffering from digestive disorders. In this group, an increase over the 2006-2011 period from 0.1% [ 0.0%, 1.2%] in 2006-28.6% [25.1%, 32.3%] in 2011 was followed by a decrease to reach 3.6% [2.3%;5.3%] in 2018. For isolates related to digestive disorders in calves, percentages increased and reached 7% in 2009 then decreased as for swine. In contrast, for poultry productions, estimated proportions and credibility intervals were constantly very close to zero.

OH-EpiCap: a semi-quantitative tool for the evaluation of One Health epidemiological surveillance capacities and capabilities.

Although international health agencies encourage the development of One Health (OH) surveillance, many systems remain mostly compartmentalized, with limited collaborations among sectors and disciplines. In the framework of the OH European Joint Programme "MATRIX" project, a generic evaluation tool called OH-EpiCap has been developed to enable individual institutes/governments to characterize, assess and monitor their own OH epidemiological surveillance capacities and capabilities. The tool is organized around three dimensions: organization, operational activities, and impact of the OH surveillance system; each dimension is then divided into four targets, each including four indicators. A semi-quantitative questionnaire enables the scoring of each indicator, with four levels according to the degree of satisfaction in the studied OH surveillance system. The evaluation is conducted by a panel of surveillance representatives (during a half-day workshop or with a back-and-forth process to reach a consensus). An R Shiny-based web application facilitates implementation of the evaluation and visualization of the results, and includes a benchmarking option. The tool was piloted on several foodborne hazards (i.e., Salmonella, Campylobacter, Listeria), emerging threats (e.g., antimicrobial resistance) and other zoonotic hazards (psittacosis) in multiple European countries in 2022. These case studies showed that the OH-EpiCap tool supports the tracing of strengths and weaknesses in epidemiological capacities and the identification of concrete and direct actions to improve collaborative activities at all steps of surveillance. It appears complementary to the existing EU-LabCap tool, designed to assess the capacity and capability of European microbiology laboratories. In addition, it provides opportunity to reinforce trust between surveillance stakeholders from across the system and to build a good foundation for a professional network for further collaboration.

Pilot testing the EARS-Vet surveillance network for antibiotic resistance in bacterial pathogens from animals in the EU/EEA.

Introduction: As part of the EU Joint Action on Antimicrobial Resistance (AMR) and Healthcare-Associated Infections, an initiative has been launched to build the European AMR Surveillance network in veterinary medicine (EARS-Vet). So far, activities included mapping national systems for AMR surveillance in animal bacterial pathogens, and defining the EARS-Vet objectives, scope, and standards. Drawing on these milestones, this study aimed to pilot test EARS-Vet surveillance, namely to (i) assess available data, (ii) perform cross-country analyses, and (iii) identify potential challenges and develop recommendations to improve future data collection and analysis. Methods: Eleven partners from nine EU/EEA countries participated and shared available data for the period 2016-2020, representing a total of 140,110 bacterial isolates and 1,302,389 entries (isolate-antibiotic agent combinations). Results: Collected data were highly diverse and fragmented. Using a standardized approach and interpretation with epidemiological cut-offs, we were able to jointly analyze AMR trends of 53 combinations of animal host-bacteria-antibiotic categories of interest to EARS-Vet. This work demonstrated substantial variations of resistance levels, both among and within countries (e.g., between animal host species). Discussion: Key issues at this stage include the lack of harmonization of antimicrobial susceptibility testing methods used in European surveillance systems and veterinary diagnostic laboratories, the absence of interpretation criteria for many bacteria-antibiotic combinations of interest, and the lack of data from a lot of EU/EEA countries where little or even surveillance currently exists. Still, this pilot study provides a proof-of-concept of what EARS-Vet can achieve. Results form an important basis to shape future systematic data collection and analysis.

Molecular typing of protease-resistant prion protein in transmissible spongiform encephalopathies of small ruminants, France, 2002-2009.

The agent that causes bovine spongiform encephalopathy (BSE) may be infecting small ruminants, which could have serious implications for human health. To distinguish BSE from scrapie and to examine the molecular characteristics of the protease-resistant prion protein (PrP(res)), we used a specifically designed Western blot method to test isolates from 648 sheep and 53 goats. During 2002-2009, classical non-Nor98 transmissible spongiform encephalopathy had been confirmed among ≈1.7 million small ruminants in France. Five sheep and 2 goats that showed a PrP(res) pattern consistent with BSE, or with the CH1641 experimental scrapie source, were identified. Later, bioassays confirmed infection by the BSE agent in 1 of the 2 goats. Western blot testing of the 6 other isolates showed an additional C-terminally cleaved PrP(res) product, with an unglycosylated band at ≈14 kDa, similar to that found in the CH1641 experimental scrapie isolate and different from the BSE isolate.

An inventory of 44 qPCR assays using hydrolysis probes operating with a unique amplification condition for the detection and quantification of antibiotic resistance genes.

Early antibiotic resistance determinants (ARDs) detection in humans or animals is crucial to counteract their propagation. The ARDs quantification is fundamental to understand the perturbation caused by disruptors, such as antibiotics, during therapies. Forty-three qPCRs on the most diffused ARDs and integrons among human and animal Enterobacterales, and one on the 16S rDNA for bacteria quantification, were developed. The qPCRs, using hydrolysis probes, operated with a unique amplification condition and were tested analytically and diagnostically performing 435 reactions on five positive and negative controls for each qPCR. Diagnostic sensitivity and specificity were confirmed by PCR and genome sequencing of control isolates, demonstrating 100% performance for all qPCRs. An easy and rapid discrimination method for the epidemiologically relevant blaCTX-Ms is provided. This large, noncommercial qPCRs inventory could serve for precise quantification of ARDs, but also as a rapid screening tool for surveillance purposes, providing the basis for further high-throughput developments.

Impact of Antibiotic Therapies on Resistance Genes Dynamic and Composition of the Animal Gut Microbiota.

Antibiotics are major disruptors of the gastrointestinal microbiota, depleting bacterial species beneficial for the host health and favoring the emergence of potential pathogens. Furthermore, the intestine is a reactor of antibiotic resistance emergence, and the presence of antibiotics exacerbates the selection of resistant bacteria that can disseminate in the environment and propagate to further hosts. We reviewed studies analyzing the effect of antibiotics on the intestinal microbiota and antibiotic resistance conducted on animals, focusing on the main food-producing and companion animals. Irrespective of antibiotic classes and animal hosts, therapeutic dosage decreased species diversity and richness favoring the bloom of potential enteropathogens and the selection of antibiotic resistance. These negative effects of antibiotic therapies seem ineluctable but often were mitigated when an antibiotic was administered by parenteral route. Sub-therapeutic dosages caused the augmentation of taxa involved in sugar metabolism, suggesting a link with weight gain. This result should not be interpreted positively, considering that parallel information on antibiotic resistance selection was rarely reported and selection of antibiotic resistance is known to occur also at low antibiotic concentration. However, studies on the effect of antibiotics as growth promoters put the basis for understanding the gut microbiota composition and function in this situation. This knowledge could inspire alternative strategies to antibiotics, such as probiotics, for improving animal performance. This review encompasses the analysis of the main animal hosts and all antibiotic classes, and highlights the future challenges and gaps of knowledge that should be filled. Further studies are necessary for elucidating pharmacodynamics in animals in order to improve therapy duration, antibiotic dosages, and administration routes for mitigating negative effects of antibiotic therapies. Furthermore, this review highlights that studies on aminoglycosides are almost inexistent, and they should be increased, considering that aminoglycosides are the first most commonly used antibiotic family in companion animals. Harmonization of experimental procedures is necessary in this research field. In fact, current studies are based on different experimental set-up varying for antibiotic dosage, regimen, administration, and downstream microbiota analysis. In the future, shotgun metagenomics coupled with long-reads sequencing should become a standard experimental approach enabling to gather comprehensive knowledge on GIM in terms of composition and taxonomic functions, and of ARGs. Decorticating GIM in animals will unveil revolutionary strategies for medication and improvement of animals' health status, with positive consequences on global health.

Pathogenic Escherichia coli in Dogs Reveals the Predominance of ST372 and the Human-Associated ST73 Extra-Intestinal Lineages.

Escherichia coli is a ubiquitous commensal and pathogen that has also been recognized as a multi-sectoral indicator of antimicrobial resistance (AMR). Given that latter focus, such as on resistances to extended-spectrum cephalosporins (ESC) and carbapenems, the reported population structure of E. coli is generally biased toward resistant isolates, with sequence type (ST)131 being widely reported in humans, and ST410 and ST648 being reported in animals. In this study, we characterized 618 non-duplicate E. coli isolates collected throughout France independently of their resistance phenotype. The B2 phylogroup was over-represented (79.6%) and positively associated with the presence of numerous virulence factors (VFs), including those defining the extra-intestinal pathogenic E. coli isolates (presence of ≥2 VFs: papA, sfaS, focG, afaD, iutA, and kpsMTII) and those more specifically related to uropathogenic E. coli (cnf1, hlyD). The major STs associated with clinical isolates from dogs were by far the dog-associated ST372 (20.7%) and ST73 (20.1%), a lineage that had commonly been considered until now as human-associated. Resistance to ESC was found in 33 isolates (5.3%), along with one carbapenemase-producing isolate, and was mostly restricted to non-B2 isolates. In conclusion, the presence of virulent E. coli lineages may be the issue, rather than the presence of ESC-resistant isolates, and the risk of transmission of such virulent isolates to humans needs to be further studied.

Utility of examining fallen stock data to monitor health-related events in equids: Application to an outbreak of West Nile Virus in France in 2015.

Few studies about the use of quantitative equine mortality data for monitoring purposes are available. Our study evaluated the utility of monitoring emerging equine diseases using mortality data collected by rendering plants. We used approaches involving modelling of historical mortality fluctuations and detection algorithm methods to analyse changes in equine mortality in connection with the West Nile Virus (WNV) outbreak that occurred between July and September 2015 along the Mediterranean coast of France. Two weeks after the first equine WNV case was detected by clinical surveillance, detection algorithms identified excess mortality. The temporal distribution of this excess mortality suggested that it was related to the WNV outbreak, which may helped to assess the impact of the WNV epizootic on equine mortality. The results suggest that real-time follow-up of mortality could be a useful tool for equine health surveillance.

Antimicrobial Usages and Antimicrobial Resistance in Commensal Escherichia coli From Veal Calves in France: Evolution During the Fattening Process.

Extended-Spectrum-Cephalosporin (ESC)-resistant Enterobacteriaceae have widely spread in all settings worldwide. In animals, Extended-Spectrum Beta-Lactamase (ESBL) producers have been frequently identified in veal calves. The objectives of this study were to investigate the trends in the ESBL load and antimicrobial resistance (AMR) proportions, and antimicrobial usages (AMU) in veal calves during the fattening process. Ten fattening farms were selected and 50 animals per farm were sampled. AMR was assessed in bacteria from the dominant flora (collected on non-selective MacConckey agar) and in ESBL/AmpC-carrying bacteria from the subdominant flora (selected on ChromID ESBL selective plates) upon arrival and 5-6 months later before slaughter. The number and types of treatments during fattening were also collected. Rates of ESBL-producing E. coli from the subdominant flora significantly decreased in all farms (arrival: 67.7%; departure: 20.4%) whereas rates of multidrug-resistant E. coli from the dominant flora have significantly increased (arrival: 60.2%; departure: 67.2%; p = 0.025). CTX-M-1 was the most frequently identified ESBL enzyme (arrival: 59.3%; departure: 52.0%). The plasmid-mediated mcr-1 gene was also identified occasionally. In parallel, levels of resistances to non-critically important antimicrobials were already high upon arrival but have still further increased over time until slaughter. Our study also highlighted that if only ESBL-producing isolates were monitored, it might have led to a partial (and partly false) picture of AMR rates globally decreasing during the fattening period. The mean number of antimicrobial treatments per calf (NTPC) was 8.75 but no association between AMU and AMR was evidenced. Most ESBL producers were clonally unrelated suggesting multiple sources and not cross-contaminations among calves during transportation. Feeding milk containing antimicrobial residues to veal calves is hypothesized to explain the high ESBL loads in animals at the entrance on farms.

Antimicrobial resistance of Pasteurella multocida isolated from diseased food-producing animals and pets.

Surveillance of Pasteurella multocida resistance in food-producing animals is essential to guide the first-line treatment of respiratory diseases and to limit economic losses. Since Pasteurella are the most common bacteria isolated from dog and cat bites, this surveillance is also needed to guide treatment in humans in case of bites. The aim of this study was to characterize the phenotypic resistance of P. multocida strains isolated from respiratory infections in animals, including both food-producing animals and pets. Data collected between 2012 and 2017 by the French national surveillance network for antimicrobial resistance referred to as RESAPATH were analyzed. The proportions of resistance to antimicrobials of relevance in veterinary and human medicines were estimated for each animal species. For cattle, resistance trends over the period were investigated using non-linear analysis applied to time-series. In total, 5356 P. multocida isolates were analyzed. Proportions of resistance of P. multocida were almost all below 20% over the period, and, more precisely, all resistance proportions were below 10% for rabbits, sheep and dogs. The highest resistance proportions to enrofloxacin were identified for cattle (4.5%) and dogs (5.2%). Despite its frequent use in livestock, resistance to florfenicol was less than 1% in P. multocida strains, regardless of the animal species considered. Time series analyses revealed continuous increases in resistance to tetracycline, tilmicosin, flumequine and fluoroquinolones in P. multocida strains isolated from cattle. These trends contrast with the decrease in use of antibiotics in cattle in France and with the decrease in resistance observed in E. coli isolated from diseased cattle.

Co-resistance to Amoxicillin and Tetracycline as an Indicator of Multidrug Resistance in Escherichia coli Isolates From Animals.

OBJECTIVES: To examine the relevance of co-resistance to amoxicillin and tetracycline as an indicator of multidrug resistance (MDR) in animal health. METHODS: Escherichia coli isolates collected between 2012 and 2016 by the French surveillance network for antimicrobial resistance in diseased animals (RESAPATH) were analyzed. The proportions of MDR isolates and the proportions of isolates presenting co-resistance to amoxicillin and tetracycline were calculated for seven animal species (cattle, horse, dog, swine, poultry, duck, and turkey). The degree of agreement between these two proportions was estimated by calculating the kappa value. RESULTS: In total, 55,904 isolates were analyzed. MDR proportions were variable among animal species, ranging from 21.9% [20.2; 23.7] in horses to 56.0% [55.4; 56.7] in cattle. A similar situation was observed for proportions of isolates with co-resistance to amoxicillin and tetracycline, with the highest value for cattle 65.0% [64.3; 65.6]. This co-resistance was also most often associated with resistance to other antibiotics, regardless of the animal species considered. Comparative analysis showed substantial agreement between MDR and this co-resistance, with a kappa value of 0.75, all animal species considered. CONCLUSION: Given the widespread use of penicillins and tetracyclines in animal health, co-resistance to amoxicillin and tetracycline could be an efficient indicator of MDR in E. coli isolates. Based on a specific resistance profile and not an arbitrary number of resistances compared with MDR, this potential indicator is also precise, convenient and suitable for routine use.

Comparative epidemiology of E. coli resistance to third-generation cephalosporins in diseased food-producing animals.

Categorized by WHO as critically important antibiotics, third-generation cephalosporins (3GCs) are one of the latest therapeutic alternatives to fight severe infectious diseases in humans. Some antibiotics belonging to this class are prescribed to treat food-producing animals in specific pathological contexts. Preserving the effectiveness of 3GCs requires characterization and careful monitoring of 3GCs resistance and the identification and implementation of measures that can limit this antimicrobial resistance (AMR). Here, we characterized the 3GCs resistance in Escherichia coli isolated from diseased animals. Using data collected from broilers, hens, calves, piglets, sows, turkeys and ducks between 2006 and 2016 by the French surveillance network of AMR in pathogenic bacteria of animal origin (called RESAPATH), we investigated the dynamics of resistance to 3GCs. Our non-linear analysis applied to time series showed that the evolution of E. coli resistance to 3GCs is specific to each animal category. From 2006 to 2010, resistance to 3GCs increased for most animal categories. We observed peaks of high-level of resistance for hens (21.5% in 2010) and broilers (26.7% in 2011), whereas trends stayed below 10% for the other animal categories throughout the study period. Resistance later decreased and, since 2014, 3GCs resistance has dropped below 10% for all animal categories. The parallel between trends and measures to limit AMR over the period shed lights on the impact of practices changes, public policies (EcoAntibio Plan) and sector-led initiatives (moratorium in swine sector). Finally, they highlight the usefulness and importance of AMR surveillance networks in animal health, such as RESAPATH.

A Bayesian zero-truncated approach for analysing capture-recapture count data from classical scrapie surveillance in France.

Capture-recapture (CR) methods are used to study populations that are monitored with imperfect observation processes. They have recently been applied to the monitoring of animal diseases to evaluate the number of infected units that remain undetected by the surveillance system. This paper proposes three bayesian models to estimate the total number of scrapie-infected holdings in France from CR count data obtained from the French classical scrapie surveillance programme. We fitted two zero-truncated Poisson (ZTP) models (with and without holding size as a covariate) and a zero-truncated negative binomial (ZTNB) model to the 2006 national surveillance count dataset. We detected a large amount of heterogeneity in the count data, making the use of the simple ZTP model inappropriate. However, including holding size as a covariate did not bring any significant improvement over the simple ZTP model. The ZTNB model proved to be the best model, giving an estimation of 535 (CI(95%) 401-796) infected and detectable sheep holdings in 2006, although only 141 were effectively detected, resulting in a holding-level prevalence of 4.4‰ (CI(95%) 3.2-6.3) and a sensitivity of holding-level surveillance of 26% (CI(95%) 18-35). The main limitation of the present study was the small amount of data collected during the surveillance programme. It was therefore not possible to build complex models that would allow depicting more accurately the epidemiological and detection processes that generate the surveillance data. We discuss the perspectives of capture-recapture count models in the context of animal disease surveillance.

Case-control study on feed risk factors for BSE cases born after the feed ban in France.

In France, after the ban on meat and bone meal (MBM) in cattle feeding in June 1990, cases of Bovine Spongiform Encephalopathy (BSE) have continued to be detected in bovines born after that ban (called BAB cases). A case-control study was therefore carried out to determine the way these cases were contaminated. A multivariate conditional model was built adjusting for the production type of the animals and taking into account the herd size. The results confirmed that feeding cattle with proprietary concentrates was at risk for BSE, with an adjusted odds ratio of 6.8 (2.5; 18.7) for the consumption of less or three different proprietary concentrates and 17.6 (5.7; 54.8) for more than three, when comparing with no consumption of proprietary concentrates, considering feeding of bovines before the age of two. The results suggest that cross-contaminations by MBM in bovine concentrates have occurred after 1990. To a lesser extent, on-farm cross-contaminations, i.e. consumption by cattle of feedstuffs initially dedicated to other animals and which could legally contain MBM, have probably also existed, since the presence on farms of poultry fed purchased feed involved an increased risk of BSE with an odds ratio of 1.8 (1.1; 3.0). The use of milk replacers, which often incorporates animal fats, was also at risk with an odds ratio of 1.8 (1.0; 3.1).

Temporal and spatial patterns of the clinical surveillance of BSE in France, analysed from January 1991 to May 2002 through a vigilance index.

Between 1991 and mid 2000, the surveillance of Bovine Spongiform Encephalopathy (BSE) in France was based solely on clinical surveillance through a Mandatory Reporting System. Since 2000, the implementation of active surveillance programmes using rapid tests, as a complementary tool targeted at dead and slaughtered cattle has shown that part of the BSE cases were not detected with the clinical surveillance. In order to obtain a better knowledge of the strength of the clinical surveillance, we analysed a vigilance index defined as the ratio of negative clinical suspicions to the cattle population in the region and period of interest. The temporal analysis of the vigilance index showed that it did not vary much between 1991 and 1999, increased sharply since 2000, and then decreased partly in 2001. The geographical analysis of the variations of the vigilance index was performed at the department level by comparing the observed number of negative clinical suspicions per department to the expected number, computed on the basis of the national average index and standardised on the production type of the cattle - dairy versus beef suckling cattle. As assumed, the data followed a Poisson distribution. We observed a high geographical variation of the vigilance index: ten departments out of 91 presented a significantly higher vigilance index than the national one, and four a significantly lower vigilance index. The vigilance index showed that the clinical surveillance was heterogeneous during the past twelve years, both in time and geographic location, in a range of one to ten. So the apparent trend in the BSE epidemic during this period as well as the differences in the spatial incidence of BSE have to be analysed with caution.