A cost-benefit analysis and the potential trade effects of the bovine viral diarrhoea eradication programme in Styria, Austria.

This study evaluated the voluntary and compulsory implementation of a bovine viral diarrhoea virus (BVDV) eradication programme in the Austrian Federal State of Styria, Austria, from an economic point of view using ex-post assessment of costs and benefits (disease losses avoided). An economic net benefit (benefit:cost ratio, BCR=1.18) of the programme was demonstrated during the voluntary programme phase (January 1998-July 2004). The break-even point was reached in 2003. If investments in the compulsory programme (August 2004-December 2016) were taken into account, a net economic loss (BCR=0.16) was demonstrated. In contrast to on-going annual testing of all cattle herds, annual testing in accordance with a revised sampling scheme could reduce total surveillance costs by more than 77%. A Bayesian structural time series model was applied to analyse a hypothesised positive impact of the compulsory BVDV programme on the Styrian cattle export market. The average number of exported cows and bulls increased significantly by 42% (P=0.03) and 47% (P=0.01), respectively, and the producer price increased by 14% (P=0.00) and 5% (P=0.16), respectively, during the compulsory programme period compared with the period prior to intervention. This equates to an average revenue increase of €29,754 for cows and €137,563 for bulls per month. These results justify the implementation of eradication programmes, which initially may not appear to be economically viable, particularly if trade effects are not included in the calculations.

[Ecology of antimicrobial resistance: Special aspects of extended-spectrum ß-lactamases]. / Ökologie der Antibiotikaresistenz: Besonderheiten der Extended-spectrum-ß-Laktamasen.

Extended-spectrum ß-lactamase (ESBL) producing Enterobacteriaceae were detected shortly after the introduction of broad spectrum cephalosporins in hospitals. Today, they are prevalent in the community, in animals, foods, and the environment. Many factors contribute to the broad distribution, especially the usage of antimicrobials in humans and animals, and due to multiple resistances, not only the usage of ß-lactams and cephalosporins.This broad distribution of ESBLs cannot be fully explained by clonal spread of successful strains. Horizontal transmission of resistance genes, located on transmissible elements, probably plays a much greater role. This gene transfer also enables new combinations of resistance genes which causes therapeutic problems.The complex interactions make it difficult to estimate the relative contribution of the different sources. Resistance genes are broadly distributed in humans, animals, and the environment and the distribution pattern seems to become more similar. It is also evident that two major transmission pathways have to be considered, human-to-human transmission, frequently in hospitals and the exchange of resistance genes between humans, animals, food, and the environment. For the latter, the transfer can go in both directions.Further studies are necessary to understand the pathways between the different reservoirs, the bacterial concentration needed, and the factors having an impact on colonization and transmission. Multiple measures on both the human and veterinary side have to complement each other and interact. A One Health approach needs to be developed and rigorously established.

DEVELOPMENT OF AN ANNOTATION SCHEME FOR STANDARDIZED DESCRIPTION OF MATHEMATICAL MODELS IN THE FIELD OF PLANT PROTECTION.

Mathematical models on properties and behavior of harmful organisms in the food chain are an increas- ingly relevant approach of the agriculture and food industry. As a consequence, there are many efforts to develop biological models in science, economics and risk assessment nowadays. However, there is a lack of international harmonized standards on model annotation and model formats, which would be neces- sary to set up efficient tools supporting broad model application and information exchange. There are some established standards in the field of systems biology, but there is currently no corresponding provi- sion in the area of plant protection. This work therefore aimed at the development of an annotation scheme using domain-specific metadata. The proposed scheme has been validated in a prototype implementation of a web-database model repository. This prototypic community resource currently contains models on aflatoxin secreting fungal Aspergillus flavus in maize, as these models have a high relevance to food safety and economic impact. Specifically, models describing biological processes of the fungus (growth, Aflatoxin secreting), as well as dose-response- and carry over models were included. Furthermore, phenological models for maize were integrated as well. The developed annotation scheme is based on the well-established data exchange format SBML, which is broadly applied in the field of systems biology. The identified example models were annotated according to the developed scheme and entered into a Web-table (Google Sheets), which was transferred to a web based demonstrator available at https://sites.google.com/site/test782726372685/. By implementation of a software demonstrator it became clear that the proposed annotation scheme can be applied to models on plant pathogens and that broad adoption within the domain could promote communication and application of mathematical models.

Oral administration of antimicrobials increase antimicrobial resistance in E. coli from chicken--a systematic review.

Antimicrobials play an important role in animal and human health care. It was the aim of this systematic review to assess the effects of oral administration of antimicrobials on the development of antimicrobial resistance (AMR) in Escherichia coli (E. coli) from chickens. Moreover, the effects of the administration of more than one antimicrobial and of different dosages were studied. Literature was searched in November 2012 from the electronic databases ISI Web of Science, PubMed, Scopus and a national literature database (DIMDI) as well as the database ProQuest LLC. The search was updated in March 2014. Original studies describing a treatment (A) and a control group of either non-treatment (C) or initial value (0) and determining AMR in E. coli at different sample points (SP) were included. The literature search resulted in 35 full text articles on the topic, seven (20%) of which contained sufficient information on the administered antimicrobial and the impact of treatment on AMR. Most papers described the use of more than one antimicrobial, several dosages, controls (non-treatment or pre-treatment) and measured AMR at different SPs leading to a total of 227 SPs on the impact of the use of antimicrobials on AMR in chickens. 74% of the SPs (168/227) described a higher AMR-rate in E. coli from treated animals than from controls. After the administration of a single antimicrobial, AMR increased at 72% of the SPs. Administration of more than one antimicrobial increased AMR at 82% of the SPs. Higher dosages were associated with similar or higher AMR rates. The limited number of studies for each antimicrobial agent and the high variability in the resistance effect call for more well designed studies on the impact of oral administration on AMR development and spread.

Methicillin-resistant Staphylococcus aureus in cattle food chains - prevalence, diversity, and antimicrobial resistance in Germany.

Livestock-associated methicillin-resistant Staphylococcus aureus (MRSA) have been found in various farm animal species throughout the world. It was the objective of this study to estimate the prevalence of MRSA in different cattle food chains (milk, beef, and veal) in Germany, to analyze the MRSA diversity along each food chain and to compare the characteristics of the different subtypes. Samples were collected between 2009 and 2012 from dairy herds (bulk tank milk), veal herds (dust from the stables), veal calves, and beef cattle at slaughter (nasal swabs) and carcasses of veal calves (surface cuts) and beef as well as veal at retail. Sampling was proportionally distributed over the country according to the cattle population (on-farm sampling), slaughterhouse capacity (abattoir samples), and the human population (meat at retail). Methicillin-resistant S. aureus were isolated using harmonized methods from all sample types and populations investigated. The highest proportion of positive samples was found in nasal swabs from veal calves at slaughter in 2012 (144/320; 45.0%) and the lowest rate in bulk tank milk in 2009 (14/388; 4.1%). Most isolates, irrespective of the origin, were from spa types t011 and t034. Both have been assigned to the clonal complex (CC) 398. Few isolates (15/632; 2.4%) were from spa types not associated with the CC398. Spa-type patterns were similar along individual food chains but differed between food chains. Antimicrobial resistance patterns differed between isolates from the different food chains and spa types. Isolates from the veal chain displayed the highest resistance rates. We conclude that there is substantial diversity in the MRSA prevalence across different cattle production sectors.

Oral antimicrobials increase antimicrobial resistance in porcine E. coli--a systematic review.

Administration of antimicrobials to livestock increases the risk of antimicrobial resistance (AMR) in commensal bacteria. Antimicrobials in pig production are usually administered per pen via feed which implies treatment of sick alongside with healthy animals. The objective of this systematic literature review was to investigate the effect of orally administered antimicrobials on AMR in Escherichia coli of swine. Studies published in peer reviewed journals were retrieved from the international online databases ISI Web of Knowledge, PubMed, Scopus and the national electronic literature data base of Deutsches Institut für Medizinische Dokumentation und Information. The studies were assessed using the eligibility criteria English or German language, access to full paper version, defined treatment and control group (initial value or non-treatment) as well as administration and resistance testing of the same antimicrobial class. In the qualitative synthesis, only studies were included presenting the summary measures odds ratio or prevalence of resistance, the category of the applied antimicrobial and the dosage. An effect of the antimicrobial on AMR in E. coli was evaluated as an "increase", "no effect" or "decrease" if the odds or alternatively the prevalence ratio were >1.0, 1.0 or <1.0, respectively. Eleven studies, describing 36 different trials, fulfilled the eligibility criteria and were finally assessed. An increase of AMR in E. coli was found in 10 out of 11 trials comparing AMR after with AMR prior to oral treatment and in 22 of the 25 trials comparing orally treated with untreated groups. Effects expressed as odds or prevalence ratios were highest for the use of aminoglycosides, quinolones and tetracycline. There was no clear association between the reported dosage and AMR towards tetracycline. Information on antimicrobial substance and dosage was missing in 4 and 5 of the 11 finally selected studies. The 36 identified trials were inhomogenous in usage and provision of information on sample size. Oral administration of antimicrobials increases the risk of AMR in E. coli from swine. There is however a lack of studies on the impact of dosage and longitudinal effects of treatment. The published studies have a number of issues concerning their scientific quality. More high quality research is needed to better address and quantifiy the effect of orally administered antimicrobials on AMR in swine.

Longitudinal monitoring of extended-spectrum-beta-lactamase/AmpC-producing Escherichia coli at German broiler chicken fattening farms.

Antimicrobial resistance of Escherichia coli to modern beta-lactam antibiotics due to the production of extended-spectrum beta-lactamases (ESBL) and/or plasmid-mediated AmpC beta-lactamases (AmpC) represents an emerging and increasing resistance problem that dramatically limits therapeutic options in both human and veterinary medicine. The presence of ESBL/AmpC genes in commensal E. coli from food-producing animals like broilers may pose a human health hazard. However, there are no data available concerning the prevalence of ESBL/AmpC-producing E. coli in German broiler flocks using selective methods. In this longitudinal study, samples were taken from seven conventional broiler fattening farms at three different times within one fattening period. Various samples originating from the animals as well as from their direct environment in the barn were investigated for the occurrence of ESBL/AmpC-producing E. coli. Average detection levels of 51, 75, and 76% in animal samples collected during the three samplings in the course of the fattening period demonstrate a colonization of even 1-day-old chicks, as well as a continuous significant (P < 0.001) increase in prevalence thereafter. The detection frequencies in housing environmental samples were relatively high, with an increase over time, and ranged between 54.2 and 100%. A total of 359 E. coli isolates were characterized by PCR and partly via the disc diffusion method. This study shows that prevalence of ESBL/AmpC-producing E. coli increases during the fattening period of the broiler flocks examined. Both colonized day-old chicks and contaminated farm environments could represent significant sources of ESBL/AmpC-producing E. coli in German broiler fattening farms.

Prevalence of extended-spectrum ß-lactamase-producing Escherichia coli on Bavarian dairy and beef cattle farms.

Extended-spectrum ß-lactamase (ESBL)-producing Escherichia coli strains are believed to be widely distributed among humans and animals; however, to date, there are only few studies that support this assumption on a regional or countrywide scale. Therefore, a study was designed to assess the prevalence of ESBL-producing E. coli in dairy cows and beef cattle in the southern part of Bavaria, Germany. The study population included 30 mixed dairy and beef cattle farms and 15 beef cattle farms. Fecal samples, boot swabs, and dust samples were analyzed for ESBL-producing E. coli using selective media. PCR was performed to screen for CTX-M and ampC resistance genes. A total of 598 samples yielded 196 (32.8%) that contained ESBL-producing E. coli, originating from 39 (86.7%) of 45 farms. Samples obtained from mixed farms were significantly more likely to be ESBL-producing E. coli positive than samples from beef cattle farms (fecal samples, P < 0.001; boot swabs, P = 0.014; and dust samples, P = 0.041). A total of 183 isolates (93.4%) of 196 ESBL-producing E. coli-positive strains harbored CTX-M genes, CTX-M group 1 being the most frequently found group. Forty-six additional isolates contained ampC genes, and 5 of the 46 isolates expressed a blaCMY-2 gene. The study shows that ESBL-producing E. coli strains are commonly found on Bavarian dairy and beef cattle farms. Moreover, to our knowledge, this is the first report of the occurrence of blaCMY-2 in cattle in Germany.

Prevalence, antimicrobial resistance, and molecular characterization of methicillin-resistant Staphylococcus aureus from bulk tank milk of dairy herds.

It was the objective of the study to estimate the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in bulk tank milk from German dairy herds and to characterize isolates from bulk tank milk with respect to their Staph. aureus protein A (spa) and staphylococcal cassette chromosome mec (SCCmec) type, their phenotypic antimicrobial resistance and resistance- resp. virulence-associated genes using broth microdilution and a microarray for Staph. aureus. Bulk tank milk samples (25 mL) were tested for MRSA using a 2-step selective enrichment protocol. Presumptive MRSA were confirmed by PCR. Thirty-six isolates collected from bulk tank milk of dairy herds in 2009 and 2010 were included in the characterization. All isolates displayed spa-types assigned to the clonal complex CC398. Based on the epidemiological cut-off values for the interpretation of minimum inhibitory concentrations isolates were resistant to tetracycline (100%), clindamycin (58%), erythromycin (52%), quinupristin/dalfopristin (36%), and kanamycin (27%). Isolates did not carry genes associated with typical virulence factors for Staph. aureus such as the Panton-Valentine leukocidin. However, they did carry hemolysin genes. Livestock-associated MRSA of CC398 does occur in German dairy herds and the strains have similar properties as described for strains from pigs.

Quo vadis? - Monitoring Campylobacter in Germany.

Campylobacter is a poorly recognized foodborne pathogen, leading the statistics of bacterially caused human diarrhoea in Europe during the last years. In this review, we present qualitative and quantitative German data obtained in the framework of specific monitoring programs and from routine surveillance. These also comprise recent data on antimicrobial resistances of food isolates. Due to the considerable reduction of in vitro growth capabilities of stressed bacteria, there is a clear discrepancy between the detection limit of Campylobacter by cultivation and its infection potential. Moreover, antimicrobial resistances of Campylobacter isolates established during fattening of livestock are alarming, since they constitute an additional threat to human health. The European Food Safety Authority (EFSA) discusses the establishment of a quantitative limit for Campylobacter contamination of broiler carcasses in order to achieve an appropriate level of protection for consumers. Currently, a considerable amount of German broiler carcasses would not comply with this future criterion. We recommend Campylobacter reduction strategies to be focussed on the prevention of fecal contamination during slaughter. Decontamination is only a sparse option, since the reduction efficiency is low and its success depends on the initial contamination concentration.

Virulence and resistance determinants of German Staphylococcus aureus ST398 isolates from nonhuman sources.

A series of 100 Staphylococcus aureus isolates ascribed to sequence type 398 (ST398) and recovered from different sources (healthy carrier and diseased pigs, dust from pig farms, milk, and meat) in Germany were investigated for their virulence and antimicrobial resistance genetic background. Antimicrobial resistance was determined by the disk diffusion method. Virulence and resistance determinants (37 and 31 genes, respectively) were tested by PCR. Only two virulence profiles, including the accessory gene regulator agrI and three or four hemolysin-encoding genes, were detected. In contrast, 33 resistance profiles were distinguished (only 11 were shown by more than one isolate). Fifty-nine isolates were multiresistant (four or more antimicrobial classes), and 98 were methicillin resistant (mecA positive). All of the ST398 isolates showed resistance to tetracycline [encoded by tet(M) alone or together with tet(K) and/or tet(L)]. In addition, 98% were resistant to other antimicrobials, including macrolide-lincosamine-streptogramin B (70%, encoded by ermA, ermB, and ermC, alone or in combination), trimethoprim (65%, mostly due to dfrK and dfrG), kanamycin and gentamicin [29% and 14%, respectively, mainly related to aac(6')-Ie-aph(2″)-Ia and/or ant(4')-Ia but also to aph(3')-IIIa], chloramphenicol (9%, fexA or cfr), quinupristin-dalfopristin (9%), ciprofloxacin (8%), and trimethoprim-sulfamethoxazole (4%). The heterogeneity of the resistance profiles underlines the ability of the ST398 clone to acquire multiple antimicrobial resistance genes. However, the virulence gene content of the tested isolates was low. Continuous surveillance is needed to clarify whether its pathogenicity potential for animals and humans will increase over time.

Livestock associated methicillin-resistant Staphylococcus aureus (LaMRSA) isolated from lesions of pigs at necropsy in northwest Germany between 2004 and 2007.

An increasing number of reported detections of methicillin-resistant Staphylococcus aureus (MRSA) in food animals since 2007 has led to the assumption that there is an emerging zoonotic problem with livestock associated (la)MRSA potentially aggravating the MRSA problem in humans. It was the objective of the study to investigate, whether MRSA was present in clinical specimens of pigs collected at post-mortem since 2004 and to further characterize these isolates. We studied 138 isolates of S. aureus collected between 2004 and 2007 from various pathological lesions of pigs at necropsy. Potential MRSA were identified by growth on selective chromogenic media. Isolates were confirmed as MRSA using multiplex PCR. Confirmed isolates were spa- and SCCmec-typed and were tested for antimicrobial resistance. Overall, 60 (43%) S. aureus isolates were identified as MRSA. The majority (57/60) of the MRSA isolates found in the altered porcine tissues were spa-types associated with MRSA ST398. Three MRSA were ST97 isolates, a type that has not been described as an MRSA in pigs before. Other clonal complexes (ST9, ST30) dominated among the methicillin-sensitive S. aureus. MRSA were found in similar frequency in all 4 years. We assume that MRSA in pigs may have occurred earlier than 2004 and might be not really 'emerging', but rather have been overlooked until recently. The potentially causative role of the MRSA in the lesions warrants further investigation.

High heterogeneity within methicillin-resistant Staphylococcus aureus ST398 isolates, defined by Cfr9I macrorestriction-pulsed-field gel electrophoresis profiles and spa and SCCmec types.

During recent years, the animal-associated methicillin-resistant Staphylococcus aureus clone ST398 has extensively been studied. The DNA of these isolates turned out to be refractory to SmaI restriction, and consequently, SmaI is unsuitable for subtyping this clone by standard pulsed-field gel electrophoresis (PFGE). Very recently, ST398 DNA was shown to be digested by Cfr9I, a neoschizomer of SmaI. In the present study, we employed Cfr9I PFGE on 100 German and 5 Dutch ST398 isolates and compared their PFGE profiles, protein A gene variable repeat regions (spa types), and types of the staphylococcal cassette chromosome mec (SCCmec). The isolates (from healthy carrier pigs, clinical samples from pigs, dust from farms, milk, and meat) were assigned to 35 profiles, which were correlated to the SCCmec type. A dendrogram with the Cfr9I patterns assigned all profiles to two clusters. Cluster A grouped nearly all isolates with SCCmec type V, and cluster B comprised all SCCmec type IVa and V* (a type V variant first identified as III) carriers plus one isolate with SCCmec type V. Both clusters also grouped methicillin-susceptible S. aureus isolates. The association of the majority of isolates with SCCmec type V in one large cluster indicated the presence of a successful subclone within the clonal complex CC398 from pigs, which has diversified. In general, the combination of Cfr9I PFGE with spa and SCCmec typing demonstrated the heterogeneity of the series analyzed and can be further used for outbreak investigations and traceability studies of the MRSA ST398 emerging clone.

Prevalence of MRSA types in slaughter pigs in different German abattoirs.

To investigate the prevalence of types of meticillin-resistant Staphylococcus aureus (MRSA) in slaughter pigs in German abattoirs, nasal swabs were collected from a total of 1026 pigs in five abattoirs after stunning in the course of two studies, and examined for MRSA. Study 1 included four abattoirs; study 2 was carried out in one large abattoir. Isolates were tested for antimicrobial susceptibility and characterised using spa-typing, multilocus sequence typing (MLST) and typing of the staphylococcal cassette chromosome, SCCmec. Overall, MRSA was isolated from 70.8 per cent of 520 samples in study 1 and from 49.0 per cent of 506 samples in study 2. The proportion of positive samples varied substantially between the abattoirs in study 1. Most isolates belonged to spa-types t011 and t034 and SCCmec types III and V. MLST of selected isolates revealed that they were all MLST ST398. Besides beta-lactams, 100 per cent of the isolates were resistant to tetracycline, 80.5 per cent were resistant to erythromycin and 80.7 per cent were resistant to clindamycin. Less than 5 per cent of the isolates were resistant to other antimicrobials.

[Intersectoral collaboration of institutions in Germany and Europe in the field of food-borne zoonoses]. / Zusammenarbeit nationaler und europäischer Behörden im Bereich lebensmittelbedingter Zoonosen.

Prevention and control of food-borne zoonoses is given high priority in Germany and in the European Union. To implement targeted control measures, detailed data are necessary on human zoonoses and on the prevalence of zoonotic agents along the food chain. EU-wide legislations have been stipulated that allow collection and collation of relevant data across member states. The necessary structures have been established and are being constantly refined. In addition, surveillance systems and early warning systems have been improved or set up, respectively, to timely investigate and control food-borne outbreaks and to transnationally communicate food safety risks. For prevention and control to be effective, well-defined responsibilities and close collaboration of public health, veterinary public health and food safety authorities are needed. This report reviews the pertinent legislation, the established structures, and the collaboration of competent authorities in Germany and particularly in Europe. In the future, data quality and collaboration on national and EU levels will likely be further improved. Targeted control measures, particularly at primary production, are expected to lead to a sustainable reduction of the incidence of food-borne zoonoses.

Salmonella in slaughter pigs of German origin: an epidemiological study.

The Salmonella prevalence in slaughter pigs of German origin was determined in seven abattoirs located in different regions of the country between February and June 1996. A total of 11,942 pigs delivered to the abattoirs in 752 batches, most of them comprised of pigs from individual finishing farms, was investigated by the bacteriological examination of faecal and gut lymph node samples, as well as of surface swabs taken from the carcasses. Salmonellae were isolated from 3.7% of the faecal samples, 3.3% of the lymph nodes and 4.7% of the surface swabs. The estimated overall prevalence of Salmonellae was 6.2% in the slaughter pigs, ranging between 1.9% and 12% in individual abattoirs. In the samples taken from carcasses, the estimated prevalence of Salmonellae reached 10.3%. 648 out of 752 batches could be included in a statistical analysis. No Salmonellae were detected in nearly 70 percent of the batches included in this analysis (n = 648). High Salmonella prevalences of more than 50 percent positive animals were detected only in 13 batches (2.0%). A statistically significant influence of the duration of the transport of slaughter pigs to the abattoirs or the waiting period in the abattoirs prior to slaughter could not be detected.

Detection of antibodies to S. enteritidis in broilers by means of indirect ELISA and chemiluminescent immunoassay (CLIA).

This study was conducted to develop a serological detection system for the monitoring of broiler flocks for Salmonella enteritidis infections. A specific S. enteritidis antigen (FG-Antigen) was used to compare the sensitivity and the specificity of the chemiluminescent immunoassay (CLIA) with those of the indirect ELISA. This comparison was performed using a total of 578 sera, which, depending on the microbiological and vaccination history, were categorized into groups. Most of the serum samples which were classified as positive showed higher titers in CLIA than in ELISA. Using the prevalence of positive reactors, significant differences between Groups were additionally demonstrated. The absorbance values of the passively immunized group showed the highest and those of the Salmonella-negative group the lowest correlation-coefficient. Using the mean net absorbance of the prevalence group, the ELISA system exhibited a sensitivity of 100% and a specificity of 96.2%, while CLIA had a sensitivity and a specificity of 85.7% and 96.2%, respectively. ELISA and CLIA can be used in the examination of non vaccinated flocks for S. enteritidis-infections as alternative to the bacteriological culture method. CLIA is distinguished for its fast and convenient procedure as well as for its wider measurement spectrum, while the indirect ELISA is almost as efficient as CLIA and requires less investment.

Pattern analysis of human Salmonella enteritidis infection.

Information on salmonella serovar, community, and date of isolation concerning 10,368 cases of S. enteritidis (SE) infection and 1163 cases of S. typhimurium (ST) infection reported in 1992 to the Salmonella Data Bank of the Land of Brandenburg have been analyzed for clusters and trends on case/time diagrams. A breakdown by district provided a suitable degree of "resolution" for discrimination of "Episodes of Increased Case Frequency" (EICF) and 7 days moving averages. Thus 39 of the 44 districts of the Land were included in the evaluation of SE cases. The population size of the remaining 5 districts was too high for clear episode discrimination. EICFs were subdivided into (a) 16 outbreaks (another 10 outbreaks occurred outside EICFs), which had also been identified and officially reported by local health services as a result of compulsory investigation of cases and their social environment, and (b) 44 "case accumulations" (ACCs), which were only identified by retrospective analysis of the case/time diagrams. By this procedure, three case categories of distinct properties have been found for SE transmission from the animal reservoir to the human population: outbreaks, ACCs, and "truly sporadic cases" scattered over the district outside outbreaks and ACCs (Table 3). Truly sporadic cases (Table 6) represented the largest proportion of SE cases. ACCs accounted for 37% and outbreaks, for 12%. The most striking result concerns the ACCs, which cover slightly larger geographical areas (mean: 3.5 communities) and last longer (mean: 3 weeks, but up to 7 weeks) than officially recorded outbreaks (means: 2 communities and 2 weeks). SE-ACCs differed from SE outbreaks also in the seasonal pattern. Otherwise, ACCs met outbreak characteristics including the average number of persons involved (mean: 64, for outbreaks: 42; Table 4). The results suggest that SE-ACCs represent an important and distinct element in the SE epidemic. This conclusion is supported by a comparison of the findings with results obtained by the same procedure for ST cases. ST outbreaks do not differ from ST-ACCs in any respect, and both types of ST-episodes are of significantly shorter duration and comprise less people than episodes due to SE. The public health significance of the SE-ACCs as a newly detected and particular element of the current SE epidemic is discussed. In view of the epidemiological significance, i.e. the high proportion of all SE cases involved, it appears justified to develop methods for the early detection of ACCs and the search for the "missing link" between the cases and their source at the community level.