Epidemiological analysis of the dynamic and diversity of Salmonella spp. in five German pig production clusters using pheno- and genotyping methods: an exploratory study.

An exploratory study in five conventional pig production clusters was carried out to investigate the dynamic and diversity of Salmonella spp. within different production stages and sample site categories (pooled feces, direct and non-direct environment). Observing two production cycles per production cluster, a total of 1276 samples were collected along the pig production chain. Following a microbiological examination via culture, 2246 subcultures were generated out of 285 Salmonella positive samples and analysed by pheno- and genotyping methods. Based on a combination of serotyping, MLVA (multiple-locus variable-number tandem repeat (VNTR) analysis), PFGE (pulse-field gel electrophoresis) and MLST (multilocus sequence typing), an amount of 22.3% Salmonella positive samples were characterized in clonal lineages and its variants. Within each production cluster, one main clonal lineage could be identified and persisted over both production cycles with a large diversity of variants and a wide distribution in sample site categories and production stages. Results underline the importance of biosecurity with emphasis on the environment to prevent persistence and circulation of Salmonella within herds. Furthermore, the combined implementation of MLVA, PFGE and MLST with conventional culture techniques for isolate classification could be successfully applied as an effective and valuable tool for identifying similar pattern of Salmonella occurrence within pig production clusters.

Campylobacter spp., Yersinia enterocolitica, and Salmonella enterica and their simultaneous occurrence in German fattening pig herds and their environment.

Campylobacter spp., Salmonella enterica, and Yersinia enterocolitica are common causes of foodborne infections in humans with pork as a potential source. Monitoring programs at farm level are, to date, only implemented for S. enterica, while epidemiological knowledge of the other two pathogens is still lacking. This study aimed to assess the pathogen load (in the pigs' environment) in fattening pig herds, their simultaneous occurrence, and the occurrence of Campylobacter spp. and Y. enterocolitica in herds in different Salmonella risk categories. In 50 fattening pig herds in northern Germany, four pooled fecal samples and 10 swab samples from the pigs' direct environment (pen walls, nipple drinkers), indirect environment (hallways, drive boards), and flies and rodent droppings were collected from each herd and submitted for cultural examination. Campylobacter spp. were detected in 38.1% of fecal, 32.7% of direct environment, 5.3% of indirect environment, and 4.6% of flies/pests samples collected, and Y. enterocolitica in 17.1, 8.1, 1.2, and 3.1% and S. enterica in 11.2, 7.7, 4.1, and 1.5%, respectively. For Campylobacter spp., Y. enterocolitica, and S. enterica, 80, 48, and 32% of herds were positive, respectively; 22 herds were positive for both Campylobacter spp. and Y. enterocolitica, 12 for Campylobacter spp. and S. enterica, and 7 for Y. enterocolitica and S. enterica. There was no significant association between the pathogens at herd level. Campylobacter spp. and Y. enterocolitica were found more often in samples from the low Salmonella risk category (odds ratio, 0.51; confidence interval, 0.36 to 0.73, and 0.3, 0.17 to 0.57), and this was also the case for Y. enterocolitica at herd level (odds ratio, 0.08; confidence interval, 0.02 to 0.3). This study provides evidence that the pigs' environment should be accounted for when implementing control measures on farms against Campylobacter spp. and Y. enterocolitica. An extrapolation from the current Salmonella monitoring to the other two pathogens does not seem feasible.

Main risk factors for Salmonella-infections in pigs in north-western Germany.

Salmonellosis is one of the major zoonotic, food-borne diseases, among others, caused by pig derived food products. As infected pigs are one of the main sources of the introduction of the bacterium into the food chain, scientific research in the last years has focussed on identifying risk factors for infection as well as developing mitigation strategies on this level of production. In order to update the knowledge of the German situation by incorporating recent changes in the German pig industry, a case-control study was set up to identify the key contributing risk factors for farms located in the western part of Lower Saxony, the region with the highest pig density in Germany. Based on an extensive and systematic literature search, a comprehensive questionnaire with 302 questions concerning such topics as personnel hygiene, animal management, biosecurity, feeding management as well as cleaning and disinfection routines was utilized in a face-to-face interview on 104 case and 67 control farms. Within a stepwise forward selection process the preliminary identified factors were grouped contextually, associations between variables were calculated and multivariable logistic regression models were conducted. Identified risk factors were: the moving of individual animals during the fattening period (OR 5.3, CI 95% 1.35-20.35), not having a separate transporter for different age groups (OR 11.4, CI 95% 1.94-66.18) and pigs having contact to other animals (OR 4.3, CI 95% 1.39-12.96). The following factors were identified as being protective: not cleaning the transporter (OR 0.2, CI 95% 0.05-0.72) and not having clean boots available (OR 0.2, CI 95% 0.07-0.64). While this study was able to identify some factors which influence the Salmonella-infection of a herd, overall the process of analysis showed that the control of Salmonella on farm is due to a series of individual factors and therefore remains extremely complex.

One world--one health: the threat of emerging diseases. A European perspective.

The paper explains the concept of 'One world-one health', which aims at new paradigms to significantly reduce the risks to human and animal health due to globalization, to climate change, to the intensification of producing food with and from animals, and to changing human-animal interfaces. In Europe, the two major 'tools' for gradually implementing the principles of 'One world-one health' are (i) the application of all aspects of the so-called risk-based meat inspection taking into account the entire food chain from 'farm to fork', and (ii) the application of all aspects of the 'European Union Animal Health Strategy 2007-2013'.

A case-control study on the occurrence of Salmonella spp. in the environment of pigs.

The objective of this study was to compare the occurrence of Salmonella spp. found in the animal environment in pig herds with different Salmonella risks (61 herds with low seroprevalence, 81 herds with high seroprevalence) on a broad scale. The environmental samples were divided into two types: direct (n=1105) and indirect (n=1220) environmental samples. All samples were tested for Salmonella spp. via real-time polymerase chain reaction. Most of the indirect environments were more often Salmonella-positive in the high-seroprevalence herds than in the low-seroprevalence herds; significantly higher were compartment aisles [odds ratio (OR) 3·45, 95% confidence interval (CI) 1·61-7·41], driving boards (OR 3·06, 95% CI 1·38-6·92) and the central aisle of the barn (OR 3·03, 95% CI 1·35-6·83). The overall results show that especially areas in the indirect environment are the major, but mostly underestimated causes of residual Salmonella.

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.

[Occurrence of MRSA in pigs and in humans involved in pig production--preliminary results of a study in the northwest of Germany]. / Zum Vorkommen von MRSA bei Schweinen und bei Menschen mit beruflicher Exposition zum Schwein--Erste Ergebnisse einer Studie in Nordwestdeutschland.

In 2007, 678 pigs of all age groups out of 347 different farms from Lower Saxony and Northrhine-Westphalia and 86 persons occupationally exposed to pigs were investigated for their nasal colonisation with methicillin-resistant Staphylococcus areus (MRSA) by the Field Station for Epidemiology of the University of Veterinary Medicine Hannover and the Robert Koch-Institute. At the individual animal level, a frequency of positive results of 13% (n = 85 positive animals) and at the herd level, a frequency of positive results of 18% (n = 62 positive herds) were found. All isolates were assigned to the Multilocus Sequence Typing Type ST398. Within MRSA-positive herds, there were more MRSA-negative than MRSA-positive animals. Among the occupationally exposed persons (veterinarians, laboratory personnel and meat inspection personnel), 20 persons (23%) showed a nasal colonisation with MRSA ST398. A quite strong association between the intensity of the contact to pigs with the frequency of nasal colonisation in the occupationally exposed persons was detected. None of the animals or the humans nasally colonised by MRSA ST398 showed any clinical symptoms of a staphylococcal infection. Conclusions are drawn on the herd and intra-herd prevalence of the nasal colonisation of pigs with MRSA ST398 in pigs, but especially on which questions need to be addressed by further research.

[Results of the evaluation of food chain information for a risk-oriented meat inspection]. / Ergebnisse zur Bewertung von Lebensmittelketteninformationen als Entscheidungsgrundlage für die risikoorientierte Fleischuntersuchung.

In a scientific project 469 slaughter groups originating from 39 farmers with 37.222 pigs in total were investigated concerning the usefulness of the food chain information. A standard statement does not include enough relevant information for the official veterinarian in the slaughterhouse to do a risk-based meat inspection. Even the food chain information for the visual meat inspection, which has certain limits, shows only farms, where the animals are of good health. Groups of fattened pigs with an extreme high rate of mortality and many abnormalities mean a potential risk for food safety. So for a risk-based meat inspection it is affordable to develop information-systems with real mortality and finding rates and the use of drugs on the farm.

[Proposals for designing the food chain information for the implementation of the risk-oriented ante- and post-mortem meat inspection]. / Vorschläge zur Gestaltung der Lebensmittelketteninformationen für die Umsetzung der risikoorientierten Schlachttier- und Fleischuntersuchung.

The recent crises in the meat industry due to meat-associated risks such as salmonella, nitrofen and dioxin prove that the traditional ante- and post mortem inspection of slaughter animals and carcasses is not any longer able to recognise and prevent the risks of today. Therefore, the EU Commission has issued Reg. (EC) 853/2004 and Reg. (EC) 854/2004 that regulate the transition of the traditional meat inspection, which demands inspecting each individual carcass in the same way, to a risk-based meat inspection, which is using relevant pieces of information about the previous production stages for making risk-based decisions on the intensity of the inspection of slaughter pig batches. The new EU legislation is not any longer prescribing exactly the inspection procedure, but defines the food safety goals. The consequence is that there are still various ideas and opinions on how to implement a reasonable risk-based meat inspection, and, in particular, on how to design the "relevant food chain information". The present paper is describing the legal framework and the objectives of the risk-based meat inspection, and proposals for designing the food chain information for the implementation of the risk-based ante- and post-mortem meat inspection are made and discussed.

[Animal health and animal health care concepts changing over time]. / Tiergesundheit und Tiergesundheitsfürsorge im Wandel der Zeit.

The term "animal health", in particular applied to herds and flocks of food animals, needs to be newly defined in the light of the growing societal concerns with modern husbandry systems and animal welfare. This paper deals with a definition of animal health, which is extended to the well being of the animals and to pre-harvest food safety aspects. The future activities of food animal veterinarians have to meet the new demands and societal expectations discussed in this paper.

[Up-to-date information from the German QS salmonella monitoring and reduction programme]. / Bisherige Erkenntnisse aus dem QS-Salmonellenmonitoring- und -reduzierungsprogramm.

In the beginning, the history, objectives and basic principles of the samonella monitoring and reduction programme that has been developed and implemented since 2002 in the framework of the German cross-sectional quality management and assurance programme "QS" for the food chain are expained in detail. It is a semi-quantitative assessment of the intra-herd prevalence of animals (60 samples per slaughter pig herd and year) with antibodies against salmonella species. By means of this asessment, herds are assigned to one of three risk categories (I = low risk, II = medium risk, and III = high risk) in terms of the probability to introduce Salmonella spp. into the food chain via slaughter pigs. The assignment to the categories is the basis of salmonella-reducing intervention measures. The implementation of the programme is considerably behind the schedule by mid-2004. The reasons for the delay are explained and conclusions for the further development of the programme are drawn.

Estimating the prevalence of Salmonella spp. in swine herds--influence of sensitivity and specificity of Salmonella detection.

Information about the proportion of truly Salmonella-free herds is required for an evaluation of the epidemiological situation, the development of control strategies and their implementation. Findings regarding the presence of salmonellas in faeces and intestinal lymph nodes as well as the presence of Salmonella antibodies in meat juice from slaughtered pigs were obtained in the context of a study conducted by a number of institutes. These data were used for an analysis of the validity of data on the prevalence of infected animals within herds and on the prevalence of infected herds. The proportion of batches or herds with exclusively negative individual findings was found to depend not only on the true proportion of truly Salmonella-free animals within herds but quite essentially also on the distribution of the proportion of infected animals within herds, the sensitivity of the methods of examination and sample sizes. When taking into account the existing dependencies, it was found that among the swine, the real numbers of Salmonella carriers were much higher than shown by bacteriological and serological examination. Regarding salmonellosis in swine, also a number of contaminated herds must be expected which is far higher than that shown by the number of herds with positive findings in at least one animal. Even a low contamination of all or almost all herds would result in the numbers of 'negative' batches observed, i.e. batches with exclusively negative individual findings. A rating of the salmonella exposure of herds as high, low, or very low is possible and may, and should be, used for measures of consumer protection, irrespective of the proportion of truly Salmonella-free herds.

Evaluation of cross-protection afforded by a Salmonella Choleraesuis vaccine against Salmonella infections in pigs under field conditions.

This field study investigated the efficacy of a Salmonella Choleraesuis live vaccine (Argus SC) to reduce the number of infections with Salmonella. Twelve groups of about 380 pigs each were randomly allocated to either vaccination (V) or no vaccination (C). The vaccine was applied orally at 3 and 16 weeks. Forty pigs per group were blood sampled at 3, 10, 16, and 24 weeks to detect possible antibodies against Salmonella. The prevalence of Salmonella in the lymph nodes was the major variable. In the V groups, only 0.6% of the lymph nodes were positive, whereas 7.2% were positive in the C groups (p < 0.001). The percentage of seropositive pigs at 24 weeks (cut-off OD > 10) was 26% and 9% in the V and C groups, respectively (p < 0.001). The present study documented that vaccination with a live modified S. Choleraesuis vaccine is a useful tool to lower the prevalence of Salmonella in swine herds.

Traceability in the pig production chain.

Traceability is becoming a subject of significant interest to all those involved in pig production and marketing. Until the 1990s, the purposes of farm and animal identification were primarily related to implementation of breeding schemes and health programmes. More recently, other aspects have been emphasised, especially in certain countries where consumer demand has led to the need to trace animals and animal products along the food chain. Pigs are identified principally through ear tags and/or tattoos which are the common 'traditional' systems. However, an important research effort has been directed towards electronic identification. Electronic identification will allow telemetric data collection for quality care in pig production. The carcasses are identified after slaughter, and the meat can also be traced back later in the process. Examples of traceability systems for pigs in various countries are described by the authors.

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.

The "colorful" epidemiology of PRRS.

The paper describes the specifics of the epidemiology of the Porcine Reproductive and Respiratory Syndrome (PRRS), that is its "behavior" as a communicable disease in porcine populations, and compares them to the general epidemiological characteristics of communicable diseases. This analysis shows that infection with the PRRS virus "behaves" epidemiologically both as an epidemic and as an endemic disease: on the one hand it can spread like an epidemic in naïve populations, and on the other it seems to linger on infinitely in an affected population with its clinical expression varying from farm to farm like an endemic disease. The paper tries to draw "epidemiological" conclusions on the general methods for controlling and/or eradicating the disease, and to identify areas of further research.

Epidemiology and quality assurance application to food safety.

The conditions for the food industry, in general, are changing. Especially in industrialized countries, the safety and quality of food is increasingly becoming an issue of concern to the consumer. This paper describes the impact of the farm-to-table concept and the implementation of HACCP plans throughout the food production chain on animal production and veterinary profession, using the example of the pork production chain.

Public health and pork: pre-harvest food safety and slaughter perspectives.

Operating conditions for the food industry in general and pork production in particular are changing. The safety and quality of food are attracting increasing concern from the consumer, especially in industrialised countries. This paper describes the impact on the swine industry and on the veterinary profession of the 'farm-to-table' concept and the implementation of hazard analysis and critical control point plans throughout the food production chain.

[Health and environmental risks after the use of anti-infective agents and antiparasitic agents in domestic animal husbandry--avoidance strategies and ways out]. / Gesundheits- und Umweltrisiken nach Anwendung von Antiinfektiva und Antiparasitika in der Nutztierhaltung--Vermeidungsstrategien und Auswege.

At the beginning, the field of controversy is described, in which the usage of antimicrobials and antiparasitics are discussed, and the areas of their every day application are analysed. Based on the evaluation of the individual kinds of application of antimicrobial substances, conclusions for their usage are drawn, with their total avoidance not being the ultimate goal, but the scientifically founded use of these valuable substances according the the principle: 1. tailored to the correct diagnosis and 2. as little as possible, but always the amount that is needed.

[Considerations on the possible application of marker vaccines against swine fever in European Union]. / Uberlegungen zur möglichen Anwendung markierter Schweinepest-Impfstoffe in der EU.

The history of how the current control strategy against the Classical Swine Fever (CSF) in the EU came into being is described as well as the possibilities for applying conventional vaccines in the framework of this strategy. Concluding from these considerations, the preconditions for the permission of the application of marker vaccines are discussed and measures to be taken already before the registration of a marker vaccine are proposed.