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Antimicrobial resistance (AMR) threatens our public health and is mainly driven by antimicrobial usage (AMU). For this reason the World Health Organization calls for detailed monitoring of AMU over all animal sectors involved. Therefore, we aimed to quantify AMU on turkey farms. First, turkey-specific Defined Daily Dose (DDDturkey) was determined. These were compared to the broiler alternative from the European Surveillance of Veterinary Antimicrobial Consumption (DDDvet), that mention DDDvet as a proxy for other poultry species. DDDturkey ranged from being 81.5% smaller to 48.5% larger compared to its DDDvet alternative for broilers. Second, antimicrobial treatments were registered on 60 turkey farms divided over France, Germany and Spain between 2014 and 2016 (20 flocks per country). Afterwards, AMU was quantified using treatment incidence (TI) per 100 days. TI expresses the percentage of the rearing period that the turkeys were treated with a standard dose of antimicrobials. Minimum, median and maximum TI at flock level and based on DDDturkey = 0.0, 10.0 and 65.7, respectively. Yet, a huge variation in amounts of antimicrobials used at flock level was observed, both within and between countries. Seven farms (12%) did not use any antimicrobials. Aminopenicillins, polymyxins, and fluoroquinolones were responsible for 72.2% of total AMU. The proportion of treating farms peaked on week five of the production cycle (41.7%), and 79.4% of the total AMU was administered in the first half of production. To conclude, not all DDDvet values for broilers can be applied to turkeys. Additionally, the results of AMU show potential for reducing and improving AMU on turkey farms, especially concerning the usage of critically important antimicrobials.

Objectives: Farm-level quantification of antimicrobial usage (AMU) in pig farms. Methods: In a cross-sectional study, AMU data on group treatments administered to a single batch of fattening pigs from birth to slaughter (group treatment data) and antimicrobials purchased during 1 year (purchase data) were collected at 180 pig farms in nine European countries. AMU was quantified using treatment incidence (TI) based on defined (DDDvet) and used (UDDvet) daily doses and defined (DCDvet) and used (UCDvet) course doses. Results: The majority of antimicrobial group treatments were administered to weaners (69.5% of total TIDDDvet) followed by sucklers (22.5% of total TIDDDvet). AMU varied considerably between farms with a median TIDDDvet of 9.2 and 7.1 for a standardized rearing period of 200 days based on group treatment and purchase data, respectively. In general, UDDvet and UCDvet were higher than DDDvet and DCDvet, respectively, suggesting that either the defined doses were set too low or that group treatments were often dosed too high and/or administered for too long. Extended-spectrum penicillins (31.2%) and polymyxins (24.7%) were the active substances most often used in group treatments, with the majority administered through feed or water (82%). Higher AMU at a young age was associated with higher use in older pigs. Conclusions: Collecting farm-level AMU data of good quality is challenging and results differ based on how data are collected (group treatment data versus purchase data) and reported (defined versus used daily and course doses).

A nationwide study on the occurrence of ESBL/AmpC in non-hospitalized horses in the Netherlands was performed. Molecular characterization was done and questionnaires were analyzed to identify factors associated with carriage. In total, 796 horse owners were approached, of which 281 submitted a fecal sample of their horse(s), resulting in 362 samples. All samples were cultured qualitatively in LB broth and subsequently on MacConkey agar, both supplemented with 1 mg/L cefotaxime (LB+ and MC+). Positive samples were subsequently cultured quantitatively on MC+. Initial ESBL/AmpC screening was performed by PCR, followed by whole genome sequencing on selected strains. Association between ESBL/AmpC carriage and questionnaire items were analyzed using a univariate generalized estimating equation (GEE) regression analysis, followed by a multiple GEE model for relevant factors. In total, 39 out of 362 samples (11%) were positive for ESBL/AmpC. blaCTX-M-1-carrying isolates were obtained from 77% of positive samples (n=30). Other ESBL/AmpC genes observed were blaCTX-M-2, blaCTX-M-14, blaCTX-M-15, blaCTX-M-32, blaSHV-12, blaCMY-2, blaACT-10. A high association between the presence of blaCTX-M-1 andIncHI1 plasmids was observed (46% of samples; n=18). Based on core genome analysis (n=48 isolates), six E. coli clusters were identified, of which three represented 80% of the isolates. A negative association between ESBL/AmpC carriage and horses being in contact with other horses at a different site was observed. The presence of a dog on the premises and housing in a more densely human-populated region were positively associated. IMPORTANCE Extended spectrum ß-lactamases (ESBL) are widespread in the human and animal population and the environment. Many different ESBL-variants exist. The dissemination of ESBLs within and between populations and the environment is also largely influenced by genetic mobile elements (e.g. plasmids) that facilitate spread of these ESBLs. In order to identify potential attributable ESBL-sources for e.g. the human population, it is important to identify the different ESBL-variants, the bacteria carrying them and the potential risk factors for ESBL carriage from other potential sources. This nationwide study focuses on ESBL-carriage in the open horse population and investigated the molecular characteristics, geographical distribution throughout the Netherlands and potential risk factors for fecal ESBL-carriage in horses. This data can be used for future attribution studies in order to reduce potential transmission of ESBL-producing bacteria between sources.

A nationwide study on the occurrence of extended-spectrum β-lactamase (ESBL)/AmpC in nonhospitalized horses in the Netherlands was performed. Molecular characterization was done, and questionnaires were analyzed to identify factors associated with carriage. In total, 796 horse owners were approached; 281 of these submitted a fecal sample from their horse(s), resulting in 362 samples. All samples were cultured qualitatively in Luria-Bertani (LB) broth and subsequently on MacConkey agar, both supplemented with 1 mg/liter cefotaxime (LB+ and MC+). Positive samples were subsequently cultured quantitatively on MC+. Initial extended-spectrum-β-lactamase (ESBL)/AmpC screening was performed by PCR, followed by whole-genome sequencing on selected strains. Associations between ESBL/AmpC carriage and questionnaire items were analyzed using a univariate generalized estimating equation (GEE) regression analysis, followed by a multiple GEE model for relevant factors. In total, 39 of 362 samples (11%) were determined to be positive for ESBL/AmpC. blaCTX-M-1-carrying isolates were obtained from 77% of positive samples (n = 30). Other ESBL/AmpC genes observed included blaCTX-M-2, blaCTX-M-14, blaCTX-M-15, blaCTX-M-32, blaSHV-12, blaCMY-2, and blaACT-10 A high association between the presence of blaCTX-M-1 and IncHI1 plasmids was observed (46% of samples; n = 18). Based on core genome analysis (n = 48 isolates), six Escherichia coli clusters were identified, three of which represented 80% of the isolates. A negative association between ESBL/AmpC carriage and horses being in contact with other horses at a different site was observed. The presence of a dog on the premises and housing in a more densely human-populated region were positively associated.IMPORTANCE Extended-spectrum β-lactamases (ESBLs) are widespread in human and animal populations and in the environment. Many different ESBL variants exist. The dissemination of ESBLs within and between populations and the environment is also largely influenced by genetic mobile elements (e.g., plasmids) that facilitate spread of these ESBLs. In order to identify potential attributable ESBL sources for, e.g., the human population, it is important to identify the different ESBL variants, the bacteria carrying them, and the potential risk factors for ESBL carriage from other potential sources. This nationwide study focuses on ESBL carriage in the open horse population and investigated the molecular characteristics, geographical distribution throughout the Netherlands, and potential risk factors for fecal ESBL carriage in horses. These data can be used for future attribution studies in order to reduce potential transmission of ESBL-producing bacteria between sources.

Animal health and welfare have become topics of increasing public interest. Especially improvements in the health and welfare of food-producing animals are currently being intensively researched. To be able to routinely assess the quality of health and welfare of individual pig herds for benchmarking purposes in a simple and robust way, a short and easy to use measuring tool is needed. Since the very elaborate assessment tools of the Welfare Quality (R) (WQ) project (FOOD-CT-2004-506508) are too time-consuming for an assessment during a regular veterinary herd visit, easy to record indicators were targetly selected and supplemented by new elements in order to combine a number of measurements in one indicator, using the theoretical concept of iceberg indicators, which are thought to trigger further scrutiny into the management of pig herds that reveal potential deficiencies. The thus created simplified Herd Health and Welfare Index (HHWI) shows a theoretical range of 10 (very good) to a maximum of 30 (very bad) index points. It has been demonstrated that it can be used as an animal welfare measurement tool to compare herds within a group of pig herds that are measured by the same set of criteria. The HHWI has proven to be a rough, semi-quantitative, and a less elaborate tool than, for example, the complete protocol of the WQ-project. All in all, the HHWI has a broader range of application possibilities than the WQ-protocol due to its reduced number of criteria for the assessment of the health and welfare status of pig herds.

Animal health and welfare have become topics of increasing public interest. Especially improvements in the health and welfare of food-producing animals are currently being intensively researched. To be able to routinely assess the quality of health and welfare of individual pig herds for benchmarking purposes in a simple and robust way, a short and easy to use measuring tool is needed. Since the very elaborate assessment tools of the Welfare Quality (R) (WQ) project (FOOD-CT-2004-506508) are too time-consuming for an assessment during a regular veterinary herd visit, easy to record indicators were targetly selected and supplemented by new elements in order to combine a number of measurements in one indicator, using the theoretical concept of iceberg indicators, which are thought to trigger further scrutiny into the management of pig herds that reveal potential deficiencies. The thus created simplified Herd Health and Welfare Index (HHWI) shows a theoretical range of 10 (very good) to a maximum of 30 (very bad) index points. It has been demonstrated that it can be used as an animal welfare measurement tool to compare herds within a group of pig herds that are measured by the same set of criteria. The HHWI has proven to be a rough, semi-quantitative, and a less elaborate tool than, for example, the complete protocol of the WQ-project. All in all, the HHWI has a broader range of application possibilities than the WQ-protocol due to its reduced number of criteria for the assessment of the health and welfare status of pig herds.

Objectives To control the emerging threat of antimicrobial resistance, international policy appeals for appropriate monitoring of antimicrobial usage (AMU) at supranational, species and farm level. The aim of this study was to quantify AMU in broilers at farm and flock level in nine European countries. Methods Antimicrobial treatment data of one flock and purchased antimicrobials over one year were collected at 181 European broiler farms. Afterwards AMU was quantified using treatment incidence (TI) per 100 days based on Defined Daily Dose (DDDvet), Defined Course Dose (DCDvet) or Used Daily Dose (UDDvet) values. Total AMU at flock level was obtained by summing the TIDDDvet of all treatments in the sampled flock (TIDDDvetFl*). Results The median TIDDDvetFl* was 9.0 (95% CI 5.5-10.8), meaning that broilers were treated with antimicrobials during 9% of their rearing period. TIDDDvetFl* varied considerably within and between countries. However, in every country at least one untreated flock was present. Average TIDDDvetFl* at country level ranged from 3.3 to 36.7. Polymyxins, extended-spectrum aminopenicillins and fluoroquinolones were the most used antimicrobials, accounting for 26%, 26% and 18% of total AMU, respectively. Twenty-six percent of the farms started a treatment on day 1 of production, and 49% of overall AMU was administered within the first week. Conclusions Results show that rearing broilers without AMU is feasible. However, a huge variation in AMU in terms of amount, moment of administration and antimicrobial classes was observed. This shows that there is still ground to be covered when it comes to AMU on broiler farms.

OBJECTIVES: Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) emergence is a major public health concern. This study was aimed at assessing risk factors for persistently carrying MRSA in veal calf farmers and their family members. We also evaluate the dynamics of MRSA environmental load during the veal-calf production cycle. DESIGN: Observational, longitudinal, repeated cross-sectional study. SETTING: 52 veal calf farms in the Netherlands. PARTICIPANTS: From the end of 2010 to the end of 2011, a total of 211 farmers, family members and employees were included in the study. PRIMARY OUTCOME AND SECONDARY OUTCOME MEASURES: Nasal swabs were taken from participants on days 0, 4, 7 and week 12. A persistent MRSA carrier was defined as a person positive for MRSA on days 0, 4 and 7. Participants filled in an extensive questionnaire to identify potential risk factors and confounders. For estimation of MRSA prevalence in calves and environmental contamination, animal nasal swabs and Electrostatic Dust Collectors were taken on day 0 and week 12. RESULTS: The presence of potential animal reservoirs (free-ranging farm cats and sheep) and the level of contact with veal calves was positively associated with persistent MRSA carriage. Interestingly, at the end of the study (week 12), there was a twofold rise in animal prevalence and a significantly higher MRSA environmental load in the stables was found on farms with MRSA carriers. CONCLUSIONS: This study supports the hypothesis that environmental contamination with MRSA plays a role in the acquisition of MRSA in farmers and their household members and suggests that other animal species should also be targeted to implement effective control strategies.

Objectives: Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) emergence is a major public health concern. This study was aimed at assessing risk factors for persistently carrying MRSA in veal calf farmers and their family members. We also evaluate the dynamics of MRSA environmental load during the veal-calf production cycle. Design: Observational, longitudinal, repeated crosssectional study. Setting: 52 veal calf farms in the Netherlands. Participants: From the end of 2010 to the end of 2011, a total of 211 farmers, family members and employees were included in the study. Primary outcome and secondary outcome measures: Nasal swabs were taken from participants on days 0, 4, 7 and week 12. A persistent MRSA carrier was defined as a person positive for MRSA on days 0, 4 and 7. Participants filled in an extensive questionnaire to identify potential risk factors and confounders. For estimation of MRSA prevalence in calves and environmental contamination, animal nasal swabs and Electrostatic Dust Collectors were taken on day 0 and week 12. Results: The presence of potential animal reservoirs (free-ranging farm cats and sheep) and the level of contact with veal calves was positively associated with persistent MRSA carriage. Interestingly, at the end of the study (week 12), there was a twofold rise in animal prevalence and a significantly higher MRSA environmental load in the stables was found on farms with MRSA carriers. Conclusions: This study supports the hypothesis that environmental contamination with MRSA plays a role in the acquisition of MRSA in farmers and their household members and suggests that other animal species should also be targeted to implement effective control strategies.

Colonization of Methicillin-Resistant Staphylococcus aureus (MRSA) in food producing animals has public health implications, but intervention targets have not yet been identified. In this field study occurrence and dynamics of MRSA in veal calves were investigated longitudinally on three farms. Determinants generally associated with MRSA carriage, such as environmental exposure and antimicrobial use, were explored. In addition, the reliability and reproducibility of MRSA detection in nasal samples from veal calves were investigated as well as the additional value of rectal samples to establish MRSA status of an individual animal. On these three farms, MRSA prevalence and MRSA air loads in stables rapidly increased during the production cycle, especially after releasing calves from their individual houses, but not simultaneously with or directly after treatment with antimicrobials. These observations constitute the hypothesis that antimicrobial use may not necessarily be the only condition for MRSA transmission in veal calves, but indicate that other factors may contribute to transmission as well. MRSA in calves was present both nasally and rectally. The reproducibility and repeatability of the nasal samples were moderate. The results of this study give a better understanding of the dynamics of MRSA in a field situation.

Traditionally,Methicillin-resistant Staphylococcus aureus (MRSA) has been considered as a hospital-associated pathogen (HA-MRSA). However, since 2004, MRSA has been found to be emerging in livestock (LA-MRSA), particularly pigs and veal calves. Animals have the capacity to act as reservoirs of MRSA, and potentially transmit this bacterium to humans in close contact with MRSA-colonized animals. This thesis focuses on MRSA in veal calf farming. The main aim of this thesis was to investigate associations between determinants and ST398 MRSA carriage in both humans and veal calves and their inter-relationship. Furthermore the persistence and dynamics of MRSA carriage in both human and veal calves were quantified. Calves were more often MRSA carrier when treated with antibiotics. However, several age-related- and farm management factors seemed to be correlated with use of antimicrobials in calves. On the other hand, farm hygiene was associated with a lower prevalence of MRSA in calves. Longitudinal data showed that MRSA prevalence and MRSA air loads in stables rapidly increased during the production cycle, especially after releasing calves from their individual houses, but not simultaneously with or directly after treatment with antimicrobials. A direct relationship between human and animal MRSA carriage was demonstrated; the number of MRSA positive calves on the farm and human carriage was positively associated. Human MRSA carriage was strongly dependent on the duration of animal contact and exposure. Human persistence and dynamics of MRSA ST398 was investigated after both short- and long-term exposure to MRSA positive animals. LA-MRSA acquisition after short-term (up to 3 hours per day maximally) occupational exposure is frequent. However, the majority of people who acquire LA-MRSA during occupational exposure, test negative for MRSA again within 24 hours. In farmers, who are long-term exposed to MRSA positive animals, the presence of LA-MRSA is strongly animal-exposure related. During absence of animal contact, MRSA prevalence decreased rapidly, which suggests that LA-MRSA is a poor persistent colonizer in humans. The findings in this thesis provide important insights that add to our understanding of LA-MRSA carriage in animals and humans. Antimicrobial use in calves is associated with higher MRSA prevalence. However, future research should be focussed on the quantitative contribution of specific antibiotic classes or dosages to MRSA occurrence in livestock environments. In addition, to reduce MRSA occurrence in veal farming, optimizing the complex structure of the veal calf production chain needs specific attention. Our data point out that exposure plays a major role in MRSA carriage in humans but it seemed that MRSA of ST398 is not a persistent colonizer in humans. This is in line with other studies in which a low nosocomial transmission rate of ST398 MRSA was demonstrated. These findings implicated that control measures as described in the Search and Destroy policy could be less stringent. However, the exact ST398-related disease risk for farmers remains unclear and needs further exploration. The ongoing evolution and development of ST398 MRSA suggests that adaptation to the human host might be happening and therefore close monitoring of its evolution and surveillance over time will be required.

INTRODUCTION: The presence of Livestock Associated MRSA (LA-MRSA) in humans is associated with intensity of animal contact. It is unknown whether the presence of LA-MRSA is a result of carriage or retention of MRSA-contaminated dust. We conducted a longitudinal study among 155 veal farmers in which repeated nasal and throat swabs were taken for MRSA detection. Periods with and without animal exposure were covered. METHODS: Randomly, 51 veal calf farms were visited from June-December 2008. Participants were asked to fill in questionnaires (n = 155) to identify potential risk factors for MRSA colonisation. Nasal and throat swabs were repeatedly taken from each participant for approximately 2 months. Swabs were analysed for MRSA and MSSA by selective bacteriological culturing. Spa-types of the isolates were identified and a ST398 specific PCR was performed. Data were analyzed using generalized estimation equations (GEE) to allow for correlated observations within individuals. RESULTS: Mean MRSA prevalence was 38% in farmers and 16% in family members. Presence of MRSA in farmers was strongly related to duration of animal contact and was strongly reduced in periods with absence of animal contact (-58%). Family members, especially children, were more often carriers when the farmer was a carrier (OR = 2, P

In 2007 is Meticillineresistente Staphylococcus aureus (MRSA) voor het eerst bij vleeskalveren en vleeskalverhouders in Nederland aangetoond. Sinds de eerste waarnemingen van dragerschap zijn meerdere studies uitgevoerd die samengevat worden in dit artikel. Er blijkt een direct verband te zijn tussen MRSA-dragerschap bij kalveren en MRSA-dragerschap bij mensen die wonen of werken op een vleeskalverhouderij. MRSA-dragerschap bij mensen blijkt sterk geassocieerd te zijn met het aantal MRSA-positieve dieren op het bedrijf. Als er geen of minder contact met dieren is zoals tijdens een vakantie of leegstand neemt de prevalentie van MRSA bij de mens af. Het grondig reinigen en desinfecteren van de stallen tijdens de leegstandperiode lijkt het vóórkomen van MRSA in vleeskalveren te reduceren. Vleeskalveren die behandeld zijn met antibiotica zijn vaker drager van MRSA dan kalveren die niet behandeld zijn. De relatie met antibioticumgebruik is echter niet eenduidig. In een longitudinale pilotstudie werd aangetoond dat de MRSA-prevalentie binnen een koppel niet sterk stijgt tijdens of direct na een antibioticabehandeling. Potentiële interventies die moeten leiden tot een lagere MRSA-prevalentie bij vleeskalverhouders liggen in een verminderd antibioticumgebruik bij dieren en hygiëne op de bedrijven.

The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) carriage in pig and veal calf farmers in the Netherlands is estimated at 25 to 35%. However, no information is available about MRSA carriage in humans after short-term occupational exposure to pigs or veal calves. This study examines the prevalence and duration of MRSA acquisition after short-term intensive exposure to pigs or veal calves for persons not exposed to livestock on a daily basis. The study was performed with field workers who took samples from the animals or the animal houses in studies on MRSA prevalence in pig and veal farms. They were tested for MRSA by taking nasal samples before, directly after, and 24 h after they visited the farms. There were 199 sampling moments from visits to 118 MRSA-positive farms. Thirty-four of these visits (17%) resulted in the acquisition of MRSA. Thirty-one persons (94%) appeared negative again after 24 h. There were 62 visits to 34 MRSA-negative farms; none of the field workers acquired MRSA during these visits. Except for that from one person, all spa types found in the field workers were identical to those found in the animals or in the dust in animal houses and belonged to the livestock-associated clone. In conclusion, MRSA is frequently present after short-term occupational exposure, but in most cases the strain is lost again after 24 h.

INTRODUCTION: Recently a specific MRSA sequence type, ST398, emerged in food production animals and farmers. Risk factors for carrying MRSA ST398 in both animals and humans have not been fully evaluated. In this cross-sectional study, we investigated factors associated with MRSA colonization in veal calves and humans working and living on these farms. METHODS: A sample of 102 veal calf farms were randomly selected and visited from March 2007-February 2008. Participating farmers were asked to fill in a questionnaire (n = 390) to identify potential risk factors. A nasal swab was taken from each participant. Furthermore, nasal swabs were taken from calves (n = 2151). Swabs were analysed for MRSA by selective enrichment and suspected colonies were confirmed as MRSA by using slide coagulase test and PCR for presence of the mecA-gene. Spa types were identified and a random selection of each spa type was tested with ST398 specific PCR. The Sequence Type of non ST398 strains was determined. Data were analyzed using logistic regression analysis. RESULTS: Human MRSA carriage was strongly associated with intensity of animal contact and with the number of MRSA positive animals on the farm. Calves were more often carrier when treated with antibiotics, while farm hygiene was associated with a lower prevalence of MRSA. CONCLUSION: This is the first study showing direct associations between animal and human carriage of ST398. The direct associations between animal and human MRSA carriage and the association between MRSA and antimicrobial use in calves implicate prudent use of antibiotics in farm animals.

The presence of Livestock Associated MRSA (LA-MRSA) in humans is related to intensity of animal contact. Little is known of the persistence and dynamics of LA-MRSA carriage. A longitudinal study was conducted among 155 veal farmers who were sampled with repeated nasal and throat swabs for MRSA detection. Periods with and without animal contact were covered. The presence of LA-MRSA in farmers is strongly animal-contact related. The rapidly decreasing MRSA prevalence during absence of animal contact suggests that LA-MRSA is a poor persistent colonizer in humans. These results are of relevance for MRSA control strategies.

Since the emergence of MRSA in livestock, screening of animals for the detection of MRSA is widely practised. Different procedures are published for animal samples but a systematic comparison of methods has not been performed. The objective of this study was to compare three available commonly used procedures and three chromogenic agars; for detecting MRSA in nasal swabs from pigs (n = 70) and veal calves (n = 100). Procedures 1 and 2 used a pre-enrichment comprising Mueller Hinton broth with 6.5% NaCl followed by selective enrichment with 4 mu g/ml oxacillin + 75 mu g/ml aztreonam (procedure 1) and 5 mu g/ml ceftizoxime + 75 mu g/ml aztreonam (procedure 2) respectively. Procedure 3 used a selective enrichment broth only, containing 4% NaCl, 5 mu g/ml ceftizoxime + 50 mu g/ml aztreonam. After selective enrichment, media were streaked on to three different chromogenic agars. Significantly more MRSA were found for pig as well as for veal calf samples with procedures 1 and 2. No significant differences were found between procedures 1 and 2. For nasal swabs from pigs significantly more MRSA-positive samples were found when MRSA Screen (Oxoid) or MRSASelect (TM) (Bio-Rad) agars were used compared to MSRA ID (bioMerieux). For calf samples no significant differences between the different agars were found. In conclusion, the results of this study show that procedures 1 and 2, both using additional high salt pre-enrichment are superior and should be recommended for MRSA detection in nasal swabs from pigs and veal calves. The preferred choice of chromogenic agar depends on the sample matrix.