查看更多>>摘要：? 2022 Elsevier B.V.Lack of hygiene and biosecurity measures in poultry farms has influence on the emergence of pathogens and antimicrobial use. Antimicrobial residues in poultry meat and their excretion by poultry can exert a selective pressure and the occurrence of multidrug resistant bacteria in litter. The objective of this study was to investigate the relationship between antimicrobial use and antimicrobial resistance using Escherichia coli as indicator isolated from poultry litter. From January to August, 2019, antimicrobial use was measured in 47 broiler farms based on daily dose (TIUDD) and animal daily dose (TIADD) methods. Antimicrobial susceptibility testing was performed on Escherichia coli isolated from poultry litter using the disk diffusion method. Overall, an average of 143.8 mg (ranging from 0.5 to 2061.79 mg/kg) of antimicrobials was used per kg of chicken produced, and treatment incidences of 69.7 daily doses per 1,000 broilers (44.44–106.35) and 87.3 daily doses per 1,000 broilers (1.74–376.43) were obtained for TIUDD and TIADD, respectively. After a susceptibility testing, 18 E. coli strains were resistant with a prevalence of 56.3% [95% CI: 39.1–73.5]. High levels of resistance were observed with doxycycline, ampicillin and norfloxacin which were observed to be mostly overdosed in farms. The high resistance of E. coli to ciprofloxacin (4/32: 13%), imipenem (6/32: 19%), levofloxacin (12/32: 38%) and ceftriaxone (22/32: 69%) which are second line treatment in hospital settings in Cameroon, and classified as Watch group by WHO, was associated to high AMR risk for public health in Cameroon. Intensification of health and educational sensitisation of farmers is essential to reduce widespread antimicrobial use in poultry farms and its impact public health.
查看更多>>摘要：? 2022 The AuthorsThere is increasing emphasis on the need to reduce antimicrobial use (AMU) on dairy farms to reduce the emergence of resistant bacteria which could compromise animal health and impact human medicine. In addition to AMU, the role of farm management is an area of growing interest and represents an alternative route for possible interventions. The aim of this study was to evaluate the impact of farm management practices and AMU on resistances of sentinel bacteria in bulk milk. Dairy farms from two, geographically separate locations within the British Isles were recruited as part of two study groups. Farm management data from study group 1 (n = 125) and study group 2 (n = 16) were collected by means of a face-to-face questionnaire with farmers carried out during farm visits. For study group 2, additional data on AMU was collated from veterinary medicine sales records. Sentinel bacterial species (Enterococcus spp. and E. coli), which have been reported to be of value in antimicrobial resistance (AMR) studies, were isolated from bulk tank milk to monitor antimicrobial susceptibilities by means of minimum inhibitory concentrations (MICs). MIC data for both groups was used to generate an overall “score” for each farm. For both groups, this overall farm mean MIC was used as the outcome variable to evaluate the impact of farm management and AMU. This was achieved through use of elastic net modelling, a regularised regression method which also featured a bootstrapping procedure to produce robust models. Inference of models was based on covariate stabilities and bootstrapped P-values to identify farm management and AMU practices that have significant effects on MICs of sentinel bacteria. Practices which were found to be of importance with respect to Enterococcus spp. included management of slurry, external entry of livestock to the dairy herd, use of bedding materials and conditioners, cubicle cleaning routines and antibiotic practices, including use of β-lactams and fluoroquinolones. Practices deemed to be of importance for E. coli MICs included cubicle and bedding management practices, teat preparation routines at milking and the milking procedure itself. We conclude that a variety of routine farm management practices are associated with MICs of sentinel bacteria in bulk milk. Amendment of these practices offers additional possible routes of intervention, alongside alterations to AMU, to mitigate the emergence and dissemination of AMR on dairy farms.
查看更多>>摘要：? 2022The recent introduction of the mastitis resistance trait into the US genomic selection index, Lifetime Net Merit 2018 (NM$), is expected to reduce the incidence of pathogen-specific clinical mastitis (PS-CM) incidence in U.S. dairy herds. To maximize the herd performance by reducing the PS-CM incidence, we compared the herd performance of 6 different replacement selection and PS-CM disease management strategies. We used an agent-based dairy simulation model in which the performance of individual animals was affected by the genetic traits included in the NM$. The genetic trends for the sires used affected the 15 yr herd performance. Each animal had a daily underlying base probability of contracting 5 different types of PS-CM (Staphylococcus aureus, Streptococcus dysgalactiae, Strep. uberis, Escherichia coli and Klebsiella) during lactation. On top of this base probability, the genetic and environmental components of the mastitis resistance trait (MAST) determined the actual incidence of PS-CM. Genomic estimated breeding values were simulated for each animal, based on which replacement selection decisions were made. The PS-CM associated milk loss, increased somatic cell count, decreased conception, and increased mortality and culling were accounted for in the simulated genomic estimated breeding values of different correlated production and reproduction traits included in NM$. The 6 different strategies illustrate the effects of replacement selection and PS-CM management decisions on PS-CM incidence, herd antibiotic use (ABU) and herd economics, over the course of 15 yr. Due to the genetic gain in the MAST, the incidence of PS-CM decreased on average by 10% points in 15 yr, which trickled down to overall reduction in herd ABU. Our PS-CM treatment and prevention strategies were assumed to be based on precise information about the 5 different PS-CM causative pathogens. Hence the corresponding ABU further decreased over the course of 15 years, when compared to blanket PS-CM therapies, which used antibiotics for all cases of CM. Our strategies illustrated the fact that herds combining genomic selection and following precise treatment and prevention strategies for PS-CM could reduce the 15-year cumulative ABU against PS-CM significantly. Capitalizing on the genetic gain in NM$ traits, the average profit per cow per year was higher on average by $1209 in year 15 when compared to year 0 for the 6 strategies simulated. We concluded that three decision strategies (genomic selection for NM$, selective therapy for PS-CM, and selective dry cow therapy for PS-CM prevention) when combined can reduce the incidence of PS-CM and the associated ABU, while increasing the profitability of the herd.
查看更多>>摘要：? 2022 The AuthorsLivestock movement between herds is one of the main routes for a pathogen to spread between herds. Understanding the contact structure, patterns and importance of specific individuals and classes can help assess dissemination risk, control, and surveillance measures. In this study, the cattle herd's contact structure in southern Chile was characterized based on the study of movement within one of the most important geographical regions for livestock production. Using Social Network Analysis, network measures of centrality, network cohesion and contact chains were estimated to identify essential features that can influence disease transmission among premises. Static and disaggregated by season networks were built for the entire set of nodes and for the Los Rios region animal flow only. For all networks, it was found that most nodes had a few movements; meanwhile, a small number of them were highly connected. Livestock markets have a powerful influence over the networks, being the most connected and central nodes, appearing as candidates for surveillance because of their possible role as super spreaders. Nodes attributes were associated with the likelihood of having high contact chains measures, such as herd class, location, and presence of markets anywhere on the contact chain. This work is the first deep analysis in livestock flows in Chile and shows the importance of animal movement data interpretation to assess pathogen risk spread in the country.
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