Limited and judicious antimicrobial usage (AMU) is considered the key to saving the success of human and veterinary medicine in treating infections. With the limited alternatives for antimicrobials, farm biosecurity (and herd management) is considered a promising tool to mitigate the non-judicious AMU and to maintain animal health, production, and welfare. The present scoping review aims to analyse the effect of farm biosecurity on AMU in livestock systems and formulate recommendations. Peer-reviewed manuscripts published between 2001–2022 were analyzed using the PRISMA framework using PubMed, Scopus, and Science Direct databases. After applying the inclusion criteria, 27 studies were found to assess the effect of farm biosecurity (or management practices) on AMU at the herd/farm level in quantitative/semi-quantitative terms. These studies were carried out in 16 countries, of which 74.1% (20/27) were from 11 European countries. The highest number of studies were from pig farms [51.8% (14/27)], followed by poultry (chicken) farms [25.9% (7/27)], cattle farms [11.1% (3/27)], and a single study from a turkey farm. Two studies include both pig and poultry farms. Most of the studies were cross-sectional [70.4% (19/27)], seven were longitudinal, and one was a case-control study. Complex interactions were observed among factors influencing AMU, such as biosecurity measures, farm characteristics, farmers’ attitudes, availability of animal health services, stewardship, etc. A positive association between farm biosecurity and reduction in AMU was observed in 51.8% (14/27) of the studies, and 18.5% (5/27) showed that improvement in farm management practices was associated with a reduction in AMU. Two studies highlighted that coaching and awareness among farmers might lead to a decrease in AMU. A single study on economic assessment concluded biosecurity practices as a cost-effective way to reduce AMU. On the other hand, five studies showed an uncertain or spurious association between farm biosecurity and AMU. We recommend the reinforcement of the concept of farm biosecurity, especially in lower- and middle-income countries (LMICs). Further, there is a need to strengthen the evidence on the association between farm biosecurity and AMU in region- and species-specific farm settings.

Implementing biosecurity measures in the pig production is crucial to optimize animal health and reduce antimicrobial usage. A legal framework may help to ensure all stakeholders understand the need of biosecurity measures and to implement them correctly. Limited knowledge is available about how implementation of biosecurity measures is regulated in European countries. Therefore, the aim of this study was to identify which biosecurity measures were mandatory by national legislation and/or by pig sector organizations of European countries for the intensive pig production under normal circumstances (i.e. no (threat of) disease outbreaks). A questionnaire including 51 biosecurity measures, 32 on external and 19 on internal, was developed and sent to national country representatives. Twenty-four European countries, of which 18 belonging to the European Union, indicated which biosecurity measures were mandatory by law. Four countries, France, Spain, Italy and Romania had a single national pig-specific biosecurity legislation, while in the other countries multiple legislations had to be consulted to complete the questionnaire. In general, there was a high heterogeneity in the number of measures that were mandatory by law per country. Most biosecurity measures addressed in the national legislation focused on external biosecurity and were measures that can be easily audited when conducting a farm visit such as the presence of a hygiene lock, fencing around the farm and the existence of documentation. A significant (p < 0.001) positive correlation was observed between the presence of external and internal biosecurity measures in the legislation. Yet, no significant association was observed between the number of biosecurity measures present in the national legislation and the size of the pig production. Fourteen countries indicated which biosecurity measures were required by pig sector organizations for intensive pig farms. The median number of biosecurity measures mandatory by pig sector organizations but not by law was 13 with a minimum of one measure in Germany and a maximum of 24 in Croatia. Different countries apply different strategies to increase the level of biosecurity. Further research is needed to investigate the impact of the different strategies on the implementation of biosecurity on intensive pig farms in the countries.

Mycoplasma hyopneumoniaeis the primary agent of enzootic pneumonia in pigs. Although cell mediated immunity (CMI) may play a role in protection againstM. hyopneumoniae, its transfer from sows to their offspring is poorly characterized. Therefore, maternally-derived CMI was studied in piglets from vaccinated and non-vaccinated sows. The potential influence of cross-fostering before colostrum ingestion on the transfer of CMI from dam to piglets was also investigated. SixM. hyopneumoniaevaccinated sows from an endemically infected herd and 47 of their piglets, of which 24 piglets were cross-fostered, were included, as well as three non-vaccinated control sows from anM. hyopneumoniae-free herd and 24 of their piglets. Vaccinated sows received a commercial bacterin intramuscularly at 6 and 3 weeks prior to farrowing. The TNF-α, IFN-γ and IL-17A production by different T-cell subsets in blood of sows, colostrum and blood of piglets was assessed using a recall assay. In blood of sows cytokine producing T-cells were increased uponM. hyopneumoniaevaccination. Similarly,M. hyopneumoniae-specific T-cells were detected in blood of 2-day-old piglets born from these vaccinated sows. In contrast, noM. hyopneumoniae-specific cytokine producing T-cells were found in blood of piglets from control sows. No difference was found inM. hyopneumoniae-specific CMI between cross-fostered and non-cross-fostered piglets. In conclusion, differentM. hyopneumoniae-specific T-cell subsets are transferred from the sow to the offspring. Further studies are required to investigate the role of these transferred cells on immune responses in piglets and their potential protective effect againstM. hyopneumoniaeinfections.

Mycoplasma hyopneumoniaeis the primary agent of enzootic pneumonia in pigs. To minimize the economic losses caused by this disease,M. hyopneumoniaevaccination is commonly practiced. However, the persistence ofM. hyopneumoniaevaccine-induced immunity, especially the cell-mediated immunity, till the moment of slaughter has not been investigated yet. Therefore, on two commercial farms, 25 pigs (n = 50) received a commercial bacterin intramuscularly at 16 days of age. Each month, the presence ofM. hyopneumoniae-specific serum antibodies was analyzed and the proliferation of and TNF-α, IFN-γ and IL-17A production by different T cell subsets in blood was assessed using recall assays. Natural infection withM. hyopneumoniaewas assumed in both farms. However, the studied pigs remainedM. hyopneumoniaenegative for almost the entire trial. Seroconversion was not observed after vaccination and all pigs became seronegative at two months of age. The kinetics of the T cell subset frequencies was similar on both farms.Mycoplasma hyopneumoniae-specific cytokine-producing CD4⁺CD8⁺T cells were found in blood of pigs from both farms at one month of age but decreased significantly with increasing age. On the other hand, T cell proliferation after in vitroM. hyopneumoniaestimulation was observed until the end of the fattening period. Furthermore, differences in humoral and cell-mediated immune responses afterM. hyopneumoniaevaccination were not seen between pigs with and without maternally derived antibodies. This study documents the long-termM. hyopneumoniaevaccine-induced immune responses in fattening pigs under field conditions. Further research is warranted to investigate the influence of a natural infection on these responses.

Background: Dam-to-piglet transmission plays an important role in the epidemiology of enzootic pneumonia on farms. AlthoughMycoplasma hyopneumoniae(M. hyopneumoniae) infections in breeding animals are often subclinical, their control could have a positive effect onM. hyopneumoniaeinfection levels in fattening pigs. This study investigated the presence ofM. hyopneumoniaein the breeding population of ten Belgian farrow-to-finish farms suspected by the herd veterinarian to beM. hyopneumoniaeinfected. Gilt vaccination againstM. hyopneumoniaeprior to first insemination was practiced on nine of the ten farms. At four different time points in the reproductive cycle 20 animals were sampled on each farm, namely 30–40 days of gestation, 75–85 days of gestation, 3–5 days after farrowing, and 1–3 days after weaning. In total, tracheobronchial swabs and blood samples were collected from 344 gilts and 456 sows (n = 80/farm). Swabs were analysed for the presence ofM. hyopneumoniaeDNA using nested PCR andM. hyopneumoniae-specific antibodies were detected in serum with a commercial ELISA. Generalized linear mixed models with farm as random factor were used to test the effect of time point in the reproductive cycle and parity onM. hyopneumoniaePCR prevalence and seroprevalence.Results: M. hyopneumoniaePCR prevalence ranged between 0% and 43.8% at the farm level and the seroprevalence between 32.5% and 93.8%. Gilts were significantly moreM. hyopneumoniaePCR positive than sows at the 2-4th parity (P = 0.02) and > 4th parity (P = 0.02). At 30–40 days of gestation, significantly more breeding animals were PCR positive as compared to 75–85 days of gestation (P = 0.04), 3–5 days after farrowing (P = 0.02) and 1–3 days after weaning (P = 0.02). Gilts had significantly more oftenM. hyopneumoniae-specific antibodies than sows (P = 0.03).Conclusions: M. hyopneumoniaePCR prevalence varied a lot between farms and due to gilt vaccination the number of animals withM. hyopneumoniae-specific antibodies was high on most farms. Gilts were more oftenM. hyopneumoniaePCR positive than sows and positive animals were mostly found at 30–40 days of gestation. This emphasizes the importance of a sufficiently long quarantine period and proper gilt acclimation practices before introducing gilts to the sow herd.