How do pig farms maintain low Salmonella prevalence: a case-control study.

Salmonella prevalence in UK pigs is amongst the highest in Europe, highlighting the need to investigate pig farms which have managed to maintain a low Salmonella seroprevalence. A total of 19 pig farms that had a consistently low (<10%) seroprevalence over 4 years (named Platinum farms) were compared against 38 randomly selected Control farms, chosen to match the same distribution of production types and geographical distribution of the Platinum farms. Each farm was visited and floor faeces and environmental samples were collected. It was shown that Control farms had a significantly higher median percentage of pooled faecal samples positive for Salmonella compared with the Platinum farms (12.1% and 0.4% for pooled faecal samples, respectively) and were more likely to have serovars of public health importance detected (S. Typhimurium/ monophasic variants or S. Enteritidis). Considering the comprehensive on-farm sampling, the identification of farms negative for Salmonella, along with the identification of those that had maintained low prevalence over a long period is important. The risk factor analyses identified pelleted feed, feed deliveries crossing farm perimeter and regular antibiotic use as associated with being a Control farm. Performance data indicated that Platinum farms were performing better for slaughter live weight than Controls. Limited assessments of available pig movement records suggested that the source of pigs was not key to Platinum status, but further study would be needed to confirm this finding. These results emphasise that maintaining very low prevalence on UK farms is achievable.

Case-control study on the use of pituitary-derived hormones from sheep as a potential risk factor for the occurrence of atypical scrapie in Great Britain.

A case-control study was conducted in 2013 to investigate the use of pituitary-derived hormones from sheep as a potential risk factor for the presence of atypical scrapie in Great Britain sheep holdings. One hundred and sixty-five holdings were identified as cases. Two equal sets of controls were selected: no case of scrapie and cases of classical scrapie. A total of 495 holdings were selected for the questionnaire survey, 201 responses were received and 190 (38.3 per cent) were suitable for analysis. The variables 'use-of-heat-synchronisation/superovulation' and 'flock size' were significantly associated with the occurrence of atypical scrapie. Farms with atypical cases were less likely (OR 0.25, 95 per cent CI 0.07 to 0.89) to implement heat synchronisation/superovulation in the flock than the control group. Atypical cases were 3.3 times (95 per cent CI 1.38 to 8.13) more likely to occur in large holdings (>879 sheep) than in small flocks (<164 sheep). If the 'use-of-heat-synchronisation/superovulation' is a proxy for the use of pituitary-derived hormones, the significant negative association between having a case of atypical scrapie and the use of these practices rules out the initial hypothesis that using these drugs is a risk factor for the occurrence of atypical scrapie. Flock size was a significant risk factor for atypical scrapie, consistent with a previous generic case-control study.

Prion protein genotype survey confirms low frequency of scrapie-resistant K222 allele in British goat herds.

Scrapie in goats is a transmissible, fatal prion disease, which is endemic in the British goat population. The recent success in defining caprine PRNP gene variants that provide resistance to experimental and natural classical scrapie has prompted the authors to conduct a survey of PRNP genotypes in 10 goat breeds and 52 herds to find goats with the resistant K222 allele. They report here the frequencies in 1236 tested animals of the resistance-associated K222 and several other alleles by breed and herd. Eight animals were found to be heterozygous QK222 goats (0.64 per cent genotype frequency, 95 per cent CI 0.28 to 1.27 per cent) but no homozygous KK222 goats were detected. The K222 allele was found in Saanen, Toggenburg and Anglo-Nubian goats. The fact that only a few goats with the K222 allele have been identified does not preclude the possibility to design and implement successful breeding programmes at national level.

Factors affecting dairy farmers' attitudes towards antimicrobial medicine usage in cattle in England and Wales.

There has been growing concern about bacterial resistance to antimicrobials in the farmed livestock sector. Attention has turned to sub-optimal use of antimicrobials as a driver of resistance. Recent reviews have identified a lack of data on the pattern of antimicrobial use as an impediment to the design of measures to tackle this growing problem. This paper reports on a study that explored use of antibiotics by dairy farmers and factors influencing their decision-making around this usage. We found that respondents had either recently reduced their use of antibiotics, or planned to do so. Advice from their veterinarian was instrumental in this. Over 70% thought reducing antibiotic usage would be a good thing to do. The most influential source of information used was their own veterinarian. Some 50% were unaware of the available guidelines on use in cattle production. However, 97% thought it important to keep treatment records. The Theory of Planned Behaviour was used to identify dairy farmers' drivers and barriers to reduce use of antibiotics. Intention to reduce usage was weakly correlated with current and past practice of antibiotic use, whilst the strongest driver was respondents' belief that their social and advisory network would approve of them doing this. The higher the proportion of income from milk production and the greater the chance of remaining in milk production, the significantly higher the likelihood of farmers exhibiting positive intention to reduce antibiotic usage. Such farmers may be more commercially minded than others and thus more cost-conscious or, perhaps, more aware of possible future restrictions. Strong correlation was found between farmers' perception of their social referents' beliefs and farmers' intent to reduce antibiotic use. Policy makers should target these social referents, especially veterinarians, with information on the benefits from, and the means to, achieving reductions in antibiotic usage. Information on sub-optimal use of antibiotics as a driver of resistance in dairy herds and in humans along with advice on best farm practice to minimize risk of disease and ensure animal welfare, complemented with data on potential cost savings from reduced antibiotic use would help improve poor practice.

Abattoir based survey of Salmonella in finishing pigs in the United Kingdom 2006-2007.

All European Union (EU) Member States (MSs) were required to conduct a baseline survey from October 2006 to September 2007 to estimate the prevalence of Salmonella infection in finisher pigs at slaughter. In the United Kingdom (UK), samples for microbiological culture were collected from the ileo-caecal lymph nodes, from carcass swabs and from caecal contents. Meat juice samples were also collected for testing in an enzyme-linked immunosorbent assay (MJE) to detect a serological response. Salmonella was isolated from 22% (CI95% 19-25%) of ileo-caecal lymph nodes, 15% (CI95% 12-18%) of carcass swabs and 22% (CI95% 19-26%) of caecal contents. A quarter (25%, CI95% 22-29%) of MJE samples were positive for Salmonella antibodies (cut-off, S/P≥0.25). The most frequently identified serovars were Salmonella typhimurium (57%) and Salmonella derby (26%). The results were used to investigate some factors associated with Salmonella infection in slaughter pigs. The weight of the carcass was significant, with a lower probability of obtaining a positive meat juice result from pigs with a weight greater than 75 kg (p=0.03). The weight of the lymph node sample was significantly associated with Salmonella status, with a heavier sample of lymph nodes being more likely to be positive (OR=2.16 CI95% 1.07-4.39). 'Carcass weight' in two of the classes - 75-79 kg and 80-84 kg - (OR=0.44 CI95% 0.28-0.70; OR=0.64 CI95% 0.49-0.85) and 'fewer-than-1500-pigs' scheduled for slaughter on the day of sampling' (OR=0.41 CI95% 0.24-0.71) were also associated with a reduced risk of isolating Salmonella from lymph node. The model for carcass swabs showed a positive association with 'time-elapsed-since-the-start-of-the-line' indicating a higher risk of contamination as the day progressed (p<0.01). This model also showed positive association between isolation of Salmonella from a carcass swab and the occurrence of Salmonella in caecal contents from the same pig (OR=2.22 CI95% 1.38-3.59) and a negative association with time in singeing units (OR=0.88 CI95% 0.79-0.98).

Application of variable number of tandem repeat analysis to track Salmonella enterica ssp. enterica serovar Typhimurium infection of pigs reared on three British farms through the production cycle to the abattoir.

AIMS: This study investigated the diversity and persistence of Salmonella strains through the pork finishing cycle, from the farm into the abattoir. METHODS AND RESULTS: Isolates from four batches of finishers, from farm to abattoir, were used. Salmonella Typhimurium isolates were subjected to molecular typing using pulsed-field gel electrophoresis and variable number of tandem repeat analysis. The results demonstrated that infection was transferred from the farm to the abattoir. Within the abattoir, infection from individual pigs contaminated the exterior of the carcass and pigs exposed to Salmonella in the lairage were infected. CONCLUSIONS: Salmonella can be introduced at various points in the pig production and slaughter process. Carcass contamination may arise from infection on farm and exposure in the lairage and abattoir environment. Pigs could be contaminated by previous batches of pigs while in lairage or during the dressing process. Salmonella infection on farms is dynamic with multiple serovars present from different sources. SIGNIFICANCE AND IMPACT OF THE STUDY: Molecular typing methods facilitated the tracing of Salm. Typhimurium through the production cycle and differentiated some farm-acquired from abattoir-acquired strains. The findings emphasize the importance of integrated control strategies along the pork food chain.