Food safety on the slaughterline: inspection of pig heads.

This paper summarises information on the current inspection procedures for pig heads on the slaughterline and their impact on food safety, and considers the implications for food safety of certain lesions. It is argued that although a modified slaughter and inspection technique would decrease the contamination of the carcase with pathogenic microorganisms, leaving lesions in the head undiscovered would be of little or no importance either for human health or for the overall supervision of animal health.

Possible impact of the "yellow card" antimicrobial scheme on meat inspection lesions in Danish finisher pigs.

In 2010, the "yellow card scheme" which was adopted by the Danish Veterinary and Food Administration imposed restrictions on pig farmers who used more antimicrobials than twice the average. To study the potential impact on pig health, we looked into antimicrobial consumption and vaccine use data from the monitoring programme Vetstat, covering all treatments conducted on Danish pigs between January 2010 and July 2011. The decrease in antimicrobial consumption was pronounced for all age groups (sows/piglets, weaners and finishers) treated for either gastro-intestinal or respiratory disease. Evaluated over 12 months, use of vaccines increased in general: PCV2-related infections (+31%), gastro-intestinal disease (27%), respiratory infections (21%) whereas use of vaccines against other infections remained almost constant (-18%). Data from meat inspection of finisher pigs from before and after introduction of the scheme were compared. This included 1.7 million finisher pigs originating from 2765 pig farms, slaughtered on one large Danish abattoir and covered the first 9 weeks in 2010 and 2011, respectively. Nine lesions of chronic nature and infectious origin and the code "condemned" were selected. The prevalence of these lesions was calculated. Logistic regression models with year and week as explanatory variables were used to identify whether the prevalence of a lesion changed from 2010 to 2011. Possible clustering due to correlation within herds and between weekly shipments of animals originating from the same herd was taken into account in the models. The most common lesion seen was chronic pleuritis (∼23%) while the other lesions occurred less-commonly (<1%). For osteomyelitis, pleuritis, chronic arthritis and condemnation, no differences were observed between the 2 years. The prevalence of chronic peritonitis (OR=1.5), umbilical hernia (OR=1.2) and chronic enteritis (OR=1.2) were statistically higher in 2011 compared to 2010, whereas it was lower for tail bite infection (OR=0.6), chronic pericarditis (OR=0.6), and chronic pneumonia (OR=0.7) (P<0.001). Moreover, in the condemned carcasses, chronic pneumonia plummeted as a lesion found in 2011 compared to 2010 (OR=0.07, P<0.0001). Our results indicate that marked reduction in use of antimicrobials is associated with a short-term increase in the prevalence of specific lesions found during meat inspection and higher coverage of vaccines against respiratory diseases might impact the prevalence of chronic pneumonia positively. Other factors that impact on pig health were not included in the study. Moreover, effect of productivity was not evaluated.

Evaluation of the antibacterial residue surveillance programme in Danish pigs using Bayesian methods.

Residues of pharmacological active substances or their metabolites might be found in food products from food-producing animals. Maximum Residue Limits for pharmacological active substances in foodstuffs of animal origin are established to assure high food safety standards. Each year, more than 20,000 samples are analysed for the presence of antibacterial residues in Danish pigs. This corresponds to 0.1% of the size of the slaughter pig population and more than 1% of the sows slaughtered. In this study, a Bayesian model was used to evaluate the Danish surveillance system accuracy and to investigate the impact of a potential risk-based sampling approach to the residue surveillance programme in Danish slaughter pigs. Danish surveillance data from 2005 to 2009 and limited knowledge about true prevalence and test sensitivity and specificity were included in the model. According to the model, the true antibacterial residue prevalence in Danish pigs is very low in both sows (∼0.20%) and slaughter pigs (∼0.01%). Despite data constraints, the results suggest that the current screening test used in Denmark presents high sensitivity (85-99%) and very high specificity (>99%) for the most relevant antibacterial classes used in Danish pigs. If high-risk slaughter pigs could be identified by taking into account antibacterial use or meat inspection risk factors, a potential risk-based sampling approach to antibacterial residue surveillance in slaughter pigs would allow reducing the sample size substantially, while increasing or maintaining the probability of detection. Hence, the antibacterial residue surveillance programme in Danish pigs would be more cost-effective than today.

Description of extended pre-harvest pig Salmonella surveillance-and-control programme and its estimated effect on food safety related to pork.

Salmonella in pork can be combated during pre- or post-harvest. For large slaughterhouses, post-harvest measures like decontamination might be cost-effective while this is less likely with small-to-medium sized slaughterhouses. In this study, pre-harvest measures might be more relevant. We describe an extended surveillance-and-control programme for Salmonella in finisher pigs, which, to establish equivalence to the Swedish control programme, is intended for implementation on the Danish island, Bornholm. The effect of the programme on food safety was estimated by analysing Salmonella data from pig carcasses originating from herds that would have qualified for the programme during 2006-2008. Food safety was interpreted as prevalence of Salmonella on carcasses as well as the estimated number of human cases of salmonellosis related to pork produced within the programme. Data from the Danish Salmonella programme were obtained from Bornholm. We used a simulation model developed to estimate the number of human cases based on the prevalence of Salmonella on carcass swabs. Herds are only accepted in the programme if they have one or less seropositive sample within the previous 6 months. In this way, the Salmonella load is kept to a minimum. The programme is not yet in operation and pigs that qualify for the programme are currently mixed at slaughter with those that do not qualify. Therefore, we had to assess the impact on the carcass prevalence indirectly. The prevalence of Salmonella in carcass swabs among qualifying herds was 0.46% for the 3 years as a whole, with 2006 as the year with highest prevalence. According to the simulation the expected number of human cases relating to pork produced within the programme was below 10. When the programme is in operation, an extra effect of separating pigs within the programme from those outside is expected to lower the prevalence of Salmonella even further.

Estimated costs of postoperative wound infections. A case-control study of marginal hospital and social security costs.

A cohort of 4515 surgical patients in ten selected intervention groups was followed. Three hundred and seventeen developed postoperative wound infections, and 291 of these cases were matched 1:1 to controls by operation, sex and age. In comparison to the controls the cases stayed longer in hospital after the intervention and had more contact after discharge with the social security system. Using data from a national sentinel reference database of the incidence of postoperative wound infections, and using national activity data, we established an empirical cost model based on the estimated marginal costs of hospital resources and social sick pay. It showed that the hospital resources spent on the ten groups, which represent half of the postoperative wound infections in Denmark, amounted to approximately 0.5% of the annual national hospital budget. This stratified model creates a better basis for selecting groups of operations which need priority in terms of preventive measures.

Survival of patients with surgical wound infection: a case-control study of common surgical interventions.

A cohort of 4515 surgical patients was selected from ten different surgical intervention groups, and 291 of 317 with a postoperative wound infection were matched 1:1 with controls with regard to intervention, sex and age. The mortality rate was investigated from the time of operation, with a follow-up period from 4 years 4 months to 8 years 4 months. Eighty-seven patients with a deep infection had a significantly increased mortality rate, with a risk ratio of 1.7. Without a distinction between superficial and deep infection the former might mask the higher mortality rate associated with the latter.