Swine health impact on carcass contamination and human foodborne risk

Abattoir-based study of Salmonella prevalence in pigs at slaughter in Great Britain

Consumption of pork and pork products can be associated with outbreaks of human salmonellosis. Salmonella infection is usually subclinical in pigs, and farm-based control measures are challenging to implement. To obtain data on Salmonella prevalence, samples can be collected from pigs during the slaughter process. Here we report the results of a Great Britain (GB) based abattoir survey conducted by sampling caecal contents from pigs in nine British pig abattoirs during 2019. Samples were collected according to a randomised stratified scheme, and pigs originating from 286 GB farms were included in this survey. Salmonella was isolated from 112 pig caecal samples; a prevalence of 32.2% [95% confidence interval (CI) 27.4–37.4]. Twelve different Salmonella serovars were isolated, with the most common serovars being S. 4,[5],12:i:-, a monophasic variant of Salmonella Typhimurium (36.6% of Salmonella-positive samples), followed by S. Derby (25.9% of Salmonella-positive samples). There was no significant difference compared to the estimate of overall prevalence (30.5% (95% CI 26.5–34.6)) obtained in the last abattoir survey conducted in the UK (2013). Abattoir-based control measures are often effective in the reduction of Salmonella contamination of carcasses entering the food chain. In this study, the effect of abattoir hygiene practices on the prevalence of Salmonella on carcasses was not assessed. Continuing Salmonella surveillance at slaughter is recommended to assess effect of farm-based and abattoir-based interventions and to monitor potential public health risk associated with consumption of Salmonella-contaminated pork products.

Critical Analysis of Pork QMRA Focusing on Slaughterhouses: Lessons from the Past and Future Trends

Foodborne microbial diseases have a significant impact on public health, leading to millions of human illnesses each year worldwide. Pork is one of the most consumed meat in Europe but may also be a major source of pathogens introduced all along the farm-to-fork chain. Several quantitative microbial risk assessment (QMRA) have been developed to assess human health risks associated with pork consumption and to evaluate the efficiency of different risk reduction strategies. The present critical analysis aims to review pork QMRA. An exhaustive search was conducted following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) methodology. It resulted in identification of a collection of 2489 papers including 42 on QMRA, after screening. Among them, a total of 29 studies focused on Salmonella spp. with clear concern on impacts at the slaughterhouse, modeling the spreading of contaminations and growth at critical stages along with potential reductions. Along with strict compliance with good hygiene practices, several potential risk mitigation pathways were highlighted for each slaughterhouse step. The slaughterhouse has a key role to play to ensure food safety of pork-based products but consideration of the whole farm-to-fork chain is necessary to enable better control of bacteria. This review provides an analysis of pork meat QMRA, to facilitate their reuse, and identify gaps to guide future research activities.

Review on the Characteristic, Properties and Analytical Methods of Cefquinomesulphate: ß-lactam Veterinary Drug

BACKGROUND

Chemotherapy as a science began within the 1st decade of the twentieth century with understanding of the principles of selective toxicity, the particular chemical relationships between microorganism pathogens and medicines, the event of drug resistance, and also the role of combined medical aid.

OBJECTIVES

This review aims to highlight the characteristics, specifically the pharmacokinetic parameters and the analytical methods reported in literature for the determination of Cefquinome, a fourth generation cephalosporine used to treat Gram-positive and Gram-negative caused infections.

CONCLUSION

Analysis of such drugs, whether used for the treatment of human or animal illness, is essential in understanding the bioavailability and therapeutic control which will ensure their activity and safety.

A Quantitative Microbiological Risk Assessment for Salmonella in Pigs for the European Union

A farm-to-consumption quantitative microbiological risk assessment (QMRA) for Salmonella in pigs in the European Union has been developed for the European Food Safety Authority. The primary aim of the QMRA was to assess the impact of hypothetical reductions of slaughter-pig prevalence and the impact of control measures on the risk of human Salmonella infection. A key consideration during the QMRA development was the characterization of variability between E.U. Member States (MSs), and therefore a generic MS model was developed that accounts for differences in pig production, slaughterhouse practices, and consumption patterns. To demonstrate the parameterization of the model, four case study MSs were selected that illustrate the variability in production of pork meat and products across MSs. For the case study MSs the average probability of illness was estimated to be between 1 in 100,000 and 1 in 10 million servings given consumption of one of the three product types considered (pork cuts, minced meat, and fermented ready-to-eat sausages). Further analyses of the farm-to-consumption QMRA suggest that the vast majority of human risk derives from infected pigs with a high concentration of Salmonella in their feces (≥10(4) CFU/g). Therefore, it is concluded that interventions should be focused on either decreasing the level of Salmonella in the feces of infected pigs, the introduction of a control step at the abattoir to reduce the transfer of feces to the exterior of the pig, or a control step to reduce the level of Salmonella on the carcass post-evisceration.

Effects of tylosin administration on C-reactive protein concentration and carriage of Salmonella enterica in pigs

OBJECTIVE

To evaluate the effects of tylosin on C-reactive protein concentration, carriage of Salmonella enterica, and antimicrobial resistance genes in commercial pigs.

ANIMALS

120 pigs on 2 commercial farms.

PROCEDURES

A cohort of sixty 10-week-old pigs in 4 pens/farm (15 pigs/pen) was randomly selected. Equal numbers of pigs were given feed containing tylosin (40 μg/g of feed) for 0, 6, or 12 weeks. C-reactive protein concentrations were measured, microbial culture for S enterica in feces was performed, and antimicrobial resistance genes in feces were quantified.

RESULTS

No significant associations were detected between C-reactive protein concentration or S enterica status and tylosin treatment. During the 12 weeks of tylosin administration, increased levels of 6 antimicrobial resistance genes did not occur.

CONCLUSIONS AND CLINICAL RELEVANCE

Treatment of pigs with tylosin did not affect C-reactive protein concentration or reduce carriage or load of S enterica. There was no evidence that pigs receiving tylosin had increased carriage of the 6 antimicrobial resistance genes measured.

IMPACT FOR HUMAN MEDICINE

S enterica is a public health concern. Use of the antimicrobial growth promoter tylosin did not pose a public health risk by means of increased carriage of S enterica.

Benefits and risks of antimicrobial use in food-producing animals

Benefits and risks of antimicrobial drugs, used in food-producing animals, continue to be complex and controversial issues. This review comprehensively presents the benefits of antimicrobials drugs regarding control of animal diseases, protection of public health, enhancement of animal production, improvement of environment, and effects of the drugs on biogas production and public health associated with antimicrobial resistance. The positive and negative impacts, due to ban issue of antimicrobial agents used in food-producing animals, are also included in the discussion. As a double-edged sword, use of these drugs in food-animals persists as a great challenge.

Effects of antimicrobials fed as dietary growth promoters on faecal shedding of Campylobacter, Salmonella and shiga-toxin producing Escherichia coli in swine

AIMS

To determine whether antimicrobials commonly used in swine diets affect zoonotic pathogen shedding in faeces.

METHODS AND RESULTS

Barrows (n = 160) were sorted into two treatments at 10 weeks of age (week 0 of the study), and fed growing, grow finishing and finishing diets in 4-week feeding periods. For each feeding phase, diets were prepared without (A-) and with (A+) dietary antimicrobials (chlortetracycline, 0-8 week; bacitracin, 9-12 week) typical of the United States. At week 0, 4, 8, 9, 10 and 12 of the study, faecal swabs or grabs were collected for analyses. Campylobacter spp. was absent at week 0, but prevalence increased over time with most isolates being identified as Campylobacter coli. When chlortetracycline was used in A+ diets (week 4 and 8), prevalence for Campylobacter spp., pathogenic Escherichia coli O26 and stx genes was lower in faeces. On week 12 after the shift to bacitracin, Campylobacter spp. and stx genes were higher in faeces from piglets fed A+ diet. Pathogenic E. coli serogroups O103 and O145 were isolated throughout the study and their prevalence did not differ due to diet. Pathogenic E. coli serogroups O111 and O121 were never found in the piglets, and Salmonella spp. prevalence was low.

CONCLUSIONS

In production swine, growing diets with chlortetracycline may have reduced pathogen shedding compared with the A-growing diets, whereas finishing diets with bacitracin may have increased pathogen shedding compared with the A-finishing diet.

SIGNIFICANCE AND IMPACT OF THE STUDY

Inclusion of antimicrobials in the diet can affect zoonotic pathogen shedding in faeces of swine.

Lesion severity at processing as a predictor of Salmonella contamination of swine carcasses

OBJECTIVE

To measure the relationship between gross lesions in swine carcasses observed at a processing plant and Salmonella contamination and to determine whether nonexpert assessments of lesion status would correspond with swine pathologists' judgments.

ANIMALS

Carcasses of 202 conventionally raised and 156 antimicrobial-free pigs in a Midwestern US processing plant examined from December 2005 to January 2006.

PROCEDURES

4 replicates were conducted. For each, freshly eviscerated carcasses were identified as having or lacking visceral adhesions by a nonexpert evaluator and digital carcass photographs were obtained. Swab specimens were obtained from carcasses before the final rinse stage of processing, and bacterial culture for Salmonella spp and Enterococcus spp was performed. Subsequently, carcass photographs were numerically scored for lesion severity by 3 veterinary pathologists. Results were used to test the ability of lesion detection to predict bacterial contamination of carcasses and the agreement between judgments of the inexperienced and experienced assessors.

RESULTS

The probability of Salmonella contamination in carcasses with lesions identified at the abattoir was 90% higher than that in carcasses lacking lesions, after controlling for replicate identity and antimicrobial use. The receiver operating characteristic curve and Cohen κ indicated close agreement between lesion detection at the abattoir and by the 3 pathologists.

CONCLUSIONS AND CLINICAL RELEVANCE

Findings indicated the presence of lesions could be used to predict Salmonella contamination of swine carcasses and that a nonexpert processing-line assessment of lesions could be used to discriminate between healthy and chronically ill swine before their entry into the human food supply.

Prevalence of Yersinia enterocolitica in pigs slaughtered in Chinese abattoirs

The distribution of Yersinia enterocolitica in slaughtered pigs in China was studied. A total of 8,773 samples were collected and examined from different pig abattoirs in 11 provinces from 2009 to 2011. Of these, 4,495 were oral-pharyngeal swab (tonsils) samples from pigs, 1,239 were from intestinal contents, and 3,039 were feces samples from abattoirs or local pigpens. The data showed that 1,132 strains were obtained, from which the isolation rate for Yersinia enterocolitica was 19.53% (878/4,495) from the tonsil samples, 7.51% (93/1,239) from intestinal contents, and 5.30% (161/3,039) from feces. Of the 850 pathogenic Yersinia strains, except for three of bioserotype 2/O:9 and three of bioserotype 4/O:3, most (844/850) were of bioserotype 3/O:3. Interestingly, pathogenic Y. enterocolitica accounted for the majority of the isolated strains from most provinces (85.17% to 100%), whereas from Heilongjiang, 96.52% (111/115) were classified as nonpathogenic biotype 1A with various serotypes, and only 3.48% of the strains (4/115) were pathogenic 3/O:3. All of the pathogenic strains were analyzed using pulsed-field gel electrophoresis (PFGE), and 49 patterns were obtained for the O:3 pathogenic strains; most of them were K6GN11C30021 (53.13%: 450/847) and K6GN11C30012 (21.37%: 181/847). Several strains from diarrhea patient samples revealed PFGE patterns identical to that from samples of local pigs, suggesting a possible link between porcine isolates and human infection. The results above suggested that Yersinia enterocolitica in slaughtered pigs from Chinese abattoirs was characterized by region-specific PFGE patterns and confirmed that strains isolated from pigs are closely related to those from human infections.

Food systems veterinary medicine

The objectives of this review are to suggest the use of the systems thinking framework to improve how veterinary medicine is applied to food production. It applies the eight essential skills of systems thinking to a few selected veterinary examples. Two of the skills determine how we approach or define a problem, and are (i) dynamic thinking (taking a longer term perspective) and (ii) the 30,000 foot view (expanding the boundary of analysis beyond the animal, farm, or even country). The other skills are (iii) system-as-cause, (iv) operational thinking, (v) closed-loop (feedback) thinking, (vi) non-linear thinking, (vii) scientific thinking and (viii) generic thinking. The challenge is to adopt and apply this systems framework to veterinary medicine and food production. The result will be a rigorous new approach to solving the complex food and health problems of the 21st century.

Longer-duration uses of tetracyclines and penicillins in U.S. food-producing animals: Indications and microbiologic effects

We review and analyze regulatory categories for longer duration of use (defined as ≥ 7 day) tetracyclines (TCs) and penicillins (PNs) approved for U.S. livestock and poultry, together with scientific studies, surveillance programs and risk assessments pertaining to antimicrobial resistance. Indications listed on a government database were grouped into three broad categories according to the terminology used to describe their use: disease control (C), treatment (T) and growth improvement (G). Consistent with mostly therapeutic uses, the majority (86%) of listed indications had C and/or T terms. Several studies showed interruption of early disease stages in animals and modulation of intestinal microflora. Longer-duration exposures are consistent with bacteriostatic modes of action, where adequate exposure time as well as concentration is needed for sufficient antimicrobial activity. Other effects identified included reduced animal pathogen prevalence, toxin formation, inflammation, environmental impacts, improved animal health, reproductive measures, nutrient utilization, and others. Several animal studies have shown a limited, dose-proportionate, selective increase in resistance prevalence among commensal animal bacteria following longer-duration exposures. Pathogen surveillance programs showed overall stable or declining resistance trends among sentinel bacteria. Quantitative, microbiologically detailed resistance risk assessments indicate small probabilities of human treatment failure due to resistance under current conditions. Evaluations of longer-duration uses of TCs, PNs, and other antimicrobial classes used in food-producing animals should consider mechanisms of activity, known individual- and population-level health and waste reduction effects in addition to resistance risks.

Microbiological identification and analysis of swine tonsils collected from carcasses at slaughter

The primary objective of this 7-month study was to determine the prevalence of porcine pathogens of the tonsil of the soft palate of swine at slaughter. Additional objectives were to determine if sampling the carcasses of normal or abnormal hogs provided different microbiological profiles and if the slaughter plant provides a feasible sampling frame and environment for detecting and monitoring important pathogens in tonsils that have health implications for both swine and humans. A total of 395 samples were collected from 264 farms. Of these, 180 tonsils were collected from normal carcasses and 215 tonsils were collected from carcasses that were diverted to the hold rail. Laboratory testing included bacteriological culture and identification as well as real time-polymerase chain reaction (PCR) testing for porcine reproductive and respiratory syndrome virus (PPRSV) and immunohistochemistry (IHC) for porcine circovirus-2 (PCV-2). The most commonly isolated bacteria included: Streptococcus suis (53.7%), Arcanobacterium pyogenes (29.9%), Pasteurella multocida (27.3%), and Streptococcus porcinus (19.5%). Virus screening revealed evidence of PRRSV and PCV-2 in 22.0% and 11.9% of the samples, respectively. Salmonella Typhimurium and Yersinia enterocolitica were isolated in 0.5% and 1.8% of the samples, respectively. Tonsils collected from the hold rail were more likely to be positive for Staphylococcus hyicus [odds ratio (OR) = 7.51, confidence interval (CI) = 2.89 to 19.54], Streptococcus porcinus (OR = 9.93, CI = 4.27 to 23.10), and Streptococcus suis (OR = 2.16, CI = 1.45 to 3.24). Tonsils collected from abnormal carcasses were less likely to be positive for Staphylococcus aureus (OR = 0.05, CI = 0.005 to 0.482).

Assessing potential human health hazards and benefits from subtherapeutic antibiotics in the United States: tetracyclines as a case study

Many scientists, activists, regulators, and politicians have expressed urgent concern that using antibiotics in food animals selects for resistant strains of bacteria that harm human health and bring nearer a "postantibiotic era" of multidrug resistant "super-bugs." Proposed political solutions, such as the Preservation of Antibiotics for Medical Treatment Act (PAMTA), would ban entire classes of subtherapeutic antibiotics (STAs) now used for disease prevention and growth promotion in food animals. The proposed bans are not driven by formal quantitative risk assessment (QRA), but by a perceived need for immediate action to prevent potential catastrophe. Similar fears led to STA phase-outs in Europe a decade ago. However, QRA and empirical data indicate that continued use of STAs in the United States has not harmed human health, and bans in Europe have not helped human health. The fears motivating PAMTA contrast with QRA estimates of vanishingly small risks. As a case study, examining specific tetracycline uses and resistance patterns suggests that there is no significant human health hazard from continued use of tetracycline in food animals. Simple hypothetical calculations suggest an unobservably small risk (between 0 and 1.75E-11 excess lifetime risk of a tetracycline-resistant infection), based on the long history of tetracycline use in the United States without resistance-related treatment failures. QRAs for other STA uses in food animals also find that human health risks are vanishingly small. Whether such QRA calculations will guide risk management policy for animal antibiotics in the United States remains to be seen.

A stochastic assessment of the public health risks of the use of macrolide antibiotics in food animals

Campylobacteriosis is an important food-borne illness with more than a million U.S. cases annually. Antibiotic treatment is usually not required. However, erythromycin, a macrolide antibiotic, is recommended for the treatment of severe cases. Therefore, it is considered a critically important antibiotic and given special attention as to the risk that food animal use will lead to resistant infections and compromised human treatment. To assess this risk, we used a retrospective approach; estimating the number of campylobacteriosis cases caused by specific meat consumption utilizing the preventable fraction. We then determined the number of cases with macrolide resistance Campylobacter spp. based on a linear model relating the resistance fraction to on-farm macrolide use. In this article, we considered the uncertainties in the parameter estimates, utilized a more elaborate model of resistance development and separated C. coli and C. jejuni. There are no published data for the probability of compromised treatment outcome due to macrolide resistance. Therefore, our estimates of compromised treatment outcome were based on data for fluoroquinolone-resistant infections. The conservative results show the human health risks are extremely low. For example, the predicted risk of suboptimal human treatment of infection with C. coli from swine is only 1 in 82 million; with a 95% chance it could be as high as 1 in 49 million. Risks from C. jejuni in poultry or beef are even less. Reduced antibiotic use can adversely impact animal health. These low human risks should be weighed against the alternative risks.