Evidence for more cost-effective surveillance options for bovine spongiform encephalopathy (BSE) and scrapie in Great Britain.

Transmissible spongiform encephalopathies (TSEs) are an important public health concern. Since the emergence of bovine spongiform encephalopathy (BSE) during the 1980s and its link with human Creutzfeldt-Jakob disease, active surveillance has been a key element of the European Union's TSE control strategy. Success of this strategy means that now, very few cases are detected compared with the number of animals tested. Refining surveillance strategies would enable resources to be redirected towards other public health priorities. Cost-effectiveness analysis was performed on several alternative strategies involving reducing the number of animals tested for BSE and scrapie in Great Britain and, for scrapie, varying the ratio of sheep sampled in the abattoir to fallen stock (which died on the farm). The most cost-effective strategy modelled for BSE involved reducing the proportion of fallen stock tested from 100% to 75%, producing a cost saving of ca GBP 700,000 per annum. If 50% of fallen stock were tested, a saving of ca GBP 1.4 million per annum could be achieved. However, these reductions are predicted to increase the period before surveillance can detect an outbreak. For scrapie, reducing the proportion of abattoir samples was the most cost-effective strategy modelled, with limited impact on surveillance effectiveness.

Rapid risk assessment tool (RRAT) to prioritize emerging and re-emerging livestock diseases for risk management.

Increasing globalization and international trade contribute to rapid expansion of animal and human diseases. Hence, preparedness is warranted to prevent outbreaks of emerging and re-emerging diseases or detect outbreaks in an early stage. We developed a rapid risk assessment tool (RRAT) to inform risk managers on the incursion risk of multiple livestock diseases, about the main sources for incursion and the change of risk over time. RRAT was built as a relational database to link data on disease outbreaks worldwide, on introduction routes and on disease-specific parameters. The tool was parameterized to assess the incursion risk of 10 livestock diseases for the Netherlands by three introduction routes: legal trade in live animals, legal trade of animal products, and animal products illegally carried by air travelers. RRAT calculates a semi-quantitative risk score for the incursion risk of each disease, the results of which allow for prioritization. Results based on the years 2016-2018 indicated that the legal introduction routes had the highest incursion risk for bovine tuberculosis, whereas the illegal route posed the highest risk for classical swine fever. The overall incursion risk via the illegal route was lower than via the legal routes. The incursion risk of African swine fever increased over the period considered, whereas the risk of equine infectious anemia decreased. The variation in the incursion risk over time illustrates the need to update the risk estimates on a regular basis. RRAT has been designed such that the risk assessment can be automatically updated when new data becomes available. For diseases with high-risk scores, model results can be analyzed in more detail to see which countries and trade flows contribute most to the risk, the results of which can be used to design risk-based surveillance. RRAT thus provides a multitude of information to evaluate the incursion risk of livestock diseases at different levels of detail. To give risk managers access to all results of RRAT, an online visualization tool was built.

Respiratory pathogens in veal calves: Inventory of circulating pathogens.

In the veal industry in The Netherlands, each year around 1.2 million "white" veal calves are produced on around 1100 farms. Bovine respiratory disease (BRD) causes serious health issues in these calves, also resulting in high usage of antimicrobials. To reduce antimicrobial usage, a more targeted treatment regime is needed, for which it is necessary to identify the causative agent. This study aimed at determining associations between pathogens and clinical disease, between prevalence of pathogens and BRD outbreaks, and BRD and performance. A cohort study was conducted involving ten veal farms, in which calf respiratory health was evaluated for the first 12 weeks. Whenever there was an outbreak of BRD, as determined by the farm veterinary surgeon, samples were taken from diseased and control calves through broncho-alveolar lavage. From these samples a broad spectrum of micro-organisms were isolated. Performance data were also collected. A total of 23 outbreaks happened during the 12 week study period, mostly in the first six weeks. BRD associated pathogens found were: BHV1, BPI3V, BRSV, BVDV, Pasteurella multocida, Mannheimia haemolytica, Trueperella pyogenes, Histophilus somni, Mycoplasma bovis, Mycoplasma bovirhinis and Mycoplasma dispar. For most BRD associated pathogens, there was no clear association between presence or prevalence of the micro-organisms and clinical issues. Only T. pyogenes (7.4% in healthy, 14.6% in diseased calves, p 0.013), M. bovis (37.6% and 63.2% respectively, p 0.001) and BVDV (9.9% and 16.9% respectively, p 0.03) were found more often in diseased animals. BPI3V was found in a few early outbreaks, which might suggest involvement in early outbreaks. It appears to be difficult to associate specific pathogens to outbreaks at the species level. BRD is the major reason for treatment with antimicrobials. More specific knowledge about the association between pathogens and health/disease could help to reduce antimicrobial use.

The diversity of Campylobacter spp. throughout the poultry processing plant.

Campylobacteriosis is the leading food-borne disease in developed countries, and poultry are a major source for human infection. The diversity of Campylobacter on chicken carcasses during processing may lead to isolates that are able to survive abattoir processing. This has important implications for public health and adds a further layer to the complexity of the epidemiology of campylobacteriosis. The diversity of the Campylobacter spp. populations on broiler carcasses was studied at three different stages of processing (post-bleed, post-scald and post-chill) in three UK processing plants, using the pulsed-field gel electrophoresis (PFGE) KpnI enzyme. One hundred and sixty Campylobacter strains from 3 processing plants were identified as C. jejuni (92.3%) with 27 PFGE subtype profiles recovered from carcasses at the post-bleed point. Change in populations was identified when carcasses move towards the end of poultry processing. Seven C. jejuni genotypes were able to survive the scalding tank stage process, and 5 genotypes surviving the entire poultry process. Confirmation by PFGE gives information on the genotypic profiles of C. jejuni on chicken carcasses and how they change according to the temperatures exposed to during processing. Diversity within C. jejuni populations produces genotypes that adapt to tolerate the processing environment, and these may be capable of causing human disease. Understanding more about the genotypes that survive the processing will have important implications for public health.

Head-Only Stunning of Turkeys Part 2: Subjective and Objective Assessment of the Application of AC and DC Waveforms.

Electrical stunning is likely to remain an important stunning method for turkeys at slaughter. The purpose of this study is to understand the application of various waveforms of alternating current (AC) and pulsed direct currents (DC), head-only, to turkeys and to improve the effectiveness of handheld stunning of turkeys. We evaluated the effectiveness of stunning by documenting physical responses and recording electroencephalograms (EEGs). For the assessment of physical responses, the stunning voltage was varied depending on the proportion of animals effectively stunned at a certain voltage level. If all turkeys in a group of 10 were stunned, the voltage was decreased, and the next group was stunned. This was repeated until not all turkeys showed signs of being effectively stunned. The experiment was then repeated at the voltage level just above the one that showed incomplete effective stunning. The effects of the stunning on the EEG recording was assessed in 16 turkeys to measure the occurrence of epileptiform EEGs, in 14 turkeys to assess epileptiform EEGs after neck-cut (bleeding), and in 14 turkeys to assess the effect of increased voltage and reduced frequency on epileptiform EEGs. Assessing EEGs in a laboratory setting contributes considerably to the understanding of electrical stunning procedures. Voltages between 125 and 250 V, depending on the waveform assessed, were effective in producing an effective stun in turkeys in this study.

Head-Only Stunning of Turkeys Part 1: The Minimum Voltage Necessary to Break Down the Inherent High Resistance.

Pre-slaughter stunning is required for humane slaughter. For turkeys, head-only electrical stunning is most often used by small scale producers. To ensure immediate and effective stunning, the impedance (resistance) of the tissue of the head of the animal situated between the two electrodes needs to be overcome swiftly. The impedance is a function of the voltage and decreases non-linearly with increasing voltage. In this paper, we describe a method to assess the minimum voltage needed at which the impedance no longer decreases, that is likely to produce an effective stun. For ethical reasons, gas stunned, electrically naïve turkeys were used to measure impedance at various levels of voltage and current. Several combinations of voltage and frequency, alternate current (AC), direct current (DC) and pulsed DC, were identified that would be sufficient to achieve the maximum decrease in the impedance, and therefore would allow the highest current and the most effective stun. A minimum, expressed as Root Mean Squared voltage, of 150 V and 50 Hz. would be required in AC, 175 V in pulsed DC at 30% cycle (150 at 50% cycle), and 225 V if voltage spikes of very short duration were used. Sinusoidal AC applied at 150 V, 50 Hz was selected for further testing.

Sanitation by Ultrasonic Cavitation of Steel Mesh Gloves Used in the Meat Industry.

The microbiological condition of steel mesh gloves commonly used in the meat industry was assessed and an adequate sanitation protocol devised in the course of three experiments conducted in the boning room of a beef packaging operation. The first pilot-experiment monitored the average bacterial load of gloves at various times during the working day, by releasing the tissue trapped inside the gloves through ultrasonic cavitation. After 2, 4, and 6 h of boning, steel mesh gloves contained ca. 9.1 and 8.3 log10 CFU/g mesophilic and psychrotrophic organisms, respectively. Enterobacteriaceae colony counts varied from ca. 5.5 to 8.5 log10 CFU/g. In the second experiment ultrasonic cavitation was followed by disinfection in a 2% Halamid® (sodium paratoluene sulfonchloramide) solution for 5 min. Aerobic mesophilic and psychrotrophic colony counts after 2 h of boning were still 7.4 and 6.7 log10 CFU/g, respectively, while the average Enterobactericeae colony count was 4.9 log10 CFU/g. In the third experiment gloves were subjected to a protocol including: 1) cleaning by ultrasonic cavitation in the presence of a suitable detergent for 5 min, 2) rinsing with tap water, 3) disinfection in a 2% Halamid® solution for 5 min, and 4) rinsing with tap water. This resulted in counts below the limits of detection for aerobic organisms and Enterobacteriaceae . After 2 h of boning the average mesophilic and psychrotrophic aerobic colony counts were ca. 5.5 and 4.9 log10 CFU/g, respectively and the Enterobacteriaceae colony count ca. 3.9 log10 CFU/g. This contrasted sharply with the much higher levels observed when no sanitation protocol was followed. Hence the developed protocol reduces the risk of cross-contamination by steel mesh gloves considerably.