Enhancing the value of meat inspection records for broiler health and welfare surveillance: longitudinal detection of relational patterns.

BACKGROUND: Abattoir data are under-used for surveillance. Nationwide surveillance could benefit from using data on meat inspection findings, but several limitations need to be overcome. At the producer level, interpretation of meat inspection findings is a notable opportunity for surveillance with relevance to animal health and welfare. In this study, we propose that discovery and monitoring of relational patterns between condemnation conditions co-present in broiler batches at meat inspection can provide valuable information for surveillance of farmed animal health and welfare. RESULTS: Great Britain (GB)-based integrator meat inspection records for 14,045 broiler batches slaughtered in nine, four monthly intervals were assessed for the presence of surveillance indicators relevant to broiler health and welfare. K-means and correlation-based hierarchical clustering, and association rules analyses were performed to identify relational patterns in the data. Incidence of condemnation showed seasonal and temporal variation, which was detected by association rules analysis. Syndrome-related and non-specific relational patterns were detected in some months of meat inspection records. A potentially syndromic cluster was identified in May 2016 consisting of infection-related conditions: pericarditis, perihepatitis, peritonitis, and abnormal colour. Non-specific trends were identified in some months as an unusual combination of condemnation reasons in broiler batches. CONCLUSIONS: We conclude that the detection of relational patterns in meat inspection records could provide producer-level surveillance indicators with relevance to broiler chicken health and welfare.

Identification of production chain risk factors for slaughterhouse condemnation of broiler chickens'.

Slaughterhouse condemnation of broiler chickens results from identification of polymorphic pathological conditions during meat inspection from arrival and on the slaughter line. While conditions that result in condemnation are multifactorial, identification of factors that are common for a number of categories could be valuable for developing strategies to reduce total condemnation. This study aimed to identify those condemnation categories that were most common in batches of broiler chickens and to determine and compare associated risk factors. In the first step, retrospective meat inspection records for 55,918 broiler batches from one large broiler integrator for 2015-2017 were used for association rules analysis. Results identified a network of nine associated condemnation categories: whole carcass condemnation for ascites, abnormal colour, perihepatitis, cellulitis, hard breast, tumours and dead on arrival, and liver only and heart only most often associated with hepatitis and pericarditis, respectively. Secondly, a longitudinal study collected data on 109 explanatory variables from broiler parental flocks to slaughterhouse characteristics between January 2015 and December 2017. Condemnation outcome data were obtained from meat inspection records for 539 broiler batches participating in the study. Parental flock-, rearing farm-, shed- and transport-level risk factors were assessed for each outcome using mixed-effects multivariable Poisson regression including shed and farm as random effects. A Poisson regression tree method was used as the first step to identify variables most relevant for analysis and comparison across the outcomes. No single production factor was associated with all nine of the condemnation outcomes investigated in this study, although some were shared across multiple outcomes: age of parental flock at time of lay, flock-level Campylobacter spp. frequency, broiler chick weight at seven days of age, weight at slaughter, type of broiler removal (i.e. thinning, final depopulation), catcher team, number of birds per transport crate, slaughterhouse shift number, and type of slaughterhouse line. Broiler chickens removed during final depopulation were at greatest risk of condemnation. Condemnation rates for cellulitis and tumours were found to be higher in broilers inspected by night shift at the slaughterhouse. Discovery of an apparent protective effect of a higher number of broilers per transport crate was unexpected. These findings provide information for the broiler industry on production chain factors that might be amenable to targeted intervention to improve future efforts for control of condemnation.

Quantitative interferon-gamma responses predict future disease progression in badgers naturally infected with Mycobacterium bovis.

The diagnosis and control of Mycobacterium bovis infection (bovine tuberculosis: TB) continues to present huge challenges to the British cattle industry. A clearer understanding of the magnitude and duration of immune response to M. bovis infection in the European badger (Meles meles) - a wildlife maintenance host - may assist with the future development of diagnostic tests, and vaccination and disease management strategies. Here, we analyse 5280 diagnostic test results from 550 live wild badgers from a naturally-infected population to investigate whether one diagnostic test (a gamma interferon release [IFNγ] assay, n = 550 tests) could be used to predict future positive results on two other tests for the same disease (a serological test [n = 2342 tests] and mycobacterial culture [n = 2388 tests]) and hence act as an indicator of likely bacterial excretion or disease progression. Badgers with the highest IFNγ optical density (OD) values were most likely to subsequently test positive on both serological and culture tests, and this effect was detectable for up to 24 months after the IFNγ test. Furthermore, the higher the original IFNγ OD value, the greater the chance that a badger would subsequently test positive using serology. Relationships between IFNγ titres and mycobacterial culture results from different types of clinical sample suggest that the route of infection may affect the magnitude of immune response in badgers. These findings identify further value in the IFNγ test as a useful research tool, as it may help us to target studies at animals and groups that are most likely to succumb to more progressive disease.

Risk factors for Taenia saginata cysticercus infection in cattle in the United Kingdom: A farm-level case-control study and assessment of the role of movement history, age and sex.

Bovine cysticercosis is caused by Taenia saginata cysticercus, the larval stage of the human tapeworm Taenia saginata. Recent European initiatives have highlighted the poor sensitivity of current surveillance for this parasite in cattle at slaughter; calling for more targeted, risk based and cost effective methods of T. saginata cysticercus detection. The aim of this study was to provide evidence that could inform such improved meat inspection activities in the United Kingdom (UK). The study included three components: (i) a farm-level case control study; (ii) the characterization of the network of movements of T. saginata cysticercus infected and non-infected animals, and an assessment of the strength of association between having passed through a farm that had previously originated an infected animal and the risk of infection; (iii) the assessment of the relationship between bovine age and gender and risk of infection. Abattoir records and cattle movement history data were used to identify farms of likely acquisition of infection (case farms) and a suitable control group. A questionnaire was used to gather farm-level characteristics and logistic regression was carried out to identify farm-level risk factors for the production of cattle found to be infected at slaughter. The case-control study provided evidence that farms situated close to a permanent potential source of human faecal contamination, and farms which used manure from animals other than cattle, were at higher risk of producing cattle later found to be infected with T. saginata cysticercus at slaughter. No other farm characteristics were identified as a risk factor for this. Analysis of the networks of animal movements showed that some individual farms played a key role as a source of T. saginata cysticercus infection; it was estimated that cattle with a history of being on a farm which previously appeared in the movement history of an infected animal were 4.27 times (P<0.001; 95% CI: 3.3-5.52) more likely to be diagnosed with T. saginata cysticercus infection at meat inspection. Male cattle aged 20 months or younger at the time of slaughter were found at lower risk of T. saginata cysticercus infection by comparison to other sex or age groups of cattle. These results, in combination with the consultation of experts and stakeholders, led to the conclusion that abattoir-based surveillance in low T. saginata cysticercus prevalence settings, such as Great Britain, could be made more targeted by stratifying cattle based on their individual movement history, sex and age characteristics.

Diagnosis of tuberculosis in groups of badgers: an exploration of the impact of trapping efficiency, infection prevalence and the use of multiple tests.

Accurate detection of infection with Mycobacterium bovis in live badgers would enable targeted tuberculosis control. Practical challenges in sampling wild badger populations mean that diagnosis of infection at the group (rather than the individual) level is attractive. We modelled data spanning 7 years containing over 2000 sampling events from a population of wild badgers in southwest England to quantify the ability to correctly identify the infection status of badgers at the group level. We explored the effects of variations in: (1) trapping efficiency; (2) prevalence of M. bovis; (3) using three diagnostic tests singly and in combination with one another; and (4) the number of badgers required to test positive in order to classify groups as infected. No single test was able to reliably identify infected badger groups if 80% sensitive, at least 94% specific, and able to be performed rapidly in the field.