A within farm clinical trial to compare two treatments (parenteral antibacterials and hoof trimming) for sheep lame with footrot

A reduced potential for lameness bacterial transmission by Lucilia sericata larvae and flies through metamorphosis

Lameness in sheep is one of the most serious issues on farms in the UK and worldwide, affecting over 90% of all UK sheep flocks. Despite its severity and prevalence, there are knowledge gaps regarding transmission routes of bacterial pathogens associated with infectious lameness in sheep. As larvae of Lucilia sericata are commonly found on foot lesions on lame sheep, it was hypothesised that the flies or their larvae could harbour lameness associated bacteria. This study examined the gut contents of larvae obtained from the foot lesions of lame sheep and compared them to control larvae collected from infested cat food on the same farm. Of particular interest, were the presence of three different bacterial genera associated with lameness; Fusobacterium necrophorum, Dichelobacter nodosus and Treponema spp., for which viability was also investigated. Larvae were cultured In vitro and some allowed to metamorphose into flies before specific PCR assays were carried out on the gut contents. Results showed a significant association between the bacteria on the feet of the sheep and those within the larvae. Although the gut contents of all larvae found on sheep feet contained one or more of the lameness bacteria, none of the bacteria were recovered from the adult flies, suggesting a level of gut remodelling during metamorphosis. Interestingly, Treponema spp. and Fusobacterium spp. were viable when isolated from gut contents of larvae. Maintenance of infection from larvae to fly did not occur. However, it still remains important to control both disease and insect populations of farms to maintain animal welfare.

"I didn't see a sheep": perspectives of lecturers and students at veterinary schools in Great Britain on learning about lameness in sheep

Introduction

Great Britain has over 15 million ewes. Lameness is one of the top three most economically important diseases for the sheep industry, costing about £80 million per annum. The prevalence of lameness reduced from 10% to 5% between 2004 and 2013 but further reduction is unlikely because many farmers and agricultural students still believe in, and use, ineffective practices to control lameness. Unfortunately, many veterinary practitioners consider themselves insufficiently knowledgeable to work confidently with sheep farmers, and many sheep farmers agree with them. Another route to improve control of lameness is to ensure that all new veterinary graduates are competent to advise farmers.

Methods

Our study investigated how veterinary students are taught about management of lameness in sheep. Ten lecturers from eight veterinary schools were interviewed, and 33 students from four veterinary schools participated in four focus groups; all were recorded, transcribed, and analysed using directed qualitative content analysis.

Results

Teaching time and opportunities for students to gain clinical experience of lameness were very limited. Students were not confident they could diagnose causes of lameness and listed many practices, including ineffective ones, to manage footrot.

Discussion

We conclude that GB veterinary students are graduating without evidence-based understanding and clinical experience necessary to advise farmers on management of lameness in sheep. Given the importance of lameness in sheep in GB we conclude that an alternative approach to education on lameness in sheep could help to ensure that new graduate veterinarians can contribute to control of lameness in sheep.

Exploring the potential of using simulation games for engaging with sheep farmers about lameness recognition

Introduction

Computer simulation games are increasingly being used in agriculture as a promising tool to study, support and influence real-life farming practices. We explored the potential of using simulation games to engage with sheep farmers on the ongoing challenge of reducing lameness. Working with UK stakeholders, we developed a game in which players are challenged with identifying all the lame sheep in a simulated flock. Here, we evaluate the game's potential to act as a tool to help assess, train and understand farmers' ability to recognize the early signs of lameness.

Methods

Participants in the UK were invited to play the game in an online study, sharing with us their in-game scores alongside information relating to their real-life farming experience, how they played the game, and feedback on the game. Mixed methods were used to analyze this information in order to evaluate the game. Quantitative analyses consisted of linear modeling to test for statistical relationships between participants' in-game recall (% of the total number of lame sheep that were marked as lame), and the additional information they provided. Qualitative analyses of participants' feedback on the game consisted of thematic analysis and a Likert Scale questionnaire to contextualize the quantitative results and identify additional insights from the study.

Results

Quantitative analyses identified no relationships between participants' (n = 63) recall scores and their real life farming experience, or the lameness signs they looked for when playing the game. The only relationship identified was a relationship between participants' recall score and time spent playing the game. Qualitative analyses identified that participants did not find the game sufficiently realistic or engaging, though several enjoyed playing it and saw potential for future development. Qualitative analyses also identified several interesting and less-expected insights about real-life lameness recognition practices that participants shared after playing the game.

Discussion

Simulation games have potential as a tool in livestock husbandry education and research, but achieving the desired levels of realism and/or engagingness may be an obstacle to realizing this. Future research should explore this potential further, aided by larger budgets and closer collaboration with farmers, stockpeople, and veterinarians.

Social behaviour and transmission of lameness in a flock of ewes and lambs

INTRODUCTION

Sheep have heterogenous social connections that influence transmission of some infectious diseases. Footrot is one of the top five globally important diseases of sheep, it is caused by Dichelobacter nodosus and transmits between sheep when infectious feet contaminate surfaces, e.g., pasture. Surfaces remain infectious for a few minutes to a few days, depending on surface moisture levels. Susceptible sheep in close social contact with infectious sheep might be at risk of becoming infected because they are likely to step onto infectious footprints, particularly dams and lambs, as they cluster together.

METHODS

High resolution proximity sensors were deployed on 40 ewes and their 54 lambs aged 5-27 days, in a flock with endemic footrot in Devon, UK for 13 days. Sheep locomotion was scored daily by using a 0-6 integer scale. Sheep were defined lame when their locomotion score (LS) was ≥2, and a case of lameness was defined as LS ≥2 for ≥2 days.

RESULTS

Thirty-two sheep (19 ewes, 9 single, and 4 twin lambs) became lame during the study, while 14 (5 ewes, 5 single, and 4 twin lambs) were lame initially. These 46 sheep were from 29 family groups, 14 families had >1 lame sheep, and transmission from ewes to lambs was bidirectional. At least 15% of new cases of footrot were from within family transmission; the occurrence of lameness was higher in single than twin lambs. At least 4% of transmission was due to close contact across the flock. Most close contact occurred within families. Single and twin lambs spent 1.5 and 0.9 hours/day with their dams, respectively, and twin lambs spent 3.7 hours/day together. Non-family sheep spent only 0.03 hours/day in contact. Lame single lambs and ewes spent less time with non-family sheep, and lame twin lambs spent less time with family sheep.

DISCUSSION

We conclude that most transmission of lameness is not attributable to close contact. However, in ewes with young lambs, some transmission occurs within families and is likely due to time spent in close contact, since single lambs spent more time with their dam than twin lambs and were more likely to become lame.

A survey to understand farmers' perceptions and risk factors for hoof diseases including footrot in sheep in New South Wales, Australia

The aims of this study were to develop an understanding of farmers' perceptions and risk factors for footrot, including its less severe forms, and other hoof diseases in sheep in New South Wales (NSW). A questionnaire was developed and administered to sheep farmers in Local Land Services (LLS) regions across NSW. LLS staff selected sheep farmers who met the inclusion criteria which included farmers with a minimum of 100 sheep, a history of having had foot problems in their flock or having expressed an interest in improving sheep health and production. Farmers completed the questionnaire either by telephone or via the REDCap online survey platform. Descriptive analyses and multivariable logistic regression models were created. The survey was completed by 43 sheep farmers with a median farm size of 1,500 Ha and flock size of 2,300; footrot was present on 39% of farms while 75.6% had other hoof diseases. A flock of >3,000 sheep were more likely to have footrot than a smaller flock (OR = 11.99, 90% CI = 3.02–63.92, P-value = 0.005) and footrot was less likely to be present on farms when an Animal Health Statement was requested while purchasing sheep (OR = 0.10, 90% CI = 0.01–0.56, P-value = 0.04). Hoof conditions other than footrot were likely to be present in flocks when foot inspections were conducted at a time other than weekly inspections (OR = 0.13, 90% CI = 0.01–0.68, P-value = 0.04) and flocks kept on undulating ground were more likely to have diseases other than footrot compared to those kept on flat ground (OR = 3.72, 90% CI = 1.02–15.80, P-value = 0.09). Most farmers agreed that footrot including its less severe forms can cause production losses and negatively affect animal health and welfare. Limitations of the study were the sample size and dry environmental conditions prior to and during study period in many regions of NSW which limited the expression of footrot.

Field Validation of a Non-carcinogenic and Eco-Friendly Disinfectant in a Stand-In Footbath for Treatment of Footrot Associated With aprV2-Positive Strains of Dichelobacter nodosus in Swiss Sheep Flocks

A national control program for virulent footrot is currently planned in Switzerland. Since commonly used disinfectants either contain heavy metals or are carcinogenic, the aim of this study was to verify the effectiveness of an eco-friendly and non-carcinogenic candidate disinfectant against aprV2-positive strains of Dichelobacter nodosus. Additionally, the effect of the selective use of long-acting oxytetracyclines was evaluated. A total of 18 farms with confirmed footrot infection, randomly allocated to two treatment groups: (1) with antibiotics (AB; n = 9) and, (2) no antibiotics (NAB; n = 9), were included. Claws were carefully trimmed and scored using a scale from 0 (clinically healthy) to 5 (complete loss of the horn capsule) and a prewash waterbath was implemented on 11 farms. Twice-weekly, repeated whole-flock stand-in footbaths with the candidate disinfectant (6%) were performed. Additionally, animals of group AB with a score ≥ 3 were administered oxytetracyclines by injection. On all farms, 10 days after last treatment, aprV2-positive strains could not be detected by risk-based sampling for real-time PCR analysis after 7–21 (median = 12) footbaths with a minimal culling rate of non-responders on nine farms. Farms without contact to other sheep remained without clinical signs of footrot for a minimum of 245 days (mean ± standard deviation: 293.6 ± 23.6). Antibiotic treatment did not reduce the number of footbaths needed. In contrast, a mean of 3.3 disinfecting footbaths could be saved by implementing a prewash waterbath. At animal level, individual and selective use of oxytetracyclines lead to a higher chance (odds ratio = 9.95; 95% CI: 3.54–27.95; p < 0.001) for a lesion score ≥ 3 to improve to a lesion score < 3 within 2 weeks compared to treatment without antibiotics. The test disinfectant is an effective and eco-friendly alternative for the planned Swiss footrot control program and selective use of oxytetracycline has a beneficial impact on the recovery of animals with lesion scores ≥ 3.

Differences in composition of interdigital skin microbiota predict sheep and feet that develop footrot

Footrot has a major impact on health and productivity of sheep worldwide. The current paradigm for footrot pathogenesis is that physical damage to the interdigital skin (IDS) facilitates invasion of the essential pathogen Dichelobacter nodosus. The composition of the IDS microbiota is different in healthy and diseased feet, so an alternative hypothesis is that changes in the IDS microbiota facilitate footrot. We investigated the composition and diversity of the IDS microbiota of ten sheep, five that did develop footrot and five that did not (healthy) at weekly intervals for 20 weeks. The IDS microbiota was less diverse on sheep 2 + weeks before they developed footrot than on healthy sheep. This change could be explained by only seven of > 2000 bacterial taxa detected. The incubation period of footrot is 8–10 days, and there was a further reduction in microbial diversity on feet that developed footrot in that incubation period. We conclude that there are two stages of dysbiosis in footrot: the first predisposes sheep to footrot and the second occurs in feet during the incubation of footrot. These findings represent a step change in our understanding of the role of the IDS microbiota in footrot pathogenesis.

Allele/haplotype variation in the MHC-DQA2 gene in Spanish sheep and its association with footrot susceptibility

Footrot is a contagious disease that affects the hoof of sheep and other ungulates. The severity of the disease varies from a slight limp to the death of the individual due to injuries that prevent them from feeding. Variants of the Major Histocompatibility Complex (MHC)-DQA2 gene (MHC-DQA2) have been associated with a greater or lesser susceptibility to footrot in Greek, New Zealand and German sheep. In this study, variation in ovine MHC-DQA2, the absence or presence of footrot and the severity of infection was analysed in 117 Spanish Merino, Black Merino and Churra Lebrijana sheep. A total of 21 alleles/haplotypes and 65 genotypes were found with different frequencies in these breeds. As found in other studies, the MHC-DQA2 allele *1101 appeared to be associated with increased susceptibility to footrot, while allele *1201 appeared to be associated with decreased susceptibility. Overall this would suggest the ovine MHC plays a role in controlling susceptibility to footrot infection and that there are breed differences in susceptibility. Sheep might therefore be able to be selected by their MHC-DQA2 alleles/haplotypes to reduce the incidence of the disease in flocks.

Impact of Strain Variation of Dichelobacter nodosus on Disease Severity and Presence in Sheep Flocks in England

AprV2 and aprB2 are variants of the apr gene of Dichelobacter nodosus, the cause of footrot in sheep. They are putative markers for severe and mild disease expression. The aim of our study was to investigate the distribution of aprV2 and aprB2 in flocks with and without footrot. Our hypotheses were that both strains are present in endemically affected flocks, with aprB2 and aprV2 associated with mild and virulent phenotypes respectively but that D. nodosus is not present in flocks without footrot. Alternatively, aprB2 persists in flocks without footrot. Despite extensive searching over 3 years only three flocks of sheep without footrot were identified. D. nodosus was not detected in these three flocks. In one further flock, only mild interdigital dermatitis was observed, and only aprB2 was detected. Twenty-four flocks with endemic footrot of all severities were sampled on three occasions and all were positive for D. nodosus and the aprV2 variant; aprB2 was detected in only 11 of these flocks. AprB2 was detected as a co-infection with aprV2 in the 22% of samples positive for aprB2 and was more likely in mild footrot phenotypes than severe. Dichelobacter nodosus serogroups were not associated with footrot phenotype. We conclude that D. nodosus, even aprB2 strains, do not persist in flocks in the absence of footrot. Our results support the hypothesis that aprB2 is associated with mild footrot phenotypes. Finally, we conclude that given the small number of flocks without footrot that were identified, footrot is highly endemic in English sheep flocks.

The severity of footrot lesions induced by aprV2-positive strains of Dichelobacter nodosus varies between strains

OBJECTIVES

The primary objective of this study was to evaluate the clinical virulence of aprV2-positive lesser virulent field isolates of footrot bacteria Dichelobacter nodosus in comparison with an aprV2-positive clinically virulent reference strain. Correlations between the clinical expression of the disease and the presence of aprV2 (detected using PCR tests) have been inconsistent. A second objective was to evaluate the elimination of D. nodosus following treatment of sheep as some strains of D. nodosus have been reported to be difficult to eliminate.

METHODS

The virulence of three aprV2-positive field isolates of D. nodosus which had lesser virulent phenotypes, and an aprV2-positive virulent reference strain was evaluated in a sheep trial using a pasture-based experimental infection model. In the second phase of the study, treatments including footbathing and a long-acting antibiotic were administered and their efficacy in elimination of these strains was evaluated.

RESULTS

Severe underrun (score 4) lesions developed in sheep infected with the aprV2-positive virulent reference strain but not in sheep infected with the field isolates; they had mild lesions (score 2 or 3). The three field isolates and the virulent reference strain of D. nodosus were eliminated by intensive foot bathing and antibiotic therapy in combination with housing the animals in dry conditions post-treatment.

CONCLUSION

The results suggest that the presence of aprV2 gene in isolates of D. nodosus may not be a reliable indicator of virulence and that further investigation of the factors that determine clinical virulence is required. While the treatment regime was successful, based on a range of considerations, the use of such an intensive treatment involving antibiotics should be limited to small groups of high-value animals, such as rams.

Prevalence and Temporal Dynamics of White Line Disease in Sheep: An Exploratory Investigation into Disease Distribution and Associated Risk Factors

Lameness in sheep is a global health, welfare and economic concern. White line disease (WLD), also known as shelly hoof, is a prevalent, non-infectious cause of lameness, characterised by the breakdown of the white line. Little is known about the predisposing factors, nor the individual disease dynamics over time. Our exploratory study aimed to investigate the prevalence and temporal dynamics of WLD, and the associated risk factors. Feet of 400 ewes from four UK commercial sheep farms were inspected for WLD at four time points across 12 months. The change in WLD state at foot-level (develop or recover) was calculated for three transition periods. We present WLD to be widespread, affecting 46.8% of foot-level and 76.6% of sheep-level observations. States in WLD changed over time, with feet readily developing and recovering from WLD within the study period. The presence of WLD at foot-level, the number of feet affected at sheep-level and dynamics in development and recovery were driven by a variety of foot-, sheep- and farm-level factors. We provide key insight into the multifaceted aetiology of WLD and corroborate previous studies demonstrating its multifactorial nature. Our study highlights an opportunity to reduce WLD prevalence and informs hypotheses for future prospective studies.

Multiple model triangulation to identify factors associated with lameness in British sheep flocks

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Multiple model triangulation identifies variables that are likely true positives.

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Triangulation increases confidence in which managements to recommend in practice.

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Effective management of ewes can lower prevalence of lameness in ewes and lambs.

Identification of factors associated with an outcome can be challenging when the number of explanatory variables is large in relation to the number of observations. Multiple model triangulation, where results from several model types are combined, improves the likelihood of identifying true predictor variables. The aim of this study was to use triangulation to identify covariates likely to be truly associated with the prevalence of lameness in sheep flocks in Great Britain.

Data were collected using a questionnaire sent to 3200 sheep farmers in Great Britain in 2018. The useable response rate was 14.1 %. The geometric mean prevalence of lameness was 1.4 % (95 % CI 1.2−1.7) for ewes, and 0.6 % (95 % CI 0.5−0.9) for lambs, however, approximately 60 % flocks had >2% prevalence of lameness in ewes.

Four model types were investigated, two generalised linear models (negative binomial and quasi-Poisson) built using stepwise selection, and two elastic net models (Poisson and Gaussian distributions) refined with selection stability estimation.

Triangulated covariates were those selected in three or all four models – 10 for ewes and 12 for lambs. Higher prevalence of lameness in ewes was associated with 5−100% feet bleeding during routine foot trimming compared with not foot trimming, footbathing the flock to treat severe footrot (SFR) and always using formalin in footbaths, both compared with not footbathing, using FootVax™ for <1 year compared with not using FootVax™, and never quarantining new or returning sheep to the farm for >3 weeks compared with always. Lower prevalence of lameness in ewes was associated with vaccinating with FootVax™ for >5 years compared with not vaccinating, peat soil compared with no peat soil, and having no lame ewes to treat.

Higher prevalence of lameness in lambs was associated with 5−100% feet bleeding during routine foot trimming, always foot trimming ewes with SFR, not knowingly selecting replacement ewes from ewes that were never lame compared with always, replacement sheep purchased and homebred compared with only homebred, treating lambs >3 days after recognition of lameness compared with 0-3 days and footbathing the flock to treat interdigital dermatitis compared with not footbathing at all. Lower prevalence of lameness in lambs was associated with peat soil, flocks in Scotland versus England, an altitude of >230−500 m compared with ≤230 m, never using antibiotic injection to treat lambs with SFR compared with always, and having no lame lambs to treat.

We conclude triangulation identified reliable management practices for farmers to implement to minimise lameness in sheep.

A Cross-Sectional Epizootiological Study and Risk Assessment of Foot-Related Lesions and Lameness in Intensive Dairy Sheep Farms

Simple Summary

Foot-related lameness is one of the most significant welfare issues in farm animals. Contrary to dairy cows and meat sheep breeds, epizootiological data on foot-lesions and associated lameness in dairy sheep are scarce. In this study, data were collected from 30 representative intensive dairy sheep farms. Multivariate statistical analysis was used to produce a typology of intensive farming systems which resulted in the assignment of farms in two distinct clusters. Six hundred adult ewes were randomly selected from six flocks (three flocks per cluster) and a cross-sectional study was implemented to investigate the epizootiology and potential risk factors of foot-related lameness, foot-lesions and diseases. Ovine interdigital dermatitis and infectious footrot were the most common infectious foot diseases, while white line disease and hoof wall cracks were the most prevalent non-infectious lesions. Infectious footrot was the main cause of lameness and increased with age, whereas body condition score was associated with increased prevalence of ovine interdigital dermatitis. Comparisons between the clusters regarding foot-related lameness, foot-diseases and lesions at the animal, the limb, and the hoof level are presented, and relevant literature, mechanisms, hypotheses, and challenges of the field are discussed.

Abstract

Foot-related lameness, foot-diseases and lesions are emerging issues in dairy sheep; however, relevant epizootiological studies are scarce, and risk factors have not been elucidated. The objectives of this cross-sectional study were (i) to address this dearth of knowledge by investigating the epizootiology of lameness-related foot-lesions and diseases, and (ii) to assess the impact of potential risk factors on foot health, in intensive dairy sheep farms. Thirty farms were assigned in two representative clusters using a multivariate statistical analysis. Three farms per cluster and 100 multiparous milking ewes per farm (total n = 600) were selected and enrolled in the study. Foot-related lameness, ovine interdigital dermatitis (OID), infectious footrot (IFR), white line disease, hoof wall cracks, as well as health and welfare traits were recorded. Overall prevalence of foot-related lameness was 9.0% and was primarily associated with IFR; however, additional infectious and non-infectious foot diseases and lesions also contributed. Among infectious foot diseases, OID was the most prevalent (21.3%) followed by IFR (8.0%); WLD and hoof wall cracks were the most prevalent non-infectious foot-lesions (37.7% and 15.3%, respectively). IFR and OID prevalence increased with age (p < 0.05) and BCS (p < 0.01), respectively, suggesting that host-related factors and husbandry practices are important determinants of its occurrence.

Characterisation of Dichelobacter nodosus on Misshapen and Damaged Ovine Feet: A Longitudinal Study of Four UK Sheep Flocks

Simple Summary

The bacterium Dichelobacter nodosus is the cause of footrot in sheep: a painful, contagious foot disease. Some sheep may be more susceptible to carrying D. nodosus on their feet, despite showing no signs of disease, and pose a risk to flock health and welfare. This study investigated whether misshapen or damaged feet (poor hoof conformation) were more likely to have D. nodosus present and in greater quantities than feet in good condition. Eighty-five ewes from four flocks were examined three times, on average, across a 12-month period. Poor hoof conformation traits were observed in over 92% of foot observations. Feet with poor sole and heel conformation were more likely to have higher quantities of D. nodosus than those in good conformation. Furthermore, on feet positive for D. nodosus, wall overgrowth contributed towards higher D. nodosus load. We highlight feet with aspects of poor conformation traits to covertly harbour D. nodosus. These feet could transmit D. nodosus to other feet of sheep. Increasing our understanding of D. nodosus infection is crucial in helping farmers improve management practices to reduce footrot.

Abstract

Dichelobacter nodosus is the causal agent of ovine footrot, a contagious disease of welfare and economic concern worldwide. Damaged feet may be subclinical carriers of D. nodosus and covertly spread infection. Accordingly, we evaluated the risk of misshapen and damaged feet on D. nodosus presence and load in four commercial UK sheep flocks. Foot-level observations and swabs (n = 972) were collected from ewes (n = 85) over 12 months. On average, ewes were sampled three times. Feet were inspected for disease and scored (good/poor) for three hoof conformation traits (sole and heel, wall, and wall overgrowth). Swabs were analysed for presence and load of D. nodosus, and mixed models were constructed. Poor hoof conformation traits were present in 92.5% of foot-level observations. Feet with poor sole and heel conformation were more likely to have higher D. nodosus loads (β = 0.19, 95% CI: 0.04–0.35) than those with good conformation. Furthermore, on feet positive for D. nodosus, wall overgrowth was associated with higher D. nodosus loads (β = 0.27, 95% CI: 0.01–0.52). Feet with aspects of poor conformation covertly harbour D. nodosus and are a source of infection. Flock management should be guided by hoof conformation to reduce disease challenge.

Ovine footrot: A review of current knowledge

Footrot is a contagious foot disease mainly affecting sheep. It is caused by the Gram-negative anaerobic bacterium Dichelobacter nodosus. Warm, wet environmental conditions favour development of footrot, and under perfect conditions, it takes just 2-3 weeks from infection to manifestation of clinical signs. Affected sheep show lameness of various degrees and often graze while resting on their carpi. Local clinical signs vary in severity and extent from interdigital inflammation (benign footrot) to underrunning of the complete horn shoe in advanced stages of virulent footrot. Laboratory diagnosis ideally involves collection of four-foot interdigital swab samples followed by competitive real time PCR, allowing for detection of the presence of D. nodosus and differentiation between benign and virulent strains. Laboratory-based diagnostics at the flock level based on risk-based sampling and pooling of interdigital swab samples are recommended. The list of treatment options of individual sheep includes careful removal of the loose undermined horn, local or systemic administration of antimicrobials, systemic administration of non-steroidal anti-inflammatories (NSAIDs) and disinfectant footbathing. Strategies for control at the flock level are manifold and depend on the environmental conditions and the procedures traditionally implemented by the respective country. Generally, measures consist of treatment/culling of infected sheep, vaccination and prevention of reinfection of disease-free flocks. Gaining deeper insight into the beneficial effects of NSAIDs, screening for eco-friendly footbath solutions, developing better vaccines, including the development of a robust, reproducible infection model and elucidation of protective immune responses, as well as the elaboration of effective awareness training programs for sheep farmers, are relevant research gaps.

A comparison of multivalent and bivalent vaccination strategies for the control of virulent ovine footrot

Virulent footrot is a significant economic and animal welfare concern. The disease can be treated, controlled, and eliminated with vaccine, but selecting the appropriate vaccination strategy can be challenging. There are two main strategies: outbreak (serogroup)-specific univalent or bivalent vaccination, or use of a multivalent vaccine containing up to nine of the most common serogroups. The objective of this study was to compare these approaches in sheep flocks infected with multiple Dichelobacter nodosus serogroups. In the first phase, we undertook an immunogenicity trial in which we compared four pre-commercial multivalent recombinant fimbrial vaccines containing six (A, B, C, G, H, I) or nine (A, B, C, D, E, F, G, H, I) serogroups, and compared them to commercial bivalent vaccines. Two multivalent vaccines stimulated significantly higher antibody responses than two other multivalent vaccines but the number of serogroups included in the multivalent vaccine formulations did not have a significant effect. In the first phase, we also compared inter-vaccination intervals of two- and three-months between sequential bivalent vaccines, and found that a two-month interval was sufficient to avoid antigenic competition. In the second phase, the most immunogenic multivalent vaccine (nine serogroups) was compared to sequential bivalent vaccines and monthly foot-bathing in a field trial in four commercial Merino flocks. The duration of protection afforded by the multivalent vaccine was likely to be less than that of the bivalent vaccines, as the antibody titres stimulated were lower and less persistent.

A Pilot Study to Investigate the Feasibility of a Multiple Locus Variable Number Tandem Repeat Analysis to Understand the Epidemiology of Dichelobacter nodosus in Ovine Footrot

Dichelobacter nodosus is the essential pathogen in ovine footrot, an important cause of lameness in sheep that reduces productivity and welfare. The aim of this study was to investigate the feasibility of using multiple locus variable number tandem repeat analysis (MLVA) developed to investigate isolates to understand the molecular epidemiology of Dichelobacter nodosus in ovine footrot by investigation of communities of strains. MLVA sensitivity was improved by optimizing PCR conditions to 100% specificity for D. nodosus. The improved MLVA scheme was used to investigate non-cultured DNA purified from swabs (swab DNA) and cultured DNA from isolates (isolate DNA) from 152 foot and 38 gingival swab samples from 10 sheep sampled on four occasions in a longitudinal study. Isolate DNA was obtained from 6/152 (3.9%) feet and 5/6 yielded complete MLVA profiles, three strains were detected. Two of the three isolate strains were also detected in isolate DNA from 2 gingival crevice cultures. Complete MLVA profiles were obtained from swab DNA from 39 (25.7%) feet. There were 22 D. nodosus community types that were comprised of 7 single strain and 15 multi-strain communities. Six community types were detected more than once and three of these were detected on the same four sheep and the same two feet over time. There were a minimum of 17 and a maximum of 25 strain types of D. nodosus in the study. The three isolate strain types were also the most frequently detected strain types in swab DNA. We conclude that the MLVA from swab DNA detects the same strains as culture, is much more sensitive and can be used to describe and differentiate communities and strains on sheep, feet and over time. It is therefore a sensitive molecular tool to study D. nodosus strains directly from DNA without culture.

Management Practices Associated With Prevalence of Lameness in Lambs in 2012-2013 in 1,271 English Sheep Flocks

The evidence base for management practices associated with low prevalence of lameness in ewes is robust. Current best practice is prompt treatment of even mildly lame sheep with parenteral and topical antibiotics with no routine or therapeutic foot trimming and avoiding routine footbathing. To date, comparatively little is known about management of lameness in lambs. Data came from a questionnaire completed by 1,271 English sheep farmers in 2013. Latent class (LC) analyses were used to investigate associations between treatment of footrot and geometric mean flock prevalence of lameness (GMPL) in lambs and ewes, with multinomial models used to investigate effects of flock management with treatment. Different flock typologies were identified for ewes and lambs. In both ewe and lamb models, there was an LC (1) with GMPL <2%, where infectious causes of lameness were rare, and farmers rarely treated lame animals. There was a second LC in ewes only (GMPL 3.2%) where infectious causes of lameness were present but farmers followed "best practice" and apparently controlled lameness. In other typologies, farmers did not use best practice and had higher GMPL than LC1 (3.9-4.2% and 2.8-3.5%, respectively). In the multinomial model, farmers were more likely to use parenteral antibiotics to treat lambs when more than 2-5% of lambs were lame compared with ≤2%. Once >10% of lambs were lame, while farmers were likely to use parenteral antibiotics, only sheep with locomotion score >2 were considered lame, leaving lame sheep untreated, potentially allowing spread of footrot. These farmers also used poor practices of routine foot trimming and footbathing, delayed culling, and poor biosecurity. We conclude there are no managements beneficial to manage lameness in lambs different from those for ewes; however, currently lameness in lambs is not treated using "best practice." In flocks with <2% prevalence of all lameness, where infectious causes of lameness were rare, farmers rarely treated lame animals but also did not practice poor managements of routine foot trimming or footbathing. If more farmers adopted "best practice" in ewes and lambs, the prevalence of lameness in lambs could be reduced to <2%, antibiotic use would be reduced, and sheep welfare would be improved.

Serogroups of Dichelobacter nodosus, the cause of footrot in sheep, are randomly distributed across England

We present the largest and most representative study of the serological diversity of Dichelobacter nodosus in England. D. nodosus causes footrot and is one of the top five globally important diseases of sheep. The commercial vaccine, containing nine serogroups, has low efficacy compared with bivalent vaccines. Our aim was to investigate the prevalence and distribution of serogroups of D. nodosus in England to elucidate whether a bivalent vaccine could protect the national flock. Farmers from 164 flocks submitted eight interdigital swabs from eight, preferably diseased, sheep. All serogroups, A-I, were detected by PCR in 687/1150 D. nodosus positive swabs, with a prevalence of 2.6-69.3% of positive swabs per serogroup. There was a median of two serogroups per flock (range 0-6). Serogroups were randomly distributed between, but clustered within, flocks, with 50 combinations of serogroups across flocks. H and B were the most prevalent serogroups, present in > 60% of flocks separately but in only 27% flocks together. Consequently, a bivalent vaccine targeting these two serogroups would protect 27% of flocks fully (if only H and B present) and partially, if more serogroups were present in the flock. We conclude that one bivalent vaccine would not protect the national flock against footrot and, with 50 combinations of serogroups in flocks, flock-specific vaccines are necessary.

Uptake of the lameness Five-Point Plan and its association with farmer-reported lameness prevalence: A cross-sectional study of 532 UK sheep farmers

The aims of this research were to determine the uptake of a national strategy to reduce lameness in the UK flock, known as the Five-Point Plan (5 P P); explore the association between footrot vaccination (Footvax®) use and 5 P P adoption; investigate the management practices associated with farmer-reported percentage lameness through risk factor analysis; and identify the population attributable fractions of these management practices. In 2014, the 5 P P was launched to provide a practical, farm-level framework to help farmers reduce lameness to reach Farm Animal Welfare Committee (FAWC) targets. No published studies have explicitly explored its uptake in UK flocks nor its association with lameness prevalence. Understanding what parts of the 5 P P farmers adopt and which elements contribute towards the greatest reduction in lameness are integral in informing future strategies. Between November 2018 and February 2019, 532 UK sheep farmers completed a cross-sectional online and paper-based survey. The geometric mean of farmer-reported percentage lameness in ewes was 3.2 % (95 % CI: 2.8-3.6). Farmers adopted a median of 3 points of the plan, but was only fully-adopted by 5.8 % of farmers. The number of points adopted increased with flock size, with larger commercial flocks more likely to cull and vaccinate against footrot, but smaller, pedigree flocks were more likely to treat individual lame sheep. Vaccination was poorly associated with the uptake of other points of the 5 P P. Eight flock management factors were associated with significantly higher percentage lameness in ewes; not carrying out measures to avoid lameness transmission, not quarantining bought in stock, not treating individual lame sheep within three days, maintaining an open flock and foot trimming were all associated with a higher risk of lameness in flocks studied. In addition, using Footvax® for ≤5 years was associated with a higher risk of lameness, although vaccination could be a consequence of high flock lameness or these farmers were not implementing other effective managements, such as treating promptly. The highest PAFs were calculated for trimming lame sheep (16.9 %), maintaining an open flock (13.5 %) and not carrying out measures to avoid lameness transmission (11.8 %). We provide new evidence documenting the benefits of adopting parts of the 5 P P on reducing lameness prevalence in UK flocks, although uptake of these measures could be improved in flocks. Encouraging uptake of these measures could make an important contribution towards reducing the prevalence of lameness and reaching 2021 FAWC ≤ 2% lameness prevalence targets.

Influencing Change: When "Best Practice" Changes and the Prototypical Good Farmer Turns Bad

Twenty-nine farmers with a flock prevalence of lameness >5% were visited in 2013. They participated in a facilitated discussion on treatment of footrot, and evidence-based new "best practice." One year later, farmers were revisited and management and motivators for change were discussed. Farmers were asked how they would persuade other farmers to adopt "best practice." Initially, most participants were resigned to having lame sheep. They believed that prototypical "good farmers" (including trusted family) practiced foot trimming, the traditional "best practice" and that the new "best practice" would be expensive and time consuming. Between 2013 and 2014 lameness prevalence reduced from 7.6 to 4.3%. The major behavioral changes were reduction in foot trimming, increased use of antibacterials to treat footrot, and treating sheep within a week of becoming lame. In 2014, participants were re-interviewed. They reported that an increased knowledge of the evidence-base, trust in the facilitator and talking to other trusted farmers who had already adopted the new "best practice" overcame concerns about the prototypical "good farmer" and motivated change. Persistent change occurred because participants observed health benefits for their sheep and that the new "best practice" had saved time and money. Participants stated that other farmers would be convinced to change to the new "best practice" because it saved time and money, ironically, these were among the original barriers to change. This is possibly an example of cognitive dissonance because farmers had become positive about the benefits of saving time and money following a change in their own behaviors.

The prevalence of Dichelobacter nodosus in clinically footrot-free sheep flocks: a comparative field study on elimination strategies

Background

Ovine footrot caused by Dichelobacter nodosus (D nodosus) is an infectious disease affecting sheep worldwide. Switzerland plans a nationwide footrot eradication program, based on PCR-testing of interdigital swab samples. The aim of this study was to test for the presence of D nodosus in clinically footrot-free sheep flocks which had been subjected to different treatment strategies, to assess whether they were feasible for the eradication process, especially focussing on antimicrobial flock treatments. Clinical scoring and PCR-results were compared. Ten farms had used hoof bathing and hoof trimming without causing bleeding, ten had used individual treatments and flock vaccines to gain the free status and ten had become free through whole-flock systemic macrolide treatment. For every farm, three risk-based collected pool samples were analysed for the occurrence of virulent and benign D nodosus by PCR detection of aprV2/aprB2.

Results

Six flocks from any treatment group tested positive for aprB2 in all pools. Clinical signs were absent at the time of sampling, but some flocks had experienced non-progressive interdigital inflammation previously. Two flocks tested aprV2-positive in the high-risk pool. One of them underwent a progressive footrot outbreak shortly after sampling. Individual retesting indicated, that virulent D nodosus most likely was reintroduced by a recently purchased ram. In the second flock, a ram was tested positive and treated before clinical signs occurred.

Conclusions

All treatment strategies eliminated the causative agent and were found to be suitable for implementation in the PCR-based eradication process. PCR-testing proved to be more sensitive than visual scoring, as it also detected clinically healthy carriers. It will be of benefit as a diagnostic tool in elimination and surveillance programs.

Automated detection of lameness in sheep using machine learning approaches: novel insights into behavioural differences among lame and non-lame sheep

Lameness in sheep is the biggest cause of concern regarding poor health and welfare among sheep-producing countries. Best practice for lameness relies on rapid treatment, yet there are no objective measures of lameness detection. Accelerometers and gyroscopes have been widely used in human activity studies and their use is becoming increasingly common in livestock. In this study, we used 23 datasets (10 non-lame and 13 lame sheep) from an accelerometer- and gyroscope-based ear sensor with a sampling frequency of 16 Hz to develop and compare algorithms that can differentiate lameness within three different activities (walking, standing and lying). We show for the first time that features extracted from accelerometer and gyroscope signals can differentiate between lame and non-lame sheep while standing, walking and lying. The random forest algorithm performed best for classifying lameness with an accuracy of 84.91% within lying, 81.15% within standing and 76.83% within walking and overall correctly classified over 80% sheep within activities. Both accelerometer- and gyroscope-based features ranked among the top 10 features for classification. Our results suggest that novel behavioural differences between lame and non-lame sheep across all three activities could be used to develop an automated system for lameness detection.

Environmental and field characteristics associated with lameness in sheep: a study using a smartphone lameness app for data recording

BACKGROUND

Sheep lameness is a major concern among farmers and policymakers with significant impacts on animal welfare standards as well as financial and production performance. The present study attempts to identify the relative importance of environmental and farm-level management characteristics on sheep lameness.

METHOD

To address this objective, data were derived from the SPiLaMM project from 18 farms that used smartphone app to collect data, the British Geological Survey and the Meteorological Office over 2016-2018. Data were analysed using a multilevel Poisson regression model.

RESULTS

Temperature and higher length of pasture had a positive relationship with lameness while concentration of Selenium in soil and flock size had a negative relationship with lameness. In addition, results showed lower lameness levels for the bedrock class mudstone, siltstone, limestone and sandstone in comparison to sandstone and finally, lambs and ewes younger than 1year old had lower levels of lameness than older ewes.

CONCLUSION

Findings of the present approach show the potential use of data collected via a smartphone app to study the epidemiology of disease. Furthermore, factors identified could be validated in intervention studies and generate data-driven disease predictive models.

Sustainable lamb production: Evaluation of factors affecting lamb growth using hierarchical, cross classified and multiple memberships models

In light of current concerns about the sustainability of red meat production in a world with increasing global demand for food from animal origin there is a need for a better understanding of factors that influence the growth rate and feed conversion efficiency of animals on commercial farms. The primary objective of this observational study was to use longitudinal data to quantify the simultaneous effects of multiple ewe and lamb factors on lamb growth rate. A secondary aim was to evaluate model structures that specifically account for lamb grouping effects during the growth period and compare these to classical hierarchical growth rate models. A total of 4172 weight recordings from 805 lambs and data on disease events were collected over a 6-month period from a commercial pedigree sheep flock. Three mixed model structures were compared, hierarchical, cross classified and multiple membership, and final estimates determined within a Bayesian framework. The multiple membership structure provided the best model fit and was used for final inference; taking account of the effect of lamb grouping over time provided the best estimates of lamb growth rate. Ewe lameness and mastitis cases had a deleterious impact on lamb growth. Lambs from ewes identified with mastitis during lactation were on average 3.0 (standard error (SE) 1.6) kg lighter during the four month growth period than lambs from unaffected ewes. Lambs from ewes that were not lame during pregnancy were 3.0 (SE 1.2) kg heavier at eight weeks of age than lambs from ewes with a least one lameness case during the same period. Lambs from ewes lame either during the first 4 weeks or between 4-8 weeks of a lamb's life (but not lame during pregnancy) were also significantly heavier at 56 days of age, than lambs reared by ewes that were lame during pregnancy (2.8 (SE 1.2) and 3.4 (SE 1.2) kg respectively). Cases of pneumonia and bacterial arthritis in lambs had a significant negative impact on lamb growth with affected lambs being on average 5.5 (SE 1.1) kg and 2.2 (SE 1.2) kg less than non-affected lambs respectively after the disease event. Prior to a case of lameness or pneumonia, lambs were significantly heavier than unaffected lambs suggesting a possible trade-off between growth and immune function. Overall, the study provides evidence that that a combination of ewe and lamb characteristics and disease events play an important role in determining lamb growth rate and that heavier lambs may be more susceptible to disease.

Increase in the flock prevalence of lameness in ewes is associated with a reduction in farmers using evidence-based management of prompt treatment: A longitudinal observational study of 154 English sheep flocks 2013-2015

Since 2006, farmers in England have received new recommendations on best practice to manage lameness in sheep through a range of knowledge exchange activities. The adoption of each recommendation varied, but in 2013 approximately 50% of farmers reported treating all lame sheep within 3 days of onset of lameness (prompt treatment), 41% did not practice routine foot trimming, 50% culled sheep that had been lame and 14% vaccinated against footrot; all recommended best practices. The aim of this study was to investigate the prevalence of lameness in ewes in England from 2013 to 2015 and to identify changes in practice to manage lameness between 2013 and 2015 and the population attributable fraction for these managements.

A longitudinal study with a cohort of 154 English sheep farmers was run for three years, farmers completed questionnaires on lameness in their flock for the previous 12 months in 2013, 2014 and 2015. The geometric mean prevalence of lameness in ewes was 4.1% in 2015, significantly higher than 3.3% and 3.2% for the same 128 farmers who provided data in both 2013 and 2014. Between 2013 and 2015 there was a significant reduction in farmers practising prompt treatment (50.6%–28.6%) but an increase in not practising routine foot trimming (40.9%–79.2%), culling sheep that had been lame (49.4%–81.8%), and vaccinating against footrot (14.3%–29.2%).

Not practising prompt treatment, ≥5% of sheep feet bleeding during routine foot trimming, vaccinating ewes for <6 years or not vaccinating at all, and other flocks mixing with the flock, were associated with a significantly higher flock prevalence of lameness. Culling sheep that had been lame was not associated with prevalence of lameness. The population attributable fractions (PAFs) for not vaccinating for>5 years, not treating lame sheep promptly, ≥5% of sheep feet bleeding during routine foot trimming, and mixing of flocks were 34.5%, 25.3%, 2.9% and 2.4%. In 2013, when 50% of farmers used prompt treatment, the PAF for not using prompt treatment was only 13.3%. We conclude that the change in practice by these farmers towards flock-level managements and a reduction in individual prompt treatment of lame sheep negatively impacted the prevalence of lameness in sheep. This change occurred despite the evidence that prompt treatment of lame sheep is highly effective at reducing the prevalence of lameness in sheep flocks and is an example of cognitive dissonance.

Sites of persistence of Fusobacterium necrophorum and Dichelobacter nodosus: a paradigm shift in understanding the epidemiology of footrot in sheep

Sites of persistence of bacterial pathogens contribute to disease dynamics of bacterial diseases. Footrot is a globally important bacterial disease that reduces health and productivity of sheep. It is caused by Dichelobacter nodosus, a pathogen apparently highly specialised for feet, while Fusobacterium necrophorum, a secondary pathogen in footrot is reportedly ubiquitous on pasture. Two prospective longitudinal studies were conducted to investigate the persistence of D. nodosus and F. necrophorum in sheep feet, mouths and faeces, and in soil. Molecular tools were used to detect species, strains and communities. In contrast to the existing paradigm, F. necrophorum persisted on footrot diseased feet, and in mouths and faeces; different strains were detected in feet and mouths. D. nodosus persisted in soil and on diseased, but not healthy, feet; similar strains were detected on both healthy and diseased feet of diseased sheep. We conclude that D. nodosus and F. necrophorum depend on sheep for persistence but use different strategies to persist and spread between sheep within and between flocks. Elimination of F. necrophorum would be challenging due to faecal shedding. In contrast D. nodosus could be eliminated if all footrot-affected sheep were removed and fade out of D. nodosus occurred in the environment before re-infection of a foot.

Aetiology, Risk Factors, Diagnosis and Control of Foot-Related Lameness in Dairy Sheep

During the last twenty years, considerable research efforts have recognized the consequences of foot-related lameness primarily in cattle, and meat and wool sheep. Despite the lack of extensive epidemiological studies, field observations and isolated research reports in dairy sheep have suggested that the problem might be more severe in semi-intensive and intensive farming systems. Footrot, contagious ovine digital dermatitis, ovine interdigital dermatitis, white line disease, and pedal joint abscess are the most common causes of foot-related lameness. Dichelobacter nodosus, Fusobacterium necrophorum, Treponema spp., and Actinomyces pyogenes are the most significant foot-related lameness-associated pathogens. Despite a documented hereditary predisposition, environmental factors are the most important in determining the occurrence of foot-related lameness. Moist and warm environment, increased parity and milk yield, inappropriate housing conditions and infrastructures, inadequate hygiene status, imbalanced nutrition, and insufficient foot care are the most critical risk factors. Furthermore, a foot-lameness control plan should include targeted implementation of claw trimming and footbathing, evidence-based planning of hygiene measures in preventive veterinary practices (i.e., antibiotic administration, vaccinations against footrot), selective breeding to footrot resistance, and, most importantly, the continuous training of farming personnel. Controlling foot-lameness in dairy sheep is critical in determining the well-being of animals, and strongly affects the farm's profitability and sustainability.

Footbathing, formalin and foot trimming: The 3Fs associated with granulomas and shelly hoof in sheep

Granulomas and shelly hoof (SH), are lesions of sheep feet. Our objective was to use data from four questionnaires on lameness sent to English sheep farmers in 2004, 2013, 2014 and 2015 to further understanding of the risks and aetiologies of both lesions. Granulomas were more likely in flocks where routine foot trimming (odds ratio [OR]=3.17; 95% confidence intervals [CI] 1.11-11.47) and routine footbathing (OR=2.38; 95% CI 1.19-4.83) were practised than where these management protocols were not. SH was more likely in flocks that were footbathed in formalin compared with not footbathing (OR=1.65; 95% CI 1.19-2.30), and was less common in flocks that stocked ewes at more than eight vs. four per acre (OR=0.34; 95% CI 0.17-0.68). There were weak associations between SH and foot trimming. In 2004 only, SH was more likely in flocks where therapeutic foot trimming was practised than not practised (OR=2.24; 95% CI 1.12-4.68). In 2014 only, SH was marginally less likely in flocks where no feet bled during trimming, compared with flocks not routinely trimmed (OR=0.55; CI 0.30-1.00); SH was not related to foot trimming once severe footrot was included. We propose that flocks with granulomas and SH would decrease if farmers stopped footbathing in general, in particular with formalin, and avoided foot trimming whether as a therapeutic or routine practice. Further work is needed to understand the role of stocking density.

Quantifying the beliefs of key players in the UK sheep industry on the efficacy of two treatments for footrot

Clinical trials have demonstrated that sheep with footrot treated with parenteral and topical antibiotics without foot trimming (treatment A), cure faster than sheep treated with foot trimming and topical antibiotics (treatment B). We investigated how key players in the UK sheep industry recommended treating footrot, and tested whether reviewing the evidence surrounding treatment of footrot changed their beliefs. Eight key players attended a workshop to investigate their current practices, and their perceived efficacy of treatments, using probabilistic elicitation. At the start of the study, all participants recommended use of antibiotic injection but only four recommended not foot trimming feet with footrot. Initial beliefs in the difference in cure rate within five days of treatment ranged from 30 to 97% in favour of treatment A (true difference 60%); this heterogeneity reduced after reviewing the evidence. Participants who believed the cure rate differed by >60% over-estimated the cure rate of treatment A whilst participants who believed the difference was <60% over-estimated the efficacy of treatment B. During discussions, participants stated that parenteral antibiotics had always been recommended as a treatment for footrot but that the new research clarified when to use them. In contrast, it was highly novel to hear that foot trimming was detrimental to recovery, and key players and farmers are taking longer to accept this evidence. Three months after the workshop, two participants stated that they now placed greater emphasis on rapid individual antibiotic treatment of lame sheep and one was no longer recommending trimming feet.

Development and assessment of management practices in a flock-specific lameness control plan: A stepped-wedge trial on 44 English sheep flocks

Lameness in sheep has economic and welfare implications, including loss of ewe body condition, lower lambing percentages, and poor lamb growth rates. It costs the UK sheep industry around £80 million per year. The majority of lameness is caused by the infectious diseases footrot and contagious ovine digital dermatitis, with white line separation, white line abscesses, and toe granulomas also reported by farmers. Most sheep farmers in the UK have other enterprises and care for their flock part-time. A lameness control plan (LCP) consisting of 37 management practices that covered all aspects of control of lameness was developed for part-time sheep farmers. Testing of the LCP was done using a stepped-wedge trial design with 7 visits to 44 flocks in England over 18 months. Flocks had 100-500 breeding ewes. Locomotion scoring was carried out at every visit, and farmers were interviewed every 6 months to record management practices. Clinical significance of changes in prevalence of lameness within each flock was analysed using the reliable change index (RCI). Management practices associated with prevalence of lameness were assessed using a multi-level multivariable over-dispersed Poisson model. The geometric mean (GM) prevalence of lameness at the start of the trial was 7.3% (95% confidence interval(CI) = 6.3-8.3%). Flocks with a clinically significant lameness reduction had a GM prevalence of lameness of 4.6% (95% CI = 4.1-5.2%), while flocks with a clinically significant increase in lameness had a GM prevalence of 10.5% (95% CI = 9.4-11.6%). Always separating lame sheep at treatment (relative risk (RR) = 0.60, 95% CI = 0.43-0.84) and culling sheep lame ≥2 occasions in a year (RR = 0.75, 95% CI = 0.61-0.92) were associated with a significant reduction in lameness. Compared with not footbathing at all, footbathing sheep when there were outbreaks of interdigital dermatitis reduced lameness (RR = 0.85, 95% CI = 0.75-0.96), however, 'routine' footbathing was not associated with a reduction in lameness. Housing during the previous lambing period was associated with a higher prevalence of lameness (RR = 1.23, 95% CI = 1.04-1.46). Vaccination in flocks with period prevalence ≥10% did not significantly reduce their risk of lameness compared to lower prevalence flocks. In conclusion, separating lame sheep at treatment, culling sheep lame ≥2 occasions per year, and only using a footbath to treat outbreaks of interdigital dermatitis are flock managements that contribute to improved control of lameness in flocks with part-time farmers.

Detection and Serogrouping of Dichelobacter nodosus Infection by Use of Direct PCR from Lesion Swabs To Support Outbreak-Specific Vaccination for Virulent Footrot in Sheep

Virulent footrot is an economically significant disease in most sheep-rearing countries. The disease can be controlled with vaccine targeting the fimbriae of virulent strains of the essential causative agent, Dichelobacter nodosus However, the bacterium is immunologically heterogeneous, and 10 distinct fimbrial serogroups have been identified. Ideally, in each outbreak the infecting strains would be cultured and serogrouped so that the appropriate serogroup-specific mono- or bivalent vaccine could be administered, because multivalent vaccines lack efficacy due to antigenic competition. If clinical disease expression is suspected to be incomplete, culture-based virulence tests are required to confirm the diagnosis, because control of benign footrot is economically unjustifiable. Both diagnosis and vaccination are conducted at the flock level. The aims of this study were to develop a PCR-based procedure for detecting and serogrouping D. nodosus directly from foot swabs and to determine whether this could be done accurately from the same cultured swab. A total of 269 swabs from the active margins of foot lesions of 261 sheep in 12 Merino sheep flocks in southeastern Australia were evaluated. DNA extracts taken from putative pure cultures of D. nodosus and directly from the swabs were evaluated in PCR assays for the 16S rRNA and fimA genes of D. nodosus Pure cultures were tested also by the slide agglutination test. Direct PCR using extracts from swabs was more sensitive than culture for detecting and serogrouping D. nodosus strains. Using the most sensitive sample collection method of the use of swabs in lysis buffer, D. nodosus was more likely to be detected by PCR in active than in inactive lesions, and in lesions with low levels of fecal contamination, but lesion score was not a significant factor. PCR conducted on extracts from swabs in modified Stuart's transport medium that had already been used to inoculate culture plates had lower sensitivity. Therefore, if culture is required to enable virulence tests to be conducted, it is recommended that duplicate swabs be collected from each foot lesion, one in transport medium for culture and the other in lysis buffer for PCR.

Drivers for precision livestock technology adoption: A study of factors associated with adoption of electronic identification technology by commercial sheep farmers in England and Wales

The UK is the largest lamb meat producer in Europe. However, the low profitability of sheep farming sector suggests production efficiency could be improved. Although the use of technologies such as Electronic Identification (EID) tools could allow a better use of flock resources, anecdotal evidence suggests they are not widely used. The aim of this study was to assess uptake of EID technology, and explore drivers and barriers of adoption of related tools among English and Welsh farmers. Farm beliefs and management practices associated with adoption of this technology were investigated. A total of 2000 questionnaires were sent, with a response rate of 22%. Among the respondents, 87 had adopted EID tools for recording flock information, 97 intended to adopt it in the future, and 222 neither had adopted it, neither intended to adopt it. Exploratory factor analysis (EFA) and multivariable logistic regression modelling were used to identify farmer beliefs and management practices significantly associated with adoption of EID technology. EFA identified three factors expressing farmer’s beliefs–external pressure and negative feelings, usefulness and practicality. Our results suggest farmer’s beliefs play a significant role in technology uptake. Non-adopters were more likely than adopters to believe that ‘government pressurise farmers to adopt technology’. In contrast, adopters were significantly more likely than non-adopters to see EID as practical and useful (p≤0.05). Farmers with higher information technologies literacy and intending to intensify production in the future were significantly more likely to adopt EID technology (p≤0.05). Importantly, flocks managed with EID tools had significantly lower farmer- reported flock lameness levels (p≤0.05). These findings bring insights on the dynamics of adoption of EID tools. Communicating evidence of the positive effects EID tools on flock performance and strengthening farmer’s capability in use of technology are likely to enhance the uptake of this technology in sheep farms.

A comparison of the efficacy of three intervention trial types: postal, group, and one-to-one facilitation, prior management and the impact of message framing and repeat messages on the flock prevalence of lameness in sheep

The aim of this study was to evaluate the effectiveness of three knowledge-transfer intervention trial types (postal, group, one-to-one) to promote best practice to treat sheep with footrot. Further aims were to investigate whether farmer behaviour (i.e. management of lameness) before the trial was associated with uptake of best practice and whether the benefits of best practice framed positively or negatively influenced change in behaviour. The intervention was a message developed from evidence and expert opinion. It was entitled "Six steps to sound sheep" and promoted (1) catch sheep within three days of becoming lame, (2) inspect feet without foot trimming, (3) correctly diagnose the cause, (4) treat sheep lame with footrot or interdigital dermatitis with antibiotic injection and spray without foot trimming, (5) record the identity of treated sheep, (6) cull repeatedly lame sheep. In 2013, 4000 randomly-selected English sheep farmers were sent a questionnaire, those who responded were recruited to the postal (1081 farmers) or one-to-one intervention (32 farmers) trials. A random sample of 400 farmers were invited to join the group trial; 78 farmers participated. A follow-up questionnaire was sent to all participants in summer 2014. There were 72%, 65% and 91% useable responses for the postal, group and one-to-one trials respectively. In both 2013 and 2014, the prevalence of lameness was lower in flocks managed by LC1 farmers than LC2 and LC3 farmers. Between 2013 and 2014, the reduction in geometric mean (95% CI) period prevalence of lameness, proportional between flock reduction in lameness and within flock reduction in lameness was greatest in the one-to-one (7.6% (7.1-8.2%) to 4.3% (3.6-5.0%), 35%, 72%) followed by the group (4.5% (3.9-5.0%) to 3.1% (2.4-3.7%), 27%, 55%) and then the postal trial (from 3.5% (3.3-3.7%) to 3.2% (3.1-3.4%), 21%, 43%). There was a marginally greater reduction in lameness in farmers using most of Six steps but slow to treat lame sheep pre-trial than those not using Six steps at all. There was no significant effect of message framing. The greatest behavioural change was a reduction in therapeutic and routine foot trimming and the greatest attitude change was an increase in negative attitudes towards foot trimming. We conclude that all three intervention trial approaches were effective to promote best practice to treat sheep with footrot with one-to-one facilitation more effective than group and postal intervention trials. Results suggest that farmers' behaviour change was greater among those practising aspects of the intervention message before the trial began than those not practising any aspect.

A financial cost-benefit analysis of eradicating virulent footrot

In 2008, virulent footrot was detected in sheep in south-west Norway. Footrot is caused by Dichelobacter nodosus, and the outbreak was linked to live sheep imported from Denmark in 2005. A large-scale program for eradicating the disease was implemented as a joint industry and governmental driven eradication project in the years 2008-2014, and continued with surveillance and control measures by the Norwegian Food Safety Authority from 2015. The cost of the eradication program including surveillance and control measures until 2032 was assumed to reach approximately €10.8 million (NOK 90 million). A financial cost-benefit analysis, comparing costs in the eradication program with costs in two simulated scenarios, was carried out. In the scenarios, designated ModerateSpread (baseline) and SlowSpread, it was assumed that the sheep farmers would undertake some voluntary measures on their own that would slow the spread of the disease. The program obtained a positive NPV after approximately 12 years. In a stochastic analysis, the probabilities of a positive NPV were estimated to 1.000 and to 0.648 after 15 years and to 0.378 and 0.016 after ten years, for the ModerateSpread and SlowSpread scenarios respectively. A rapid start-up of the program soon after the detection of the disease was considered crucial for the economic success as the disease would have become more widespread and probably raised the costs considerably at a later start-up.

Within-Flock Population Dynamics of Dichelobacter nodosus

Footrot causes 70-90% of lameness in sheep in Great Britain. With approximately 5% of 18 million adult sheep lame at any one time, it costs the UK sheep industry £24-84 million per year. The Gram-negative anaerobe Dichelobacter nodosus is the causative agent, with disease severity influenced by bacterial load, virulence, and climate. The aim of the current study was to characterize strains of D. nodosus isolated by culture of swabs from healthy and diseased feet of 99 ewes kept as a closed flock over a 10-month period and investigate persistence and transmission of strains within feet, sheep, and the flock. Overall 268 isolates were characterized into strains by serogroup, proline-glycine repeat (pgr) status, and multi-locus variable number tandem repeat analysis (MLVA). The culture collection contained 87 unique MLVA profiles and two major MLVA complexes that persisted over time. A subset of 189 isolates tested for the virulence marker aprV2 were all positive. The two MLVA complexes (76 and 114) comprised 62 and 22 MLVA types and 237 and 28 isolates, respectively. Serogroups B, and I, and pgrB were associated with MLVA complex 76, whereas serogroups D and H were associated with MLVA complex 114. We conclude that within-flock D. nodosus evolution appeared to be driven by clonal diversification. There was no association (P > 0.05) between serogroup, pgr, or MLVA type and disease state of feet. Strains of D. nodosus clustered within sheep and were transmitted between ewes over time. D. nodosus was isolated at more than one time point from 21 feet, including 5 feet where the same strain was isolated on two occasions at an interval of 1-33 weeks. Collectively, our results indicate that D. nodosus strains persisted in the flock, spread between sheep, and possibly persisted on feet over time.

Mathematical modeling of ovine footrot in the UK: the effect of Dichelobacter nodosus and Fusobacterium necrophorum on the disease dynamics

Dichelobacter nodosus is a virulent, invasive, anaerobic bacterium that is believed to be the causative agent of ovine footrot, an infectious bacterial disease of sheep that causes lameness. Another anaerobe, Fusobacterium necrophorum, has been intimately linked with the disease occurrence and severity. Here we examine data from a longitudinal study of footrot on one UK farm, including quantitative PCR (qPCR) estimates of bacterial load of D. nodosus and F. necrophorum. The data is at foot level; all feet were monitored for five weeks assessing disease severity (healthy, interdigital dermatitis (ID), or severe footrot (SFR)) and bacterial load (number of bacteria/swab). We investigate the role of D. nodosus and F. necrophorum in the progress of the disease using a continuous-time Markov model with 12 different states characterising the foot. The transition rates between the adjacent states are the (34) model parameters, these are determined using Metropolis Hasting MCMC. Our aim is to determine the predictive relationship between past and future D. nodosus and F. necrophorum load and disease states. We demonstrate a high level of predictive accuracy at the population level for the D. nodosus model, although the dynamics of individual feet is highly stochastic. However, we note that this predictive accuracy at population level is only high in more diseased states for F. necrophorum model. This supports our hypothesis that D. nodosus load and status of the foot work in combination to give rise to severe footrot and lameness, and that D. nodosus load plays the primary role in the initiation and progression of footrot, while F. necrophorum load rather increases disease severity of SFR.

Inter-observer agreement for clinical examinations of foot lesions of sheep

In sheep, the diagnosis of foot lesions is routinely based on physical examination of the hoof. Correct diagnosis is important for the effective treatment, prevention and control of both infectious and non-infectious causes of lameness. Therefore, the aim of this study was to evaluate the level of inter-observer agreement for clinical examination of ovine foot lesions. Eight observers of varying experience, training and occupation performed foot examinations on a total of 1158 sheep from 38 farms across North England and Wales. On each farm, a group of two to four observers independently examined a sample of 24 to 30 sheep to diagnose the presence or absence of specific foot lesions including white line lesions (WL), contagious ovine digital dermatitis (CODD), footrot (FR), inter-digital dermatitis (ID) and toe granuloma (TG). The inter-observer agreement of foot lesion assessments was examined using Fleiss kappa (κ), and Cohen's κ examined the paired agreement between the test standard observer (TSO) and each observer. Scoring differences with the TSO were examined as the percentage of scoring errors and assessed for evidence of systematic scoring bias. With the exception of WL (maximum error rate 33.3%), few scoring differences with the TSO occurred (maximum error rate 3.3%). This suggests that observers can achieve good levels of reliability when diagnosing most of the commonly observed foot conditions associated with lameness in sheep.

Whole-flock, metaphylactic tilmicosin failed to eliminate contagious ovine digital dermatitis and footrot in sheep: a cluster randomised trial

The aim of this study was to evaluate the clinical success of whole-flock systemic tilmicosin and enhanced biosecurity in eliminating active contagious ovine digital dermatitis (CODD) from sheep flocks. Thirty flocks in the UK were randomly allocated to receive either treatment as usual (as per the farmer's normal routine) or whole-flock treatment with tilmicosin, together with isolation and extended treatment of clinically affected individuals and isolation and treatment of purchased sheep during the study period. All flocks were visited once at onset of the trial to examine all sheep. One year later, all sheep were re-examined to determine the presence/absence of clinical lesions. The primary outcome was the clinical elimination of CODD from flocks. Secondary outcomes were reduction in prevalence of CODD, clinical elimination of footrot and reduction in prevalence of footrot. The analysis included 11 control flocks and 13 intervention flocks, with initially 3460 and 4686 sheep, respectively. For CODD: at follow-up, in the intervention group, 6/13 (46 per cent) flocks had a prevalence of zero compared with 1/11 (9 per cent) in the control group (P=0.12). For footrot: at follow-up, no flocks had a prevalence of zero. Therefore, the intervention is not recommended for the elimination of CODD or footrot in the UK.

Associations between sheep farmer attitudes, beliefs, emotions and personality, and their barriers to uptake of best practice: The example of footrot

There is interest in understanding how farmers' behaviour influences their management of livestock. We extend the theory of planned behaviour with farmers attitudes, beliefs, emotions and personality to investigate how these are associated with management of livestock disease using the example of footrot (FR) in sheep. In May 2013 a one-year retrospective questionnaire was sent to 4000 sheep farmers in England, requesting data on lameness prevalence, management of footrot, farm/flock descriptors, and farmer-orientated themes: barriers to treating footrot, opinions and knowledge of footrot, relating to other people and personality. Principal component analysis (PCA) was used to make composite variables from explanatory variables and latent class (LC) analysis was used to subgroup farmers, based on nine managements of FR. Associations between LC and composite variables were investigated using multinomial logistic regression. Negative binomial regression was used to investigate associations between the proportion of lame sheep and composite and personality variables. The useable response rate was 32% and 97% of farmers reported having lame sheep; the geometric mean prevalence of lameness (GMPL) was 3.7% (95% CI 3.51%-3.86%). Participants grouped into three latent classes; LC1 (best practice-treat FR within 3days of sheep becoming lame; use injectable and topical antibiotics; avoid foot trimming), 11% farmers), LC2 (slow to act, 57%) and LC3 (slow to act, delayed culling, 32%), with GMPL 2.95%, 3.60% and 4.10% respectively. Farmers who reported the production cycle as a barrier to treating sheep with FR were more likely to be in LC2 (RRR 1.36) than LC1. Negative emotions towards FR were associated with higher risk of being in LC2 (RRR 1.39) than LC1. Knowledge of preventing FR spread was associated with a lower risk of being in LC2 (RRR 0.46) or LC3 (RRR 0.34) than LC1. Knowledge about FR transmission was associated with a lower risk of being in LC3 (RRR 0.64) than LC1. An increased risk of lameness was associated with the production cycle being a barrier to treating sheep with FR (IRR 1.13), negative emotions towards FR (IRR 1.13) and feelings of hopelessness towards FR (IRR 1.20). Conscientiousness (IRR 0.95) and understanding the importance of active control of lameness (IRR 0.76) were associated with reduced risk of lameness. We conclude that emotions and personality are associated with differences in farmer management of FR and prevalence of lameness. Further understanding how personality and emotions influence change in behaviour is key to increasing uptake of new information.

Factors associated with the presence and prevalence of contagious ovine digital dermatitis: A 2013 study of 1136 random English sheep flocks

In 2013, a questionnaire was used to gather data on risks for introduction, and factors associated with prevalence, of contagious ovine digital dermatitis (CODD). There were 1136 (28.4%) usable responses from 4000 randomly selected sheep farmers in England. CODD was present in 58% (662) of flocks, with a reported prevalence of CODD lesions of 2.3%. The geometric mean period prevalence of all lameness was 4.2% and 2.8% in CODD positive and negative flocks respectively. Factors associated with a greater risk of presence of CODD were purchasing replacement ewes, not always checking the feet of sheep before purchase, not isolating purchased sheep, foot bathing returning ewes, foot trimming the flock more than twice in the year all compared with not doing these activities and increasing log10 flock size. Farmers who vaccinated sheep with Footvax™ were less likely to report presence of CODD. Factors associated with increasing prevalence of CODD lesions were not always checking the feet of purchased sheep, flocks that mixed with other flocks and sheep that left the farm for summer grazing and later returned. In addition, flocks where farmers followed the current recommended managements for control of footrot, had a lower prevalence of CODD whilst those who used foot bathing and where feet bled during routine foot trimming had a higher prevalence of CODD. The prevalence of CODD decreased with each log10 increase in flock size. We conclude that CODD is an infectious cause of lameness in sheep of increasing importance in GB. Introduction is linked to poor biosecurity with one likely source of the pathogen being introduction of or mixing with infected sheep. As with footrot, prevalence of CODD was lower in flocks where farmers focused on individual treatment to manage lameness and avoided foot bathing and trimming feet. We conclude that most of the currently recommended biosecurity and treatment approaches to control footrot in GB are also effective for control of CODD.

A case report of lameness in two dairy goat herds; a suspected combination of nutritional factors concurrent with treponeme infection

BACKGROUND

Two dairy goat farms with high level of lameness in lactating animals were presented for further investigation. Farm 1 and Farm 2 presented with 37 and 67% morbidity, respectively. Both farms had an all year round indoor system, feeding ad libitum concentrate with forage available at all times.

CASE PRESENTATION

The lameness was found to be based in the foot. Previous treatments consisting of biweekly footbathing with zinc sulphate, spraying lesions with oxytetracycline spray and packing lesions with copper crystals on a single occasion and single injections with long acting oxytetracycline had not been successful. Mild cases had signs of haemorrhaging in the white line or on the sole of the foot. Moderate cases showed under running of the wall horn or small areas of exposed sole corium. Severe cases would consist of horn or wall separation with the corium exposed and infected. In extreme cases only the wall horn of the claw remained, with a large area of necrotic tissue in the centre and no healthy corium visible. Only one animal was seen to have interdigital lesions. Polymerase chain reaction (PCR) and culture of swabs taken from exposed corium and the interdigital space were negative for Dichelobacter nodosus but PCR for treponemes were positive in both the adults and the youngstock tested. Due to the high level of concentrate in the diet of these goats, nutrition was thought to contribute to the problem. Transcutaneous rumen fluid samples were taken and pH was measured on both farms, with 35% of the samples below pH value 5.5.

CONCLUSION

No definite diagnosis could be made. However, the results suggest both treponemes and nutrition play a role in the aetiology of the lameness. The initial sole or wall horn lesions were thought to be secondarily infected by treponemes. Further investigation is needed to definitively diagnose the cause and contributing factors for this lameness.