Looking after the individual to reduce disease in the flock: a binomial mixed effects model investigating the impact of individual sheep management of footrot and interdigital dermatitis in a prospective longitudinal study on one farm

Gamithromycin in sheep: Pharmacokinetics and clinical evaluation against ovine footrot

In the context of a development program to obtain the market authorization of injectable gamithromycin 15% w/v solution (Zactran®, Boehringer Ingelheim) for use in sheep against footrot, the pharmacokinetic profile of gamithromycin was established and the safety and efficacy of the treatment were confirmed in a multicenter field study in Europe. The basic pharmacokinetic parameters established in healthy young Merino sheep administered gamithromycin at 6 mg/kg body weight based on the analysis of plasma samples which were collected in intervals up to 12 days after subcutaneous injection were: area under the curve until last quantifiable concentration, 8.88 ± 2.33 μg*h/mL; maximum plasma concentration, 448 ± 180 ng/mL; terminal half-life, 42.5 ± 5.25 h. The safety and clinical efficacy against footrot of gamithromycin 15% w/v solution were evaluated in comparison to tilmicosin 30% w/v solution (Micotil®, Elanco) treatment in 364 sheep of various breeds, sex and age from commercial farms in the United Kingdom (2 sites), Germany (3 sites) and France (1 site). Animals were enrolled based on lesions characteristic of footrot and lameness associated with the presence of footrot-related bacterial pathogens and were randomly allocated and treated in a 1:1 ratio with a single subcutaneous dose of gamithromycin or tilmicosin at label dosage (6 or 10 mg/kg body weight, respectively). Lameness and footrot lesions were evaluated at five and 21 days after treatment; the injection site in all animals was examined the day after treatment and followed up daily in the animals with injection site reaction until complete injection site reaction resolution. Samples of 310 and 120 animals tested positive for Dichelobacter nodosus and Fusobacterium necrophorum, respectively, at inclusion, and data of 359 animals were included into the combined analyses (5 animals excluded for unintentional overdosing [1], lack of follow-up [1], concurrent antibiotic medication for non-footrot conditions [3]). Lameness scores at 21 days after treatment demonstrated a significantly (p = 0.0396) better success for the gamithromycin treatment compared to the tilmicosin treatment (97.8% vs. 93.3%). Post-dosing footrot lesion scores followed similar trends of rapid and marked decrease (improvement) for both treatments with similar (p = 0.127) treatment success for the gamithromycin and tilmicosin treatments (97.8% and 96.0%, respectively). Both treatments were safe; injection site reactions noted in 19 gamithromycin- and 25 tilmicosin-treated animals resolved within five days or six days of treatment, respectively. Gamithromycin 15% w/v solution administered once to sheep by subcutaneous injection at 6 mg/kg body weight demonstrated a pharmacokinetic profile similar to that reported previously in sheep and cattle and was confirmed to be a safe and efficacious treatment for naturally occurring ovine footrot in a multicenter clinical field study conducted in Europe.

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.

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.

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.

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.

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.

Drug Target Identification and Prioritization for Treatment of Ovine Foot Rot: An In Silico Approach

Ovine foot rot is an infection of the feet of sheep, mainly caused by Dichelobacter nodosus. In its virulent form, it is highly contagious and debilitating, causing significant losses in the form of decline in wool growth and quality and poor fertility. Current methods of treatment are ineffective in complete eradication. Effective antibiotic treatment of foot rot is hence necessary to ensure better outcomes during control phases by reduction in culling count and the possibility of carriers of the infection. Using computational approaches, we have identified a set of 297 proteins that are essential to the D. nodosus and nonhomologous with sheep proteins. These proteins may be considered as potential vaccine candidates or drug targets for designing antibiotics against the bacterium. This core set of drug targets have been analyzed for pathway annotation to identify 67 proteins involved in unique bacterial pathways. Choke-point analysis on the drug targets identified 138 choke-point proteins, 29 involved in unique bacterial pathways. Subcellular localization was also predicted for each target to identify the ones that are membrane associated or secreted extracellularly. In addition, a total of 13 targets were identified that are common in at least 10 pathogenic bacterial species.

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.

Survival of the ovine footrot pathogen Dichelobacter nodosus in different soils

Dichelobacter nodosus (D. nodosus) is the causative agent of footrot in sheep; one of the most important health and welfare issues of sheep worldwide. For control programmes to be effective, it is essential that the transmission cycle of D. nodosus is understood and bacterial reservoirs in the environment are better defined. This study evaluated the survival of D. nodosus in different soils using soil microcosms. Cultivation independent and dependent methods were used to detect D. nodosus over 40 days from seeding in soil. A D. nodosus specific probe was used for quantification by qPCR and viability was assessed by cell permeability to an intercalating dye, PMA, and by culture. Survival varied dramatically depending on soil type, matric potential (MP) and temperature. Our findings indicate that D. nodosus survival was higher at 5 °C compared with 25 °C in all soils and significantly longer at both temperatures in clay soil (>44% clay) compared with other soil types. Survival under all conditions was longer than 30 days for both culture independent and dependent methods, this is substantially longer than previous studies and, if this is an infectious dose, longer than the current recommendation of resting a field for 14 days to prevent onward infection.

The role of the environment in transmission of Dichelobacter nodosus between ewes and their lambs

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Lambs’ feet were D. nodosus-negative at birth.

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However D. nodosus was detected on lambs’ feet within 5–13 h of birth.

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Multiple pgrA and MLVA alleles were detected on the feet of ewes and lambs.

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D. nodosus on lambs’ feet originated from sources other than just their mother's feet.

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The environment plays a key role in D. nodosus transmission between ewes and lambs.

Dichelobacter nodosus (D. nodosus) is the essential causative agent of footrot in sheep. The current study investigated when D. nodosus was detectable on newborn lambs and possible routes of transmission. Specific qPCR was used to detect and quantify the load of D. nodosus in foot swabs of lambs at birth and 5–13 h post-partum, and their mothers 5–13 h post-partum; and in samples of bedding, pasture, soil and faeces. D. nodosus was not detected on the feet of newborn lambs swabbed at birth, but was detected 5–13 h after birth, once they had stood on bedding containing naturally occurring D. nodosus. Multiple genotypes identified by cloning and sequencing a marker gene, pgrA, and by multi locus variable number tandem repeat analysis (MLVA) of community DNA from swabs on individual feet indicated a mixed population of D. nodosus was present on the feet of both ewes and lambs. There was high variation in pgrA tandem repeat number (between 3 and 21 repeats), and multiple MLVA types. The overall similarity index between the populations on ewes and lambs was 0.45, indicating moderate overlap. Mother offspring pairs shared some alleles but not all, suggesting lambs were infected from sources(s) other than just their mother's feet. We hypothesise that D. nodosus is transferred to the feet of lambs via bedding containing naturally occurring populations of D. nodosus, probably as a result of transfer from the feet of the group of housed ewes. The results support the hypothesis that the environment plays a key role in the transmission of D. nodosus between ewes and lambs.

Dynamics and impact of footrot and climate on hoof horn length in 50 ewes from one farm over a period of 10 months

Footrot, including interdigital dermatitis, is caused by Dichelobacter nodosus cause the majority of lameness in sheep in the UK. Lame sheep often have overgrown hoof horn but recent evidence has indicated that trimming overgrown hoof horn increases recovery time, and that routine foot trimming of the flock does not reduce the prevalence or incidence of lameness. The objectives of this study were to investigate the temporal associations between hoof horn length, footrot and climate. Fifty multiparous ewes were monitored for 10 months. On eight occasions hoof horn length, foot lesions and body condition were recorded. At the first examination, ewes were assigned to one of two treatment groups. All ewes that became lame with footrot were treated at one time point per week, either by trimming hoof horn and applying a topical antibiotic spray or with parenteral antibiotic and topical antibiotic spray.

Hoof horn length in ewes at pasture varied over the year and was associated with temperature and rainfall. New cases of footrot occurred all year round and were associated with prior prevalence of footrot in the flock and prior temperature and rainfall. Overgrown hoof horn did not precede lameness but occurred once the sheep were lame. One year of prompt treatment of footrot reduced the range in hoof horn length in the sheep in both treatment groups. At the end of the study the hoof lengths of ewes in both groups were not significantly different. On this farm, hoof horn length was self-regulating in both non-lame and treated lame sheep whether trimming was part of the treatment or not and there would have been no benefit from routine foot trimming of this flock.

A longitudinal study of the role of Dichelobacter nodosus and Fusobacterium necrophorum load in initiation and severity of footrot in sheep

Footrot is an infectious bacterial disease of sheep that causes lameness. The causal agent is Dichelobacter nodosus. There is debate regarding the role of Fusobacterium necrophorum in disease initiation. This research used an observational longitudinal study of footrot, together with quantitative PCR (qPCR) of bacterial load of D. nodosus and F. necrophorum, to elucidate the roles of each species in the development of disease. All feet of 18 a priori selected sheep were monitored for five weeks assessing disease severity (healthy, interdigital dermatitis (ID) and severe footrot (SFR)) and bacterial load. A multinomial model was used to analyse these data.

Key unadjusted results were that D. nodosus was detected more frequently on feet with ID, whereas F. necrophorum was detected more frequently on feet with SFR. In the multinomial model, ID was associated with increasing log₁₀ load of D. nodosus the week of observation (OR = 1.28 (95% CI = 1.08–1.53)) and the week prior to development of ID (OR = 1.20 (95% CI = 1.01–1.42). There was no association between log₁₀ load² of F. necrophorum and presence of ID (OR = 0.99 (95% CI = 0.96–1.02))). SFR was associated with increasing log₁₀ load of D. nodosus the week before disease onset (OR = 1.42 (95% CI = 1.02–1.96)) but not once SFR had occurred. SFR was positively associated with log₁₀ load² of F. necrophorum once disease was present (OR = 1.06 (95% CI = 1.01–1.11)). In summary, there was an increased risk of increasing D. nodosus load the week prior to development of ID and SFR and during an episode of ID. In contrast, F. necrophorum load was not associated with ID before or during an episode, and was only associated with SFR once present. These results contribute to our understanding of the epidemiology of footrot and highlight that D. nodosus load plays the primary role in disease initiation and progression, with F. necrophorum load playing a secondary role. Further studies in more flocks and climates would be useful to confirm these findings. This study identifies that D. nodosus load is highest during ID. This supports previous epidemiological findings, which demonstrate that controlling ID is the most effective management strategy to prevent new cases of ID and SFR.

Assessment of farmer recognition and reporting of lameness in adults in 35 lowland sheep flocks in England

The aim of this study was to assess the accuracy of farmer recognition and reporting of lameness in their sheep flock when compared with the prevalence of lameness observed by a researcher. Thirty-five sheep farms were visited. Farmers were asked for estimates of the prevalence of lameness in 2008, in the flock and in one group of sheep that was inspected by the researcher the same day. These estimates were then compared with the researcher's estimate of lameness. All farmers were able to recognise lame sheep but they slightly under reported the prevalence of lameness in the group selected for examination when compared with the researcher's estimate. The proportion underestimated increased as the prevalence of lameness in the group increased. Farmer estimates on the day were consistently, closely and significantly correlated to that of the researcher's estimate of prevalence of lameness. We conclude that farmer estimates of prevalence of lameness in sheep are a sufficiently accurate and reliable tool for risk factor studies. The prevalence of lameness in sheep, nationally, is probably higher than the current estimate of 10% by 2-3%.

Ovine pedomics: the first study of the ovine foot 16S rRNA-based microbiome

We report the first study of the bacterial microbiome of ovine interdigital skin based on 16S rRNA by pyrosequencing and conventional cloning with Sanger-sequencing. Three flocks were selected, one a flock with no signs of footrot or interdigital dermatitis, a second flock with interdigital dermatitis alone and a third flock with both interdigital dermatitis and footrot. The sheep were classified as having either healthy interdigital skin (H) and interdigital dermatitis (ID) or virulent footrot (VFR). The ovine interdigital skin bacterial community varied significantly by flock and clinical condition. The diversity and richness of operational taxonomic units was greater in tissue from sheep with ID than H or VFR-affected sheep. Actinobacteria, Bacteriodetes, Firmicutes and Proteobacteria were the most abundant phyla comprising 25 genera. Peptostreptococcus, Corynebacterium and Staphylococcus were associated with H, ID and VFR, respectively. Sequences of Dichelobacter nodosus, the causal agent of ovine footrot, were not amplified because of mismatches in the 16S rRNA universal forward primer (27F). A specific real-time PCR assay was used to demonstrate the presence of D. nodosus, which was detected in all samples including the flock with no signs of ID or VFR. Sheep with ID had significantly higher numbers of D. nodosus (10(4)-10(9) cells per g tissue) than those with H or VFR feet.

Treatment and control of hoof disorders in sheep and goats

Lame sheep experience pain and should be treated as soon as reasonably practical. Treatment and control should be based on a firm diagnosis, and farmers should be encouraged to seek veterinary attention for animals that do not respond quickly to administered treatment. Overall flock lameness should be minimized through implementing appropriate control measures for the common types of foot lameness caused by infectious agents, including vaccination, antibiotic treatment, footbathing, biosecurity, and culling.

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

From observational studies, farmers who use parenteral antibacterials to promptly treat all sheep with footrot (FR) or interdigital dermatitis (ID) have a prevalence of lameness of < 2% compared with a prevalence of 9% lameness reported by farmers who treat lame sheep by trimming affected feet. We tested the hypothesis that prompt treatment of sheep lame with naturally developing FR or ID with parenteral and topical antibacterials reduces the prevalence and incidence of lameness with these conditions compared with less frequent treatment with trimming of hoof horn and applying topical antibacterials.A further hypothesis was that reduction of ID and FR would improve productivity. A lowland sheep flock with 700 ewes was used to test these hypotheses in an 18-month within farm clinical trial with four groups of ewes: two intervention and two control. The duration and severity of lameness was used to categorise sheep into three weighted scores of lameness (WLS): never lame (WLS0), mildly lame/lame for < 6 days (WLS1) and severely or chronically lame (WLS2). The intervention reduced the prevalence of lameness due to FR and ID in ewes and lambs and the incidence of lameness in ewes. The WLS was also significantly lower in sheep in the intervention groups. Ewes with a higher WLS were subsequently significantly more likely to have a body condition score < 2.5 and to have lame lambs. Significantly more ewes lambed and successfully reared more lambs that were ready for slaughter at a younger age in the intervention versus control groups. There was an increase in the gross margin of Pound630/100 ewes mated in the intervention group, including the cost of treatment of Pound150/100 ewes mated. We conclude that prompt parenteral and topical antibacterial treatment of sheep lame with ID and FR reduced the prevalence and incidence of these infectious conditions and led to improved health, welfare and productivity.

Ovine footrot: new approaches to an old disease

Footrot is a bacterial disease that has substantial economic and welfare impacts in sheep and can be difficult to manage. Research is focussed on reducing the impact that footrot has on farmers and their flocks and better understanding the aetiology of the disease. Key areas of current research include, developing better vaccines, deploying tailored vaccines in a specific and targeted fashion on individual farms, analysing and developing better farm management practices to suit specific sheep farming environments, elucidating the virulence genes and bacterial population dynamics that drive footrot and using genetic testing in combination with selective breeding to produce stock that are more resilient to disease.

Footrot and interdigital dermatitis in sheep: farmer satisfaction with current management, their ideal management and sources used to adopt new strategies

The aims of this research were to identify management practices that sheep farmers currently use to treat and prevent footrot in sheep and whether they consider that these are successful management tools and to find out how sheep farmers would ideally like to manage footrot in their flock. Over 90% of lameness in sheep in the UK is caused by Dichelobacter nodosus, which presents clinically as interdigital dermatitis (ID) alone or with separation of hoof horn (FR). A questionnaire was sent to 265 farmers to investigate their current management and their satisfaction with current management of the spectrum of clinical presentations of footrot. Farmers were also asked their ideal management of footrot and their interest in, and sources of information for, change. Approximately 160 farmers responded. Farmers satisfied with current management reported a prevalence of lameness < or = 5%. These farmers caught and treated lame sheep within 3 days of first seeing them lame, and treated sheep with FR and ID with parenteral antibacterials. Farmers dissatisfied with their management reported a prevalence of lameness >5%. These farmers practised routine foot trimming, footbathing and vaccination against footrot. Whilst 89% of farmers said they were satisfied with their management of FR over 34% were interested in changing management. Farmers identified veterinarians as the most influential source for new information. Farmers reported that ideally they would control FR by culling/isolating lame sheep, sourcing replacements from non-lame parents, trimming feet less, using antibacterial treatments less and using vaccination more. Footbathing was a commonly used management that was linked with dissatisfaction and that also was listed highly as an ideal management. Consequently, some of the ideal managements are in agreement with our understanding of disease control (culling and isolation, sourcing healthy replacements) but others are in contrast with our current knowledge of management and farmers self-reporting of satisfaction of management of footrot (less use of antibacterial treatment, more footbathing and vaccination). One explanation for this is the theory of cognitive dissonance where belief follows behaviour, i.e. farmers report that they believe an ideal which is what they are currently doing, even if the management is sub-optimal.

Randomized clinical trial of long-acting oxytetracycline, foot trimming, and flunixine meglumine on time to recovery in sheep with footrot

BACKGROUND

Internationally, foot trimming is used by most farmers, and parenteral antibacterials by some, to treat sheep with footrot. Nonsteroidal anti-inflammatory drugs (NSAID) are sometimes used. No clinical trials have compared these treatments.

OBJECTIVES

To investigate the above treatments on time to recovery from lameness and foot lesions in sheep with footrot.

ANIMALS

Fifty-three sheep with footrot on a commercial farm in England.

METHODS

In a randomized factorial design, the sheep were allocated to 6 treatment groups. The treatments were oxytetracycline spray to all sheep (positive control) and one or more of parenteral administration of long-acting oxytetracycline, flunixine meglumine, and foot trimming on day 1 or 6 of diagnosis. Follow-up was for 15 days. Time to recovery from lameness and lesions was investigated with discrete-time survival models.

RESULTS

There was significant association (P < .05) between recovery from lameness and lesions. Sheep receiving antibacterials parenterally recovered faster from lameness (odds ratio [OR]: 4.92 [1.20-20.10]) and lesions (OR: 5.11 [1.16-22.4]) than positive controls, whereas sheep foot trimmed on day 1 (lameness-OR: 0.05 [0.005-0.51]; lesions-OR: 0.06 [0.008-0.45]) or day 6 of diagnosis (lameness OR: 0.07 [0.01-0.72]; lesions OR: 0.07 [0.01-04).56]) recovered more slowly than positive controls. NSAID had no significant effect on recovery.

CONCLUSIONS AND CLINICAL IMPORTANCE

If foot trimming on day 1 or 6 of diagnosis was stopped and parenteral antibacterials were used, then over 1 million sheep/annum lame with footrot in the United Kingdom would recover more rapidly with benefits to productivity. Globally, this figure would be much higher.

Farmers' practices and factors associated with the prevalence of all lameness and lameness attributed to interdigital dermatitis and footrot in sheep flocks in England in 2004

The aim of this study was to investigate whether the risk factors associated with all causes of lameness in sheep differed from those associated with the lesion specific causes of lameness, interdigital dermatitis (ID) and footrot (FR). A total of 809 randomly selected English sheep farmers participated in a postal survey in 2005. Data were requested on their management of lameness in 2004 and whether this had changed from 2003 and the prevalence of all lameness, and lameness caused by ID and FR. The farmer ability to recognise ID and FR was assessed from their responses to a written and pictorial description. On 443 farms where both ID and FR were correctly named by the farmer, the mean prevalence of all lameness, and lameness caused by ID and FR were 10.0% (95% CI: 8.9, 10.8), 6.5% (95% CI: 5.8, 7.3) and 3.1% (95% CI: 2.8, 3.6), respectively. The mean prevalence of all lameness on all 809 farms was not significantly different at 10.2% (95% CI: 9.2, 11.0). The data were analysed using negative binomial regression models with the three outcomes farmer estimated prevalence of all lameness and lameness caused by ID or FR in 2004. Farmers who changed management of sheep between 2003 and 2004 were excluded from the analysis, thus all fixed effects were the farmers' managements in 2003 and 2004 to ensure that the management was in place for at least one year before the prevalence estimates. Routine foot trimming>or=once/year compared with no routine foot trimming was significantly associated with an increased prevalence of all lameness (prevalence ratio (PR)=1.34), ID (PR=1.50) and FR (PR=1.35). Footbathing was also significantly associated with increased prevalence of all lameness (PR=1.67), ID (PR=1.68) and FR (PR=1.76). A stocking density of >8 ewes/ha was associated with a significantly increased prevalence of all lameness (PR=1.26) and ID (PR=1.39). There was a significantly lower prevalence of FR (PR=0.73; PR=0.70, respectively) on farms in the North East and South East of England. Separating lame sheep at pasture was associated with a decreased prevalence of all lameness and ID (PR=0.75; PR=0.73) and location of the farm in South East England was associated with a lower prevalence of all lameness and ID (PR=0.75; PR=0.71, respectively). We conclude that management factors associated with all lameness, and lameness attributed to ID and FR are similar.

Recognition of lameness and decisions to catch for inspection among sheep farmers and specialists in GB

Background

Epidemiological studies have used farmer estimates of the prevalence of lameness in their flocks. This assumes that farmers can identify lame sheep. Eight movie clips of sheep with locomotion from sound to moderately lame were used to investigate the ability of farmers and sheep specialists to recognise lame sheep. Each participant was asked to complete a form and indicate, for each movie clip, whether they thought the sheep was lame and whether they would catch it if it was the only lame sheep or if 2 – 5, 6 – 10 or > 10 sheep were equally lame. The farmers' responses were compared with their estimates of flock lameness prevalence and the interval between observing a lame sheep and catching it.

Results

178 farmers and 54 sheep specialists participated. Participants could identify even mildly lame sheep but made a separate decision on whether to catch them. This decision was dependent on the severity of lameness and the number of sheep lame in a group. Those who said they would catch the first lame sheep in a group were significantly more likely to catch mildly lame sheep (farmer-reported median prevalence of lameness 5% (IQR: 2%–6%)). In contrast, farmers who waited for several sheep to be lame indicated that they would only catch more severely lame sheep (farmer reported median flock lameness 11% (IQR: 9%–15%)). Approximately 15% of farmers did not catch individual lame sheep (farmer reported median flock lameness 15% (IQR: 10%–15%)). The flock prevalence of lameness increased as time to treatment increased and time to treatment was positively correlated with only catching more severely lame sheep.

Conclusion

If movie-clips are similar to the flock situation, farmers and specialists can recognise even mildly lame sheep but vary in their management from prompt treatment of the first lame sheep in a group to no individual sheep treatments. The former practices would be appropriate to minimise transmission of footrot, a common, infectious cause of lameness and so reduce its incidence. The analysis also suggests that farmers estimate lameness prevalence relatively accurately because farmers who treated the first mildly lame sheep in a group also reported the lowest prevalence of lameness in their flock.

Naming and recognition of six foot lesions of sheep using written and pictorial information: a study of 809 English sheep farmers

In 2005, 3000 questionnaires were sent to a random sample of English sheep farmers from a list kept by the English Beef and Lamb Executive (EBLEX) to investigate whether farmers could correctly name six common foot lesions in sheep from a characteristic picture and a written description. The lesions were interdigital dermatitis (ID), footrot (FR), contagious ovine digital dermatitis (CODD), shelly hoof, foot abscess and toe granuloma. In addition, farmers were asked to report the total percent of lame sheep in their flock in 2004 and the percent of this lameness attributable to each of the six lesions listed above. The overall response percentage was 44 with a useable response of 32%. Fifty-nine farmers out of 262 (23%) who answered all six questions named all six lesions correctly. This was greater than expected by chance. The same questionnaire of six lesions was presented at a meeting of specialist sheep advisors, primarily veterinarians, 37/47 (79%) responders named all six lesions correctly. From the six lesions listed above, the percent correctly named by farmers was approximately 83%, 85%, 36%, 28%, 65% and 43% and the percent incorrectly attributed to another lesion was 5%, 47%, 10%, 13%, 35% and 7%, respectively. The most commonly used incorrect name was FR, with farmers tending to name any hoof horn lesion as FR. A comparison of the distribution of sheep lame by a lesion correctly named compared with the same lesion incorrectly named as FR suggested that farmers recognised lesions but did not name them correctly; the distribution of lameness fitted the pattern for the correctly named lesion rather than the pattern of lameness attributed to FR. The results were validated with farm visits and a repeatability study of the questionnaire. The mean farmer-estimated prevalence for all lameness was 10.4%; with 6.9%, 3.7%, 2.4%, 1.9%, 0.9% and 0.8% of the sheep lame with ID, FR, CODD, shelly hoof, foot abscess and toe granuloma respectively from respondents who correctly named these lesions. Whilst ID and FR were the most prevalent causes of lameness in most flocks it is possible that in up to 17% flocks the primary cause of lameness was a different lesion.

Assessment of current knowledge of footrot in sheep with particular reference to Dichelobacter nodosus and implications for elimination or control strategies for sheep in Great Britain

A brief summary of the currently accepted aetiology and pathogenesis of footrot and interdigital dermatitis in sheep in Great Britain is presented together with a description of the transmission dynamics of Dichelobacter nodosus. Approaches that may be successful for control or elimination of the disease are proposed and areas of uncertainty in current knowledge highlighted. Research and practice in Great Britain is compared with that from other countries and the proposal made that the environment and/or carrier (non-diseased) sheep may assist persistence of footrot.