The impact of glutaraldehyde based footbaths on Dichelobacter nodosus prevalence and the antimicrobial resistant community of the ovine interdigital skin.

Ovine footrot, is a highly contagious polymicrobial bacterial infection, primarily caused by Dichelobacter nodosus. Preventative bactericidal footbaths are commonly used in the sheep industry to reduce the spread of bacteria. However, their effect on the bacterial community is poorly understood. This is the first study to investigate the impact of 2% Digicur (ProGiene,UK) footbath on the bacterial community of the ovine interdigital skin following a common UK footbathing routine. Swab samples were analysed by qPCR to determine prevalence and load of D. nodosus and numerated on MacConkey agar in the presence or absence of tetracycline and ampicillin to determine phenotypic antimicrobial resistance. Metagenomics were used to determine the impact of a single footbath on the bacterial community and genotypic antimicrobial resistance. The results suggest 2% Digicur is ineffective at reducing the load of D. nodosus when applied as a one off or weekly footbath, however sheep may act as a reservoir for multi-drug resistant bacteria creating opportunities to spread antimicrobial resistance to other sheep and their environment.

Risk factors associated with the infection of sheep with Dichelobacter nodosus.

Ovine footrot is a highly contagious foot disease caused by the gram-negative bacterium Dichelobacter nodosus (D. nodosus). In a recent report, we showed a prevalence of 42.9% D. nodosus positive swabs across Germany. In this follow-up study, we used real-time PCR results for D. nodosus and footrot scores of 9297 sheep from 208 flocks and collated these data with survey data on herd and animal characteristics and herd management. The aims of the present study were to investigate herd and animal factors associated with D. nodosus infection and footrot scores in individual sheep. Multivariable analyses with generalized mixed models showed that month of recording, breed, herdbook membership, use of antibiotics, and footbaths in the past 3-10 years, signs of footrot in the past 12 months and flock environment of the sheep, modelled as a random farm effect within region, were significant risk factors. Among the 21 different breeds, Romney had the lowest risk of D. nodosus infection, while Swifter had the highest risk and German Merino and German White Heath were the next breeds at highest risk of D. nodosus infection. The variance between farms in the prevalence of D. nodosus was large and accounted for 84% of the total variance in the mixed model analysis. We conclude that specific and as yet unknown effects influencing D. nodosus infections in flocks, as well as breed and weather, are the most important effects on D. nodosus infection in sheep, pointing towards the need to establish adequate infection control at farm level.

Development of breeding values for susceptibility to virulent footrot in sheep: A strategy to accommodate variable disease progression at time of scoring.

Genetic evaluations utilising footrot scores from industry flocks in their essence, incorporate data from a wide range of challenge environments, resulting in potentially large differences in means, variances and distribution of scores across challenges. The date that commencement of infection occurs is generally unknown, and progression of the infection varies with the prevailing environmental and management conditions, virulence of the bacterium Dichelobacter nodosus, as well as the genetic potential and (permanent) environmental ability of animals to resist footrot. In practice, animals are unlikely to be repeatedly scored to identify the best time for comparison, or monitor development of disease progression. Furthermore, field challenges are limited by the need to treat animals before their welfare is compromised. Therefore, the duration and intensity of infection varies and this affects comparisons between animals for their susceptibility. Diseases such as footrot are characterised by multiple categorical scores reflecting clinical stages that describe the progression and relative impact of the disease. This provides the opportunity for the transformation of the data to a standardised prevalence. Scoring events from multiple footrot field challenges under a standardised protocol were used to establish a series of transition matrices to describe disease progression between scores over time. These transition matrices were used to standardise challenge events to the more severe scoring events, observed later in the challenge. The accuracy of the transition technique was tested by comparing the ranking of animals and sires against the observed scores. Transitioning the data from low disease prevalence to the higher prevalence at the subsequent scoring event improved the correlations between the scoring events, at the animal level, by upwards of 0.10 across challenges. The utilisation of a transition matrix to transform low prevalence disease challenges by taking into account the natural biological rate of progression through the clinical stages of the disease provides a more accurate technique to account for variation in disease prevalence. The transition technique increases the acceptable range of disease expression targeted by producers when scoring virulent footrot challenges reducing the need for repeat scoring and allowing earlier treatment and reducing the impact of the disease on the host animal.

Prevalence of bacterial species associated with ovine footrot and contagious ovine digital dermatitis in Swedish slaughter lambs.

BACKGROUND: Ovine footrot and contagious ovine digital dermatitis (CODD) are contagious mixed bacterial infections with major impacts on animal health and production. In Sweden, ovine footrot and CODD were first detected in 2004 and 2019, respectively. In 2009, a voluntary control programme for footrot was established, and a prevalence study in slaughter lambs was conducted, however, the distribution of footrot and CODD-associated bacteria is still unknown. This study examined the prevalence of Dichelobacter nodosus, Fusobacterium necrophorum and Treponema spp., as well as the current prevalence of footrot and CODD, in Swedish slaughter lambs. RESULTS: A total of 2048 feet, from 512 slaughter lambs, were collected from eight slaughterhouses throughout Sweden in autumn 2020. All feet were visually examined for lesions of footrot and CODD and sampled for subsequent real-time polymerase chain reaction (PCR) analysis. Nine lambs (1.8%) had at least one foot affected with footrot (footrot score ≥ 2). A CODD grade 1 lesion was detected in a single lamb (0.2%). The prevalence of D. nodosus, F. necrophorum and Treponema spp. was 6.1%, 7.6% and 90.6%, respectively. The D. nodosus detected were benign strains. CONCLUSIONS: The prevalence of footrot in Swedish slaughter lambs has been significantly reduced, from 5.8 to 1.8%, during the past 11 years. This indicates that preventive measures, such as the national control programme and elimination of footrot from affected flocks, have been effective. A single lamb (0.2%) was found with a CODD lesion (grade 1). In Sweden, benign rather than virulent strains of D. nodosus seem to be the most common. Neither D. nodosus nor F. necrophorum were widespread among Swedish slaughter lambs, but both were more likely to be found in lambs with footrot. Treponema spp. was very commonly found in lambs with and without footrot, but there is a lack of information on the individual Treponema spp. present in Swedish slaughter lambs and their potential pathogenicity.

Ovine footrot in Southern Portugal: Detection of Dichelobacter nodosus and Fusobacterium necrophorum in sheep with different lesion scores.

The Mediterranean climate region of Alentejo in the Southern of Portugal is an important sheep production centre but little is known about the presence and characteristics of Dichelobacter nodosus in association with Fusobacterium necrophorum in the different footrot lesion scores. DNA from 261 interdigital biopsy samples, taken from 14 footrot affected flocks and from three non-affected flocks, were analysed for the presence of D. nodosus and F. necrophorum by real-time PCR. Both virulence and serogroup were determined for 132 and 53 D. nodosus positive biopsy samples, respectively. The co-infection with both bacteria was the commonest epidemiological finding associated with a greater disease severity. There was a statistically significant association (p = 0.002) between footrot-affected flocks and the presence of D. nodosus. Most D. nodosus positive samples were virulent (96.2 %) and belonged to serogroup B (90 %).

Efficacy of bivalent fimbrial vaccines to control and eliminate intermediate forms of footrot in sheep.

OBJECTIVE: The aim of this study was to determine the efficacy of serogroup-specific bivalent fimbrial vaccines in the control and elimination of relatively mild (intermediate) forms of footrot in sheep flocks in NSW, there being some evidence that such forms are difficult to control. METHODS: Four flocks of sheep with history of footrot of intermediate virulence were selected based on clinical and bacteriological diagnoses. Dichelobacter nodosus serogroups included in bivalent vaccines at each farm were based on on-farm serogroup-prevalence data. Two doses of bivalent vaccine were administered with a 4-week interval between doses. Repeated post-vaccination inspections of all feet of between 100 and 119 animals per mob were conducted and foot swabs were collected for bacteriological testing. Blood samples were collected from 10 to 24 individually identified animals per flock at each inspection to check for agglutinating antibody responses. RESULTS: In the majority of animals, antibody levels for serogroups included in each vaccine were above the level believed to be required for protective immunity. Footrot disappeared on farm 1 prior to vaccination, but did not reappear postvaccination. Footrot was controlled but not eliminated on farms 2, 3, and 4, where the prevalence and severity of the disease and number of serogroups present were reduced. CONCLUSION: Serogroup-specific bivalent vaccines can be effective at controlling footrot caused by intermediate strains of D. nodosus.

First report on outbreaks of contagious ovine digital dermatitis in Sweden.

BACKGROUND: Contagious ovine digital dermatitis (CODD) is considered widespread in the United Kingdom but was only recently reported in mainland Europe, as one outbreak in Germany. The disease can cause severe lameness in sheep and, if left untreated, can lead to total avulsion of the hoof capsule. CODD is considered to have multifactorial and polymicrobial aetiology, in which Treponema medium/Treponema vincentii phylogroup, Treponema phagedenis phylogroup and Treponema pedis are believed to play a significant role. Footrot and CODD have a close connection and footrot is considered an important risk factor for CODD. CASE: Lameness, mainly in lambs aged 1.5 months, was reported on a farm in Sweden in spring 2018. The animals showed no signs of footrot and the causative agent, Dichelobacter nodosus, was not found. CODD was suspected but not confirmed, and the clinical signs subsided when the animals were turned out to pasture. In February 2019, young lambs and ewes were lame again and this time CODD was diagnosed. After treatment, the whole flock was slaughtered later in 2019 due to CODD. In autumn 2020, CODD was diagnosed on another Swedish farm, this time as part of a mixed infection with D. nodosus. The animals were treated with footbaths in zinc sulphate 10% by the farmer, but lameness recurred soon afterwards. The animals were treated, but ultimately the whole flock was slaughtered. No connection was found between the two farms. CONCLUSION: The first two outbreaks of CODD in Sweden have been diagnosed and are described in this case report. If it spreads, CODD could have a negative impact on the Swedish sheep industry in terms of animal welfare, production and antibiotic use.

OCCURRENCE OF FOOTROT IN FREE-RANGING ALPINE IBEX (CAPRA IBEX) COLONIES IN SWITZERLAND.

Footrot is a worldwide economically important, debilitating disease caused by Dichelobacter nodosus. In sheep (Ovis aries), it is characterized by lesions of varying severity, depending on the strain, whereas Alpine ibex (Capra ibex) seem to develop severe lesions, whatever the strain. Healthy carriers occur in livestock but are rare in wild ruminants. Using a triangulation approach (retrospective questionnaire survey, necropsy database screening, and pathogen prevalence estimation in selected ibex colonies with and without footrot), we aimed at evaluating the importance of footrot in the ibex population, identifying potential risk factors for disease occurrence in this species, and defining the epidemiological role of ibex. Our study revealed that footrot occurs throughout the entire ibex territory (34% of the Swiss ibex colonies affected) but only as a sporadic disease (mostly one case per disease event), although the situation differed among footrot-positive colonies because half of them had experienced outbreak recurrences. Risk factor analysis for the occurrence of footrot in ibex colonies suggested an absence of an effect of meteorologic conditions, region, contacts with sheep or cattle (known to be very common healthy carriers of D. nodosus) and existing local disease control program. We found a significant effect only of contacts with sheep having footrot. Pathogen prevalence was very low in all investigated colonies. In conclusion, our results support previous data suggesting that ibex are susceptible spillover hosts, likely infected mainly by sympatric sheep displaying clinical signs.

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.

Identifying maintenance hosts for infection with Dichelobacter nodosus in free-ranging wild ruminants in Switzerland: A prevalence study.

Footrot is a worldwide economically important, painful, contagious bacterial foot disease of domestic and wild ungulates caused by Dichelobacter nodosus. Benign and virulent strains have been identified in sheep presenting with mild and severe lesions, respectively. However, in Alpine ibex (Capra ibex ibex), both strains have been associated with severe lesions. Because the disease is widespread throughout sheep flocks in Switzerland, a nationwide footrot control program for sheep focusing on virulent strains shall soon be implemented. The aim of this cross-sectional study was to estimate the nationwide prevalence of both strain groups of D. nodosus in four wild indigenous ruminant species and to identify potential susceptible wildlife maintenance hosts that could be a reinfection source for domestic sheep. During two years (2017-2018), interdigital swabs of 1,821 wild indigenous ruminant species (Alpine ibex, Alpine chamois (Rupicapra rupicapra), roe deer (Capreolus capreolus), red deer (Cervus elaphus)) were analysed by Real-Time PCR. Furthermore, observed interspecies interactions were documented for each sample. Overall, we report a low prevalence of D. nodosus in all four indigenous wild ruminants, for both benign (1.97%, N = 36, of which 31 red deer) and virulent (0.05%, N = 1 ibex) strains. Footrot lesions were documented in one ibex with virulent strains, and in one ibex with benign strains. Interspecific interactions involving domestic livestock occurred mainly with cattle and sheep. In conclusion, the data suggest that wild ungulates are likely irrelevant for the maintenance and spread of D. nodosus. Furthermore, we add evidence that both D. nodosus strain types can be associated with severe disease in Alpine ibex. These data are crucial for the upcoming nationwide control program and reveal that wild ruminants should not be considered as a threat to footrot control in sheep in this context.

Dichelobacter nodosus in sheep, cattle, goats and South American camelids in Switzerland-Assessing prevalence in potential hosts in order to design targeted disease control measures.

Footrot is a contagious foot disease caused by the bacterium Dichelobacter nodosus (D. nodosus) that affects sheep worldwide. Due to substantial economic and welfare impact, various countries have developed control programs against footrot. The aim of this cross-sectional study was to estimate the national prevalence of virulent and benign D. nodosus in Switzerland in the four domestic ruminant species sheep, cattle, goats and South American camelids (SAC) to detect potential host populations and to propose targeted disease control measures. Risk factors for infection with the virulent strain of D. nodosus, based on a survey carried out among farmers, were investigated on animal and herd level. Overall, 613 farms and 2920 animals were investigated during 2017-18 applying a two-stage cluster sampling strategy. A Real-Time PCR method for simultaneous detection of virulent and benign strains of D. nodosus was used for the first time in such a large study. On animal level, the true prevalence (TP) of virulent D. nodosus in sheep was estimated at 16.9% (95% confidence interval (CI95%): 9.5-24.3%). In cattle and goats no virulent D. nodosus was detected and in SAC an apparent prevalence (AP) of 0.2% (CI95%: 0.0-0.4%) was observed. On farm level, a TP of virulent D. nodosus of 16.2% (CI95%: 8.4-25.2%) for sheep and an AP of 1.5% (CI95%: 0.3-5.2%) for SAC herds was estimated. Since the Swiss control program only targets the virulent strains of D. nodosus, it was concluded that cattle, goats and SAC do not play a role in footrot epidemiology in Switzerland. Adult sheep were at higher risk of infection for virulent D. nodosus compared to lambs and yearlings. On herd level, risk factors for infection with virulent D. nodosus in sheep were earlier occurence of footrot, winter compared to summer and autumn, and goat contact on pasture. Liming pastures had a protective effect on D. nodosus infection. For benign D. nodosus, the TP in sheep was 6.3% (CI95%: 1.6-11.0%) and in cattle 88.4% (CI95%: 83.8-93.0%). The TP for benign D. nodosus in sheep farms was 2.8% (CI95%: 0.0-10.5%) and in cattle farms 95.9% (CI95%: 91.7-98.1%). In goat and SAC farms, the AP was 6.6% (CI95%: 3.4-11.5%) and 7.4% (CI95%: 3.8-13.1%), respectively. These findings could be relevant for wild ruminants such as Alpine ibex (Capra ibex ibex), which can develop clinical footrot after infection with benign D. nodosus. The findings of this study are crucial for assessing targeted disease control measures in Switzerland.

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.

Early Infection Dynamics of Dichelobacter nodosus During an Ovine Experimental Footrot In Contact Infection.

INTRODUCTION: Ovine footrot caused by Dichelobacter nodosus is a highly contagious and painful disease representing an economic as well as an animal welfare problem. In order to get more information on the infection dynamics, 26 lambs and 4 ewes enrolled in an in-contact infection trial were monitored over two weeks for the presence of D. nodosus-specific DNA. Two D. nodosus-positive ewes were housed together with 13 confirmed negative lambs. The control group consisted of another 13 lamb siblings and two confirmed D. nodosus-negative ewes. Every foot of all sheep was sampled seven times over the two weeks experiment period and subsequently analyzed for the presence of D. nodosus by quantitative real-time PCR. The control group was negative at the beginning and the end of the experiment and showed no clinical symptoms of footrot. The two positive ewes showed a high, but hundred fold differing level of virulent D. nodosus that remained constant over time with one of the ewes being also weakly positive for benign D. nodosus. All lambs of the infection group were positive for virulent D. nodosus at 14 days post infection (dpi). The first positive animals were observed on 3 dpi. The D. nodosus load remained at a low level and only increased in a few lambs at the end of the trial. Five of the contact lambs showed suspicious clincal signs (score 1-2) at 14 dpi corroborating the PCR results and indicating that the disease starts as early as two weeks after contact with positive sheep.

INTRODUCTION: Le piétin causé par Dichelobacter nodosus est une maladie hautement contagieuse et douloureuse qui représente à la fois un problème économique et de bien-être animal. Pour avoir plus informations sur la dynamique de l'infection, 26 agneaux et 4 brebis appartenant à un groupe d'essai d'infection par contact ont été contrôlés pendant deux semaines quant à la présence d'ADN spécifique de D. nodosus. Deux brebis positives pour D. nodosus ont été mises en contact avec 13 agneaux confirmés négatifs. Le groupe témoin était formé de 13 autres agneaux et deux brebis confirmées négatives. Sept échantillons sur écouvillon ont été prélevés sur chaque pied de chaque mouton au cours des deux semaines de la période expérimentale et analysés quant à la présence de D. nodosus par PCR quantitative en temps réel. Le groupe témoin était négatif au début et à la fin de l'expérience et n'a montré aucun symptôme clinique de piétin. Les deux brebis positives ont montré une forte présence de D. nodosus virulent, mais de cent niveaux différents, qui est restée constant dans le temps, l'une des brebis étant aussi faiblement positive pour D. nodosus bénin. Tous les agneaux du groupe infecté étaient positifs pour D. nodosus virulent 14 jours après l'infection (dpi). Les premiers animaux positifs ont été observés à 3 dpi. La charge de D. nodosus est restée faible et n'a augmenté que chez quelques agneaux à la fin de l'expérience. Cinq des agneaux en contact ont présenté des symptômes suspects (score 1-2) à 14 dpi, corroborant les résultats de la PCR et indiquant que l'infection commence dès deux semaines après le contact avec des moutons positifs.

Direct serogrouping of Dichelobacter nodosus from Victorian farms using conventional multiplex polymerase chain reaction.

OBJECTIVE: Dichelobacter nodosus is the causative agent of footrot in sheep. Ovine footrot is a major problem in Australia that results in large economic losses and a represents a very significant animal welfare issue. D. nodosus is divided into 10 serogroups (A-I, M), based on sequence variation in the type IV fimbriae gene, fimA. Control of the bacteria is possible through use of serogroup-specific vaccination, however traditional identification of the serogroups of D. nodosus on infected sheep is time-consuming and costly. With the aim of reducing time and cost, a PCR assay was used to identify serogroups of D. nodosus directly from foot swabs of infected sheep in Victoria. RESULTS: It was shown that serogroup B was most common (10 locations), followed by A, G and H (4 locations), I and C (2 locations), D, E and F (1 location). Infections with multiple serotypes were observed in 50% of farms, with the remaining 50% having only a single serogroup detected. The ability to identify serogroups quickly and cheaply direct from foot swabs will aid the understanding of the epidemiology of D. nodosus and support control programs.

Sheep and farm level factors associated with footrot: a longitudinal repeated cross-sectional study of sheep on six farms in the UK.

Footrot is an ovine foot disease of infectious origin and a cause of serious welfare and economic compromise in affected animals and flocks. The development of footrot in sheep is associated with the infectious agent Dichelobacter nodosus, which may invade as a primary pathogen, but the risk of disease is increased following damage to the interdigital skin of the foot. In this study, we used data from six farms in North Wales collected between June 2012 and October 2013 to model the dynamic changes of footrot prevalence over time and investigate the association of footrot with multiple farm, management, environmental and sheep factors. Footrot prevalence varied widely within and between farms and overall varied with season with an increase in prevalence shown in late summer and again in the spring. In addition, sheep were more likely to have footrot when the flock size was larger, when grazing poached pasture or when grazing a longer sward, and yearling sheep were less likely to have footrot when compared with lambs and adult sheep. These data may be helpful for advising farmers of likely environmental events, risk groups and management practices that may increase the probability of sheep developing footrot.

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.

Artificial infection of sheep with multiple strains of Dichelobacter nodosus to induce footrot.

OBJECTIVES: To establish multiple strains of Dichelobacter nodosus in two flocks of sheep and to assess the virulence of five of these strains. METHODS: In experiment 1, sheep were challenged with five D. nodosus strains, which varied in both virulence and serotype. In experiment 2, consisting of four replicates (paddock groups), sheep were challenged with seven different strains of D. nodosus. In experiment 3, sheep were challenged with one of five D. nodosus strains. RESULTS: In experiment 1, at 28 days post challenge, four of the five challenge strains were present. Multiple-strain infections were present in 27 feet, with isolates from three serogroups being recovered from 5 feet, and four serogroups from 1 foot. Challenged hind feet were more frequently affected (P < 0.001). In experiment 2, four of the seven strains were recovered from one replicate and three strains from the remaining three replicates. Significantly more hind feet were affected (262/471, 55.6%) than front feet (198/481, 42%) (P < 0.001). Clinically, in both experiments 1 and 2 the footrot resembled an intermediate form, despite the inclusion of a virulent strain of D. nodosus. In experiment 3, this virulent strain caused a higher prevalence of more severe footrot, a greater mean total foot score and, in Merino sheep, resulted in significantly lower weight gains (P < 0.05). Interaction between D. nodosus strain and breed occurred, with Polwarth sheep being significantly more severely affected by one strain than Merino sheep. DISCUSSION: The clinical expression of multiple-strain infections has implications for both research and control of footrot. A novel method of control is proposed.

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.

Cost-benefit analysis of management practices for ewes lame with footrot.

The aim of this study was to investigate the cost-benefit of different strategies to treat and control ovine footrot. In November 2006, 162 sheep farmers in England responded to a survey on prevalence and management of lameness. The costs of lameness per ewe per year (PEPY) were calculated for 116 flocks. Linear regression was used to model the overall cost of lameness PEPY by management method. Associations between farmer satisfaction and time and money spent managing lameness were investigated. The median prevalence of lameness was 5% (inter-quartile range, IQR, 4-10%). The overall cost of lameness PEPY in flocks with ≥10% lameness was UK £6.35 versus £3.90 for flocks with <5% lameness. Parenteral antibiotic treatment was associated with a significantly lower overall cost of lameness by £0.79 PEPY. Routine foot trimming and foot bathing were associated with significantly higher overall costs of lameness PEPY of £2.96 and £0.90, respectively. Farmers satisfied with time managing lameness spent significantly less time (1.46 h PEPY) than unsatisfied farmers (1.90 h PEPY). Farmers satisfied with money spent managing lameness had significantly lower treatment (£2.94 PEPY) and overall (£5.00 PEPY) costs than dissatisfied farmers (£5.50 and £7.60 PEPY, respectively). If the farmers in this study adopted best practice of parenteral antibiotic treatment with no routine foot trimming, and minimised foot bathing to treatment/prevention of interdigital dermatitis, the financial benefits would be approximately £4.65 PEPY. If these costs are similar on other farms the management changes would lead to significant economic benefits for the sheep industry.

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.