The virulence of Dichelobacter nodosus, measured by the elastase test, is an important predictor for virulent footrot diagnosis in New South Wales sheep flocks.

Ovine footrot is a contagious bacterial disease that causes foot lesions, and depending on the virulence of the causative strains, may lead to severe underrunning of the hoof and lameness. Virulent footrot can be identified, treated and controlled more effectively than less virulent benign forms. The in vitro elastase test for virulence of the causative bacteria, Dichelobacter nodosus, has been used to support clinical diagnosis. However, not all laboratory-designated virulent D. nodosus strains cause clinical signs of virulent footrot. This study evaluated retrospectively how well the elastase test supported clinical footrot diagnosis in 150 sheep flocks examined for suspect footrot in New South Wales between August 2020 and December 2021. Flocks were included if measures of clinical disease, environmental conditions and the virulence of D. nodosus isolates were available. Variation in the elastase activity result between D. nodosus isolated from the same flock made bacterial virulence hard to interpret, but calculating the mean elastase rate for all isolates from the same flock made correlations between bacterial virulence and flock footrot diagnosis possible. Simplifying bacterial virulence into whether there were any elastase-positive D. nodosus isolates before 12 days increased the predictive value of elastase results for virulent diagnosis, compared with using the first day that any isolate was elastase positive or the percentage of elastase-positive isolates by 12 days, but not all clinically virulent flocks had isolates with elastase activity before 12 days. Logistic regression models were fitted to identify the minimum number of predictors for virulent footrot diagnosis, with models suggesting that virulent footrot diagnosis was best predicted by adding the elastase test result and environmental conditions to the prevalence of severe foot lesions (score 4 and 5). However, performing the same analysis with different breeds, ages of sheep and seasons might highlight other factors important in the diagnosis of virulent footrot.

Comparison of clinical cure rates from footrot and contagious ovine digital dermatitis using zinc sulphate foot bathing and topical oxytetracycline: A randomised trial.

BACKGROUND: This study reports the clinical cure rates of topical oxytetracycline and 10% zinc sulphate foot bathing for treatment of interdigital dermatitis (ID), footrot (FR) and contagious ovine digital dermatitis (CODD) in lambs. METHODS: The study was a randomised controlled trial of 75 lambs. Group A (n = 38) was foot bathed daily for 5 days in 10% zinc sulphate for 15 minutes and group B was treated with daily topical oxytetracycline for 5 days. On days 0, 7, 14, 28 and 42, lambs were scored for locomotion and foot lesions were recorded. RESULTS: The initial cure rates for ID were 96.20% and 97.00%; for FR, 100% and 95%; and for CODD, 90.09% and 83.33% for zinc sulphate and oxytetracycline, respectively. By day 42, these had changed to 53.16% and 61% for ID; 47.82% and 70% for FR; and 100% and 83.33% for CODD. There were no significant differences in cure rates between the treatments for most time points. LIMITATIONS: The sample size was small, and further studies in larger cohorts and different classes of sheep are required before the findings can be translated into recommendations for clinical practice. CONCLUSION: Both treatments achieved cure rates that are comparable to reported cure rates using systemic antibiotics and could be an effective alternative.

[First case description of contagious ovine digital dermatitis in Switzerland]. / Erstbeschreibung der Krankheit «Kontagiöse ovine digitale Dermatitis¼ in der Schweiz.

INTRODUCTION: Contagious ovine digital dermatitis (CODD) is an emerging infectious foot disease in sheep. To date, CODD has been described in Great Britain, Ireland, Sweden and Germany and now in Switzerland for the first time. Unlike foot rot, the CODD lesions do not spread from the interdigital space, but usually begin at the dorsal/abaxial coronary band. The changes can spread to the hoof wall and the sole and finally can lead to exungulation, similar to foot rot. Treponema spp. are often found in CODD lesions analogous to digital dermatitis (Mortellaro's disease) in cattle. Involvement of Dichelobacter nodosus (D. nodosus) is considered a risk factor, but the presence of the bacterium is not mandatory. In February 2022, ulcerative lesions in the dorso-axial coronary band area were noticed on both claws of the left forelimb in an ewe. Histology of the biopsy showed hyperkeratosis and erosion with exocytosis and crust formation. Treponema spp. PCR and fluorescence in situ hybridization (FISH) were positive for Treponema phylotype 1 (PT1). In addition, D. nodosus and Porphyromonas levii could be detected in the biopsy using PCR. A single local application of chlortetracycline spray led to clinical healing within two weeks, no recurrence was seen within the following two months. Three control sheep, which were kept together with the diseased sheep, did not show any clinical signs of CODD. Treponema spp could not be found in interdigital and coronary band biopsies by PCR or FISH. This is the first description of CODD in Switzerland and aims to sensitize veterinarians to CODD as a differential diagnosis for foot diseases in sheep.

INTRODUCTION: La dermatite digitale contagieuse ovine (contagious ovine digital dermatitis; CODD) est une maladie infectieuse des onglons des moutons d'importance croissante. À ce jour, la CODD a été décrite en Grande-Bretagne, Irlande, Suède et Allemagne, et maintenant pour la première fois également en Suisse. Au contraire du piétain, les lésions de CODD ne s'étendent pas à partir de l'espace interdigité, mais elles commencent en général au bord coronaire dorsal/abaxial. De là, les lésions peuvent s'étendre à la corne de la paroi et à la sole, ce qui peut finalement conduire à une perte complète de la boite cornée de l'onglon, comme en cas de piétain. En analogie à la dermatite digitale (maladie de Mortellaro) chez les bovins, des tréponèmes sont souvent mis en évidence dans les lésions de CODD. La présence de Dichelobacter nodosus (D. nodosus) est considérée comme un facteur de risque, mais elle n'est pas indispensable au développement de la CODD. Des lésions ulcératives dans la région du bord coronaire dorso-axial des deux onglons antérieurs d'une brebis ont été remarqués en février 2022. L'examen histologique de la biopsie de la lésion de CODD a montré une hyperkératose ainsi que des érosions avec de l'exocytose et la formation de croûtes. Aussi bien la PCR pour les Treponema spp. que l'hybridisation in-situ à fluorescence (FISH) étaient positives pour Treponema Phylotype 1 (PT1). De plus, D. nodosus et Porphyromonas levii ont été mis en évidence dans la biopsie. Une application locale unique de spray à la tétracycline après le prélèvement de la biopsie a conduit à une guérison clinique en deux semaines, et aucune récidive n'a été observée dans le deux mois suivants. Trois moutons de boucherie qui étaient détenus avec la brebis malade mais ne présentaient pas de lésions de CODD ont servi de contrôles négatifs. Des Treponema spp. n'ont été mis en évidence chez ces animaux, ni dans des biopsies du bord coronaire ni dans celles de l'espace interdigité. Cette étude représente la première description de la CODD en Suisse et est destinée à sensibiliser la profession vétérinaire à la CODD comme diagnostic différentel en cas de maladies des onglons chez les moutons.

Eficácia in sílico do florfenicol no tratamento de pododermatite infecciosa por Fusobacterium necrophorum em ovelhas / In sílico efficacy of florfenicol in the treatment of Fusobacterium necrophorum infectious pododermatitis in sheep

Objetivou-se comparar o efeito in silico do florfenicol nas doses de 20 e 30 mg/Kg em ovinos pelas vias intravenosa (IV) e intramuscular (IM), usando a modelagem PK/PD. Realizou-se uma simulação de Monte Carlo com base nos dados de concentração plasmática de um estudo publicado anteriormente. Calculou-se a área sob a curva (ASC) e as taxas de eficácia do florfenicol para os efeitos bacteriostático, bactericida e de erradicação bacteriológica. A dose de 20 mg/Kg IV demonstrou efeitos de erradicação de 100, 93 e 0% para CIM de 0,5, 1 e acima, respectivamente. O efeito bacteriostático foi de 99 e 90% para CIM de 4 e 2 µg/ml, enquanto o bactericida foi de 14% para CIM de 2 µg/ml. A dose de 30 mg/Kg IV apresentou 100% de erradicação para CIM de 1 µg/mL e 100% de efeito bactericida para CIM de 2 µg/mL. Há 100% de efeito bacteriostático em CIM de 4 µg/ml. As doses de 20 e 30 mg/Kg IM mostraram 100% de erradicação para CIM até 1 µg/mL e 0% para CIM maiores. O efeito bacteriostático foi mantido em 100% para uma CIM de 4 µg/mL em ambas as doses. Este estudo mostra o efeito de erradicação bacteriológica do florfenicol nas doses de 20 e 30 mg/Kg, IV e IM. Recomenda-se que seja feito um estudo de eficácia in vivo com a dose de 30mg/Kg IM em ovinos infectados por F. necrophorum com MIC superior a 2 µg/mL.

We aimed to compare the in silico effect of florfenicol at doses of 20 and 30 mg/Kg in sheep by intravenous (IV) and intramuscular (IM) routes, using PK/PD modeling. We performed a Monte Carlo simulation based on plasma concentration data from a previously published study. We calculated the area under the curve (AUC) and the efficacy rates of florfenicol to bacteriostatic, bactericidal, and bacteriological eradication effects. The dose of 20 mg/Kg IV demonstrated 100, 93, and 0% eradication effects for MICs of 0.5, 1, and above, respectively. The bacteriostatic effect was 99 and 90% for MIC of 4 and 2 µg/ml, while the bactericide was 14% for MIC of 2 µg/ml. The 30 mg/Kg IV dose showed 100% eradication for MIC of 1 µg/mL and 100% bactericidal effect for MIC of 2 µg/mL. There is a 100% of bacteriostatic effect at MIC of 4 µg/ml. Doses of 20 and 30 mg/Kg IM showed 100% eradication for MIC up to 1 µg/mL and 0% for MIC above. The bacteriostatic effect was maintained at 100% for a MIC of 4 µg/mL at both doses. This study shows the bacteriological eradication effect of florfenicol at doses of 20 and 30 mg/Kg, IV, and IM. Therefore, we recommend an in vivo efficacy study with a dose of 30mg/Kg IM in sheep infected with F. necrophorum with MIC greater than two µg/mL.

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.

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.

Relationship between the likelihood of footrot elimination from a flock and the virulence of the strain of Dichelobacter nodosus present.

OBJECTIVE: To assess ability to eliminate different strains of footrot in sheep using inspection and culling of affected sheep. METHODS: A flock of 1417 Polwarth sheep that had deliberately been infected with seven different strains of Dichelobacter nodosus and undergone different control measures prior to eradication, including zinc sulfate footbathing and vaccination, were subjected to visual foot inspection on a number of occasions. Sheep identified as infected or having any foot abnormalities were removed from the flock at each inspection. The experiment had three replicates and a small number of untreated control animals. Sheep were examined following the inspections to assess the effectiveness of elimination and additional measures were implemented in two of the three replicates in an attempt to eliminate all strains of D. nodosus. RESULTS: Three strains of D. nodosus were apparently successfully eliminated from all replicates (strains A, E and H). Strains B and C were detected in one replicate each, despite additional inspections. The three stains that were eliminated were the more virulent strains and the two strains that remained were the least virulent. No assessment could be made on a further two strains. CONCLUSIONS: The application of a rigorous inspection and culling program resulted in the elimination of the more virulent D. nodosus strains, but did not result in the elimination of all D. nodosus strains on all occasions.

[Claw infections in sheep - treatment options in veterinary practice, with special emphasis on ovine footrot treatment. - An update]. / Klaueninfektionen beim Schaf ­ Therapiemöglichkeiten in der tierärztlichen Praxis unter besonderer Berück sichtigung der Moderhinkebekämpfung.

Infectious causes of lameness in sheep remain of considerable clinical importance. Because of the availability of newly licensed drugs, important changes in therapy options, particularly for ovine footrot, have occurred. This paper provides an overview of common and rarer infectious causes of lameness in sheep, and presents a detailed review of recent advances in research regarding the aetiology, diagnosis, prevention, treatment and control of ovine foot rot. Despite the recent release of several antibiotics licensed for the treatment of footrot in sheep, the use of footbaths following the cascade of regulations remains a crucial part of many integrated treatment and control programmes. The sustainable control of foot rot requires recent advances in science to be put into practice, with tailor-made control programmes for each individual farm. The article presents various treatment options and potential routes of control and eradication.

Pathogenesis and Treatment of Bovine Foot Rot.

Bovine foot rot (BFR) is an infectious disease of the interdigital skin and subcutaneous tissues of beef and dairy cattle that occurs under a variety of management and environmental settings. The anaerobic, gram-negative bacteria Fusobacterium necrophorum, Porphyromonas levii, and Prevotella intermedia are commonly isolated from lesions. A multitude of host, agent, and environmental factors contribute to the development of BFR. Initiation of systemic antimicrobial therapy early in the course of disease commonly leads to resolution. Delays in treatment may result in extension of infection into deeper bone, synovial structures, or ligamentous structures, and the prognosis for recovery is reduced.

Elimination of virulent strains (aprV2) of Dichelobacter nodosus from feet of 28 Swiss sheep flocks: A proof of concept study.

Virulent ovine footrot caused by Dichelobacter nodosus is an endemic disease worldwide. It is associated with severe pain, impaired animal welfare and economic losses. The competitive real-time PCR for the differentiation of virulent aprV2 and benign aprB2 strains of Dichelobacter nodosus provides an objective, rapid and sensitive diagnostic tool for footrot surveillance, especially as it enables early detection of subclinical carriers of virulent strains. The aim of this study was to evaluate the feasibility of complete elimination of Dichelobacter nodosus strains carrying the aprV2 gene from sheep flocks. The treatment protocol was based on careful removal of loose and severely overgrown claw horn, weekly stand-in foot baths of the entire flock for 10 min per sheep, using a 10% zinc sulphate disinfectant solution, clinical and PCR follow-up and isolation or culling of non-responders. Dichelobacter nodosus strains carrying the aprV2 gene were successfully eliminated from the feet of the sheep of all 28 flocks (100%) participating in the study within 6-19 weeks of weekly foot bathing. A strong correlation between the length of time for weekly foot bathing to eliminate the virulent strains and the within-flock prevalence of clinical footrot at the beginning was observed (rho, 0.68; P <0.001). A statistically significant correlation was not detected between flock size and the length of time for weekly foot bathing (rho, 0.28; P = 0.14), or the prevalence of clinical footrot at study commencement (rho, -0.04; P = 0.82), respectively. In conclusion, a complete elimination of Dichelobacter nodosus strains carrying the aprV2 gene in sheep flocks was possible with a protocol based on careful trimming, weekly stand-in foot baths, and identification of infection using a specific PCR-test and isolation or culling of non-responders.

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.

Clinical evidence for individual animal therapy for papillomatous digital dermatitis (hairy heel wart) and infectious bovine pododermatitis (foot rot).

Data supporting individual animal therapy for papillomatous digital dermatitis (PDD) and infectious pododermatitis (IP) in cattle are available for treatment with multiple drugs in the form of randomized, prospective clinical trials conducted in naturally occurring disease with negative controls and masked subjective evaluators. In the case of PDD, these trials support the use of topical tetracycline and oxytetracycline, lincomycin, a copper-containing preparation, and a nonantimicrobial cream. In individual therapy for IP, trial evidence is available to support systemic treatment with ceftiofur, florfenicol, tulathromycin, and oxytetracycline. However, it was not available for IP standards such as penicillin G, sulfadimethoxine, and tylosin.

[Metaphylactic antibiotic treatment of footrot in sheep using Florfenicol]. / Metaphylaktische Behandlung von Moderhinke bei Schafen mit Florfenicol.

A case report describes the metaphylactic antibiotic treatment of 520 sheep suffering from footrot (lameness prevalence > 60%) in late pregnancy (targeted selective treatment). Because of the lack of pharmaceuticals licensed for sheep and footrot in Germany in 2009, Florfenicol was used off label. Clinical recovery was observed a few days after a one shot application of florfenicol without any further treatment. The examination of all feet after weaning revealed no clinical symptoms in 96% of the sheep. Complete healing of almost all affected sheep was achieved. No transmission of footrot to lambs was noticed. Since the goal of the treatment was relief from pain and suffering under the particular conditions of late pregnancy and not a clinical study on efficacy no untreated control group was established for comparison. The suitability of the method for eliminating footrot in sheep flocks during the housing period in winter is discussed.

Targeted antibiotic treatment of lame sheep with footrot using either oxytetracycline or gamithromycin.

A study on parenteral antibiotic treatment in sheep footrot was conducted on 10 farms in southern Germany to obtain information on the efficacy of gamithromycin under practical use conditions compared with a positive control. On each farm, 20 (10 on one farm) lame sheep were clinically evaluated and divided into two groups. On day 1, sheep were treated once according to group with either long-acting oxytetracycline (OTC) at 20 mg/kg bodyweight or gamithromycin at 6 mg/kg; clinical responses were assessed 21 days later. When compared with day 1, both treatments reduced clinical lameness, as reflected in the reduction in the number of footrot-affected feet (OTC: 79.3 per cent; gamithromycin: 93.7 per cent) and in the severity of the lesions. The difference between the two treatments was significant (P<0.01) with an OR of 6.1 in favour of gamithromycin. Of the 33 sheep that were still lame on day 21, nine mildly affected animals were not re-treated and the remaining 24 sheep were re-treated with gamithromycin. On day 42, all but two (on the same farm) of the 33 sheep were cured, giving an overall response rate in this study to one or two parenteral antibiotic treatments of 99 per cent.

How does reviewing the evidence change veterinary surgeons' beliefs regarding the treatment of ovine footrot? A quantitative and qualitative study.

Footrot is a widespread, infectious cause of lameness in sheep, with major economic and welfare costs. The aims of this research were: (i) to quantify how veterinary surgeons' beliefs regarding the efficacy of two treatments for footrot changed following a review of the evidence (ii) to obtain a consensus opinion following group discussions (iii) to capture complementary qualitative data to place their beliefs within a broader clinical context. Grounded in a Bayesian statistical framework, probabilistic elicitation (roulette method) was used to quantify the beliefs of eleven veterinary surgeons during two one-day workshops. There was considerable heterogeneity in veterinary surgeons' beliefs before they listened to a review of the evidence. After hearing the evidence, seven participants quantifiably changed their beliefs. In particular, two participants who initially believed that foot trimming with topical oxytetracycline was the better treatment, changed to entirely favour systemic and topical oxytetracycline instead. The results suggest that a substantial amount of the variation in beliefs related to differences in veterinary surgeons' knowledge of the evidence. Although considerable differences in opinion still remained after the evidence review, with several participants having non-overlapping 95% credible intervals, both groups did achieve a consensus opinion. Two key findings from the qualitative data were: (i) veterinary surgeons believed that farmers are unlikely to actively seek advice on lameness, suggesting a proactive veterinary approach is required (ii) more attention could be given to improving the way in which veterinary advice is delivered to farmers. In summary this study has: (i) demonstrated a practical method for probabilistically quantifying how veterinary surgeons' beliefs change (ii) revealed that the evidence that currently exists is capable of changing veterinary opinion (iii) suggested that improved transfer of research knowledge into veterinary practice is needed (iv) identified some potential obstacles to the implementation of veterinary advice by farmers.

Impact of footrot vaccination and antibiotic therapy on footrot and contagious ovine digital dermatitis.

Footrot and contagious ovine digital dermatitis (CODD) are common causes of foot disease of sheep in the UK. The study reported here is a split flock randomised treatment trial undertaken on a group of 748 fattening lambs on a UK sheep farm affected by CODD and footrot. The sheep were randomly assigned to one of two treatment protocols. In protocol A, all sheep were given two doses of footrot vaccine (Footvax, MSD), plus targeted antibiotic therapy (long-acting amoxicillin, Betamox LA, Norbrook Pharmaceuticals) to sheep with foot lesions likely to be associated with a bacterial infection. In protocol B, the sheep only received targeted antibiotic therapy. Sheep were re-examined and foot lesions recorded five and nine weeks later. New infection rates in the footrot vaccinated group were lower compared with the vaccinated group for both CODD (18.2 per cent compared with 26.4 per cent, P=0.014) and footrot (12.55 per cent compared with 27.5 per cent, P<0.001). Recovery rates were unaffected for CODD (80.46 per cent compared with 70.97 per cent, P=0.14) but higher for footrot (92.09 per cent compared with 81.54 per cent, P=0.005) in sheep which received the vaccine. On this farm, a footrot vaccine efficacy of 62 per cent was identified against footrot and 32 per cent against CODD infection. An association between a sheep having footrot at visit 1 and subsequently acquiring CODD was identified (odds ratio [OR] 3.83, 95 per cent CI 2.61 to 5.62, P<0.001). These results suggest a role for infection with Dichelobacter nodosus in the aetiopathogenesis of CODD on this farm.

Antimicrobial resistance determinants among anaerobic bacteria isolated from footrot.

Antibiotic resistance has been evaluated among 36 Gram negative and anaerobic bacilli (10 Bacteroides, 11 Prevotella, 7 Porphyromonas and 8 Fusobacterium strains) isolated from clinical cases of caprine and ovine footrot (necrotic pododermatitis). The initial analysis on this bacterial consortium evaluates the relationships existing among antimicrobial resistance determinants, phenotype expression and mobilization potential. The Bacteroides strains were generally resistant to penicillins, first-generation cephalosporins, tetracycline and erythromycin, and expressed low level of ß-lactamase activity. The main determinants found among the Bacteroides strains were cepA and tetQ genes, conferring resistance to ß-lactams and tetracycline, respectively. A general susceptibility to ß-lactams was shown for most Prevotella, Porphyromonas and Fusobacterium strains, where none of the ß-lactamase genes described in Bacteroides was detected. Resistance to tetracycline and/or erythromycin was found among the three bacterial groups. Although tetQ genes were detected for several Prevotella and Porphyromonas strains, a unique ermF positive was revealed among Prevotella strains. The expression of resistance markers was not related with the polymorphism of their coding sequences. However, the finding of sequence signatures for conjugative transposons in the vicinities of tetQ and ermF suggests a mobilization potential that might have contributed to the spread of antimicrobial resistance genes.

Higher whole-blood selenium is associated with improved immune responses in footrot-affected sheep.

We reported previously that sheep affected with footrot (FR) have lower whole-blood selenium (WB-Se) concentrations and that parenteral Se-supplementation in conjunction with routine control practices accelerates recovery from FR. The purpose of this follow-up study was to investigate the mechanisms by which Se facilitates recovery from FR. Sheep affected with FR (n = 38) were injected monthly for 15 months with either 5 mg Se (FR-Se) or saline (FR-Sal), whereas 19 healthy sheep received no treatment. Adaptive immune function was evaluated after 3 months of Se supplementation by immunizing all sheep with a novel protein, keyhole limpet hemocyanin (KLH). The antibody titer and delayed-type hypersensitivity (DTH) skin test to KLH were used to assess humoral immunity and cell-mediated immunity, respectively. Innate immunity was evaluated after 3 months of Se supplementation by measuring intradermal responses to histamine 30 min after injection compared to KLH and saline, and after 15 months of Se supplementation by isolating neutrophils and measuring their bacterial killing ability and relative abundance of mRNA for genes associated with neutrophil migration. Compared to healthy sheep, immune responses to a novel protein were suppressed in FR-affected sheep with smaller decreases in FR-affected sheep that received Se or had WB-Se concentrations above 250 ng/mL at the time of the immune assays. Neutrophil function was suppressed in FR-affected sheep, but was not changed by Se supplementation or WB-Se status. Sheep FR is associated with depressed immune responses to a novel protein, which may be partly restored by improving WB-Se status (> 250 ng/mL).

Factors associated with changes of state of foot conformation and lameness in a flock of sheep.

The aim of this research was to investigate transitions between foot conformation, lameness and footrot in sheep. Data came from one lowland flock of approximately 700 ewes studied for 18 months. Multilevel multistate analyses of transitions between good and poor foot conformation states in ewes, and lame and non-lame states in ewes and lambs were conducted. Key results were that the longer sheep had feet in good conformation, the more likely they were to stay in this state; similarly, the longer a ewe was not lame the more likely she was not to become lame. Ewes with poor foot conformation were more likely to become lame (OR: 1.83 (1.24-2.67)) and to be >4 years (OR: 1.50 (1.09-2.05)). Ewes with footrot were less likely to move to good foot conformation (OR: 0.48 (0.31-0.75)) and were more likely to become lame (OR: 3.81 (2.60-5.59)). Ewes lame for >4 days and not treated with parenteral antibacterials had a higher risk of developing (OR: 2.00 (1-3.61)), or remaining in (OR: 0.49 (0.29-0.95)), poor foot conformation compared with ewes never lame. Treatment of ewes lame with footrot with parenteral antibacterials increased the probability of transition from a lame to a non-lame state (OR: 1.46 (1.05-2.02)) and these ewes, even if lame for >4 days, were not more likely to develop poor foot conformation. The risk of a ewe becoming lame increased when at least one of her offspring was lame (OR: 2.03 (1.42-2.92)) and when the prevalence of lameness in the group was ≥5% (OR: 1.42 (1.06-1.92)). Lambs were at increased risk of becoming lame when they were male (OR: 1.42 (1.01-2.01)), single (OR: 1.86 (1.34-2.59)) or had a lame dam or sibling (OR: 3.10 (1.81-5.32)). There were no explanatory variables associated with lambs recovering from lameness. We conclude that poor foot conformation in ewes increases the susceptibility of ewes to become lame and that this can arise from untreated footrot. Treatment of ewes lame with footrot with parenteral antibacterials leads to recovery from lameness and prevents or resolves poor foot conformation which then reduces the susceptibility to further lameness with footrot.