Footrot In Sheep Research Articles

Fusobacterium necrophorum, and not Dichelobacter nodosus, is associated with equine hoof thrush

The aim of this study was to determine which of the two species, Fusobacterium necrophorum or Dichelobacter nodosus, are associated with hoof thrush in horses. Fourteen hoof samples, collected from eight horses with thrush and 14 samples collected from eight horses with healthy hooves, were examined for the presence of F. necrophorum, Fusobacterium equinum and D. nodosus. Only isolates with phenotypic characteristics representing Fusobacterium could be cultured. Total DNA extracted from the 28 hoof samples was amplified by using DNA primers designed from gene lktA, present in F. necrophorum subsp. necrophorum, F. necrophorum subsp. funduliforme and F. equinum, and gene fimA, present in D. nodosus. The lktA gene was amplified from five of the 14 infected hoof samples and from one hoof sample without thrush. The DNA sequence of the amplified ltkA gene was identical to the lktA gene of the type strain of F. necrophorum (GenBank accession number AF312861). The isolates were phenotypically differentiated from F. equinum. No DNA was amplified using the fimA primer set, suggesting that F. necrophorum, and not D. nodosus, is associated with equine hoof thrush. Hoof thrush in horses is thus caused by F. necrophorum in the absence D. nodosus. This is different from footrot in sheep, goats, cattle and pigs, which is caused by the synergistic action of F. necrophorum and D. nodosus.

Evaluating observer agreement of scoring systems for foot integrity and footrot lesions in sheep.

BackgroundA scoring scale with five ordinal categories is used for visual diagnosis of footrot in sheep and to study its epidemiology and control. More recently a 4 point ordinal scale has been used by researchers to score foot integrity (wall and sole horn damage) in sheep. There is no information on observer agreement using either of these scales. Observer agreement for ordinal scores is usually estimated by single measure values such as weighted kappa or Kendall’s coefficient of concordance which provide no information where the disagreement lies. Modeling techniques such as latent class models provide information on both observer bias and whether observers have different thresholds at which they change the score given. In this paper we use weighted kappa and located latent class modeling to explore observer agreement when scoring footrot lesions (using photographs and videos) and foot integrity (using post mortem specimens) in sheep. We used 3 observers and 80 photographs and videos and 80 feet respectively.ResultsBoth footrot and foot integrity scoring scales were more consistent within observers than between. The weighted kappa values between observers for both footrot and integrity scoring scales ranged from moderate to substantial. There was disagreement between observers with both observer bias and different thresholds between score values. The between observer thresholds were different for scores 1 and 2 for footrot (using photographs and videos) and for all scores for integrity (both walls and soles). The within observer agreement was higher with weighted kappa values ranging from substantial to almost perfect. Within observer thresholds were also more consistent than between observer thresholds. Scoring using photographs was less variable than scoring using video clips or feet.ConclusionsLatent class modeling is a useful method for exploring components of disagreement within and between observers and this information could be used when developing a scoring system to improve reliability.

Impact of rapid treatment of sheep lame with footrot on welfare and economics and farmer attitudes to lameness in sheep

AbstractThis review article summarises the evidence for an effective management protocol for footrot to sheep, the welfare and economic benefits of such a protocol and its likely uptake by farmers. Over 90% of lameness in sheep in England is caused by Dichelobacter nodosus, the aetiological agent of footrot. Farmers can recognise lame sheep both from video clips and when examining their own sheep but make a separate decision about whether to catch lame sheep. Only farmers who catch and treat mildly lame sheep immediately report a low prevalence of lameness (< 5%). From a within-farm clinical trial, treatment of sheep lame with footrot with parenteral antibiotic and topical spray led to over 90% recovery from lameness within 10 days whilst only 25% of sheep treated with foot trimming and topical spray recovered in 10 days. In parallel, a within-farm clinical trial with approximately 800 ewes was run for 18 months to test the hypothesis that rapid appropriate treatment led to reduced prevalence of lameness. Ewes were stratified and randomly allocated to one of two groups. The prevalence and incidence of lameness decreased in the treatment group, where lame sheep were treated with parenteral and topical antibacterials within three days of being observed lame, but remained at approximately 8% in the control group where lame sheep were treated with trimming hoof horn and topical antibacterial spray when the farm shepherd considered them sufficiently lame. Sheep in the treatment group had a higher body condition and produced more lambs that grew faster. The net economic benefit to all sheep (whether lame or not) in 2006 was £6 per ewe put to the ram. A group of 265 farmers were asked about their satisfaction with methods to manage footrot. Satisfied farmers reported a prevalence of lameness of ≤ 5% and used rapid individual treatment. Dissatisfied farmers reported a prevalence of lameness of > 5% and used whole-flock footbathing and vaccination. Overall, farmers stated that their ideal managements would be footbathing and vaccination. One explanation for this apparent inconsistency is that farmers want effective vaccines and footbaths; an alternative explanation is that this is an example of cognitive dissonance, where subjects adopt a belief because it is their current practice despite evidence that it is not effective. We conclude that farmers can identify lame sheep and that rapid treatment of individual sheep lame with footrot with intramuscular and topical antibacterials is currently the most effective control of interdigital dermatitis and footrot in sheep but that in future effective measures that prevent footrot would be ideal.

Possible cross-infection of Dichelobacter nodosus between co-grazing sheep and cattle

BackgroundThe aim of this study was to investigate possible cross-infection of Dichelobacter nodosus in Norwegian farms practising co-grazing of sheep and cattle.MethodsThirteen farms practising co-grazing of sheep and cattle were included in this descriptive study: five farms with a history of severe ovine footrot (Group I) and eight farms with free-stall housing of cattle and signs of mild or no footrot in sheep (Group II). Sampling for PCR detection of D. nodosus was performed from animals in all farms, and clinical claw examination of sheep and cattle was performed in Group II. D. nodosus positive samples were analysed by a multiplex PCR method that detects variants of the fimA gene corresponding to D. nodosus serogroups A through I.ResultsD. nodosus serogroup A was identified more frequently in sheep from farms with a history of severe footrot (Group I) versus from Group II, and in most of the farms with a history of severe footrot there was a coexistence of D. nodosus serogroup A in sheep and cattle. In one farm heel horn erosion and dermatitis emerged in cattle after co-grazing with sheep suffering from severe footrot where D. nodosus serogroup A was detected. Six months later heel horn erosion and dermatitis were still diagnosed, and D. nodosus serogroup A was identified. Out of the 16 D. nodosus positive sheep samples from Group II, ten of the samples were positive by the fimA serogrouping PCR. Among these 10 samples all serogroups except G were detected. All the D. nodosus serogroups detected in sheep were also present in the corresponding cattle herds.ConclusionThe clinical findings and the coexistence of the same serogroups in co-grazing sheep and cattle could indicate cross-infection. However, further research including isolation of the bacterial strains, virulence-testing and genetic identification, is needed.

A clinical trial comparing parenteral oxytetracyline and enrofloxacin on time to recovery in sheep lame with acute or chronic footrot in Kashmir, India

BackgroundNo clinical trials have been conducted in India on the efficacy of parenteral antibacterials to treat footrot in sheep. In addition, there are no studies worldwide on the efficacy of parenteral antibacterials to treat chronic footrot. Sixty two sheep with acute footrot and 30 sheep with chronic footrot from 7 villages in Kashmir, India were recruited into two separate trials. Sheep with acute footrot were allocated to one of three treatments using stratified random sampling: long acting parenteral oxytetracycline, long acting parenteral enrofloxacin and topical application of potassium permanganate solution (a traditional treatment used by sheep farmers in India). In a quasi pre-post intervention design, sheep with chronic footrot that had not responded to treatment with potassium permanaganate were randomly allocated to treatment with one of the two parenteral antibacterials mentioned above. Sheep with acute footrot were treated on day 0 and those with chronic footrot on days 0, 3, 6 and 9. Sheep were monitored for up to 28 days after treatment. Time to recovery from lameness and initial healing of lesions was assessed using Kaplan-Meier survival curves, nonparametric log-rank and Wilcoxon sign-rank tests.ResultsThere was significant correlation in recovery from lameness and presence of healing lesions in sheep with acute (r = 0.94) or chronic (r = 0.98) footrot. Sheep with acute footrot which were treated with parenteral antibacterials had a significantly more rapid recovery from lameness and had healing lesions (median = 7 days) compared with those treated with topical potassium permanganate solution (less than 50% recovered in 28 days). The median time to recovery in sheep with chronic footrot treated with either antibacterial was 17 days; this was significantly lower than the median of 75 days lame before treatment with antibacterials. The median time to recovery for both acute and chronic footrot increased as the severity of lesions increased. There was no difference in time to recovery by age, body condition score, duration lame, or presence of pus in the foot within acute and chronically affected sheep.ConclusionsWe conclude that use of parenteral antibacterials to treat sheep lame with either acute or chronic footrot in India is highly effective. This is likely to improve welfare and give economic benefits to the farmers.

In this issue – January/February 2012

Options for eradication of footrot in sheep · Johne's disease in Australian beef cattle herds · Digital extensor tendon transections in racehorses · Abalone viral ganglioneuritis · Haemochromatosis in a Brazilian tapir · Disseminated Scedosporium prolificans infection in a German Shepherd dog · Osteosarcoma and orthopaedic implants · Torsion of liver lobes and gallbladder · Intimate partner violence and companion animal welfare

Implications of Host Genetic Variation on the Risk and Prevalence of Infectious Diseases Transmitted Through the Environment

Previous studies have shown that host genetic heterogeneity in the response to infectious challenge can affect the emergence risk and the severity of diseases transmitted through direct contact between individuals. However, there is substantial uncertainty about the degree and direction of influence owing to different definitions of genetic variation, most of which are not in line with the current understanding of the genetic architecture of disease traits. Also, the relevance of previous results for diseases transmitted through environmental sources is unclear. In this article a compartmental genetic–epidemiological model was developed to quantify the impact of host genetic diversity on epidemiological characteristics of diseases transmitted through a contaminated environment. The model was parameterized for footrot in sheep. Genetic variation was defined through continuous distributions with varying shape and degree of dispersion for different disease traits. The model predicts a strong impact of genetic heterogeneity on the disease risk and its progression and severity, as well as on observable host phenotypes, when dispersion in key epidemiological parameters is high. The impact of host variation depends on the disease trait for which variation occurs and on environmental conditions affecting pathogen survival. In particular, compared to homogeneous populations with the same average susceptibility, disease risk and severity are substantially higher in populations containing a large proportion of highly susceptible individuals, and the differences are strongest when environmental contamination is low. The implications of our results for the recording and analysis of disease data and for predicting response to selection are discussed.

Prevalence of footrot in Swedish slaughter lambs

BackgroundFootrot is a world-wide contagious disease in sheep and goats. It is an infection of the epidermis of the interdigital skin, and the germinal layers of the horn tissue of the feet. The first case of footrot in Swedish sheep was diagnosed in 2004. Due to difficulties in distinguishing benign footrot from early cases of virulent footrot and because there is no possibility for virulence testing of strains of Dichelobacter nodosus in Sweden, the diagnosis is based of the presence or absence of clinical signs of footrot in sheep flocks. Ever since the first diagnosed case the Swedish Animal Health Service has worked intensively to stop the spread of infection and control the disease at flock level. However, to continue this work effectively it is important to have knowledge about the distribution of the disease both nationally and regionally. Therefore, the aims of this study were to estimate the prevalence of footrot in Swedish lambs at abattoirs and to assess the geographical distribution of the disease.MethodsA prevalence study on footrot in Swedish lambs was performed by visual examination of 2000 feet from 500 lambs submitted from six slaughter houses. Each foot was scored according to a 0 to 5 scoring system, where feet with score ≥2 were defined as having footrot. Moreover, samples from feet with footrot were examined for Dichelobacter nodosus by culture and PCR.ResultsThe prevalence of footrot at the individual sheep level was 5.8%, and Dichelobacter nodosus was found by culture and PCR in 83% and 97% of the samples from feet with footrot, respectively. Some minor differences in geographical distribution of footrot were found in this study.ConclusionsIn a national context, the findings indicate that footrot is fairly common in Swedish slaughter lambs, and should be regarded seriously.

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.

Detection and diversity of a putative novel heterogeneous polymorphic proline-glycine repeat (Pgr) protein in the footrot pathogen Dichelobacter nodosus

Dichelobacter nodosus, a Gram-negative anaerobic bacterium, is the essential causative agent of footrot in sheep. Currently, depending on the clinical presentation in the field, footrot is described as benign or virulent; D. nodosus strains have also been classified as benign or virulent, but this designation is not always consistent with clinical disease. The aim of this study was to determine the diversity of the pgr gene, which encodes a putative proline-glycine repeat protein (Pgr). The pgr gene was present in all 100 isolates of D. nodosus that were examined and, based on sequence analysis had two variants, pgrA and pgrB. In pgrA, there were two coding tandem repeat regions, R1 and R2: different strains had variable numbers of repeats within these regions. The R1 and R2 were absent from pgrB. Both variants were present in strains from Australia, Sweden and the UK, however, only pgrB was detected in isolates from Western Australia. The pgrA gene was detected in D. nodosus from tissue samples from two flocks in the UK with virulent footrot and only pgrB from a flock with no virulent or benign footrot for >10 years. Bioinformatic analysis of the putative PgrA protein indicated that it contained a collagen-like cell surface anchor motif. These results suggest that the pgr gene may be a useful molecular marker for epidemiological studies.

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 ≤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.

Deletion of the C-terminus of polynucleotide phosphorylase increases twitching motility, a virulence characteristic of the anaerobic bacterial pathogenDichelobacter nodosus

The Gram-negative anaerobe Dichelobacter nodosus is the causative agent of footrot in sheep. Different strains of D. nodosus cause disease of differing severities, ranging from benign to virulent. Virulent strains have greater twitching motility and secrete proteases that are more thermostable than those secreted by benign strains. We have identified polynucleotide phosphorylase (PNPase) as a putative virulence regulator and have proposed that PNPase expression is modulated by the adjacent integration of genetic elements. In this study, we compared PNPase activity in three virulent and four benign strains of D. nodosus and found that PNPase activity is lower in virulent strains. We disrupted the pnpA gene in three benign D. nodosus strains and two virulent strains and showed that deletion of the S1 domain of PNPase reduced catalytic activity. In all but one case, deletion of the PNPase S1 domain had no effect on the thermostability of extracellular proteases. However, this deletion resulted in an increase in twitching motility in benign, but not in virulent strains. Reconstruction of the pnpA gene in two mutant benign strains reduced twitching motility to the parental level. These results support the hypothesis that PNPase is a virulence repressor in benign strains of D. nodosus.

The intD mobile genetic element from Dichelobacter nodosus, the causative agent of ovine footrot, is associated with the benign phenotype

The Gram-negative anaerobic pathogen Dichelobacter nodosus is the principal causative agent of footrot in sheep. The intA, intB and intC elements are mobile genetic elements which integrate into two tRNA genes downstream from csrA (formerly glpA) and pnpA in the D. nodosus chromosome. CsrA homologues act as global repressors of virulence in several bacterial pathogens, as does polynucleotide phosphorylase, the product of pnpA. We have proposed a model in which virulence in D. nodosus is controlled in part by the integration of genetic elements downstream from csrA and pnpA, altering the expression of these putative global regulators of virulence. We describe here a novel integrated genetic element, the intD element, which is 32 kb in size and contains an integrase gene, intD, several genes related to genes on other integrated elements of D. nodosus, a type IV secretion system and a putative mobilisation region, suggesting that the intD element has a role in the transfer of other genetic elements. Most of the D. nodosus strains examined which contained the intD gene were benign, with intD integrated next to pnpA, supporting our previous observation that virulent strains of D. nodosus have the intA element next to pnpA.

Effect of Parenteral Selenium Administration to Sheep on Prevalence and Recovery from Footrot

Insufficient intake of selenium (Se) is common in many regions, and can contribute to increased susceptibility to and prolonged recovery from infectious diseases. To determine the effect of Se administration in decreasing the severity and prevalence of footrot in sheep. Thirty-eight footrot-affected and 19 nonaffected sheep from a commercial flock of known high incidence of footrot. Placebo-controlled, prospective, 15-month clinical trial. Footrot-affected sheep were randomly assigned into 2 groups (n = 19) and injected with either 5 mg Se (footrot [FR]-Se) or saline (FR-Sal) at 1-month intervals for the duration of the study. Unaffected sheep (controls) received no treatment. Sheep feet were examined, trimmed, and scored for footrot with a scale of 0 (no footrot) to 4 (extensive) at 0, 3, 6, 9, and 15 months. Sheep were also bled at time 0 and then at 3, 6, and 15 months to assess whole blood Se concentrations. At time 0, control sheep (255 +/- 11 ng/mL) had higher (P < .05) whole blood Se concentrations compared with FR-Se (205 +/- 12 ng/mL) and FR-Sal (211 +/- 14 ng/mL) sheep. By 6 months, FR-Se sheep (317 +/- 9 ng/mL) had whole blood Se concentrations greater (P < .05) than both control (281 +/- 14 ng/mL) and FR-Sal (277 +/- 16 ng/mL) sheep. FR-Se ewes showed a faster decline in highest lesion score at 3 (P= .012) and 6 (P= .0036) months, and a greater decrease in the number of feet with foot score >0 at 6 (P= .020) months compared with FR-Sal ewes. Sheep with blood Se concentrations <300 ng/mL were at 3.5 times greater risk (1.1-12.1 confidence interval, odds ratio) for FR, although this relationship was only significant (P= .04) at 6 months of the study. In sheep with footrot, improved Se status in conjunction with routine control practices result in more rapid improvement of foot lesions.

A genetic epidemiological model to describe resistance to an endemic bacterial disease in livestock: application to footrot in sheep

Selection for resistance to an infectious disease not only improves resistance of animals, but also has the potential to reduce the pathogen challenge to contemporaries, especially when the population under selection is the main reservoir of pathogens. A model was developed to describe the epidemiological cycle that animals in affected populations typically go through; viz. susceptible, latently infected, diseased and infectious, recovered and reverting back to susceptible through loss of immunity, and the rates at which animals move from one state to the next, along with effects on the pathogen population. The equilibrium prevalence was estimated as a function of these rates. The likely response to selection for increased resistance was predicted using a quantitative genetic threshold model and also by using epidemiological models with and without reduced pathogen burden. Models were standardised to achieve the same genetic response to one round of selection. The model was then applied to footrot in sheep. The only epidemiological parameters with major impacts for prediction of genetic progress were the rate at which animals recover from infection and the notional reproductive rate of the pathogen. There are few published estimates for these parameters, but plausible values for the rate of recovery would result in a response to selection, in terms of changes in the observed prevalence, double that predicted by purely genetic models in the medium term (e.g. 2–5 generations).

Breeding for resistance to footrot – the use of hoof lesion scoring to quantify footrot in sheep

So that genetic studies can be undertaken on footrot in sheep, it is necessary that a reliable and repeatable method to categorise the phenotype is available. This paper summarises the methods used and results obtained from 1600 hoof lesion scores of 100 mixed-age ewes independently scored twice by two trained operators. Using a 5-pont scale describing the severity of foot lesions, residual correlations were used to assess agreement between scorers and scoring occasions. Data were analysed using both zero-1 and continuous data methods. The average prevalence of any score >0 was 15%, and of scores >1 was 12%. The residual correlation between scorers for SUM_FR was 0.87 and between scoring occasions it was also 0.87, indicating high repeatability or agreement both within and between scorers. No significant differences were detected between scorers or between scoring occasions for any of the traits analysed, or different analytical methods used.

Fusobacterium equinum possesses a leukotoxin gene and exhibits leukotoxin activity

Fusobacterium equinum, a gram negative, rod-shaped and an obligate anaerobic bacterium is a newly described species. The organism is associated with necrotic infections of the respiratory tract in horses that include necrotizing pneumonia, pleuritis and paraoral infections. The species is closely related to F. necrophorum that causes liver abscesses in cattle and sheep, calf-diphtheria in cattle, and foot-rot in sheep and cattle. Leukotoxin, an exotoxin, is an important virulence factor in bovine strains of F. necrophorum. Our objective was to examine strains ( n = 10) of F. equinum for leukotoxin ( lktA) gene and its toxic effects on equine leukocytes. Southern hybridization and partial DNA sequencing revealed that all the 10 strains had the lktA gene with greater similarities to F. necrophorum subsp. necrophorum. The secreted leukotoxin was detected in the culture supernatant and its biological activity was determined by viability assays with equine polymorphonuclear cells (PMNs) using flow cytometry. While culture supernatants of four strains (E1, E7, E9, and E10) were highly toxic to equine PMNs; strain E5 was moderately toxic and the remaining strains (E2, E3, E4, E6, and E8) were only mildly toxic. Our data indicated that F. equinum isolates had lktA gene and its product was toxic to equine leukocytes. Therefore, leukotoxin may be an important virulence factor in F. equinum infections.

Contemporary approach in diagnostics, prophylaxis and treatment of footrot in sheep

Footrot in sheep is a chronic, infectious disease of the acropodium in sheep, less frequently in goats and mountain goats, of a multifactor nature, which is also considered to be a disease of poor management in sheep breeding. Over the recent years, Dichelobacter nodosus is given as the main cause, previously known as Bacteroides nodosus. Coaction with several other saprophytic and pathogenic bacteria is no longer so significant in etiopathogenesis, and it is considered more important to determine the virulence of the strain D. nodosus. The disease is called contagiousus ovine digital dermatitis (CODD) if the infection was caused by a very virulent strain of D. nodosus, and the disease often ends with the so-called removal of the foot. A speedy identification of the agent can provide insight into the clinical form of the disease, its course and predicted outcome. A benign strain of the agent causes only a mild to medium virulent laminitis, with poorly expressed interdigital dermatitis, when the animal openly limps on one or two legs. A very virulent strain leads to a grave form of infectious interdigital dermatitis, as a supurous-necrotic dermatitis, with significant damage to the bone and expressed limping of the animal. Footrot is present in sheep in almost all countries of the world, in particular in countries with a developed sheep production (New Zealand, Australia and the United Kingdom), where it causes significant economic damages. In our country, footrot in sheep occurs mainly in the Raska district, eastern Serbia and Vojvodina province, but the percentage varies from herd to herd. The irregular and incorrect processing of hoofs (an important zootechnical measure) significantly contributes to the occurrence and spreading of this disease, as well as a series of other contributing factors, such as soft and moist earch, bad climatic conditions (warm and humid weather). In activities on prevention and prophylaxis of this disease, as well as the treatment of footrot in sheep, which is complex in nature, there have been attempts to apply different disinfectants. For instance, disinfection with 10% copper sulphate, 5-8% formalin, as well as, more recently, zink sulphate, either in the form of a powder or as a solution (from 10-20% ZnSO4), several times during different time intervals, are recommended in literature and are being implemented in practice. There are a number of prescriptions for disinfection of hoofs and some of them have been shown to be very efficient. Zinc sulphate has certain advantages in hoof disinfection: it is a bactericide, it penetrates deeper into the tissue in the crucial spot, it protects the horny part of the hoof, it is less toxic, ecologically acceptable (more readily disposable), and less expensive than other mentioned disinfectants. The use of antibiotics is justified only in individual isolated cases, in the treatment of interdigital dermatitis diagnosed on several legs. However, the application of wide-specter antibiotics sprayed into the interdigital space has proven justified and efficient. Immunoprophylaxis yields different results and is mostly implemented in lambs and sheep in early stages of gravidity. Only regular and expert processing of hoofs, using a zinc sulphate disinfectant in the form of a solution according to a prescribed procedure, the use of antibiotics in rare cases, putting animals to pasture in well-drained soil, and vaccination of certain categories of animals can all significantly contribute to the efficient eradication of this persistent disease in sheep.

Minimum inhibitory concentrations for 25 selected antimicrobial agents against Dichelobacter nodosus and Fusobacterium strains isolated from footrot in sheep of Portugal and Spain.

The agar dilution method was used to determine the inhibitory activity of 25 antimicrobial agents against 69 strains of Dichelobacter nodosus and 108 strains of the genus Fusobacterium, all of which were isolated from 90 clinical cases of ovine footrot between October 1998 and November 2000. In the case of the micro-organisms belonging to the genus Fusobacterium, the six beta-lactams studied (benzyl penicillin, ampicillin, cloxacillin, cefadroxil, cefuroxime and cephalexine) proved to be, in general, the most effective antimicrobial agents. Chloramphenicol, clindamycin and doxycycline were also quite active against Fusobacterium spp. With regard to the 69 strains of D. nodosus tested, the levels of resistance remain low.

Risk factors associated with the prevalence of footrot in sheep from 1999 to 2000

A postal survey of the techniques being used for the treatment and control of footrot in sheep flocks between November 1999 and October 2000 was conducted in England and Wales...