Identification and characterization of Dichelobacter nodosus serogroup H from ovine footrot in India.

A total of 56 foot swabs were collected from inter digital spaces of sheep with footrot lesions were screened for 16 rRNA of Dichelobacter nodosus by PCR. Out of the 56 samples, 38(67.85%) were found to be positive. All the positive samples were subjected to multiplex PCR targeting fimA gene for identification of serogroups of D. nodosus. Serogroup H was found along with serogroup B in 12 (55.26%) samples and with serogroup I in 8 (22.2%) samples. The serogroup H was identified for the first time from the Indian subcontinent. The phylogenetic analysis of the present sequence with the available serogroup H sequences of GenBank revealed to be in close association with the serotype H1.

Outbreak of severe foot rot associated with benign Dichelobacter nodosus in an Alpine ibex colony in the Swiss Prealps.

An outbreak of foot rot occurred in the ibex colony "Vanil Noir" in Switzerland from May to December 2014. This article describes field observations and the analyses carried out on the limbs of 3 animals submitted for postmortem examination. Disease signs observed in the field included lameness, poor body condition and overgrown hooves. Macroscopic examination of selected limbs revealed severe lesions in all of them, including interdigital inflammation with ulceration and malodorous exudation. Histological changes were consistent with chronic laminitis with bone resorption, which was not detected at radiographical examination. Grocott-positive organisms compatible with Dichelobacternodosus were detected in the lesions. Samples collected from the lesions were positive by polymerase chain reaction for benign D. nodosus, which is typically associated with only mild lesions in domestic sheep. Whether D. nodosus is endemic in the colony or had previously been transmitted from sympatric domestic livestock is unclear. The unusual warm and humid weather conditions in 2014 may well have contributed to the outbreak.

Immunological response of lame sheep to clinical interdigital dermatitis and footrot: Procalcitonin, acute phase proteins, and pro-inflammatory cytokines.

In many countries, sheep lameness is a cause of economic concern and a contributing factor to a declining economy. This study aimed to investigate changes in procalcitonin (PCT), acute phase proteins (APPs), and cytokines (CYTs) in response to interdigital dermatitis and footrot in sheep under field conditions, to emphasize their role in the disease pathogenesis, diagnosis, as well as monitoring treatment response. Fifty-three sheep with foot diseases (26 clinical cases with interdigital dermatitis and 27 clinical cases with footrot) and 20 clinically healthy naemi sheep were used in this study. Real time PCR for detection of Fusobacterium necrophorum (F. necrophorum) and Dichelobacter nodosus (D. nodosus) revealed that, all samples collected from lame sheep (N = 53) were positive for D. nodosus (100 %), whereas F. necrophorum was detected in 19 out of 53 samples (35.84 %). The virulent D. nodosus was detected in 48 lameness cases where non-virulent D. nodosus were identified in 5 cases (in concurrent with F. necrophorum). The mean serum levels of PCT, C-reactive protein (CRP), serum amyloid A (SAA), haptoglobin (HP), fibrinogen (Fg) and CYTs (IL1-ß, IL-1α, IFN-γ, IL-6 and TNF-α) in sheep with clinical interdigital dermatitis and footrot were remarkably higher than those detected in control healthy sheep. The serum levels of PCT, CRP, SAA, HP, Fg, and CYTs markers in lame sheep pre- and post-treatment were measured. A substantial decline was detected in serum levels of tested biomarkers of lame sheep after 14 days of treatment. The ROC curves were created. The AUC was assessed to evaluate the accuracy of each variable in distinguishing diseased and healthy sheep. Based on the ROC curves and AUCs; PCT, CRP, SAA, HP, and CYTs were highly diagnostic and predictive for the treatment response of sheep with clinical interdigital dermatitis and footrot. Moreover, all tested biomarkers had a noteworthy role in disease immuno-pathogenesis. Nevertheless, PCT and CRP are better than other tested APPs and CYTs as diagnostic markers for interdigital dermatitis and footrot. However, PCT only has the ability to differentiate sheep with different lameness score.

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.

Genome sequence of Dichelobacter nodosus JKS-07B isolate from J&K, India associated with virulent footrot of sheep.

INTRODUCTION: Virulent footrot of sheep caused by Dichelobacter nodosus is associated with tremendous economic losses due to recurrent treatment costs and increased culling rates. This organism being a fastidious anaerobe is difficult to isolate on ordinary media that does not support its growth. The D. nodosus serogroup B isolate described in the present study has been used in the preparation of the whole-cell killed vaccine against footrot in India. D. nodosus serogroup B is the predominant serogroup involved in virulent footrot (lesion score 4) in India as well as in many sheep-rearing countries of the globe. METHODS: Genomic DNA was extracted using wizard Genomic DNA purification kit. The whole genome of the D. nodosus strain B was sequenced using an Illumina HiSeq 2500 platform and annotated according to functional gene categories. Annotations were performed using in-house developed Perl scripts using Nr/Nt database, uniprot, Pfam, KEGG, Panther DB, and GO database. RESULT: The assembled genome size is 1.311,533 Mb and GC content is 44.38. A total of 1215 protein-coding genes, 44tRNA and 7 rRNA were identified. The genome shows 98.63% sequence homology with the reference genome. However, 21 new genes have been identified in this genome. The information will provide insights into the various genes and regulators necessary for D. nodosus growth and survival. DISCUSSION: The genome information of this serogroup B of D. nodosus isolate involved in 85-90% cases of virulent footrot of sheep in India provides further insights for improvement of the killed vaccine (B serogroup) developed recently in India. For the development of an efficacious vaccine against virulent footrot, it is essential to know the serological diversity as well as the virulent status of the strains of the D. nodosus. This serogroup isolate is a potential vaccine candidate to mitigate ovine footrot in India as the majority of virulent footrot cases belong to serogroup B of D. nodosus.

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, Fusobacterium necrophorum and the epidemiology of footrot.

Footrot is a debilitating disease of sheep resulting in lameness, production losses and suffering. To study the basic bacteriology of the disease, a survey was initiated across commercial farms and non-commercial research flocks to compare the bacteriology of symptomatic footrot infected sheep with healthy asymptomatic sheep. Of the 80 farmers initially contacted, 14 collected hoof swabs and returned the swabs by post. Following DNA extraction, species-specific PCR was used to identify if Dichelobacter nodosus (D. nodosus) or Fusobacterium necrophorum (F. necrophorum) species were present on each swab. Of the 42 swabs taken from symptomatic footrot infected sheep, 17 were positive for both F. necrophorum and D. nodosus, two were positive for F. necrophorum only, two for D. nodosus only and 23 swabs were negative for both F. necrophorum and D. nod osus. Of the 50 swabs received from healthy asymptomatic sheep, one was positive for F. necrophorum only and 49 were negative for both D. nodosus and F. necrophorum. This suggests that both F. necrophorum and D. nodosus are linked to footrot in the field in a pastoral farming system. If these bacteria are linked together and collectively cause footrot, this may need to be considered when managing a footrot outbreak, or maintaining a quarantine.

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

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

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.

Characterisation of Dichelobacter nodosus and detection of Fusobacterium necrophorum and Treponema spp. in sheep with different clinical manifestations of footrot.

The aim of this study was to determine the proportion of Dichelobacter nodosus, Fusobacterium necrophorum and Treponema spp. in sheep with different clinical manifestations of footrot compared to healthy sheep both at flock and individual level. The second aim was to characterise D. nodosus with respect to virulence, presence of intA gene and the serogroups. Swab samples (n=1000) from footrot-affected (n=10) and healthy flocks (n=10) were analysed for the presence of D. nodosus, F. necrophorum and Treponema spp. by real-time PCR and culturing (D. nodosus only). Dichelobacter nodosus isolates (n=78) and positive swabs (n=474) were analysed by real-time PCR for the aprV2/B2 and the intA genes and by PCR for the fimA gene (isolates only). D. nodosus was more commonly found in flocks affected with footrot than in clinically healthy flocks. A significant association was found between feet with severe footrot lesions and the aprV2 gene and between feet with moderate or no lesions and the aprB2 gene, respectively. F. necrophorum was more commonly found in flocks with footrot lesions than in flocks without lesions. No significant association was found between sheep flocks affected with footrot and findings of Treponema spp. or the intA gene. Benign D. nodosus of six different serogroups was detected in twelve flocks and virulent D. nodosus of serogroup G in one. In conclusion, D. nodosus and F. necrophorum were more commonly found in feet with footrot than in healthy feet. The majority of D. nodosus detected was benign, while virulent D. nodosus was only detected in a single flock.

A retrospective study of clinical and laboratory characteristics of ovine footrot.

The infection of the feet of sheep by the anaerobic bacterium Dichelobacter nodosus results in a spectrum of diseases ranging from virulent through intermediate to benign footrot. By examining the clinical characteristics of various forms of footrot from 22 properties in Victoria, Australia in association with the results of several laboratory tests including the gene probe-based dot blot hybridisation, it was shown that virulent footrot could not be differentiated from intermediate footrot using the clinical characteristics alone. In addition, D. nodosus isolates from sheep with benign footrot as diagnosed by the clinical manifestations might in fact show characteristics associated with those causing virulent, intermediate or benign footrot as determined by the laboratory tests. Although the elastase test, gelatin gel test and dot blot were in agreement with isolates from 9 of the 22 properties under investigation, they displayed differences from one another in many other cases, especially those with clinical benign footrot. The results of the elastase test appeared to be slightly closer to those of the dot blot compared with the gelatin gel test. Like any other tests based on the measurements of phenotypic characteristics of D. nodosus bacteria, the elastase test and gelatin gel test are subject to changes with factors that affect bacterial growth and metabolism. The use of DNA based detection methods would eliminate many of the problems associated with the conventional tests for differentiating strains causing virulent, intermediate and benign footrot.

Association between alleles of the ovine major histocompatibility complex and resistance to footrot.

Variation in natural resistance to footrot may be genetically derived, implying that genetic markers for resistance may exist and allow selection of superior animals. In this study association between variation within the ovine MHC class II region and resistance to footrot was investigated in two trials. Half-sib progeny were subjected to a field challenge with footrot and their condition subsequently recorded. The animals were then typed at their MHC class II loci to investigate associations between inherited paternal haplotype and footrot status. In the first trial an association between MHC haplotype and footrot status was observed across all animals (P = 0.005), when the self-curing and resistant animals were combined (P = 0.002) and when the self-curing animals were excluded from the analysis (P = 0.001). No association was observed in the second trial, a result attributed to the dry weather conditions which led to poor disease transmission and unreliable disease classification.

Grading the lesions of ovine footrot.

Sixteen methods of grading the lesions of ovine footrot were assessed on the basis of the effect of the lesions on the humoral immune response of the host to a causative bacterium, Dichelobacter nodosus. Methods that allowed for qualitative and quantitative differences in lesion scores between sheep were the best predictors of host response, and methods that assessed the lesions in each of the eight digits were more efficient than methods that did not grade the digits within feet. Weighting the scores for lesions that involved underrunning of the keratin of the hoof provided the most powerful means of predicting host response. The correlations between host response and the more elaborate weighted scores were close to the highest possible among additive linear estimators. Total weighted footscore, which is the sum of the footscores of the four feet weighted for underrun lesions, is proposed as a simple and effective grading system for sheep with lesions of footrot. There was a significant association within sheep between the number of underrun feet and the severity of lesions in individual feet.

The role of elastase in the differentiation of Bacteroides nodosus infections in sheep and cattle.

Eighty-seven Bacteroides nodosus isolates were examined for elastase production by clearing of elastin particles in TAS agar medium. These included 54 ovine virulent isolates, 28 ovine benign isolates and five bovine isolates. In addition 22 ovine virulent, 16 ovine benign and two bovine isolates were examined for decline in proteolytic activity over a 13-day period in the degrading proteinase test using hide power-azure as substrate. There was a remarkable correlation between elastase production, relative stability of proteolytic activity in the hide powder-azure test and virulence of B nodosus. Ovine virulent isolates invariably produced elastase whereas ovine benign isolates and bovine isolates were elastase negative. Bovine isolates produced only mild lesions in the feet of challenged sheep.

Efficacy of ethylenediamine dihydriodide in the prevention of naturally occurring foot rot in cattle.

The efficacy of an ethylenediamine dihydriodide containing salt mixture was evaluated with regard to the prevention of naturally occurring foot rot in pastured cattle. Ninety-six cattle were assigned to the treatment group and 96 were assigned to the control group. The groups were allowed consumption of salt-mineral mixtures, ad libitum, that were identical, except with respect to iodine concentration. The control group's mixture contained 0.0025% iodine and the treatment group's mixture contained 0.125% iodine (0.156% ethylenediamine dihydriodide). The incidence of foot rot was measured, as was the severity of the lesions and accompanying lameness. The incidence of foot rot in the control group (20.8%) was significantly (P less than 0.05) greater than the incidence in the treatment group (8.3%). The severity of foot rot was greater (P = 0.024) in the control calves vs the treatment calves. Total serum iodine concentrations were measured in the 2 groups on days 0, 46, and 130 of the experiment. The serum iodine values of the treatment group on day 46 (46 +/- 19.8 g/dl) and day 130 (23 +/- 12.3 g/dl) were significantly different (P less than 0.01) than the serum iodine concentrations of the control animals and the pretreatment values (day 0) of both groups. Production was measured via calf weaning weights. There were no detectable differences between the 205-day adjusted weaning weights of the calves in the control group vs the calves in the treatment group. Clinical signs of iodism were not observed in the cattle involved in this study.

Fusobacterium necrophorum and Bacteroides melaninogenicus as etiologic agents of foot rot in cattle.

Fusobacterium necrophorum (Sphaerophorus necrophorus) and Bacteroides melaninogenicus were the predominant bacteria isolated from biopsy specimens of lesions in cattle affected with foot rot. Mixed inoculums of the 2 bacteria, applied to the scarified interdigital skin or inoculated intradermally into the interdigital skin of test cattle, induced typical lesions of foot rot. Both bacteria were reisolated in large numbers from the induced lesions.

Comparison of ceftiofur sodium and oxytetracycline for treatment of acute interdigital phlegmon (foot rot) in feedlot cattle.

OBJECTIVE: To determine whether ceftiofur sodium would be useful for treatment of acute interdigital phlegmon (foot rot) in cattle. DESIGN: Randomized controlled trial. ANIMALS: 308 cross-bred yearling steers with clinical signs of acute interdigital phlegmon (i.e., lameness with interdigital swelling, interdigital lesions, or both). PROCEDURE: Steers were randomly assigned to 1 of 3 treatment groups: ceftiofur at a dosage of 0.1 mg/kg (0.045 mg/lb) of body weight, IM, every 24 hours; ceftiofur at a dosage of 1.0 mg/kg (0.45 mg/lb), IM, every 24 hours, and oxytetracycline at a dosage of 6.6 mg/kg (3 mg/lb), IM, every 24 hours. All animals were treated for 3 days; treatment was considered successful if animals were no longer lame on day 4. Biopsy specimens were collected prior to treatment from 5 animals in each group and submitted for anaerobic bacterial culture and histologic examination. RESULTS: Success rates for the high-dosage ceftiofur (94/129; 73%) and oxytetracycline (87/128; 68%) groups were significantly higher than that for the low-dosage ceftiofur group (5/50; 10%), but there were no significant differences between the high-dosage ceftiofur and oxytetracycline groups. Anaerobic bacteria most frequently isolated from biopsy specimens were Porphyromonas levii and Provetella intermedia. CLINICAL IMPLICATIONS: Use of ceftiofur at a dosage of 1.0 mg/kg for treatment of cattle with acute interdigital phlegmon was as effective as use of oxytetracycline at a dosage of 6.6 mg/kg. However, ceftiofur has a negligible withdrawal time and, therefore, may be a better choice for treatment of near-market weight animals.

Foot rot of pigs: the influence of biotin supplementation on foot lesions in sows.

A herd of 116 sows with a high frequency of foot lesions and lameness was divided into two groups, A and B. Group B was supplemented with 1160 microgram per day of biotin in pregnancy and 2320 microgram per day in lactation, over a 12-month period. No improvement occurred in the condition of the feet or skin. Gilts introduced as replacements to the herd were allocated alternately to the groups. Those receiving biotin (group B) showed significantly fewer lesions of heel erosion, white-line, heel bruising and "corn", and the severity and number of lesions of the lateral hind claws were also significantly improved.

A comprehensive review of ceftiofur sodium and hydrochloride formulations for treatment of acute bovine foot rot.

Seven well-controlled studies conducted under multiple management conditions demonstrated that ceftiofur, a late-generation veterinary parenteral cephalosporin, is effective for the treatment of bovine foot rot in beef and dairy cattle. Two preliminary dosage titration studies using a challenge model compared the efficacy of ceftiofur (1.1 mg or 2.2 mg ceftiofur equivalents [CE]/kg administered once daily for 3 days) with placebo. One preliminary clinical study evaluated the efficacy of ceftiofur sodium (1.0 mg CE/kg once daily for 3 days) in lactating dairy cows. Two clinical trials evaluated the efficacy of ceftiofur sodium versus placebo for naturally occurring foot rot, and two trials compared the efficacy of ceftiofur sodium or hydrochloride (1.0 mg CE/kg) with oxytetracycline (6.6 or 10 mg/kg), each administered once daily for 3 days, for treatment of acute foot rot in beef cattle. All trials demonstrated the efficacy of ceftiofur for treatment of acute bovine foot rot. Ceftiofur and oxytetracycline were comparable in efficacy, with ceftiofur having excellent injection-site tolerance and short or no milk discard or preslaughter withdrawal.