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At least 217 records · Page 12Linked to original sources
PubMed1984

Reactivity of sera from sheep immunised with individual outer membrane proteins of Bacteroides nodosus against heterologous bacterial strains.

In order to identify those bacterial antigens which might be involved in immunity against ovine footrot, antisera were raised in sheep to 6 proteins in the outer membrane complex (OMC) of one strain of Bacteroides nodosus. Examination of the specificity of these antisera by Western blotting, crossed immunoelectrophoresis (XIEP) and IEP, revealed that they recognized the homologous OMC protein, but did not precipitate either undenatured pili or OMC, nor could they agglutinate the homologous bacteria. In contrast, anti-OMC and anti-pili sera could precipitate OMC or pili respectively, and agglutinate whole bacteria. Subsequent analysis of these sera against 5 strains of B. nodosus from different serogroups revealed that Proteins 1, 3 and 4 had a similar antigenic structure in all strains examined. The reactivity of anti-pili sera was restricted to homologous bacteria whereas anti-pilin sera (raised against denatured pili) also reacted with pilin from 2 of 3 heterologous strains. However, none of the patterns of staining or absorption of any of these sera matched the spectrum of cross-protection afforded by vaccination of sheep with B. nodosus strain 198 cells. The results question the role of individual OMC proteins in cross-protective immunity and may imply that interactions between several bacterial components are involved in the phenomenon.

Agglutination Tests↗
PubMed1985

Motility in relation to virulence of Bacteroides nodosus.

Fourteen Bacteroides nodosus isolates from footrot lesions of sheep were examined microscopically and all were found to have twitching motility. The mean percentage of cells showing motility was 40% and 9% for virulent and benign strains, respectively. This corresponded with mean agar colony diameters of 17 mm and 7 mm, respectively, for these strains. Two strains of intermediate virulence had values of motility and colony diameter similar to the benign strains. However, the intermediate and the virulent strains produced relatively stable protease compared to the benign strains. All virulent, benign and intermediate strains produced abundant pili. Included for comparison in this study was an avirulent variant strain which was highly motile, formed large colonies and produced stable protease, but showed no pili on electron microscopy. It was concluded that the properties of motility and protease stability may be used to distinguish, in the laboratory, wild-type virulent, benign and intermediate strains of B. nodosus.

Animals↗
PubMed1986

Comparative antigenic analysis of extracellular proteins of Bacteroides nodosus isolated from virulent and benign ovine footrot.

Antigens in the extracellular protein (ECP) complexes of Bacteroides nodosus, isolated from sheep with either benign or virulent footrot, were studied by immunoelectrophoresis (IEP). Rabbit antisera against ECP from virulent and benign strains, were used in homologous and heterologous crossed IEP. Four precipitin peaks unique to the virulent strain, and five peaks unique to the benign strain were identified. In an attempt to characterize the different antigens in ECP, rabbit antisera were raised against an outer membrane protein (OMP, mol. wt. 35 000 daltons), pili and various proteases of virulent and benign strains of B. nodosus. No precipitin band was observed when ECP from both B. nodosus strains were reacted against anti-OMP and anti-pilus antisera. However, single precipitin bands unique to one protease from the benign strain and one protease from the virulent strain were identified. The results suggest that specific antigens other than proteases or pili are important in determining whether a B. nodosus isolate is virulent or benign.

Animals↗
PubMed1987

Protection of sheep against footrot with a recombinant DNA-based fimbrial vaccine.

Recombinant Pseudomonas aeruginosa cells containing the Bacteroides nodosus fimbrial subunit gene under the transcriptional control of a strong promoter produce large amounts of B. nodosus-type fimbriae. We have carried out vaccination trials which show that these fimbriae are just as effective as either natural fimbriae or whole cell preparations of B. nodosus in inducing protective immunity against homologous footrot challenge. The recombinant-produced fimbriae are also effective therapeutically in accelerating the rate of healing of pre-existing footrot lesions. These results confirm that the structural subunit of the fimbrial strand is a primary protective antigen against footrot, and demonstrate the practicality and potential of recombinant DNA approaches to the development of new vaccines against B. nodosus and other Type 4 fimbriate pathogens.

Animals↗
PubMed1991

Characterisation of virulent and benign strains of Bacteroides nodosus.

The extracellular proteases of 395 isolates of B. nodosus from ovine, bovine and caprine foot lesions were classified as either thermostable or thermolabile. Stable protease was associated with one and unstable protease with four distinctive isoenzyme patterns, each pattern differentiated by the relative mobility of paired isoenzymes. Pathogenicity tests on 64 isolates showed a correlation between the production of stable protease and the production of virulent ovine footrot lesions. The mean values for total protease activity, twitching motility and colony diameter were significantly higher for virulent compared to benign isolates, but the range of values overlapped. SDS-PAGE whole-cell electrophoretic profiles of virulent isolates were similar to the profiles of some benign isolates.

Analysis of Variance↗
PubMed1991

The effect of dissociation of Bacteroides nodosus pili on their efficacy as a protective antigen against ovine footrot.

Previous studies have shown that pili from homologous Bacteroides nodosus provide protective immunity in sheep against footrot, whereas denatured pilin subunits are ineffective. The aim of the present study was to examine whether pili that were dissociated into pilin subunits under less vigorous, non-denaturing treatment conditions, would provide an effective level of protective immunity. Using the techniques of gel permeation chromatography, light scattering and susceptibility to proteolysis as measures of disruption, it was shown that pili were dissociated either by the neutral detergents n-octyl-beta-D-glucopyranoside (NOG) and Tween 80 or by lowering the pH with 1 M phosphoric acid to pH 2.2. Circular dichroic spectra indicated, however that the samples were not denatured by these treatments. Electron microscopic monitoring of detergent dissociated material following exhaustive dialysis showed the presence of protein-detergent micelles and "in-line" aggregates which gave the appearance of short fibres. Within these monitored preparations, there was no evidence of native undissociated pili. Pili dissociated by NOG or acid were tested in protection trials and shown to provide protective immunity, although agglutination titres of serum taken from the vaccinated sheep were significantly lower than those of animals inoculated with intact pili.

Animals↗
PubMed1993

Dichelobacter nodosus: differentiation of virulent and benign strains by gene probe based dot blot hybridisation.

Gene probes specific for benign and virulent strains of Dichelobacter nodosus were used in a dot blot hybridisation procedure involving 96 strains of D. nodosus isolated from cases of ovine footrot. The performance of the probes was compared with that of the elastase test. All 27 strains with elastase activity at 7 days and 12 of 25 strains with elastase activity at 14 days reacted with the virulent-specific probe. Twenty-four strains with elastase activity between 21-28 days, and 20 strains with negative elastase activity up to 28 days did not bind with this probe. On the other hand, the benign-specific probe failed to bind with the 27 strains with elastase activity at 7 days, and 13 of the 25 strains with elastase activity at 14 days but reacted with 20 of the 24 strains with elastase activity at 21-28 days, and 19 of the 20 strains with negative elastase activity up to 28 days. The 12 strains with elastase activity at 14 days which were detected by the virulent-specific probe were not those recognised by the benign-specific probe. The use of virulent and benign specific gene probes in combination provides a rapid and precise screening system for differentiation of virulent and higher intermediate footrot from benign and lower intermediate footrot.

Animals↗
PubMed1993

Detection of Dichelobacter nodosus using species-specific oligonucleotides as PCR primers.

Dichelobacter nodosus is an essential causative agent of ovine footrot, a disease of major economic significance. Four oligonucleotides complementary to variable regions of the 16S rRNA of D. nodosus were identified, synthesized and tested for their specificity and sensitivity as probes for the detection of D. nodosus. In hybridization reactions using total RNA as the target nucleic acid, three probes were found to be both sensitive and species-specific. When these probes were used as primers in PCR reactions, on both purified D. nodosus DNA and whole cells, the sensitivity of detection was increased by several orders of magnitude. Using PCR, it was possible to detect the presence of D. nodosus by direct examination of lesion material from footrot infected sheep.

Animals↗
PubMed1993

A gelatin test to detect activity and stability of proteases produced by Dichelobacter (Bacteroides) nodosus.

Previously reported tests to distinguish thermostable and thermolabile proteases of Dichelobacter nodosus used hide powder azure as a test substrate. This paper describes an alternative test for protease stability using gelatin, an inexpensive and convenient substrate. The test required less equipment and time than the hide powder tests, and simplified the testing of multiple samples. Proteases from 2965 isolates of D. nodosus from samples collected as part of a footrot eradication scheme were tested using the gelatin method, 1707 produced thermostable, and 1258 produced thermolabile protease. Production of thermostable protease was used to identify isolates of D. nodosus which had the potential to cause the virulent form of ovine footrot. Comparisons were made with a hide powder test on 47 isolates. Further characterisation of all proteases was undertaken using polyacrylamide gel electrophoresis. Isoenzyme patterns of thermostable protease producing isolates were identified as S1 (1688 isolates) and S2 (19) whilst thermolabile protease producing isolates showed patterns U1 (1104 isolates), U2 (40), U3 (32), U4 (47), U5 (6), U6 (28) and S1 (1).

Animals↗
PubMed1995

A polymerase chain reaction assay for improved determination of virulence of Dichelobacter nodosus, the specific causative pathogen for ovine footrot.

Three sets of oligonucleotide primers (Vf1 and Vr1, Vf2 and Vr2, Bf and Br) were derived from a D. nodosus virulent-specific clone pV470-13 (2146 bp) and a benign-specific clone pB645-335 (737 bp), respectively. Using the virulent-specific primers Vf1 and Vr1 in a polymerase chain reaction (PCR) enabled amplification of a DNA fragment of 460 bp in 25/27 virulent, 9/25 high intermediate, 9/24 low intermediate and 2/20 benign isolates of D. nodosus. On the other hand, using the second set of the virulent-specific primers Vf2 and Vr2 resulted in the production of either a fragment of 857 bp or 1300 bp in virulent, intermediate and 3/20 benign isolates. There appeared to be some correlation between the amplification of the smaller fragment (857 bp) and higher elastase activity and between the amplification of the larger fragment (1300 bp) and lower elastase activity of D. nodosus. The use of the benign-specific primers Bf and Br in PCR enabled amplification of a fragment of 609 bp in all 20 benign, 23/24 low intermediate, 20/25 high intermediate and 0/27 virulent isolates. The combination of the virulent-specific primers Vf2 and Vr2 and benign-specific primers Bf and Br in PCR would provide a rapid, specific and sensitive differentiation of strains of D. nodosus causing virulent, intermediate or benign footrot.

Animals↗
PubMed1994

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.

Animals↗
PubMed1994

Application of ELISA to the serological diagnosis of virulent ovine footrot.

The sensitivity and specificity of an ELISA that detects antibody in the serum of sheep against Dichelobacter nodosus was investigated. The sensitivity of the assay was determined in two trials in which sheep free of virulent footrot were exposed to a virulent strain of D. nodosus. In the first trial up to 96.6% of sheep that developed severe foot lesions were seropositive 2 weeks later. The proportion of seropositive sheep depended on the interval between exposure to D. nodosus and collection of blood samples and reached a maximum 6 weeks after exposure in the first trial and plateaued from 8 weeks after exposure in the second trial. Of sheep with severe lesions present for only 1 week, 40.0% became seropositive, while 98.3% of sheep with severe lesions present for 3 or more weeks became seropositive in Trial 1. Of the unexposed control sheep from the same flock, 93.3% remained seronegative. At least 75% of sheep that were vaccinated with commercial footrot vaccines remained seropositive for at least 24 months after last vaccination and 58.5% remained seropositive for at least 36 months. The specificity of the assay in flocks of sheep from different geographical regions was determined also. Overall, 95.2% of 2978 sheep free of virulent footrot were seronegative. However the rate of false positive serological reactions ranged from 1.6% to 11.3% between flocks and was higher in older sheep (7.0%) compared with sheep less than 1.5 years old (2.7%). Passively acquired colostral antibodies against D. nodosus were measured in 22 lambs and did not persist beyond 55 days mean age. Non-specific reactions with cross reactive antigens were proposed to explain age related changes in serological results. Applications of this ELISA in footrot control programmes are discussed.

Animals↗
PubMed1996

Assessment of gelatin gel and elastase tests for detection of protease activity of Dichelobacter nodosus isolates from ovine footrot.

Protease tests (the gelatin gel protease thermostability test, the elastase test or both) were performed on 4296 isolates of Dichelobacter nodosus derived from 452 outbreaks of ovine footrot occurring in New South Wales. Both tests showed a high level of repeatability. In the gelatin gel test, culture broths were heated for 16 min at 66.8 degrees C. Heated broths containing thermostable protease digested gelatin (positive gelatin gel test) while those broths containing thermolabile protease failed to digest gelatin (negative gelatin gel test). Gelatin gel positive isolates were unable to be graded into subcategories on the basis of the percentage stability of their protease. In the elastase test, the ability of isolates to digest (positive elastase test) or not digest elastin particles (negative test) was measured up to 28 days incubation. Individual elastase positive isolates yielded a graded result based on the number of days to reach a positive result. There was a very high level of agreement between the gelatin gel and the elastase tests consistent with their separating isolates into two groups based on protease activity (either gelatin gel positive and elastase positive or gelatin gel negative and elastase negative). Either test is suitable for use in footrol control and eradication schemes. The gelatin gel test provides clearcut separation of isolates into positive and negative categories and has the major advantage of yielding a more rapid result than the elastase test. The elastase test should be utilised where a graded assessment of protease activity is desired.

Animals↗
PubMed1996

Comparison of gene probe and conventional methods for the differentiation of ovine footrot isolates of Dichelobacter nodosus.

In a collaborative study that involved four Australian veterinary diagnostic laboratories a gene probe test based on the recombinant plasmids pJIR318, pJIR314B, and pJIR313, which contain genomic vap or vrl regions, was compared with conventional tests used for the differential diagnosis of ovine footrot. A total of 771 clinical dichelobacter nodosus isolates were tested and designated as belonging to one of several gene probe categories. The results showed that 87% of the virulent isolates belonged to gene probe category 1, compared to only 6% of the benign isolates. It was concluded that there was good correlation between the gene probe test and the virulence designation of these isolates as well as the results of elastase, gelatin-gel and protease isoenzyme tests. Furthermore, the gene probe test was converted to a polymerase chain reaction (PCR)-based test. It is suggested that diagnostic laboratories consider carrying out both this PCR test and tests based on the extracellular proteases of D. nodosus.

Animals↗
PubMed2004

Molecular detection and characterization of Dichelobacter nodosus in ovine footrot in India.

Dichelobacter nodosus was detected in three clinical cases of ovine footrot in Kashmir, India. The detection was done by PCR in three clinical specimens directly, without isolating the organism, using species-specific 16S rDNA primers. Positive results were indicated by amplification of a 783 bp product. All the three samples were subjected to serogrouping by multiplex PCR using group (A-I) specific primers. All the three samples revealed the presence of serogroup B of D. nodosus by yielding a single band of 283 bps.

Animals↗
PubMed2006

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

A total of 160 ewes on one farm in England were studied for 18 months. The incidence of footrot and interdigital dermatitis in individually identified sheep and treatment and flock control measures were recorded. A binomial mixed effect model with the incidence of footrot or interdigital dermatitis as the outcome was used to investigate patterns of association between treatments, flock control measures and the incidence of footrot or interdigital dermatitis. In this one flock, the incidence of footrot and interdigital dermatitis was positively associated with the incidence of footrot and interdigital dermatitis and with trimming of feet and negatively associated with the use of parenteral antibiotics and topical antibiotic sprays in either the first and/or second 2-week period prior to the incidence of interest. These results provide two hypotheses: one that 'footrot and interdigital dermatitis are infectious diseases that can be controlled, in part, through the use of antibiotic therapy, which acts to reduce the infectious period of diseased sheep' and two, that 'routine trimming of diseased and healthy feet exacerbate disease, through environmental contamination and/or through increased susceptibility of sheep with recently trimmed feet'.

Animal Husbandry↗
PubMed2005

Current approaches to the management of ovine footrot.

Ovine footrot remains the most important cause of lameness in sheep flocks in the UK, despite the existence of proven methods for the control of the disease. Recent research suggests that sheep farmers may be unaware of these methods and may allocate greater resources to treatment of footrot rather than to its prevention. Foot paring, topical treatments, vaccination and parenteral antibiotic therapy all have a role in treating sheep with advanced footrot infections, but prevention of severe infections is best achieved by the timely implementation of control programmes. These are usually based on footbathing and vaccination. For control programmes to be effective it is essential that the pathogenesis and epidemiology of footrot is understood and that control methods are implemented at appropriate times in the season, depending on climatic and pasture conditions. This article reviews these strategies and makes recommendations for steps to reduce the spread of footrot between flocks and to reduce the incidence of footrot within UK flocks.

Administration, Topical↗
PubMed2006

Distribution and prevalence of footrot in Bhutan.

The first cases of footrot in Bhutan were reported in sheep in 1990 at the National Sheep Breeding Centre (NSBC), which supplies breeding animals to village sheep flocks throughout Bhutan. Despite the presence of footrot at the Centre the distribution of apparently disease-free sheep continued. Cases of footrot were reported in village flocks soon after the disease was diagnosed at NSBC. A national survey was designed to establish the distribution and prevalence of footrot in Bhutan. This detected footrot in 19/94 village sheep flocks surveyed. The 19 affected flocks were distributed among nine different administrative districts whereas the villages selected were in 13 of a total of 16 sheep growing districts. The highest within-flock prevalences were among the seven flocks sampled in Bumthang district (mean 20.4%). The prevalence of the disease within flocks was generally much lower in other affected districts and in three districts a single affected animal was identified in the sample of 14 sheep examined in each village. Nationally, footrot prevalence was estimated to be 3.1% (95% CI 2.16-4.04%). There was a positive association between the receipt of animals from NSBC and the presence of footrot. The prevalence of the disease was higher in flocks with a migratory system of management than in those using a sedentary system. The relative risk of there being footrot in a migratory flock was nine-times higher than in a non-migratory flock. Only one strain of Dichelobacter nodosus (serogroup B) was identified among the 234 isolates obtained from the 19 affected flocks. Sheep with footrot healed quickly when treated with a vaccine made from this strain.

Animals↗