Detection and Serogrouping of Dichelobacter nodosus Infection by Use of Direct PCR from Lesion Swabs To Support Outbreak-Specific Vaccination for Virulent Footrot in Sheep

McPherson, Andrew S.; Dhungyel, Om P.; Whittington, Richard J.

doi:10.1128/jcm.01730-17

Cited by 12 publications

(14 citation statements)

References 41 publications

(80 reference statements)

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“…The strength of the current study is the number of flocks investigated nationally which provides the robust estimates of the prevalence of serogroups. The percentage of flocks and feet with multiple serogroups and the maximum number of serogroups per flock are higher than reported in previous UK studies 12 – 14 , 39 this is probably partly due to the increased sensitivity of PCR directly from DNA without culture 15 . Despite this, the number of serogroups detected in flocks is likely to be underestimated.…”

Section: Discussioncontrasting

confidence: 59%

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Serogroups of Dichelobacter nodosus, the cause of footrot in sheep, are randomly distributed across England

Prosser

Monaghan

Green

et al. 2020

Sci Rep

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We present the largest and most representative study of the serological diversity of Dichelobacter nodosus in England. D. nodosus causes footrot and is one of the top five globally important diseases of sheep. The commercial vaccine, containing nine serogroups, has low efficacy compared with bivalent vaccines. Our aim was to investigate the prevalence and distribution of serogroups of D. nodosus in England to elucidate whether a bivalent vaccine could protect the national flock. Farmers from 164 flocks submitted eight interdigital swabs from eight, preferably diseased, sheep. All serogroups, A–I, were detected by PCR in 687/1150 D. nodosus positive swabs, with a prevalence of 2.6–69.3% of positive swabs per serogroup. There was a median of two serogroups per flock (range 0–6). Serogroups were randomly distributed between, but clustered within, flocks, with 50 combinations of serogroups across flocks. H and B were the most prevalent serogroups, present in > 60% of flocks separately but in only 27% flocks together. Consequently, a bivalent vaccine targeting these two serogroups would protect 27% of flocks fully (if only H and B present) and partially, if more serogroups were present in the flock. We conclude that one bivalent vaccine would not protect the national flock against footrot and, with 50 combinations of serogroups in flocks, flock-specific vaccines are necessary.

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Section: Discussioncontrasting

confidence: 59%

“…McPherson et al 15 . Previous UK studies have used culture and slide agglutination to detect serogroups, but PCR is more sensitive 15 consequently the number of serogroups per flock is likely to be higher than previous estimates.…”

Section: Introductionmentioning

confidence: 99%

Serogroups of Dichelobacter nodosus, the cause of footrot in sheep, are randomly distributed across England

Prosser

Monaghan

Green

et al. 2020

Sci Rep

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“…One major challenge in footrot elimination is the development of diagnostic tests which can discriminate reliably between target and non-target strains [1]. Regional elimination programs are usually aimed at virulent D nodosus, as large-scale elimination of benign D nodosus is not economically justifiable [25]. In Switzerland, the use of the PCR test was found to be the most economic and sensitive way to eliminate footrot in the planned nationwide control program [18].…”

Section: Discussionmentioning

confidence: 99%

The prevalence of Dichelobacter nodosus in clinically footrot-free sheep flocks: a comparative field study on elimination strategies

Kraft

Ströbel²,

Hilke³

et al. 2020

BMC Vet Res

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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.

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“…They reported that D. nodosus strains clustered within sheep and were transmitted between ewes over time. D. nodosus isolation is challenging and time consuming, because of the organism's fastidious and anaerobic nature and direct PCR from swab DNA is more sensitive than culture ( 15 , 22 ).…”

Section: Introductionmentioning

confidence: 99%

A Pilot Study to Investigate the Feasibility of a Multiple Locus Variable Number Tandem Repeat Analysis to Understand the Epidemiology of Dichelobacter nodosus in Ovine Footrot

2020

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Dichelobacter nodosus is the essential pathogen in ovine footrot, an important cause of lameness in sheep that reduces productivity and welfare. The aim of this study was to investigate the feasibility of using multiple locus variable number tandem repeat analysis (MLVA) developed to investigate isolates to understand the molecular epidemiology of Dichelobacter nodosus in ovine footrot by investigation of communities of strains. MLVA sensitivity was improved by optimizing PCR conditions to 100% specificity for D. nodosus. The improved MLVA scheme was used to investigate non-cultured DNA purified from swabs (swab DNA) and cultured DNA from isolates (isolate DNA) from 152 foot and 38 gingival swab samples from 10 sheep sampled on four occasions in a longitudinal study. Isolate DNA was obtained from 6/152 (3.9%) feet and 5/6 yielded complete MLVA profiles, three strains were detected. Two of the three isolate strains were also detected in isolate DNA from 2 gingival crevice cultures. Complete MLVA profiles were obtained from swab DNA from 39 (25.7%) feet. There were 22 D. nodosus community types that were comprised of 7 single strain and 15 multi-strain communities. Six community types were detected more than once and three of these were detected on the same four sheep and the same two feet over time. There were a minimum of 17 and a maximum of 25 strain types of D. nodosus in the study. The three isolate strain types were also the most frequently detected strain types in swab DNA. We conclude that the MLVA from swab DNA detects the same strains as culture, is much more sensitive and can be used to describe and differentiate communities and strains on sheep, feet and over time. It is therefore a sensitive molecular tool to study D. nodosus strains directly from DNA without culture.

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Detection and Serogrouping of Dichelobacter nodosus Infection by Use of Direct PCR from Lesion Swabs To Support Outbreak-Specific Vaccination for Virulent Footrot in Sheep

Cited by 12 publications

References 41 publications

Serogroups of Dichelobacter nodosus, the cause of footrot in sheep, are randomly distributed across England

Serogroups of Dichelobacter nodosus, the cause of footrot in sheep, are randomly distributed across England

The prevalence of Dichelobacter nodosus in clinically footrot-free sheep flocks: a comparative field study on elimination strategies

A Pilot Study to Investigate the Feasibility of a Multiple Locus Variable Number Tandem Repeat Analysis to Understand the Epidemiology of Dichelobacter nodosus in Ovine Footrot

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