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Smith K, Whittington RJ, Green AC, Dhand NK, Moses A, Grove A, Thane T, Dhungyel OP. A survey to understand farmers' perceptions and risk factors for hoof diseases including footrot in sheep in New South Wales, Australia. Front Vet Sci 2022; 9:1000295. [PMCID: PMC9634747 DOI: 10.3389/fvets.2022.1000295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 10/10/2022] [Indexed: 11/13/2022] Open
Abstract
The aims of this study were to develop an understanding of farmers' perceptions and risk factors for footrot, including its less severe forms, and other hoof diseases in sheep in New South Wales (NSW). A questionnaire was developed and administered to sheep farmers in Local Land Services (LLS) regions across NSW. LLS staff selected sheep farmers who met the inclusion criteria which included farmers with a minimum of 100 sheep, a history of having had foot problems in their flock or having expressed an interest in improving sheep health and production. Farmers completed the questionnaire either by telephone or via the REDCap online survey platform. Descriptive analyses and multivariable logistic regression models were created. The survey was completed by 43 sheep farmers with a median farm size of 1,500 Ha and flock size of 2,300; footrot was present on 39% of farms while 75.6% had other hoof diseases. A flock of >3,000 sheep were more likely to have footrot than a smaller flock (OR = 11.99, 90% CI = 3.02–63.92, P-value = 0.005) and footrot was less likely to be present on farms when an Animal Health Statement was requested while purchasing sheep (OR = 0.10, 90% CI = 0.01–0.56, P-value = 0.04). Hoof conditions other than footrot were likely to be present in flocks when foot inspections were conducted at a time other than weekly inspections (OR = 0.13, 90% CI = 0.01–0.68, P-value = 0.04) and flocks kept on undulating ground were more likely to have diseases other than footrot compared to those kept on flat ground (OR = 3.72, 90% CI = 1.02–15.80, P-value = 0.09). Most farmers agreed that footrot including its less severe forms can cause production losses and negatively affect animal health and welfare. Limitations of the study were the sample size and dry environmental conditions prior to and during study period in many regions of NSW which limited the expression of footrot.
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Risk factors associated with the infection of sheep with Dichelobacter nodosus. Sci Rep 2022; 12:10032. [PMID: 35705578 PMCID: PMC9200780 DOI: 10.1038/s41598-022-13933-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 05/30/2022] [Indexed: 11/08/2022] Open
Abstract
Ovine footrot is a highly contagious foot disease caused by the gram-negative bacterium Dichelobacter nodosus (D. nodosus). In a recent report, we showed a prevalence of 42.9% D. nodosus positive swabs across Germany. In this follow-up study, we used real-time PCR results for D. nodosus and footrot scores of 9297 sheep from 208 flocks and collated these data with survey data on herd and animal characteristics and herd management. The aims of the present study were to investigate herd and animal factors associated with D. nodosus infection and footrot scores in individual sheep. Multivariable analyses with generalized mixed models showed that month of recording, breed, herdbook membership, use of antibiotics, and footbaths in the past 3–10 years, signs of footrot in the past 12 months and flock environment of the sheep, modelled as a random farm effect within region, were significant risk factors. Among the 21 different breeds, Romney had the lowest risk of D. nodosus infection, while Swifter had the highest risk and German Merino and German White Heath were the next breeds at highest risk of D. nodosus infection. The variance between farms in the prevalence of D. nodosus was large and accounted for 84% of the total variance in the mixed model analysis. We conclude that specific and as yet unknown effects influencing D. nodosus infections in flocks, as well as breed and weather, are the most important effects on D. nodosus infection in sheep, pointing towards the need to establish adequate infection control at farm level.
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Smith KJ, Whittington RJ, Corrigan MA, Edmonstone BI, Cronin NA, Dhand NK, Dhungyel OP. Efficacy of bivalent fimbrial vaccines to control and eliminate intermediate forms of footrot in sheep. Aust Vet J 2021; 100:121-129. [PMID: 34897647 DOI: 10.1111/avj.13138] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 11/16/2021] [Accepted: 11/19/2021] [Indexed: 11/29/2022]
Abstract
OBJECTIVE The aim of this study was to determine the efficacy of serogroup-specific bivalent fimbrial vaccines in the control and elimination of relatively mild (intermediate) forms of footrot in sheep flocks in NSW, there being some evidence that such forms are difficult to control. METHODS Four flocks of sheep with history of footrot of intermediate virulence were selected based on clinical and bacteriological diagnoses. Dichelobacter nodosus serogroups included in bivalent vaccines at each farm were based on on-farm serogroup-prevalence data. Two doses of bivalent vaccine were administered with a 4-week interval between doses. Repeated post-vaccination inspections of all feet of between 100 and 119 animals per mob were conducted and foot swabs were collected for bacteriological testing. Blood samples were collected from 10 to 24 individually identified animals per flock at each inspection to check for agglutinating antibody responses. RESULTS In the majority of animals, antibody levels for serogroups included in each vaccine were above the level believed to be required for protective immunity. Footrot disappeared on farm 1 prior to vaccination, but did not reappear postvaccination. Footrot was controlled but not eliminated on farms 2, 3, and 4, where the prevalence and severity of the disease and number of serogroups present were reduced. CONCLUSION Serogroup-specific bivalent vaccines can be effective at controlling footrot caused by intermediate strains of D. nodosus.
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Affiliation(s)
- K J Smith
- Farm Animal Health, Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, Camden, New South Wales, 2570, Australia
| | - R J Whittington
- Farm Animal Health, Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, Camden, New South Wales, 2570, Australia
| | - M A Corrigan
- Murray LLS, Albury, New South Wales, 2640, Australia
| | - B I Edmonstone
- Central West LLS, Forbes, New South Wales, 2871, Australia
| | - N A Cronin
- Central West LLS, Forbes, New South Wales, 2871, Australia
| | - N K Dhand
- Farm Animal Health, Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, Camden, New South Wales, 2570, Australia
| | - O P Dhungyel
- Farm Animal Health, Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, Camden, New South Wales, 2570, Australia
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Monaghan EM, Prosser NS, Witt J, Lewis KE, Nabb E, Keeling MJ, Purdy KJ, Green LE. Impact of Strain Variation of Dichelobacter nodosus on Disease Severity and Presence in Sheep Flocks in England. Front Vet Sci 2021; 8:713927. [PMID: 34485440 PMCID: PMC8415419 DOI: 10.3389/fvets.2021.713927] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Accepted: 07/22/2021] [Indexed: 11/13/2022] Open
Abstract
AprV2 and aprB2 are variants of the apr gene of Dichelobacter nodosus, the cause of footrot in sheep. They are putative markers for severe and mild disease expression. The aim of our study was to investigate the distribution of aprV2 and aprB2 in flocks with and without footrot. Our hypotheses were that both strains are present in endemically affected flocks, with aprB2 and aprV2 associated with mild and virulent phenotypes respectively but that D. nodosus is not present in flocks without footrot. Alternatively, aprB2 persists in flocks without footrot. Despite extensive searching over 3 years only three flocks of sheep without footrot were identified. D. nodosus was not detected in these three flocks. In one further flock, only mild interdigital dermatitis was observed, and only aprB2 was detected. Twenty-four flocks with endemic footrot of all severities were sampled on three occasions and all were positive for D. nodosus and the aprV2 variant; aprB2 was detected in only 11 of these flocks. AprB2 was detected as a co-infection with aprV2 in the 22% of samples positive for aprB2 and was more likely in mild footrot phenotypes than severe. Dichelobacter nodosus serogroups were not associated with footrot phenotype. We conclude that D. nodosus, even aprB2 strains, do not persist in flocks in the absence of footrot. Our results support the hypothesis that aprB2 is associated with mild footrot phenotypes. Finally, we conclude that given the small number of flocks without footrot that were identified, footrot is highly endemic in English sheep flocks.
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Affiliation(s)
- Emma M Monaghan
- Institute of Microbiology and Infection, College of Life and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Naomi S Prosser
- School of Veterinary Medicine and Science, University of Nottingham, Leicestershire, United Kingdom
| | - Jessica Witt
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Katharine E Lewis
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Elizabeth Nabb
- Institute of Microbiology and Infection, College of Life and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Matt J Keeling
- Zeeman Institute, SBIDER: Systems Biology & Infectious Disease Epidemiology Research, Warwick Mathematics Institute, University of Warwick, Coventry, United Kingdom
| | - Kevin J Purdy
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Laura E Green
- Institute of Microbiology and Infection, College of Life and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom
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5
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Zanolari P, Dürr S, Jores J, Steiner A, Kuhnert P. Ovine footrot: A review of current knowledge. Vet J 2021; 271:105647. [PMID: 33840488 DOI: 10.1016/j.tvjl.2021.105647] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 02/17/2021] [Accepted: 02/18/2021] [Indexed: 12/14/2022]
Abstract
Footrot is a contagious foot disease mainly affecting sheep. It is caused by the Gram-negative anaerobic bacterium Dichelobacter nodosus. Warm, wet environmental conditions favour development of footrot, and under perfect conditions, it takes just 2-3 weeks from infection to manifestation of clinical signs. Affected sheep show lameness of various degrees and often graze while resting on their carpi. Local clinical signs vary in severity and extent from interdigital inflammation (benign footrot) to underrunning of the complete horn shoe in advanced stages of virulent footrot. Laboratory diagnosis ideally involves collection of four-foot interdigital swab samples followed by competitive real time PCR, allowing for detection of the presence of D. nodosus and differentiation between benign and virulent strains. Laboratory-based diagnostics at the flock level based on risk-based sampling and pooling of interdigital swab samples are recommended. The list of treatment options of individual sheep includes careful removal of the loose undermined horn, local or systemic administration of antimicrobials, systemic administration of non-steroidal anti-inflammatories (NSAIDs) and disinfectant footbathing. Strategies for control at the flock level are manifold and depend on the environmental conditions and the procedures traditionally implemented by the respective country. Generally, measures consist of treatment/culling of infected sheep, vaccination and prevention of reinfection of disease-free flocks. Gaining deeper insight into the beneficial effects of NSAIDs, screening for eco-friendly footbath solutions, developing better vaccines, including the development of a robust, reproducible infection model and elucidation of protective immune responses, as well as the elaboration of effective awareness training programs for sheep farmers, are relevant research gaps.
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Affiliation(s)
- Patrik Zanolari
- Clinic for Ruminants, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Salome Dürr
- Veterinary Public Health Institute, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Jörg Jores
- Institute of Veterinary Bacteriology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Adrian Steiner
- Clinic for Ruminants, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
| | - Peter Kuhnert
- Institute of Veterinary Bacteriology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
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McPherson AS, Whittington RJ, Hall E, Cook EJ, Jones JV, Qi Ang Y, McTavish EL, Dhungyel OP. A comparison of multivalent and bivalent vaccination strategies for the control of virulent ovine footrot. Vaccine 2021; 39:1736-1745. [PMID: 33622590 DOI: 10.1016/j.vaccine.2021.02.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 01/31/2021] [Accepted: 02/07/2021] [Indexed: 11/28/2022]
Abstract
Virulent footrot is a significant economic and animal welfare concern. The disease can be treated, controlled, and eliminated with vaccine, but selecting the appropriate vaccination strategy can be challenging. There are two main strategies: outbreak (serogroup)-specific univalent or bivalent vaccination, or use of a multivalent vaccine containing up to nine of the most common serogroups. The objective of this study was to compare these approaches in sheep flocks infected with multiple Dichelobacter nodosus serogroups. In the first phase, we undertook an immunogenicity trial in which we compared four pre-commercial multivalent recombinant fimbrial vaccines containing six (A, B, C, G, H, I) or nine (A, B, C, D, E, F, G, H, I) serogroups, and compared them to commercial bivalent vaccines. Two multivalent vaccines stimulated significantly higher antibody responses than two other multivalent vaccines but the number of serogroups included in the multivalent vaccine formulations did not have a significant effect. In the first phase, we also compared inter-vaccination intervals of two- and three-months between sequential bivalent vaccines, and found that a two-month interval was sufficient to avoid antigenic competition. In the second phase, the most immunogenic multivalent vaccine (nine serogroups) was compared to sequential bivalent vaccines and monthly foot-bathing in a field trial in four commercial Merino flocks. The duration of protection afforded by the multivalent vaccine was likely to be less than that of the bivalent vaccines, as the antibody titres stimulated were lower and less persistent.
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Affiliation(s)
- Andrew S McPherson
- Farm Animal Health, Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, 425 Werombi Rd, Camden, New South Wales 2570, Australia
| | - Richard J Whittington
- Farm Animal Health, Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, 425 Werombi Rd, Camden, New South Wales 2570, Australia
| | - Evelyn Hall
- Farm Animal Health, Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, 425 Werombi Rd, Camden, New South Wales 2570, Australia
| | - Emma J Cook
- Farm Animal Health, Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, 425 Werombi Rd, Camden, New South Wales 2570, Australia
| | - Jeremy V Jones
- Farm Animal Health, Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, 425 Werombi Rd, Camden, New South Wales 2570, Australia
| | - Yan Qi Ang
- Farm Animal Health, Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, 425 Werombi Rd, Camden, New South Wales 2570, Australia
| | - Emma L McTavish
- Farm Animal Health, Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, 425 Werombi Rd, Camden, New South Wales 2570, Australia
| | - Om P Dhungyel
- Farm Animal Health, Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, 425 Werombi Rd, Camden, New South Wales 2570, Australia.
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Sites of persistence of Fusobacterium necrophorum and Dichelobacter nodosus: a paradigm shift in understanding the epidemiology of footrot in sheep. Sci Rep 2019; 9:14429. [PMID: 31594981 PMCID: PMC6783547 DOI: 10.1038/s41598-019-50822-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2019] [Accepted: 09/05/2019] [Indexed: 01/09/2023] Open
Abstract
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.
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8
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Allworth MB, Egerton JR. Relationship between the likelihood of footrot elimination from a flock and the virulence of the strain of Dichelobacter nodosus
present. Aust Vet J 2018; 96:400-407. [DOI: 10.1111/avj.12750] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 04/16/2018] [Accepted: 07/12/2018] [Indexed: 11/27/2022]
Affiliation(s)
- MB Allworth
- Fred Morley Centre and Graham Centre, School of Animal and Veterinary Sciences; Charles Sturt University; Wagga Wagga NSW Australia
| | - JR Egerton
- Fred Morley Centre and Graham Centre, School of Animal and Veterinary Sciences; Charles Sturt University; Wagga Wagga NSW Australia
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9
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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. J Clin Microbiol 2018; 56:JCM.01730-17. [PMID: 29436426 DOI: 10.1128/jcm.01730-17] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 02/02/2018] [Indexed: 11/20/2022] Open
Abstract
Virulent footrot is an economically significant disease in most sheep-rearing countries. The disease can be controlled with vaccine targeting the fimbriae of virulent strains of the essential causative agent, Dichelobacter nodosus However, the bacterium is immunologically heterogeneous, and 10 distinct fimbrial serogroups have been identified. Ideally, in each outbreak the infecting strains would be cultured and serogrouped so that the appropriate serogroup-specific mono- or bivalent vaccine could be administered, because multivalent vaccines lack efficacy due to antigenic competition. If clinical disease expression is suspected to be incomplete, culture-based virulence tests are required to confirm the diagnosis, because control of benign footrot is economically unjustifiable. Both diagnosis and vaccination are conducted at the flock level. The aims of this study were to develop a PCR-based procedure for detecting and serogrouping D. nodosus directly from foot swabs and to determine whether this could be done accurately from the same cultured swab. A total of 269 swabs from the active margins of foot lesions of 261 sheep in 12 Merino sheep flocks in southeastern Australia were evaluated. DNA extracts taken from putative pure cultures of D. nodosus and directly from the swabs were evaluated in PCR assays for the 16S rRNA and fimA genes of D. nodosus Pure cultures were tested also by the slide agglutination test. Direct PCR using extracts from swabs was more sensitive than culture for detecting and serogrouping D. nodosus strains. Using the most sensitive sample collection method of the use of swabs in lysis buffer, D. nodosus was more likely to be detected by PCR in active than in inactive lesions, and in lesions with low levels of fecal contamination, but lesion score was not a significant factor. PCR conducted on extracts from swabs in modified Stuart's transport medium that had already been used to inoculate culture plates had lower sensitivity. Therefore, if culture is required to enable virulence tests to be conducted, it is recommended that duplicate swabs be collected from each foot lesion, one in transport medium for culture and the other in lysis buffer for PCR.
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10
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Evaluation of Genotypic and Phenotypic Protease Virulence Tests for Dichelobacter nodosus Infection in Sheep. J Clin Microbiol 2017; 55:1313-1326. [PMID: 28202796 PMCID: PMC5405250 DOI: 10.1128/jcm.02403-16] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 02/02/2017] [Indexed: 11/20/2022] Open
Abstract
Dichelobacter nodosus is a fastidious, strictly anaerobic bacterium, an obligate parasite of the ruminant hoof, and the essential causative agent of virulent ovine footrot. The clinical disease results from a complex interplay between the pathogen, the environment, and the host. Sheep flocks diagnosed with virulent but not benign footrot in Australia may be quarantined and required to undergo a compulsory eradication program, with costs met by the farmer. Virulence of D. nodosus at least partially depends on the elaboration of a protease encoded by aprV2 and manifests as elastase activity. Laboratory virulence tests are used to assist diagnosis because clinical differentiation of virulent and benign footrot can be challenging during the early stages of disease or when the disease is not fully expressed due to unfavorable pasture conditions. Using samples collected from foot lesions from 960 sheep from 40 flocks in four different geographic regions, we evaluated the analytical characteristics of qPCR tests for the protease gene alleles aprV2 and aprB2, and compared these with results from phenotypic protease (elastase and gelatin gel) tests. There was a low level of agreement between clinical diagnosis and quantitative PCR (qPCR) test outcomes at both the flock and sample levels and poor agreement between qPCR test outcomes and the results of phenotypic virulence tests. The diagnostic specificity of the qPCR test was low at both the flock and individual swab levels (31.3% and 18.8%, respectively). By contrast, agreement between the elastase test and clinical diagnosis was high at both the flock level (diagnostic sensitivity [DSe], 100%; diagnostic specificity [DSp], 78.6%) and the isolate level (DSe, 69.5%; DSp, 80.5%).
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11
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Phythian CJ, Cripps PJ, Grove-White D, Michalopoulou E, Duncan JS. Inter-observer agreement for clinical examinations of foot lesions of sheep. Vet J 2016; 216:189-95. [PMID: 27687951 DOI: 10.1016/j.tvjl.2016.08.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 03/28/2016] [Accepted: 08/12/2016] [Indexed: 11/17/2022]
Abstract
In sheep, the diagnosis of foot lesions is routinely based on physical examination of the hoof. Correct diagnosis is important for the effective treatment, prevention and control of both infectious and non-infectious causes of lameness. Therefore, the aim of this study was to evaluate the level of inter-observer agreement for clinical examination of ovine foot lesions. Eight observers of varying experience, training and occupation performed foot examinations on a total of 1158 sheep from 38 farms across North England and Wales. On each farm, a group of two to four observers independently examined a sample of 24 to 30 sheep to diagnose the presence or absence of specific foot lesions including white line lesions (WL), contagious ovine digital dermatitis (CODD), footrot (FR), inter-digital dermatitis (ID) and toe granuloma (TG). The inter-observer agreement of foot lesion assessments was examined using Fleiss kappa (κ), and Cohen's κ examined the paired agreement between the test standard observer (TSO) and each observer. Scoring differences with the TSO were examined as the percentage of scoring errors and assessed for evidence of systematic scoring bias. With the exception of WL (maximum error rate 33.3%), few scoring differences with the TSO occurred (maximum error rate 3.3%). This suggests that observers can achieve good levels of reliability when diagnosing most of the commonly observed foot conditions associated with lameness in sheep.
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Affiliation(s)
- C J Phythian
- Department of Epidemiology, Institute of Global Health and Infection, and Population Health, University of Liverpool, Leahurst, Neston CH64 7TE, UK; Section for Small Ruminant Research, Norwegian University of Life Sciences (NMBU), Høyland, 4325 Sandnes, Norway.
| | - P J Cripps
- Department of Epidemiology, Institute of Global Health and Infection, and Population Health, University of Liverpool, Leahurst, Neston CH64 7TE, UK
| | - D Grove-White
- Department of Epidemiology, Institute of Global Health and Infection, and Population Health, University of Liverpool, Leahurst, Neston CH64 7TE, UK
| | - E Michalopoulou
- Department of Epidemiology, Institute of Global Health and Infection, and Population Health, University of Liverpool, Leahurst, Neston CH64 7TE, UK
| | - J S Duncan
- Department of Epidemiology, Institute of Global Health and Infection, and Population Health, University of Liverpool, Leahurst, Neston CH64 7TE, UK
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Drug Target Identification and Prioritization for Treatment of Ovine Foot Rot: An In Silico Approach. Int J Genomics 2016; 2016:7361361. [PMID: 27379247 PMCID: PMC4917682 DOI: 10.1155/2016/7361361] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 05/16/2016] [Indexed: 02/06/2023] Open
Abstract
Ovine foot rot is an infection of the feet of sheep, mainly caused by Dichelobacter nodosus. In its virulent form, it is highly contagious and debilitating, causing significant losses in the form of decline in wool growth and quality and poor fertility. Current methods of treatment are ineffective in complete eradication. Effective antibiotic treatment of foot rot is hence necessary to ensure better outcomes during control phases by reduction in culling count and the possibility of carriers of the infection. Using computational approaches, we have identified a set of 297 proteins that are essential to the D. nodosus and nonhomologous with sheep proteins. These proteins may be considered as potential vaccine candidates or drug targets for designing antibiotics against the bacterium. This core set of drug targets have been analyzed for pathway annotation to identify 67 proteins involved in unique bacterial pathways. Choke-point analysis on the drug targets identified 138 choke-point proteins, 29 involved in unique bacterial pathways. Subcellular localization was also predicted for each target to identify the ones that are membrane associated or secreted extracellularly. In addition, a total of 13 targets were identified that are common in at least 10 pathogenic bacterial species.
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Vinod Kumar N, Sreenivasulu D, Karthik A. Identification and characterization of Dichelobacter nodosus serogroup H from ovine footrot in India. Anaerobe 2016; 40:100-2. [PMID: 27259362 DOI: 10.1016/j.anaerobe.2016.05.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Revised: 04/13/2016] [Accepted: 05/24/2016] [Indexed: 10/21/2022]
Abstract
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.
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Affiliation(s)
- N Vinod Kumar
- Department of Veterinary Microbiology, College of Veterinary Science, Tirupati, AP, India.
| | - D Sreenivasulu
- College of Veterinary Science, Tirupati, 517 502, AP, India.
| | - A Karthik
- Department of Veterinary Microbiology, College of Veterinary Science, Tirupati, AP, India.
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14
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Kumar NV, Karthik A, Vijayalakhsmi S, Sreenivasulu D. Phylogenetic analysis of Dichelobacter nodosus serogroup-specific fimA gene from ovine footrot in Andhra Pradesh. Vet World 2016; 8:567-71. [PMID: 27047136 PMCID: PMC4774714 DOI: 10.14202/vetworld.2015.567-571] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2014] [Revised: 03/24/2015] [Accepted: 03/30/2015] [Indexed: 11/24/2022] Open
Abstract
Aim: Identification of different serogroups of Dichelobacter nodosus prevailing in the region and to understand the degree of genetic heterogeneities among the different isolates of D. nodosus. Materials and Methods: A total of 150 exudate samples of footrot lesions with a lesion score of 2-4 were collected from naturally infected sheep. The samples were screened by polymerase chain reaction (PCR) targeting D. nodosus specific 16srRNA. Of 150 samples screened, 70 samples were found to be positive. The positive samples were attempted for isolation of D. nodosus, out of which 16 isolates were recovered. All the isolates were subjected to serogrouping by multiplex PCR targeting fimA gene using A-I serogroup specific primers. Results: Of 16 isolates, 7 (43.75%) isolates were serogroup B, 4 (25.00%) isolates were serogroup A, 3 isolates (18.75%) were serogroup I and 2 (12.5%) isolates yielded both serogroup A and B. phylogenetic analysis was performed using neighbor-joining algorithm of the ClustelX2 software in order to study whether the serogroups isolated in the present investigation differed genetically from other published serogroups. The fimA gene sequence of present isolates of serogroups A, B, and I were segregated into three distinct groups with high bootstrap values. The serogroup B clustered with Australian isolate of serotype B1 suggesting high genetic similarity of the present isolate with serotype B1. Conclusions: The clinical samples were collected from suspected outbreaks of footrot and identified the prevalence of D. nodosus by PCR targeting 16srRNA gene. Identified serogroups A, B, and I from different districts of Andhra Pradesh. The phylogenetic analysis will help for the tentative identification of serotypes present in the serogroup and to understand the degree of genetic heterogeneities among the different isolates of D. nodosus.
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Affiliation(s)
- N Vinod Kumar
- Department of Veterinary Microbiology, College of Veterinary Science, Sri Venkateswara Veterinary University, Tirupati - 517 502, Andhra Pradesh, India
| | - A Karthik
- Department of Veterinary Microbiology, College of Veterinary Science, Sri Venkateswara Veterinary University, Tirupati - 517 502, Andhra Pradesh, India
| | - S Vijayalakhsmi
- Department of Veterinary Microbiology, College of Veterinary Science, Sri Venkateswara Veterinary University, Tirupati - 517 502, Andhra Pradesh, India
| | - D Sreenivasulu
- Department of Veterinary Microbiology, College of Veterinary Science, Sri Venkateswara Veterinary University, Tirupati - 517 502, Andhra Pradesh, India
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Lacasta D, Ferrer L, Ramos J, González J, Ortín A, Fthenakis G. Vaccination schedules in small ruminant farms. Vet Microbiol 2015. [DOI: 10.1016/j.vetmic.2015.07.018] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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16
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Dhungyel O, Schiller N, Whittington R. Identification and characterization of serogroup M Dichelobacter nodosus from sheep with virulent footrot. Vet Microbiol 2015; 176:378-81. [DOI: 10.1016/j.vetmic.2015.01.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Revised: 01/05/2015] [Accepted: 01/16/2015] [Indexed: 11/30/2022]
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18
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Bhardwaj V, Dhungyel O, de Silva K, Whittington RJ. Investigation of immunity in sheep following footrot infection and vaccination. Vaccine 2014; 32:6979-6985. [PMID: 25454866 DOI: 10.1016/j.vaccine.2014.10.031] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2014] [Revised: 10/07/2014] [Accepted: 10/16/2014] [Indexed: 11/17/2022]
Abstract
Ovine footrot is a major disease affecting sheep welfare and production. The anaerobic Gram-negative bacterium Dichelobacter nodosus is the essential transmitting agent. Monovalent or bivalent vaccines induce high levels of D. nodosus antibodies and are the basis of several successful footrot treatment, control and eradication programs. Due to the rapid rate of disease transmission within a flock, the presence of therapeutic vaccination non-responders has major implications for a control program. The aim of this study was to assess the immunological basis of a therapeutic vaccination non-response. Sheep (n=120) were infected with D. nodosus in an artificial pen challenge. Once disease had established, animals were vaccinated with a serogroup specific D. nodosus fimbrial vaccine. Based on the response to therapeutic vaccination, animals were allocated into one of three groups: (i) TVNR where disease persisted despite vaccination (ii) non-diseased, where disease never established and (iii) TVR, where disease was established but resolved with vaccination. Factors related to both the innate and adaptive immune pathways were assessed. These included antigen-specific serum antibodies, interferon-γ, interleukin-10, proliferation of lymphocyte subsets and phagocytic activity of leukocytes. There was no significant difference between the three groups of sheep for any of these parameters. All three groups of sheep produced antibody in excess of a previously published minimum antibody titre required for protection. Opsonising activity in sera from the three groups of sheep was also not significantly different and phagocytic cells from sheep from all three groups were able to destroy D. nodosus intracellularly. These findings show that the measured systemic adaptive and innate immune responses were unlikely to be the cause of a therapeutic vaccination non-response. They also show that the accepted minimum protective titre may be incorrect and may need further examination.
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Affiliation(s)
- Vidya Bhardwaj
- Farm Animal and Veterinary Public Health, Faculty of Veterinary Science, University of Sydney, 425 Werombi Road, Camden 2570, NSW, Australia
| | - Om Dhungyel
- Farm Animal and Veterinary Public Health, Faculty of Veterinary Science, University of Sydney, 425 Werombi Road, Camden 2570, NSW, Australia
| | - Kumudika de Silva
- Farm Animal and Veterinary Public Health, Faculty of Veterinary Science, University of Sydney, 425 Werombi Road, Camden 2570, NSW, Australia.
| | - Richard J Whittington
- Farm Animal and Veterinary Public Health, Faculty of Veterinary Science, University of Sydney, 425 Werombi Road, Camden 2570, NSW, Australia
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19
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20
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Footrot vaccines and vaccination. Vaccine 2014; 32:3139-46. [DOI: 10.1016/j.vaccine.2014.04.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Revised: 03/25/2014] [Accepted: 04/01/2014] [Indexed: 12/19/2022]
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21
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22
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Dhungyel O, Schiller N, Eppleston J, Lehmann D, Nilon P, Ewers A, Whittington R. Outbreak-specific monovalent/bivalent vaccination to control and eradicate virulent ovine footrot. Vaccine 2013; 31:1701-6. [PMID: 23395621 DOI: 10.1016/j.vaccine.2013.01.043] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Revised: 01/17/2013] [Accepted: 01/23/2013] [Indexed: 11/27/2022]
Abstract
Footrot is a contagious disease of small ruminants which is caused by the bacterium Dichelobacter nodosus. In its virulent form there are severe economic losses and a very significant animal welfare issue. Sheep and goats can be vaccinated for treatment and prevention of the disease. There are 10 different serogroups of D. nodosus (A-I and M) and immunity is serogroup-specific. When all 10 serogroups are presented together in a vaccine, protection persists for only a few months due to "antigenic competition". Consequently we evaluated the use of sequential monovalent or bivalent vaccines to control/eliminate/eradicate virulent footrot in a longitudinal intervention study on 12 commercial farms in southeast Australia with flock sizes of approximately 1200-4200 sheep. Overall, virulent footrot was eradicated from 4 of the flocks, 2 of which had 2 serogroups, and the others 4 or 5 serogroups. Where there were only 1 or 2 serogroups (3 farms) the clinical response was rapid and dramatic; prevalence was reduced from 45 to 50% before vaccination to 0% (2 farms) or 0.4% (1 farm) after one round of vaccination. In the remaining 9 flocks there were more than 2 serogroups and successive bivalent vaccines were administered leading to eradication of virulent footrot on 2 farms over 4 years and control of the disease on all but 3 of the others. Of the latter farms, 1 discontinued, and 2 initially had poor response to vaccine due to misdiagnosis of serogroup 'M', which was previously unknown in Australia. Control was achieved after administration of a serogroup M vaccine. These results provide clear evidence for control, elimination and eradication of virulent footrot by outbreak-specific vaccination in Australia.
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Affiliation(s)
- Om Dhungyel
- Farm Animal and Veterinary Public Health, Faculty of Veterinary Science, The University of Sydney, 425 Werombi Road, Camden, NSW 2570, Australia.
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23
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Petrov KK, Dicks LM. Footrot in Clawed and Hoofed Animals: Symptoms, Causes and Treatments. BIOTECHNOL BIOTEC EQ 2013. [DOI: 10.5504/bbeq.2012.0103] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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24
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Gilhuus M, Vatn S, Dhungyel OP, Tesfamichael B, L'Abée-Lund TM, Jørgensen HJ. Characterisation of Dichelobacter nodosus isolates from Norway. Vet Microbiol 2012; 163:142-8. [PMID: 23332560 DOI: 10.1016/j.vetmic.2012.12.020] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Revised: 12/12/2012] [Accepted: 12/16/2012] [Indexed: 11/26/2022]
Abstract
An outbreak of ovine footrot in Norway in 2008, the first reported since 1948, prompted action to investigate Norwegian isolates of Dichelobacter nodosus. A total of 579 isolates from 124 different farms were characterised. These included 519 isolates from sheep, 52 isolates from cattle and 8 isolates from goats. The potential virulence of the isolates was assessed by the gelatin gel test (GG-test) and the elastin agar test, that test the heat stability and elastase activity of bacterial proteases, respectively. The isolates were also tested for the presence of intA by PCR, and allocated to serogroups by differentiation of fimA variants using multiplex PCR or sequencing. Thirty of the isolates were also serogrouped by slide agglutination. Three hundred and five isolates were defined as virulent by the GG-test. All these were from sheep from 52 farms located in the county of Rogaland in the south west of Norway. All isolates from cattle and goats were defined as benign by the GG-test. IntA was only detected in 6 (2.0%) of the virulent isolates. All serogroups except D and F were detected. Three hundred and seventy-two (64.3%) of the isolates belonged to serogroup A, and 96% of the virulent isolates belonged to this serogroup. On the grounds that virulent isolates were only found in one county, and that the majority belonged to the same serogroup (A), it is believed that a virulent D. nodosus strain was introduced to Norway relatively recently and that so far it has only spread locally.
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Affiliation(s)
- Marianne Gilhuus
- Norwegian Veterinary Institute, P.O. Box 750 Sentrum, N-0106 Oslo, Norway
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25
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The interaction of host genetics and disease processes in chronic livestock disease: a simulation model of ovine footrot. Prev Vet Med 2012. [PMID: 23194893 DOI: 10.1016/j.prevetmed.2012.11.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A stochastic, individual-based, simulation model of footrot in a flock of 200 ewes was developed that included flock demography, disease processes, host genetic variation for traits influencing infection and disease processes, and bacterial contamination of the environment. Sensitivity analyses were performed using ANOVA to examine the contribution of unknown parameters to outcome variation. The infection rate and bacterial death rate were the most significant factors determining the observed prevalence of footrot, as well as the heritability of resistance. The dominance of infection parameters in determining outcomes implies that observational data cannot be used to accurately estimate the strength of genetic control of underlying traits describing the infection process, i.e. resistance. Further work will allow us to address the potential for genetic selection to control ovine footrot.
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26
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Bhat M, Wani S, Hussain I, Magray S, Muzafar M. Identification of two new serotypes within serogroup B of Dichelobacter nodosus. Anaerobe 2012; 18:91-5. [DOI: 10.1016/j.anaerobe.2011.12.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2011] [Revised: 11/16/2011] [Accepted: 12/12/2011] [Indexed: 10/14/2022]
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27
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Kennan RM, Han X, Porter CJ, Rood JI. The pathogenesis of ovine footrot. Vet Microbiol 2011; 153:59-66. [PMID: 21596496 DOI: 10.1016/j.vetmic.2011.04.005] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Revised: 04/04/2011] [Accepted: 04/06/2011] [Indexed: 12/01/2022]
Abstract
Ovine footrot is a contagious and debilitating disease that is of major economic significance to the sheep meat and wool industries. The causative bacterium is the gram negative anaerobe Dichelobacter nodosus. Research that has used a classical molecular genetics approach has led to major advances in our understanding of the role of the key virulence factors of D. nodosus in the disease process. D. nodosus strains produce polar type IV fimbriae and extracellular serine proteases. Mutagenesis of the fimbrial subunit gene fimA and the pilT gene, which is required for fimbrial retraction, and subsequent testing of these mutants in sheep virulence trials has shown that type IV fimbriae-mediated twitching motility is essential for virulence. The extracellular protease genes aprV2, aprV5 and bprV have also been mutated. Analysis of these mutants has shown that ArpV5 is the major extracellular protease and that AprV2 is the thermostable protease that is responsible for the extracellular elastase activity. Structural analysis of AprV2 has revealed that it contains several novel loops, one of which appears to act as an exosite that may modulate substrate accessibility. Finally, virulence experiments in sheep have shown that the AprV2 protease is required for virulence.
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Affiliation(s)
- Ruth M Kennan
- ARC Centre of Excellence in Structural and Functional Microbial Genomics, Department of Microbiology, Monash University, Clayton, Victoria 3800, Australia
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28
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Rather M, Wani S, Hussain I, Bhat M, Kabli Z, Magray S. Determination of prevalence and economic impact of ovine footrot in central Kashmir India with isolation and molecular characterization of Dichelobacter nodosus. Anaerobe 2011; 17:73-7. [DOI: 10.1016/j.anaerobe.2011.02.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Revised: 01/26/2011] [Accepted: 02/12/2011] [Indexed: 11/29/2022]
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29
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Winter AC. Treatment and control of hoof disorders in sheep and goats. Vet Clin North Am Food Anim Pract 2010; 27:187-192. [PMID: 21215902 DOI: 10.1016/j.cvfa.2010.10.018] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Lame sheep experience pain and should be treated as soon as reasonably practical. Treatment and control should be based on a firm diagnosis, and farmers should be encouraged to seek veterinary attention for animals that do not respond quickly to administered treatment. Overall flock lameness should be minimized through implementing appropriate control measures for the common types of foot lameness caused by infectious agents, including vaccination, antibiotic treatment, footbathing, biosecurity, and culling.
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Affiliation(s)
- Agnes C Winter
- 2Fossbridge House, Walmgate York, North Yorkshire, YO1 9SY, UK; School of Veterinary Science, University of Liverpool, UK.
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30
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Ovine footrot: new approaches to an old disease. Vet Microbiol 2010; 148:1-7. [PMID: 20926208 DOI: 10.1016/j.vetmic.2010.09.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2010] [Revised: 09/02/2010] [Accepted: 09/02/2010] [Indexed: 11/20/2022]
Abstract
Footrot is a bacterial disease that has substantial economic and welfare impacts in sheep and can be difficult to manage. Research is focussed on reducing the impact that footrot has on farmers and their flocks and better understanding the aetiology of the disease. Key areas of current research include, developing better vaccines, deploying tailored vaccines in a specific and targeted fashion on individual farms, analysing and developing better farm management practices to suit specific sheep farming environments, elucidating the virulence genes and bacterial population dynamics that drive footrot and using genetic testing in combination with selective breeding to produce stock that are more resilient to disease.
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31
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Zhou H, Lottner S, Ganter M, Hickford JG. Identification of two new Dichelobacter nodosus strains in Germany. Vet J 2010; 184:115-7. [DOI: 10.1016/j.tvjl.2009.02.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2008] [Revised: 02/01/2009] [Accepted: 02/02/2009] [Indexed: 11/25/2022]
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32
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Hill AE, Dhungyel OP, Whittington RJ. Diagnostic sampling strategies for virulent ovine footrot: simulating detection of Dichelobacter nodosus serogroups for bivalent vaccine formulation. Prev Vet Med 2010; 95:127-36. [PMID: 20303191 DOI: 10.1016/j.prevetmed.2010.02.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2008] [Revised: 12/30/2009] [Accepted: 02/22/2010] [Indexed: 11/16/2022]
Abstract
Dichelobacter nodosus is a slow-growing anaerobic bacterium that is the causative agent of virulent ovine footrot. Vaccination targeted at up to two specific serogroups can eliminate those serogroups from infected flocks, but requires identification of serogroups present in infected flocks. Serogroups can be identified using slide agglutination or polymerase chain reaction (PCR) methods. The objectives of this project were to use stochastic simulation modeling to estimate the efficacy of sampling strategies encompassing 5-40 sheep per flock and 2-4 colonies per sheep, and to compare efficacies based on slide agglutination or multiplex PCR test results. Foot swabs collected from sheep in 12 flocks were used as the basis for a sampling strategy simulation model. None of the evaluated sampling strategies identified the two most common serogroups in the flock, or all serogroups present in the flock, in 95% of iterations. However, a simulated sample of 22 sheep/flock and 2 colonies/sheep resulted in a simulated vaccine that protected 95% of the sheep that could be protected by a single bivalent vaccine, while a sample of 24 sheep/flock and 2 colonies/sheep resulted in a series of simulated bivalent vaccines that protected 95% of diseased infected sheep. The difference in outcome was due to the distribution and frequency of serogroups within certain flocks where some serogroups were uncommon and others dominant. A sampling strategy (>40 sheep/flock, 4 colonies/sheep) that will identify the two most common serogroups in a flock 95% of the time may not be cost effective. Evaluating efficacy based on the expected effect on the flock may be more useful than one which seeks to determine the most common serogroups. These findings are broadly applicable to diseases where more than one strain or type of pathogen may be present and must be represented in a vaccine.
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Affiliation(s)
- Ashley E Hill
- Animal Population Health Institute, Campus Delivery 1644, Colorado State University, Fort Collins, CO 80523-1644, USA.
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Dhungyel OP, Whittington RJ. Modulation of inter-vaccination interval to avoid antigenic competition in multivalent footrot (Dichelobacter nodosus) vaccines in sheep. Vaccine 2009; 28:470-3. [PMID: 19853681 DOI: 10.1016/j.vaccine.2009.10.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2009] [Revised: 09/30/2009] [Accepted: 10/05/2009] [Indexed: 10/20/2022]
Abstract
Virulent footrot is a significant disease of sheep in most sheep farming countries; a strain/serogroup of the anaerobic bacterium Dichelobacter nodosus is the essential transmitting agent. Commercial multivalent footrot vaccines containing nine fimbrial serogroups (A through I) of D. nodosus produce relatively low and short term antibody responses due to antigenic competition, in contrast to higher and longer responses provided by monovalent or bivalent vaccines. The latter were important components of successful eradication programs for endemic footrot caused by either one or two serogroups of D. nodosus in Nepal, Bhutan, and several flocks in Australia. However, the presence of up to six serogroups in some Australian flocks and the use of an annual bivalent vaccination regime to progressively eradicate serogroups would require a long term program. In this study we report the results of a sequential vaccination trial testing different time intervals between different bivalent vaccinations. Intervals of 12, 9, 6, 3 and 0 months were tested. The 1st vaccination was with recombinant fimbrial antigens for serogroups A and B while the 2nd vaccination was with D and E. There were no significant differences between the antibody responses for time intervals of 3, 6, 9 and 12 months whereas there was a reduced response when sheep were vaccinated with two bivalent vaccines (four antigens) concurrently, indicating antigenic competition. Therefore an inter-vaccination interval of 3 months can be applied between two different bivalent vaccines without detrimental impact on the humoral immune responses to the various fimbrial antigens of D. nodosus. These results could have wider applications in vaccination against diseases caused by multivalent or multistrain microbes.
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Affiliation(s)
- Om P Dhungyel
- Faculty of Veterinary Science, The University of Sydney, Camden NSW 2570, Australia.
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34
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Hussain I, Wani S, Qureshi S, Farooq S. Serological diversity and virulence determination of Dichelobacter nodosus from footrot in India. Mol Cell Probes 2009; 23:112-4. [DOI: 10.1016/j.mcp.2009.01.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Revised: 12/18/2008] [Accepted: 01/07/2009] [Indexed: 11/29/2022]
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35
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Bennett G, Hickford J, Sedcole R, Zhou H. Dichelobacter nodosus, Fusobacterium necrophorum and the epidemiology of footrot. Anaerobe 2009; 15:173-6. [PMID: 19239925 DOI: 10.1016/j.anaerobe.2009.02.002] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Revised: 02/03/2009] [Accepted: 02/12/2009] [Indexed: 11/26/2022]
Abstract
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.
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Affiliation(s)
- Grant Bennett
- Agriculture and Life Sciences Division, P.O. Box 84, Lincoln University, Lincoln 7647, New Zealand.
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36
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Dhungyel O, Lehmann D, Whittington R. Pilot trials in Australia on eradication of footrot by flock specific vaccination. Vet Microbiol 2008; 132:364-71. [DOI: 10.1016/j.vetmic.2008.05.027] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2008] [Revised: 05/23/2008] [Accepted: 05/26/2008] [Indexed: 10/22/2022]
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37
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Gurung RB, Dhungyel OP, Tshering P, Egerton JR. The use of an autogenous Dichelobacter nodosus vaccine to eliminate clinical signs of virulent footrot in a sheep flock in Bhutan. Vet J 2006; 172:356-63. [PMID: 16019243 DOI: 10.1016/j.tvjl.2005.04.032] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
An outbreak of virulent footrot was investigated in a flock of 605 Merino cross-bred sheep in Bhutan. Conventional control methods in the preceding eight years had reduced its prevalence from 36-79% in different components of the flock to about 15% overall. Only one serogroup (B) of Dichelobacter nodosus was identified among 40 isolates cultured from affected sheep. A vaccine prepared from this strain was used in a pilot trial to compare the response of 14 treated and 14 untreated sheep. All affected, vaccinated animals in this trial healed quickly and were protected against re-infection while additional cases developed among untreated sheep during a period favourable for the spread of footrot. The serogroup B vaccine was administered to the whole flock for two successive years. No other footrot treatment was given during these or subsequent years. The whole flock was examined three times, foot by foot, for two years and twice yearly for another two years. When vaccination began there were 88 affected sheep in the flock, an affected sheep being defined as an animal with a foot-score of 2 or greater in one or more feet. There were neither affected sheep in the flock 30 days after the first dose of vaccine nor were any identified in later inspections. Virulent footrot, originating from the farm under investigation, persisted in neighbouring village flocks during this period. It was concluded that whole flock specific D. nodosus vaccination made a major contribution to the elimination of all clinical signs of footrot from the flock of 605 sheep where the condition had previously persisted for 10 years.
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Affiliation(s)
- R B Gurung
- Regional Veterinary Laboratory, Bumthang, Bhutan
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