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Houben RMAC, Newton JR, van Maanen C, Waller AS, Sloet van Oldruitenborgh-Oosterbaan MM, Heesterbeek JAP. Untangling the stranglehold through mathematical modelling of Streptococcus equi subspecies equi transmission. Prev Vet Med 2024; 228:106230. [PMID: 38772119 DOI: 10.1016/j.prevetmed.2024.106230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2023] [Revised: 05/02/2024] [Accepted: 05/14/2024] [Indexed: 05/23/2024]
Abstract
Strangles, a disease caused by infection with Streptococccus equi subspecies equi (S. equi), is endemic worldwide and one of the most frequently diagnosed infectious diseases of horses. Recent work has improved our knowledge of key parameters of transmission dynamics, but important knowledge gaps remain. Our aim was to apply mathematical modelling of S. equi transmission dynamics to prioritise future research areas, and add precision to estimates of transmission parameters thereby improving understanding of S. equi epidemiology and quantifying the control effort required. A compartmental deterministic model was constructed. Parameter values were estimated from current literature wherever possible. We assessed the sensitivity of estimates for the basic reproduction number on the population scale to varying assumptions for the unknown or uncertain parameters of: (mean) duration of carriership (1∕γC), relative infectiousness of carriers (f), proportion of infections that result in carriership (p), and (mean) duration of immunity after natural infection (1∕γR). Available incidence and (sero-)prevalence data were compared to model outputs to improve point estimates and ranges for these currently unknown or uncertain transmission-related parameters. The required vaccination coverage of an ideal vaccine to prevent major outbreaks under a range of control scenarios was estimated, and compared available data on existing vaccines. The relative infectiousness of carriers (as compared to acutely ill horses) and the duration of carriership were identified as key knowledge gaps. Deterministic compartmental simulations, combined with seroprevalence data, suggest that 0.05
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Affiliation(s)
- R M A C Houben
- Department of Clinical Sciences, faculty of Veterinary medicine, Utrecht University, the Netherlands.
| | - J R Newton
- Equine Infectious Disease Surveillance (EIDS), Department of Veterinary Medicine, Cambridge, UK
| | | | - A S Waller
- Intervacc AB, Stockholm, Sweden; Department of Biomedical Science and Veterinary Public Health, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | | | - J A P Heesterbeek
- Department of Population Health Sciences, faculty of Veterinary Medicine, Utrecht University, the Netherlands
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Zu H, Sun R, Li J, Guo X, Wang M, Guo W, Wang X. Development of a Real-Time Recombinase-Aided Amplification Method for the Rapid Detection of Streptococcus equi subsp. equi. Microorganisms 2024; 12:777. [PMID: 38674721 PMCID: PMC11052427 DOI: 10.3390/microorganisms12040777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Revised: 03/09/2024] [Accepted: 03/10/2024] [Indexed: 04/28/2024] Open
Abstract
Streptococcus equi subspecies equi (S. equi) is the causative pathogen of strangles in horses, donkeys, and other equine animals. Strangles has spread globally and causes significant losses to the horse industry. In response to the urgent need for effective disease control, this study introduces a novel nucleic acid diagnostic method known as a real-time recombinase-assisted amplification (RAA) assay, developed based on the eqbE gene, for the rapid detection of S. equi nucleic acid. The real-time RAA method employs specifically designed probes and primers targeting the eqbE gene, enhancing the overall specificity and sensitivity of the detection. After efficiency optimization, this real-time RAA method can detect 10 or more copies of nucleic acid within 20 min. The method demonstrates high specificity for S. equi and does not cross-react with other clinically relevant pathogens. Real-time RAA diagnostic performance was evaluated using 98 nasal swab samples collected from horses and compared with the real-time PCR detection method. Results revealed that 64 and 65 samples tested positive for S. equi using real-time RAA and real-time PCR, respectively. The overall agreement between the two assays was 96.94% (95/98), with a kappa value of 0.931 (p < 0.001). Further linear regression analysis indicated a significant correlation in the detection results between the two methods (R2 = 0.9012, p < 0.0001), suggesting that the real-time RAA assay exhibits a detection performance comparable to that of real-time PCR. In conclusion, the real-time RAA assay developed here serves as a highly specific and reliable diagnostic tool for the detection of S. equi in equine samples, offering a potential alternative to real-time PCR methods. In conclusion, the real-time RAA nucleic acid diagnostic method, based on the eqbE gene, offers rapid and accurate diagnosis of S. equi, with the added advantage of minimal equipment requirements, thus contributing to the efficient detection of strangles in horses.
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Affiliation(s)
- Haoyu Zu
- State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China (M.W.)
| | - Rongkuan Sun
- State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China (M.W.)
- College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China
| | - Jiaxin Li
- State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China (M.W.)
| | - Xing Guo
- State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China (M.W.)
| | - Min Wang
- State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China (M.W.)
| | - Wei Guo
- State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China (M.W.)
- Institute of Western Agriculture, The Chinese Academy of Agricultural Sciences, Changji 831100, China
| | - Xiaojun Wang
- State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China (M.W.)
- Institute of Western Agriculture, The Chinese Academy of Agricultural Sciences, Changji 831100, China
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3
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Boyle AG. Streptococcus equi Subspecies equi. Vet Clin North Am Equine Pract 2023; 39:115-131. [PMID: 36737294 DOI: 10.1016/j.cveq.2022.11.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Strangles, caused by the bacteria Streptococcus equi subsp equi, is a highly contagious disease of equids classically characterized by a high fever and enlarged lymph nodes of the head. Diagnostic sampling depends on the stage of the disease. The goal of treating strangles is to control transmission and to eliminate infection while providing future host immunity. Daily temperature checking and isolation of febrile horses is the key to controlling outbreaks. Eradication of this disease will not be possible until S equi carriers are eliminated from the equine population.
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Affiliation(s)
- Ashley G Boyle
- Department of Clinical Studies, New Bolton Center, University of Pennsylvania, School of Veterinary Medicine, 382 West Street Road, Kennett Square, PA 19348, USA.
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Pringle J, Aspán A, Riihimäki M. Repeated nasopharyngeal lavage predicts freedom from silent carriage of Streptococcus equi after a strangles outbreak. J Vet Intern Med 2022; 36:787-791. [PMID: 35072293 PMCID: PMC8965236 DOI: 10.1111/jvim.16368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Revised: 01/13/2022] [Accepted: 01/13/2022] [Indexed: 11/28/2022] Open
Abstract
Background The value of repeated nasopharyngeal lavage (NPL) to detect silent carriers of Streptococcus equi has not been investigated. Hypothesis/Objectives Determine if results of serial testing for S. equi by NPL predicts subsequent true carrier status as determined by both NPL and guttural pouch lavage. Animals An outbreak of strangles with 100% morbidity in 41 mature Icelandic horses was followed prospectively to investigate development of silent carriers. All were initially positive to S. equi on NPL. The farm was closed to horse movement during the entire study. Methods Prospective observational study. Testing for S. equi was performed by NPL at weeks 18, 28, 29, and 30 postindex case and subsequently at week 45 by both NPL and guttural pouch lavage. Carrier status at week 45 was compared to results obtained at weeks 18, 28, 29, and 30. Descriptive statistics were calculated. Comparisons were made using Fisher's exact test or the Freeman‐Halton extension with a P < .05 level of significance. Results Of 24 noncarriers at week 45, only 4 horses were negative on all 3 consecutive weekly NPL samples at weeks 28 to 30. However, 10 of the 11 horses with at least 3 negative NPL obtained from weeks 18, 28, 29, and 30 were S. equi‐free at week 45 (P = .03). Conclusions and Clinical Importance Repeated NPL on at least 3 separate occasions can assist in predicting S. equi carrier‐free status in horses after recovery from a strangles outbreak.
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Affiliation(s)
- John Pringle
- Department of Clinical Sciences, Faculty of Veterinary Medicine and Animal Science, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Anna Aspán
- The National Veterinary Institute, Uppsala, Sweden
| | - Miia Riihimäki
- Department of Clinical Sciences, Faculty of Veterinary Medicine and Animal Science, Swedish University of Agricultural Sciences, Uppsala, Sweden
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McGlennon A, Waller A, Verheyen K, Slater J, Grewar J, Aanensen D, Newton R. Surveillance of strangles in UK horses between 2015 and 2019 based on laboratory detection of Streptococcus equi. Vet Rec 2021; 189:e948. [PMID: 34570896 DOI: 10.1002/vetr.948] [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: 02/23/2021] [Revised: 07/21/2021] [Accepted: 09/09/2021] [Indexed: 11/08/2022]
Abstract
BACKGROUND Previously national surveillance data for monitoring strangles (Streptococcus equi infection) in UK horses was limited. Improved awareness and knowledge of positive diagnoses would permit the optimisation of biosecurity protocols, decreasing the prevalence of strangles. METHODS Seven UK laboratories reported positive strangles diagnoses between 1 January 2015 and 31 December 2019 based on identifying Streptococcus equi via agent detection assays from field-based practitioner-submitted samples. Associated clinical history and animal signalment were collected where provided, and descriptive analysis undertaken. RESULTS Within the study period, 1617 laboratory-confirmed diagnoses occurred from samples submitted by 315 veterinary practices. Of these, 51.6% were swabs and 44.0% guttural pouch lavages. Diagnoses were primarily based on qPCR alone (59.6%), qPCR and culture (35.8%), or culture alone (4.6%). A total of 1791 clinical signs were reported for 713 diagnoses, where nasal discharge (31.3%) and pyrexia (20.5%) were most frequently reported. Regions with the highest number of diagnoses included North Yorkshire (n = 75, 4.6%), Staffordshire (n = 71, 4.4%) and West Sussex (North East) (n = 63, 3.9%). CONCLUSION This study presents important insights into the diagnosis and clinical features of strangles in UK horses, even though limited and/or missing clinical history and signalment on laboratory submission forms restricts the completeness of the data.
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Affiliation(s)
- Abigail McGlennon
- Department of Pathobiology and Population Sciences, Royal Veterinary College, Hatfield, UK.,Centre for Preventive Medicine, Animal Health Trust, Newmarket, UK
| | - Andrew Waller
- Centre for Preventive Medicine, Animal Health Trust, Newmarket, UK.,Intervacc, Hägersten, Stockholm, Sweden
| | - Kristien Verheyen
- Department of Pathobiology and Population Sciences, Royal Veterinary College, Hatfield, UK
| | - Josh Slater
- University of Melbourne Veterinary School, Werribee, Victoria, Australia
| | | | - David Aanensen
- Wellcome Trust Sanger Institute, Hinxton, Saffron Walden, England
| | - Richard Newton
- Centre for Preventive Medicine, Animal Health Trust, Newmarket, UK.,British Horseracing Authority, London, UK
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Differences in the genome, methylome, and transcriptome do not differentiate isolates of Streptococcus equi subsp. equi from horses with acute clinical signs from isolates of inapparent carriers. PLoS One 2021; 16:e0252804. [PMID: 34125848 PMCID: PMC8202921 DOI: 10.1371/journal.pone.0252804] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 05/21/2021] [Indexed: 12/13/2022] Open
Abstract
Streptococcus equi subsp. equi (SEE) is a host-restricted bacterium that causes the common infectious upper respiratory disease known as strangles in horses. Perpetuation of SEE infection appears attributable to inapparent carrier horses because it neither persists long-term in the environment nor infects other host mammals or vectors, and infection results in short-lived immunity. Whether pathogen factors enable SEE to remain in horses without causing clinical signs remains poorly understood. Thus, our objective was to use next-generation sequencing technologies to characterize the genome, methylome, and transcriptome of isolates of SEE from horses with acute clinical strangles and inapparent carrier horses—including isolates recovered from individual horses sampled repeatedly—to assess pathogen-associated changes that might reflect specific adaptions of SEE to the host that contribute to inapparent carriage. The accessory genome elements and methylome of SEE isolates from Sweden and Pennsylvania revealed no significant or consistent differences between acute clinical and inapparent carrier isolates of SEE. RNA sequencing of SEE isolates from Pennsylvania demonstrated no genes that were differentially expressed between acute clinical and inapparent carrier isolates of SEE. The absence of specific, consistent changes in the accessory genomes, methylomes, and transcriptomes of acute clinical and inapparent carrier isolates of SEE indicates that adaptations of SEE to the host are unlikely to explain the carrier state of SEE. Efforts to understand the carrier state of SEE should instead focus on host factors.
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Boyle AG, Mitchell C, Stefanovski D, Waller AS. Horses vaccinated with live attenuated intranasal strangles vaccine seroconvert to SEQ2190 and SeM. Equine Vet J 2021; 54:299-305. [PMID: 33630353 DOI: 10.1111/evj.13443] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2020] [Revised: 02/07/2021] [Accepted: 02/11/2021] [Indexed: 01/16/2023]
Abstract
BACKGROUND The dual antigen iELISA uses two Streptococcus equi subsp equi surface protein antigens composed of N-terminal portions of SEQ2190 (Antigen A) and SeM (Antigen C). It is currently used to identify animals exposed to S. equi which have developed an immune response to the target antigens. OBJECTIVES To determine the usefulness of the dual antigen iELISA in a population of horses vaccinated with Pinnacle IN. We hypothesised that horses vaccinated for strangles with a live attenuated, non-encapsulated SeM-2 strain of S. equi, would seroconvert when tested 5 weeks later by the dual antigen iELISA. STUDY DESIGN Prospective case-control study. METHODS Three separate serum samples were obtained from 26 client-owned horses vaccinated annually with Pinnacle® IN and 26 university-owned (non-vaccinates): at annual strangles vaccination (S1), 5-week post-vaccination (S2) from vaccinates, and a third (S3) (at 10 weeks) from vaccinates who received a booster. Seropositivity was defined as an OD450 nm value ≥0.5 for one or both antigens. Mixed-effects ordered logistic regression analysis was used to identify factors associated with a suspect seropositive and seropositive value on the combined Antigen A and Antigen C iELISA. Post hoc pairwise comparisons of linear predictive margins were used to assess the differences in OD450 at a specific time between Antigens A and C. RESULTS Nineteen of 25 (76%) vaccinates were seropositive at S2 compared to 1 of 26 (4%) non-vaccinates. When adjusted for sample number, vaccinates were more likely to be seropositive or suspect than non-vaccinates (OR 14; P = .02, 95% CI 1.62-122.03). The OD450 value was significantly larger for Antigen C than Antigen A for vaccinates (P < .001; 95% CI 0.13-0.26) when normalised by age, sex and breed. MAIN LIMITATIONS Guttural pouch sampling for S. equi in seroconverted horses was unavailable. CONCLUSIONS With a high rate of seroconversion to both antigens, the use of the dual antigen iELISA is not recommended in populations vaccinated with Pinnacle® IN.
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Affiliation(s)
- Ashley G Boyle
- Department of Clinical Studies New Bolton Center, University of Pennsylvania, Kennett Square, PA, USA
| | - Catriona Mitchell
- Department of Microbiology, Animal Health Trust, Kentford, Newmarket, Suffolk, UK
| | - Darko Stefanovski
- Department of Clinical Studies New Bolton Center, University of Pennsylvania, Kennett Square, PA, USA
| | - Andrew S Waller
- Department of Microbiology, Animal Health Trust, Kentford, Newmarket, Suffolk, UK.,Intervacc AB, Hägersten, Sweden
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Pringle J, Venner M, Tscheschlok L, Waller AS, Riihimäki M. Markers of long term silent carriers of Streptococcus equi ssp. equi in horses. J Vet Intern Med 2020; 34:2751-2757. [PMID: 33074578 PMCID: PMC7694814 DOI: 10.1111/jvim.15939] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 10/02/2020] [Accepted: 10/07/2020] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Difficulty in detection of silent carriers of Streptococcus equi is a key reason for its continued spread to immunologically naïve groups of horses. OBJECTIVE To determine whether clinical examination, markers of inflammation, or serology differentiate silent carriers of S. equi in recovered comingled horses. ANIMALS Ninety-eight warmblood yearlings and 72 unaffected mares on a large breeding farm (outbreak A), 38 mature Icelandic horses at a riding stable (outbreak B), and 27 mixed breed horses at a boarding stable (outbreak C). METHODS Prospective observational study 6 months to 2 years after strangles outbreaks. Carriers were defined as any animal positive on culture or qPCR to S. equi from nasopharyngeal lavage or guttural pouch endoscopy and lavage. Most horses had complete physical exams and 1 group included evaluation of white blood cell counts and serum amyloid A. Sera from all horses was tested for antibodies to antigens A and C of S. equi using an enhanced indirect ELISA. Descriptive statistics were calculated. Data were compared using paired t tests, Wilcoxon ranked test, chi square, or the Fishers exact test. Significance was set at P < .05. RESULTS Apart from weanlings at 6 months in outbreak A, there was no significant association between any clinical markers or serology with carrier state (P = .06-1). Moreover, 3/12 culture positive carriers were seronegative to S. equi. CONCLUSIONS AND CLINICAL IMPORTANCE Silent carriers of S. equi do not differ clinically or on markers of inflammation to their noncarrier herd-mates. Moreover, serology alone will not distinguish carriers in comingled horses.
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Affiliation(s)
- John Pringle
- Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | | | | | | | - Miia Riihimäki
- Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden
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Wright S. Highlights of recent clinically relevant papers. EQUINE VET EDUC 2020. [DOI: 10.1111/eve.13359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Ivens PAS, Pirie S. Streptococcus equi subspecies equi diagnosis. Equine Vet J 2020; 53:15-17. [PMID: 32772398 DOI: 10.1111/evj.13319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 07/02/2020] [Indexed: 11/30/2022]
Affiliation(s)
- Philip A S Ivens
- Buckingham Equine Vets Ltd, Sparrow Lodge Farm, Wicken, Buckingham, UK
| | - Scott Pirie
- University of Edinburgh, Royal (Dick) School of Veterinary Studies, Veterinary Clinical Sciences, Easter Bush Campus, Easter Bush, Roslin, Midlothian, UK
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