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Practical Approaches t o Managing Strangles

Practical Approaches t o Managing Strangles. Nicola Jarvis BVetMed , CertAVP (EM), CertAVP (ESST), MRCVS. Streptococcus equi. 600 UK outbreaks/year First recorded 1251 Reportable in USA (2017) 80% horse owners would be likely or very likely to use a yard with screening policy

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Practical Approaches t o Managing Strangles

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  1. Practical Approaches to Managing Strangles Nicola Jarvis BVetMed, CertAVP(EM), CertAVP(ESST), MRCVS

  2. Streptococcus equi • 600 UK outbreaks/year • First recorded 1251 • Reportable in USA (2017) • 80% horse owners would be likely or very likely to use a yard with screening policy • 13% of yards have any kind of screening for infectious disease (Redwings 2017) • > 240 strains – now identifiable – genome sequencing

  3. Clinical signs • Incubation period 3-21 days • Acute onset pyrexia – 42C (107.6F) • Depression • Pharyngitis • Anorexia/dysphagia • Lymphadenopathy/rupture • Parotid/retrobulbarl.n. • Dyspnoea • Purulent nasal discharge

  4. Complications • Younger horses • Immune comprimised • URT obstruction • Laryngeal hemiplegia • ‘Bastard’ strangles • Pneumonia • Purpurahaemorrhagica • Death • Carrier status

  5. Pathogenesis • Enters via nasal/oral route • Lingual, palatine, pharyngeal tonsils • Translocates to mandibular and retropharyngeal l.n. within hours • Hyaluronic acid capsule and mulitple anti-phagocytic factors (SeM protein) • Abscess formation

  6. Pathogenesis • Nasal shedding 2-3 days after onset of pyrexia • Shed bacteria 2-3 weeks • May shed for up to 6 weeks • 75% long term immunity • 20-25% poor residual immunity • 10% carrier status • Atypical strangles

  7. Transmission • Active strangle cases • Purulent discharge, saliva • Direct transmission • Indirect transmission • Water tanks (4 to 6 weeks) • Fencing/soil (1 to 3 days) • Subclinical carriers • Effective strangles control measures require detection, segregation and treatment of carrier animals (2018 consensus)

  8. Detection – Sample Types • Lymph node needle aspirate • Nasal swab • Nasopharyngeal swab • Nasopharyngeal wash • Guttural pouch lavage

  9. Laboratory testing • Culture – 2 days – live bacteria • Polymerase Chain Reaction Assays (PCR) • Triplex qPCR UK – 1 to 2 hrs • 93.9% sensitivity • 96.6% specificity • Carrier animals – GP lavage and qPCR

  10. Serology • iELISA – Indirect Enzyme Linked Immunosorbant Assay • IgG • Combined Antigen A and C • 93.3% sensitivity • 99.3% specificity • Identify recent infection as early as 2 weeks • Identify carrier animals

  11. Quarantine • Full versus partial????? • Isolation • Field quarantine • Nose to nose contact/fomites • Clinical disease • Signage • Disinfectant – freshly made, correct concentration • Only take in what you are prepared to disinfect!

  12. Strangles: Speak Out! • BEVA endorsed • Second edition 2018 • For owners & yard managers • Free download at redwings.org.uk/strangles • Order up to 10 free hard copies on the Strangles Hub redwings.org.uk/strangles/for-vets • Practical resources and accessible information

  13. New Horses Entering Yard • Quarantine – 3 weeks (field or stable) • iELISA blood sample on arrival • Twice daily temperature checks • Repeat iELISA after two weeks • If iELISA positive OR pyrexia OR clinical signs perform endoscopic guttural pouch lavage for qPCR and visualisation • iELISA/qPCR negative - enter herd

  14. Events/Competitions • At event – avoid nose to nose contact, use own equipment, take fresh water, avoid communal grazing • Disinfect temporary stabling • Ideally Q on return • Take temperature twice daily as minimum and if pyrexia, isolate immediately

  15. Strangles Outbreak • Cease all horse movements • Whilst awaiting diagnostics…… • Red Zone: Horses with one or more signs consistent with strangles • Amber Zone: Horses that may have had direct or indirect contact with Red Zone horses and could be incubating the disease • Green Zone: Horses with no known contact with Red Zone equines

  16. Strangles Outbreak • Quarantine training essential redwings.org.uk/strangles • Temperature check twice daily • Pyrexia – move to red zone • Minimum 3 weeks after resolution of last case commence carrier screening (iELISA) • Any iELISA positive horses and ALL RED ZONE horses to have endoscopy and guttural pouch lavage • Commence treatment of carriers

  17. Communication • Encourage communication • Farriers • Feed merchants • Muck collection • PR can be positive

  18. Vaccine Technology • DIVA – differentiate infected from vaccinated animals • Equilis Strep E (MSD) – 50-70% immunity • Live attentuated vaccine • Culture/iELISA/PCR • Submucosal • 3mthly boosters

  19. Future Vaccines • Strangvac 4 • 2020 IM vaccine • 8 subunit – surface and secreted proteins • No DNA, antigen A or C • DIVA criteria met • 90% immunity? • 6 mthly boosters

  20. More information

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