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2018 EHV-1 Outbreaks in the United States: Regulatory Perspective

Explore the regulatory perspective of the 2018 EHV-1 outbreaks in the United States, including virus strains, transmission modes, clinical manifestations, vaccination, and economic impact.

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2018 EHV-1 Outbreaks in the United States: Regulatory Perspective

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  1. 2018 EHV-1 Outbreaks in the United States: Regulatory Perspective United States Animal Health Association Meeting Committee on Equine October 2018 Dr. Katie Flynn Dr. Peter Timoney CA Dept of Food and Agriculture Gluck Equine Research Center

  2. Equine Herpesvirus-1 • Virus Strains • A2254 genotype, wild strain, non-neuropathogenic • G2254 genotype, mutant strain, neuropathogenic • Transmission: • Direct or indirect • Respiratory Transmission • High viral loads • Horse to horse contact • Contaminated hands • Equipment, tack, and feed • Incubation 2 -10 days • Ubiquitous in the environment • Carrier state occurs in 40-60% of adult horses • Short lived immunity post infection

  3. EHV-1 Clinical Manifestations • Respiratory disease • Contagious abortion • Myeloencephalopathy • Viral pneumonitis in foals • Infrequent cause of uveitis and chorioretinal lesions in foals • Rare fatal non-neurologic pulmonary vasculotropic syndrome

  4. Respiratory Disease • Characterized by rhinopharyngitis and a tracheobronchitis • Reinfections are not common in older horses • Secondary bacterial infections are common • Severity of illness depends on age and pre-existing immunity

  5. Myeloencephalopathy • Increasing frequency over past 15-20 years • Sequel to primary respiratory infection, abortion or fever • Clinical signs depends on location and severity of CNS lesions • Leads to neuronal degeneration, axonal swelling and foci of malacia

  6. Epidemiology • Factors involved in causation of EHV-1 related disease: • Virus strain • Modes of transmission • Immunity • Carrier State • Pregnancy status • Management practices • Vaccination

  7. Vaccination • Not fully protective against disease • Reduces risk of outbreaks of EHV-1 respiratory disease and abortion but does not protect against EHM • Does not prevent establishment or reactivation of latency • Reduces severity of clinical signs, duration of viral shedding and viral load shed • Most effective with herd vaccination

  8. Economic Impact • Horse mortalities • Treatment • Quarantine • Canceled events • Inability of horses to compete and perform in events • Cost of vaccination

  9. EHV-1 as a Regulatory Disease

  10. Re-Emerging Disease • From 1970 – 2000 • 19 outbreaks in U.S. • From 2007-2011 • 43 outbreaks in U.S. • Since January 1, 2018: • 52 outbreaks in 19 states (as of 10/4/18) • Improved recognition, diagnostics

  11. Reportable Disease • During the 2011 Ogden multistate outbreak, EHM was reportable in 36 states • Currently, EHM is reportable in 49 states and respiratory EHV-1 cases are reportable in 26 states • Based on 2016 survey of SAHO’s

  12. EHV-1 Workshop Highlights Need for Consensus • In 2013, AAEP and USAHA Committee on Infectious Disease of Horses sponsored an EHV-1 workshop • Developed consensus on: • Case and outbreak definitions • Quarantine parameters • Diagnostic testing • Biosecurity practices • USAHA subcommittee on EHV-1 established • Publication of EHM Incident Guidelines for State Animal Health Officials Published in 2015 and revised in 2018

  13. Incident Response • No one size fits all plan • General response protocols are intended to • Evaluate current disease situation onsite • Determine site specific risk factors • Determine equine population risk factors • Determine feasible workable onsite response • Determine level of state oversight

  14. Goals for State Animal Health Officials (SAHO’s) • During EHM incidents, goals for SAHO’s include: • Prevent spread of the disease agent • Use science-based disease control protocols • Ensure compliance of quarantine • Minimize impact on equine movement • Ensure business continuity

  15. 2018 EHV-1 Incidents in the United States Based on State Survey Responses

  16. EHV-1 Incident Data Sources

  17. EHV-1 Incidents • Date Range for Data Collection • October 2017 to August 2018 • Criteria: • One confirmed EHV-1 clinical case • SAHO involvement with case • 17 states submitted data • 49 EHV-1 incidents • 11 states had multiple incidents • 43 incidents had at least one EHM case • 6 febrile/ respiratory cases only

  18. Confirmed Case Definitions • EHV-1 Case: • Laboratory detection of EHV-1 virus in a horse displaying fever or respiratory signs • EHM Case • Laboratory detection of EHV-1 virus in a horse displaying neurologic signs • Definitions in accordance with USAHA 2018 EHM Incident Guidance Document

  19. SAHO’s Quarantines • Official quarantines issued for 44/49 incidents* • 31/44 (70%) entire premises quarantine • 11/44 (25%) partial premises quarantine • Quarantine duration* • Average length = 30.3 days • Shortest quarantine = 14 days • Longest quarantine = 92 days * Quarantine information not provided for 2 incidents

  20. Equines Involved in the Incidents • 1188 exposed horses • Positive Case: Gender demographics • EHV-1 respiratory/febrile cases • 29/74 (39%) mares • 44/74 (60%) geldings • 1/74 (1%) stallion • EHM cases • 54/80 (68%) mares • 25/80 (31%) geldings • 1/80 (1%) stallion

  21. Confirmed EHV-1Virus Detection in Clinical Cases • 154 Confirmed Cases • 74 EHV-1 febrile/respiratory cases • 80 confirmed EHM cases • 28 Confirmed EHM Cases were euthanized or died • 28/154 (18%) of total number of confirmed cases, • 28/80 (35%) of all EHM cases

  22. Facilities Affected • Boarding facilities • Private barns • Event grounds • Racing facilities • Rescue/sanctuary • Veterinary clinics

  23. EHV-1 Strain • Incidents: 49 total • 38/49 incidents (78%) involved non-neuropathogenic/ A Strain • 10/49 (20%) involved mutant neuropathogenic/ G Strain • One incident didn’t report strain type • Cases: 154 total • 89/154 (58%) involved non-neuropathogenic/ A Strain • 63/154 (41%) involved mutant neuropathogenic/ G Strain

  24. Cases by Strain Type

  25. EHV-1 Strain • EHV-1 Febrile/Respiratory Cases • 49/74 cases (66%) involved non-neuropathogenic/ A Strain • 24/74 cases (32%) involved mutant neuropathogenic/ G Strain • EHM Cases • 40/80 cases (50%) involved non-neuropathogenic/ A Strain • 39/80 cases (49%) involved mutant neuropathogenic/ G Strain

  26. EHV-1 Strain • Euthanized horses • 13/89 (15%) non-neuropathogenic/ A Strain • 14/63 (22%) mutant neuropathogenic/ G Strain • Strain was not reported for one of the euthanized horses

  27. EHV-1 Incidents by Month Seasonality?

  28. Case Gender Demographics for Confirmed Cases

  29. Observations • Strain types: • Wild Type/Non-neuropathogenic has been the more prevalent strain identified • Slightly higher fatality percentage with mutant/neuropathogenic type • More febrile/respiratory cases identified with the wild type/non-neuropathogernic strain • EHV-1 incidents can occur anytime but peaks in winter and spring • EHM is more common in mares

  30. Lessons Learned • Lack of funding and experience to respond to equine incidents • Unique challenges and issues at every incident • Laboratory Challenges • Delay or lack of reporting of diagnostic test results • Private vs Regulatory laboratory results • Some laboratories do not provide strain or viral load

  31. Lessons Learned, Cont. • Incident Related Challenges • Obtaining accurate inventories onsite • Compliance with biosecurity measures • Twice daily temperature monitoring logs • Falsification of logs • Use of NSAIDs and Cut off Temperatures for sampling • Inconsistent compliance (good one day bad two days later) • Need for onsite monitoring of compliance • Critical need for early identification and isolation of horses shedding virus

  32. Lessons Learned, cont. • Testing Challenges • Initial test negative then test positive on subsequent testing • Screening of non-clinical horses • How to handle high CT values/ low viral loads • Compliance with recommended testing parameters • Financial costs of testing • Limited isolation stabling • Preplanning is essential • Veterinary hospitals may not be willing to take horses • Ensuring business continuity • Continued exercise of exposed horses and non-exposed horses • Communication Challenges • Lack of contact information or distribution lists • Early and often communication to all parties is key

  33. Questions to Ponder • Should strain type influence SAHO’s response? • What data should SAHOs be collecting and providing to EDCC to monitor EHV-1? • Case data? • Demographics- breed, age sex • Vaccination • Anti-viral use • Exposed horse data? 3. What changes should be made to guidelines? 4. What EHV-1 research would be beneficial to SAHO’s?

  34. Acknowledgements • SAHOs in Arizona, California, Colorado, Idaho, Maryland, Maine, North Dakota, New Jersey, New York, Ohio, Oregon, Pennsylvania, South Dakota, Texas, Virginia, Washington, Wyoming • Ms. Katie Hatch, Equine Research Scientist for CA Department of Food and Agriculture

  35. Questions? Contact Information: Dr. Katie Flynn kflynn@cdfa.ca.gov 916-900-5039

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