u.s bluetongue surveillance strategy: pilot study update
TRANSCRIPT
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U.S BLUETONGUE SURVEILLANCE STRATEGY: PILOT STUDY UPDATE
D R . D AV I D H S IV E T E R I N A R Y E P I D E M I O LO G I S TU. S . D E PA R T M E N T O F A G R I C U LT U R EA N I M A L A N D P L A N T H E A LT H I N S P E C T I O N S E R V I C EV E T E R I N A R Y S E R V I C E SO C TO B E R 1 8 , 2 0 1 7
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Background
▪ USAHA combined resolutions 6 and 11 (2014) and 3 and 7 (2015)
▪ No large-scale BTV surveillance since 2002
▪ Recommendations from the 2013 USDA ARS OrbivirusesGap Analysis Workshop
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Multi-tiered BTV surveillance strategy:
• Tier 1: Serologic surveillance of cattle slaughter brucellosis samples
• Tier 2: Aggregation of testing data from bovine semen collection centers
• Tier 3: Sentinel and vector surveillance
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Proposed Strategy
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• Identify low prevalence or free areas of BTV, per OIE guidance for trade support
• Based upon BTV prevalence and distribution; assess current ecology and weather patterns
• Begin to establish a BTV serotype distribution map to monitor future changes
• Help develop national BTV surveillance strategy
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Objectives
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Serologic Surveillance Methodology
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▪Provide baseline information
▫ State or region seroprevalence
▪ If State or region seroprevalence<2.0%
▫ Low prevalence or free
▪Traceback of positive samples
▫ Origin of cattle
▪ Limitations
▫ Infection timing, serotypes, geography
▪Utilizes routinely collected samples (majority for brucellosis)
▫ CIS approach
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Serologic Surveillance Methodology
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▪ n= 600 sera per each low incidence/ free State or region for a total of ~6600 samples
▫ ME, MA, CT, RI, VT, and NH (New England)
▫ DE/MD (one region)
▫ NJ/PA (one region)
▫ NY, WV, OH, MI, IN, WI, MN, and ND
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Serologic Surveillance Methodology
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Testing Protocol
KY Federal LaboratoryVMRD cELISA
Positives
NVSL sero-repeatibility
VMRD cELISAVDT cELISA
+/- AGID
Traceback investigation
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• Initial discrepancies in sample results found with repeatability testing
• KY Federal Brucellosis lab and NVSL worked extensively to troubleshoot sample selection and testing protocol
• Delayed testing several months and necessitated restarting serologic surveillance
• No performance issues identified with the VMRD test kit
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Diagnostic Testing Challenges
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▪ Testing variables investigated:
✓ Sample quality and collection method
✓ Sample temperature
✓ Software used to run plates
✓ Wavelength filters
✓ Wash solution
✓ Plate washing method
✓ Plate washer calibration
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Testing Troubleshooting
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• All (6,626) samples collected
• Initial testing completed
• Finalizing trace-backs
• Results from tier 1 anticipated at the beginning of 2018
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Current Status Update
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Questions?
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Dr. David Hsi Veterinary EpidemiologistU.S. Department of AgricultureAnimal and Plant Health Inspection ServiceVeterinary [email protected]