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Laboratory Procedures: West Nile Virus Testing - Overview and Challenges

This document provides an overview of laboratory testing procedures for West Nile Virus (WNV) including HI test principles, viral antigen testing, and challenges faced by laboratories. It covers test procedures, statistics, challenges, and future considerations for WNV testing in a laboratory setting.

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Laboratory Procedures: West Nile Virus Testing - Overview and Challenges

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  1. West Nile Virus 2002Laboratory PerspectivesLaboratories Branch MOHLTC Pauline George

  2. Overview Test procedures WNV Statistics Laboratory Challenges

  3. Principle of HI Test Viral Antigen + Goose RBCs = Agglutination Serum (Abs) + VAg + GRBCs = No Agglut/Reactive Serum ( no Abs) + VAg + GRBCs = Agglut/Nonreactive

  4. Test Procedures-Single Serum HI Test Process • Day 1 Extraction • Day 2 Absorption • Day 2 Test Screen/Titrate • Day 3 Add RBCs • Day 3 Read

  5. Confirmatory TestWinnipeg Federal Lab • 2 week TAT • Plaque Reduction Neutralization test Testing on paired serum against likely viruses Presence/absence neutralizing antibody • PCR Tissue/CSF

  6. WNV Tests 1999-2002

  7. WNV Tests May - Oct1999-2002

  8. Confirmed West Nile Human Cases - Ontario (to Nov 4, 2002)

  9. Probable* West Nile Human Cases - Ontario (to Nov 4, 2002)

  10. WVN CasesSummary (to Nov 4, 2002) • Confirmed * (PRNT) 49 • Did not confirm *(PRNT) 9 • Probable * (HI) 89 • Suspect ^ 176 * seroconversion ^ seropositive

  11. Laboratory Challenges 2002 • Substantially increased test volumes • Staffing resources • Reagent Availability • Equipment • Antigenic Variation • Increased incoming/outgoing telephone calls • Other routine tests • Training • TDG • Space Allocation

  12. Future Challenges 2002 and Beyond • Funding • Staffing • In-house tests vs Commercial Tests Availability? • Case criteria • Data Analysis • Training • Confirmatory Test Availability • Antigen consistency • Antigen source/cost?

  13. Future Challenges2002 and Beyond cont’d • For confirmatory testing in Ontario • Requires Level 3 Biosafety lab • PRNT confirmatory assay • PCR • Culture

  14. Acknowledgements OPHL Arboviruses & Rickettsiae Laboratory Staff Dr. M. Fearon, I Guglielmi, E Cheung, Canadian Science Centre for Human & Animal Health , Winnipeg Viral Zoonotic Staff Dr. M. Drebot

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