1 / 44

Six Years of West Nile Virus in Tarrant County, Texas

Six Years of West Nile Virus in Tarrant County, Texas. Guy C. Dixon, Ph.D. West Nile Virus Background. West Nile Virus Background. Family: Flaviviridae Genus: Flavivirus

alaura
Download Presentation

Six Years of West Nile Virus in Tarrant County, Texas

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Six Years of West Nile Virus in Tarrant County, Texas Guy C. Dixon, Ph.D. Tarrant County Public Health North Texas Regional Laboratory

  2. West Nile Virus Background Tarrant County Public Health North Texas Regional Laboratory

  3. West Nile Virus Background • Family: Flaviviridae • Genus: Flavivirus • Over seventy identified viruses in the genus and includes the medically important arthropod borne viruses (arboviruses) such as Dengue, Yellow fever, Japanese encephalitis and St. Louis encephalitis Tarrant County Public Health North Texas Regional Laboratory

  4. West Nile Virus Background • Flaviviruses are 40 to 50 nm in diameter and have a spherical nucleocapsid surrounded by a lipid bilayer envelope • The flavivirus genome is a positive sense, single-stranded RNA genome of about 11,000 nucleotides • The envelope (E) proteins mediate host receptor binding and are thus a major factor in virus virulence Tarrant County Public Health North Texas Regional Laboratory

  5. West Nile Virus Background • WNV was first isolated from a human patient with a fever in Uganda in 1937 • WNV host range is broad and includes birds, horses and humans • Historically, WNV was found in Europe, Africa, the Middle East and Asia • In 1999, WNV emerged in North America and arrived in Texas in 2002 Tarrant County Public Health North Texas Regional Laboratory

  6. West Nile Virus Background • WNV is typically transmitted by Culex mosquitoes with wild birds serving as the viremic hosts • Humans, horses, and dogs are incidental hosts and do not develop a significant enough viremia to perpetuate transmission Tarrant County Public Health North Texas Regional Laboratory

  7. West Nile Virus Surveillance 2002 Tarrant County Public Health North Texas Regional Laboratory

  8. West Nile Virus Surveillance Tarrant County Public Health North Texas Regional Laboratory

  9. West Nile Virus Surveillance Tarrant County Public Health North Texas Regional Laboratory

  10. West Nile Virus Surveillance • June 2002: WNV detected in two blue jays in Harris County • June 2002: First WNV detection in a mosquito in Tarrant County • July 2002: WNV detected in a bird from Tarrant County • July 2002: First case of human WNV in Texas is detected in man from Orange County Tarrant County Public Health North Texas Regional Laboratory

  11. West Nile Virus Surveillance • August 2002: First case of human WNV detected in Tarrant County • September 2002: First case of equine WNV detected in Tarrant County Tarrant County Public Health North Texas Regional Laboratory

  12. Tarrant County WNV Project 2003 - 2008 Tarrant County Public Health North Texas Regional Laboratory

  13. Tarrant County WNV Project • In 2003, Tarrant County Public Health implemented a comprehensive WNV surveillance project that included the collaborative efforts of the Epidemiology, Environmental Health, and Laboratory divisions. • Epidemiology received and tracked the human cases Tarrant County Public Health North Texas Regional Laboratory

  14. Tarrant County WNV Project • Environmental Health coordinated the efforts of local municipalities to collect mosquito samples, assisted with vector control activities, and provided public education • Laboratory staff performed RT-PCR testing of mosquito pools • The Public Information Office provided regular updates to media outlets • The local Public Health Authority and Public Health Director provided media interviews and briefings Tarrant County Public Health North Texas Regional Laboratory

  15. Tarrant County WNV Project • Environmental Health purchased gravid traps to distribute to local municipalities with grant funds from Texas DSHS • The first training session was held on March 27, 2003, for participating local municipalities Tarrant County Public Health North Texas Regional Laboratory

  16. Tarrant County WNV Project • Around 29 cities participated in the first year of mosquito surveillance • 565 mosquito pools were submitted for testing with WNV detected in 127 pools • 23 of the 29 participating cities had WNV positive mosquitoes detected Tarrant County Public Health North Texas Regional Laboratory

  17. Tarrant County WNV Project Tarrant County Public Health North Texas Regional Laboratory

  18. Tarrant County WNV Project • Environmental Health received the mosquito samples and sorted the frozen mosquitoes into tubes for testing • Lab staff homogenized the mosquito samples prior to RNA extraction Tarrant County Public Health North Texas Regional Laboratory

  19. Tarrant County WNV Project • The laboratory then performed real-time polymerase chain reaction using the Roche LightCycler • West Nile and St. Louis encephalitis virus were eventually multiplexed so that both results are available from a single reaction well or tube Tarrant County Public Health North Texas Regional Laboratory

  20. Tarrant County WNV Project • Environmental Health used GIS to map the location of mosquito sampling sites Tarrant County Public Health North Texas Regional Laboratory

  21. Tarrant County WNV Project Tarrant County Public Health North Texas Regional Laboratory

  22. Tarrant County WNV Project • In 2004, the West Nile virus surveillance project received a Best Practice Award from the Texas Association of Counties • Also in 2004, the Tarrant County WNV project was recognized by NACCHO as a Model Public Health Practice Tarrant County Public Health North Texas Regional Laboratory

  23. Tarrant County WNV Project • In 2005, Environmental Health added Mosquito Fish (Gambusia affinis) as an additional means of biological control available to participating cities Tarrant County Public Health North Texas Regional Laboratory

  24. Tarrant County WNV Project • After a large number of human cases and deaths in 2006 the public information office prepared several mini brochures aimed at reducing the risk of exposure to WNV Tarrant County Public Health North Texas Regional Laboratory

  25. Tarrant County WNV Project Tarrant County Public Health North Texas Regional Laboratory

  26. Tarrant County WNV Trends 2002 - 2008 Tarrant County Public Health North Texas Regional Laboratory

  27. Tarrant County WNV Trends Tarrant County Public Health North Texas Regional Laboratory

  28. Tarrant County WNV Trends Tarrant County Public Health North Texas Regional Laboratory

  29. Tarrant County WNV Geographical Information 2003 - 2008 Tarrant County Public Health North Texas Regional Laboratory

  30. Tarrant County WNV Geography Tarrant County Public Health North Texas Regional Laboratory

  31. Tarrant County WNV Geography Tarrant County Public Health North Texas Regional Laboratory

  32. Tarrant County WNV Geography Tarrant County Public Health North Texas Regional Laboratory

  33. Tarrant County WNV Geography Tarrant County Public Health North Texas Regional Laboratory

  34. Tarrant County WNV Geography Tarrant County Public Health North Texas Regional Laboratory

  35. Tarrant County WNV Geography Tarrant County Public Health North Texas Regional Laboratory

  36. Tarrant County WNV Geography Tarrant County Public Health North Texas Regional Laboratory

  37. Tarrant County WNV Geography Tarrant County Public Health North Texas Regional Laboratory

  38. Tarrant County WNV Geography Tarrant County Public Health North Texas Regional Laboratory

  39. Tarrant County WNV Geography Tarrant County Public Health North Texas Regional Laboratory

  40. Tarrant County WNV Geography Tarrant County Public Health North Texas Regional Laboratory

  41. Tarrant County WNV Geography Tarrant County Public Health North Texas Regional Laboratory

  42. Conclusions • The biology of the virus and its interactions with the host and the environment is very complex • The Northeast quadrant of Tarrant County appears to consistently have more positive mosquitoes and more human cases appear in the eastern half of the county Tarrant County Public Health North Texas Regional Laboratory

  43. Future Opportunities • Research utilizing additional geographic and climatological information to better understand the ecology of the vector and host interaction • Research using the mosquito sample bank to explore genetic changes in virulence factors • Assess the role of sampling bias in trap locations and the relevance to positive trap locations Tarrant County Public Health North Texas Regional Laboratory

  44. Acknowledgements • Michelle Markham, Environmental Health - GIS • Kaylene Ryza, Environmental Health • Dr. Anita Kurian, Epidemiology • Vanassa Joseph, Public Information Office • Jason Nagati, North Texas Regional Laboratory Tarrant County Public Health North Texas Regional Laboratory

More Related