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

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

Tarrant County Public Health North Texas Regional Laboratory 3 West Nile Virus Background Family: FlaviviridaeFamily: Flaviviridae Genus: FlavivirusGenus: 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 encephalitisOver 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 envelopeFlaviviruses 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 nucleotidesThe 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 virulenceThe 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 1937WNV was first isolated from a human patient with a fever in Uganda in 1937 WNV host range is broad and includes birds, horses and humansWNV host range is broad and includes birds, horses and humans Historically, WNV was found in Europe, Africa, the Middle East and AsiaHistorically, WNV was found in Europe, Africa, the Middle East and Asia In 1999, WNV emerged in North America and arrived in Texas in 2002In 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 hostsWNV 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 transmissionHumans, 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 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 CountyJune 2002: WNV detected in two blue jays in Harris County June 2002: First WNV detection in a mosquito in Tarrant CountyJune 2002: First WNV detection in a mosquito in Tarrant County July 2002: WNV detected in a bird from Tarrant CountyJuly 2002: WNV detected in a bird from Tarrant County July 2002: First case of human WNV in Texas is detected in man from Orange CountyJuly 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 CountyAugust 2002: First case of human WNV detected in Tarrant County September 2002: First case of equine WNV detected in Tarrant CountySeptember 2002: First case of equine WNV detected in Tarrant County

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

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.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 casesEpidemiology 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 educationEnvironmental 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 poolsLaboratory staff performed RT-PCR testing of mosquito pools The Public Information Office provided regular updates to media outletsThe Public Information Office provided regular updates to media outlets The local Public Health Authority and Public Health Director provided media interviews and briefingsThe 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 DSHSEnvironmental 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 municipalitiesThe 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 surveillanceAround 29 cities participated in the first year of mosquito surveillance 565 mosquito pools were submitted for testing with WNV detected in 127 pools565 mosquito pools were submitted for testing with WNV detected in 127 pools 23 of the 29 participating cities had WNV positive mosquitoes detected23 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 testingEnvironmental Health received the mosquito samples and sorted the frozen mosquitoes into tubes for testing Lab staff homogenized the mosquito samples prior to RNA extractionLab 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 LightCyclerThe 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 tubeWest 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 sitesEnvironmental 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 CountiesIn 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 PracticeAlso 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 citiesIn 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 WNVAfter 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 Tarrant County WNV Trends

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 Tarrant County WNV Geographical Information

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 complexThe 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 countyThe 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 interactionResearch 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 factorsResearch 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 locationsAssess 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 - GISMichelle Markham, Environmental Health - GIS Kaylene Ryza, Environmental HealthKaylene Ryza, Environmental Health Dr. Anita Kurian, EpidemiologyDr. Anita Kurian, Epidemiology Vanassa Joseph, Public Information OfficeVanassa Joseph, Public Information Office Jason Nagati, North Texas Regional LaboratoryJason Nagati, North Texas Regional Laboratory