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Burkett-Cadena ND, Day JF, Unnasch TR. Ecology of Eastern Equine Encephalitis Virus in the Southeastern United States: Incriminating Vector and Host Species Responsible for Virus Amplification, Persistence, and Dispersal. JOURNAL OF MEDICAL ENTOMOLOGY 2022; 59:41-48. [PMID: 34734635 DOI: 10.1093/jme/tjab076] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Indexed: 06/13/2023]
Abstract
Eastern equine encephalitis virus (EEEV; family Togaviridae, genus Alphavirus) is a mosquito-borne pathogen found in eastern North America that causes severe disease in humans and horses. The mosquito Culiseta melanura (Coquillett) (Diptera: Culicidae) is the primary enzootic vector of EEEV throughout eastern North America while several mosquito species belonging to diverse genera serve as bridge vectors. The ecology of EEEV differs between northern and southern foci, with respect to phenology of outbreaks, important vertebrate hosts, and bridge vector species. Active transmission is limited to roughly half of the year in northern foci (New York, New Hampshire, Massachusetts, Connecticut), while year-round transmission occurs in the southeastern region (particularly Florida). Multiple phylogenetic analyses indicate that EEEV strains circulating in northern foci are likely transported from southern foci by migrating birds. Bird species that overwinter or migrate through Florida, are bitten by Cs. melanura in late spring, and arrive at northern breeding grounds in May are the most likely candidates to disperse EEEV northward. Available data indicate that common yellowthroat and green heron satisfy these criteria and could serve as virus dispersers. Understanding the factors that drive the phenology of Cs. melanura reproduction in the south and the timing of avian migration from southern foci could provide insight into how confluence of these biological phenomena shapes outbreaks of EEE throughout its range. This information could be used to develop models predicting the likelihood of outbreaks in a given year, allowing vector control districts to more efficiently marshal resources necessary to protect their stakeholders.
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Affiliation(s)
- Nathan D Burkett-Cadena
- Florida Medical Entomology Laboratory, University of Florida IFAS, 200 9th Street SE, Vero Beach, FL 32962, USA
| | - Jonathan F Day
- Florida Medical Entomology Laboratory, University of Florida IFAS, 200 9th Street SE, Vero Beach, FL 32962, USA
| | - Thomas R Unnasch
- Center for Global Health Infectious Disease Research, University of South Florida, 3720 Spectrum Blvd., Suite 304, Tampa, FL 33612, USA
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Ciota AT. Eastern Equine Encephalitis Virus Taxonomy, Genomics, and Evolution. JOURNAL OF MEDICAL ENTOMOLOGY 2022; 59:14-19. [PMID: 34734630 DOI: 10.1093/jme/tjab079] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Indexed: 06/13/2023]
Abstract
Eastern equine encephalitis virus (EEEV; Togaviridae, Alphavirus) is an arthropod-borne virus (arbovirus) primarily maintained in an enzootic cycle between Culiseta melanura (Coquillett) and passerine birds. EEEV, which has the highest reported case- fatality rate among arbovirus in the Americas, is responsible for sporadic outbreaks in the Eastern and Midwest United States. Infection is associated with severe neurologic disease and mortality in horses, humans, and other vertebrate hosts. Here, we review what is known about EEEV taxonomy, functional genomics, and evolution, and identify gaps in knowledge regarding the role of EEEV genetic diversity in transmission and disease.
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Affiliation(s)
- Alexander T Ciota
- The Arbovirus Laboratory, Wadsworth Center, New York State Department of Health, Slingerlands, NY
- Department of Biomedical Sciences, State University of New York at Albany School of Public Health, Rensselaer, NY
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Hughes HR, Velez JO, Davis EH, Laven J, Gould CV, Panella AJ, Lambert AJ, Staples JE, Brault AC. Fatal Human Infection with Evidence of Intrahost Variation of Eastern Equine Encephalitis Virus, Alabama, USA, 2019. Emerg Infect Dis 2021; 27:1886-1892. [PMID: 34152960 PMCID: PMC8237905 DOI: 10.3201/eid2707.210315] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Eastern equine encephalitis virus (EEEV) is an arbovirus in the family Togaviridae, genus Alphavirus, found in North America and associated with freshwater/hardwood swamps in the Atlantic, Gulf Coast, and Great Lakes regions. EEEV disease in humans is rare but causes substantial illness and death. To investigate the molecular epidemiology and microevolution of EEEV from a fatal case in Alabama, USA, in 2019, we used next-generation sequencing of serum and cerebrospinal fluid (CSF). Phylogenetic inference indicated that the infecting strain may be closely related to isolates from Florida detected during 2010-2014, suggesting potential seeding from Florida. EEEV detected in serum displayed a higher degree of variability with more single-nucleotide variants than that detected in the CSF. These data refine our knowledge of EEEV molecular epidemiologic dynamics in the Gulf Coast region and demonstrate potential quasispecies bottlenecking within the central nervous system of a human host.
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Heberlein-Larson LA, Tan Y, Stark LM, Cannons AC, Shilts MH, Unnasch TR, Das SR. Complex Epidemiological Dynamics of Eastern Equine Encephalitis Virus in Florida. Am J Trop Med Hyg 2019; 100:1266-1274. [PMID: 30860014 PMCID: PMC6493969 DOI: 10.4269/ajtmh.18-0783] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 01/07/2019] [Indexed: 11/07/2022] Open
Abstract
Eastern equine encephalitis virus (EEEV) infection results in high mortality in infected horses and humans. Florida has been identified as an important source of EEEV epidemics to other states in the United States. In this study, we further characterized the epidemiological and evolutionary dynamics of EEEV in Florida. Epidemiological analysis of sentinel chicken seroconversion rates to EEEV infections during 2005-2016 suggested significant seasonality of EEEV activity in Florida. We observed significant annual activity of EEEV in the North and North Central regions, with little significant seasonality in the Panhandle region. Phylogenetic analysis of complete EEEV genome sequences from different host sources and regions in Florida during 1986-2014 revealed extensive genetic diversity and spatial dispersal of the virus within Florida and relatively more clustering of the viruses in the Panhandle region. We found no significant association between EEEV genetic variation and host source. Overall, our study revealed a complex epidemiological dynamic of EEEV within Florida, implicating the Panhandle region as a possible source of the virus with sustained year-round transmission. These findings will help in implementing targeted control measures that can have the most impact in reducing or eliminating EEEV and other mosquito-borne viral infections within Florida and in the rest of the United States.
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Affiliation(s)
- Lea A. Heberlein-Larson
- Florida Department of Health, Bureau of Public Health Laboratories, Tampa, Florida
- Global Health Infectious Disease Research Program, Department of Global Health, College of Public Health, University of South Florida, Tampa, Florida
| | - Yi Tan
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Lillian M. Stark
- Florida Department of Health, Bureau of Public Health Laboratories, Tampa, Florida
| | - Andrew C. Cannons
- Florida Department of Health, Bureau of Public Health Laboratories, Tampa, Florida
| | - Meghan H. Shilts
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Thomas R. Unnasch
- Global Health Infectious Disease Research Program, Department of Global Health, College of Public Health, University of South Florida, Tampa, Florida
| | - Suman R. Das
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
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Downs J, Vaziri M, Jenkins A, Unnasch T. Validation of a Risk Index Model for Predicting Eastern Equine Encephalitis Virus Transmission to Horses in Florida. JOURNAL OF MEDICAL ENTOMOLOGY 2018; 55:1143-1149. [PMID: 29722818 DOI: 10.1093/jme/tjy067] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Indexed: 06/08/2023]
Abstract
Eastern Equine Encephalitis Virus (EEEV) is the most pathogenic arbovirus endemic to the United States. EEEV primarily infects birds but can be fatal to humans, horses, and some other mammals. Although EEEV transmission occurs in the Northeastern, Southeastern, and Midwestern United States, the largest number of horse and human cases have been reported in Florida, the only state where transmission occurs year round. Currently, a GIS-based risk index (RI) model is used to map EEE transmission risk to horses in Florida. This study validates that RI model using a 5-yr dataset of horse cases in Florida. RI values were similar between summer (N = 152, x¯ = 0.59) and winter (N = 25, x¯ = 0.66) cases, suggesting the model is effective for mapping risk during both transmission seasons. These risk values were larger and remained similar when a 100-m buffer was applied to the case locations to account for modest spatial errors in case reporting (summer x¯ = 0.73, winter x¯ = 0.77). In both comparisons, RI values for summer and winter cases were higher than expected at random in the Panhandle, North, and Central regions of the state, although the analysis was inconclusive in the South, where only two cases were observed. This suggests the RI map could be used to target EEEV surveillance, prevention, and control efforts in both transmission seasons in Florida.
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Affiliation(s)
- Joni Downs
- School of Geosciences, University of South Florida, Tampa, FL
| | - Mehrdad Vaziri
- School of Geosciences, University of South Florida, Tampa, FL
| | - Alexandra Jenkins
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL
| | - Thomas Unnasch
- Department of Global Health, University of South Florida, Tampa, FL
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Large-Scale Complete-Genome Sequencing and Phylodynamic Analysis of Eastern Equine Encephalitis Virus Reveals Source-Sink Transmission Dynamics in the United States. J Virol 2018; 92:JVI.00074-18. [PMID: 29618651 DOI: 10.1128/jvi.00074-18] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Accepted: 03/30/2018] [Indexed: 11/20/2022] Open
Abstract
Eastern equine encephalitis virus (EEEV) has a high case-fatality rate in horses and humans, and Florida has been hypothesized to be the source of EEEV epidemics for the northeastern United States. To test this hypothesis, we sequenced complete genomes of 433 EEEV strains collected within the United States from 1934 to 2014. Phylogenetic analysis suggested EEEV evolves relatively slowly and that transmission is enzootic in Florida, characterized by higher genetic diversity and long-term local persistence. In contrast, EEEV strains in New York and Massachusetts were characterized by lower genetic diversity, multiple introductions, and shorter local persistence. Our phylogeographic analysis supported a source-sink model in which Florida is the major source of EEEV compared to the other localities sampled. In sum, this study revealed the complex epidemiological dynamics of EEEV in different geographic regions in the United States and provided general insights into the evolution and transmission of other avian mosquito-borne viruses in this region.IMPORTANCE Eastern equine encephalitis virus (EEEV) infections are severe in horses and humans on the east coast of the United States with a >90% mortality rate in horses, an ∼33% mortality rate in humans, and significant brain damage in most human survivors. However, little is known about the evolutionary characteristics of EEEV due to the lack of genome sequences. By generating large collection of publicly available complete genome sequences, this study comprehensively determined the evolution of the virus, described the epidemiological dynamics of EEEV in different states in the United States, and identified Florida as one of the major sources. These results may have important implications for the control and prevention of other mosquito-borne viruses in the Americas.
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Diseases of the Nervous System. Vet Med (Auckl) 2017. [PMCID: PMC7322266 DOI: 10.1016/b978-0-7020-5246-0.00014-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Bingham AM, Burkett-Cadena ND, Hassan HK, Unnasch TR. Vector Competence and Capacity of Culex erraticus (Diptera: Culicidae) for Eastern Equine Encephalitis Virus in the Southeastern United States. JOURNAL OF MEDICAL ENTOMOLOGY 2016; 53:473-476. [PMID: 26659606 PMCID: PMC5853673 DOI: 10.1093/jme/tjv195] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 11/12/2015] [Indexed: 06/05/2023]
Abstract
Field studies of the ecology of eastern equine encephalitis virus (EEEV; family Togaviridae, genus Alphavirus) in the southeastern United States have demonstrated that Culex erraticus (Dyar and Knab) is the most common mosquito at many enzootic sites and is often infected with the virus. However, the competence of Cx. erraticus for EEEV has not been explored in detail. Culex erraticus females were collected from the field and fed upon EEEV-infected chicks. The infected mosquitoes were provided honey for nutrition and to monitor for time to infectiveness. Of the mosquitoes that survived the 14-d postfeeding period, 89% were infected and 84% had evidence of a disseminated infection, though titers were generally low. EEEV was first detected in honey 6 d postinfection and was detected in samples collected from 94% of the mosquitoes with a disseminated infection overall. These data and others were then employed to estimate the relative vectorial capacity of Cx. erraticus at an EEEV enzootic site in Alabama. The vectorial capacity of Cx. erraticus at this site was 44% of Culiseta melanura (Coquillett), the accepted enzootic vector, suggesting Cx. erraticus may play a role in transmitting EEEV in areas where it is abundant and Cs. melanura rare.
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Affiliation(s)
- Andrea M. Bingham
- Global Health Infectious Disease Program, University of South Florida, 3720 Spectrum Blvd., Tampa, FL 33612 (
;
;
)
- Present address: Florida Department of Health, Division of Disease Control and Health Protection, Bureau of Epidemiology, 4052 Bald Cypress Way, Bin A12 Tallahassee, FL 32399-1710
| | - Nathan D. Burkett-Cadena
- University of Florida IFAS, Florida Medical Entomology Laboratory, 200 9th St. SE, Vero Beach, FL 32962 (
), and
| | - Hassan K. Hassan
- Global Health Infectious Disease Program, University of South Florida, 3720 Spectrum Blvd., Tampa, FL 33612 (
;
;
)
| | - Thomas R. Unnasch
- Global Health Infectious Disease Program, University of South Florida, 3720 Spectrum Blvd., Tampa, FL 33612 (
;
;
)
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Bingham AM, Burkett-Cadena ND, Hassan HK, McClure CJW, Unnasch TR. Field investigations of winter transmission of eastern equine encephalitis virus in Florida. Am J Trop Med Hyg 2014; 91:685-93. [PMID: 25070997 DOI: 10.4269/ajtmh.14-0081] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Studies investigating winter transmission of Eastern equine encephalitis virus (EEEV) were conducted in Hillsborough County, Florida. The virus was detected in Culiseta melanura and Anopheles quadrimaculatus in February 2012 and 2013, respectively. During the winter months, herons were the most important avian hosts for all mosquito species encountered. In collections carried out in the summer of 2011, blood meals taken from herons were still common, but less frequently encountered than in winter, with an increased frequency of mammalian- and reptile-derived meals observed in the summer. Four wading bird species (Black-crowned Night Heron [Nycticorax nycticorax], Yellow-crowned Night Heron [Nyctanassa violacea], Anhinga [Anhinga anhinga], and Great Blue Heron [Ardea herodias]) were most frequently fed upon by Cs. melanura and Culex erraticus, suggesting that these species may participate in maintaining EEEV during the winter in Florida.
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Affiliation(s)
- Andrea M Bingham
- Global Health Infectious Disease Research Program, Department of Global Health, University of South Florida, Tampa, Florida; Florida Medical Entomology Laboratory, Entomology and Nematology Department, University of Florida, Vero Beach, Florida; The Peregrine Fund, Boise, Indiana
| | - Nathan D Burkett-Cadena
- Global Health Infectious Disease Research Program, Department of Global Health, University of South Florida, Tampa, Florida; Florida Medical Entomology Laboratory, Entomology and Nematology Department, University of Florida, Vero Beach, Florida; The Peregrine Fund, Boise, Indiana
| | - Hassan K Hassan
- Global Health Infectious Disease Research Program, Department of Global Health, University of South Florida, Tampa, Florida; Florida Medical Entomology Laboratory, Entomology and Nematology Department, University of Florida, Vero Beach, Florida; The Peregrine Fund, Boise, Indiana
| | - Christopher J W McClure
- Global Health Infectious Disease Research Program, Department of Global Health, University of South Florida, Tampa, Florida; Florida Medical Entomology Laboratory, Entomology and Nematology Department, University of Florida, Vero Beach, Florida; The Peregrine Fund, Boise, Indiana
| | - Thomas R Unnasch
- Global Health Infectious Disease Research Program, Department of Global Health, University of South Florida, Tampa, Florida; Florida Medical Entomology Laboratory, Entomology and Nematology Department, University of Florida, Vero Beach, Florida; The Peregrine Fund, Boise, Indiana
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Bingham AM, Graham SP, Burkett-Cadena ND, White GS, Hassan HK, Unnasch TR. Detection of eastern equine encephalomyelitis virus RNA in North American snakes. Am J Trop Med Hyg 2012; 87:1140-4. [PMID: 23033405 DOI: 10.4269/ajtmh.2012.12-0257] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The role of non-avian vertebrates in the ecology of eastern equine encephalomyelitis virus (EEEV) is unresolved, but mounting evidence supports a potential role for snakes in the EEEV transmission cycle, especially as over-wintering hosts. To determine rates of exposure and infection, we examined serum samples from wild snakes at a focus of EEEV in Alabama for viral RNA using quantitative reverse transcription polymerase chain reaction. Two species of vipers, the copperhead (Agkistrodon contortrix) and the cottonmouth (Agkistrodon piscivorus), were found to be positive for EEEV RNA using this assay. Prevalence of EEEV RNA was more frequent in seropositive snakes than seronegative snakes. Positivity for the quantitative reverse transcription polymerase chain reaction in cottonmouths peaked in April and September. Body size and sex ratios were not significantly different between infected and uninfected snakes. These results support the hypothesis that snakes are involved in the ecology of EEEV in North America, possibly as over-wintering hosts for the virus.
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Affiliation(s)
- Andrea M Bingham
- Department of Biological Sciences, Auburn University, Auburn, AL, USA.
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VANDER KELEN PATRICKT, DOWNS JONIA, BURKETT-CADENA NATHAND, OTTENDORFER CHRISTYL, HILL KEVIN, SICKERMAN STEPHEN, HERNANDEZ JOSÉ, JINRIGHT JOSEPH, HUNT BRENDA, LUSK JOHN, HOOVER VICTOR, ARMSTRONG KEITH, UNNASCH ROBERTS, STARK LILLIANM, UNNASCH THOMASR. Habitat associations of eastern equine encephalitis transmission in Walton County Florida. JOURNAL OF MEDICAL ENTOMOLOGY 2012; 49:746-56. [PMID: 22679885 PMCID: PMC3552394 DOI: 10.1603/me11224] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Eastern Equine Encephalitis virus (EEEV; family Togaviridae, genus Alphavirus) a highly pathogenic mosquito-borne virus is endemic to eastern North America. The ecology of EEEV in Florida differs from that in other parts of the United States; EEEV in the northeastern United States is historically associated with freshwater wetlands. No formal test of habitat associations of EEEV in Florida has been reported. Geographical Information Sciences (GIS) was used in conjunction with sentinel chicken EEEV seroconversion rate data as a means to examine landscape features associated with EEEV transmission in Walton County, FL. Sentinel sites were categorized as enzootic, periodically enzootic, and negative based on the number of chicken seroconversions to EEEV from 2005 to 2009. EEEV transmission was then categorized by land cover usage using Arc GIS 9.3. The land classification data were analyzed using the Kruskal-Wallis test for each land use class to determine which habitats may be associated with virus transmission as measured by sentinel chicken seroconversion rates. The habitat class found to be most significantly associated with EEEV transmission was tree plantations. The ecological factor most commonly associated with reduced levels of EEEV transmission was vegetated nonforest wetlands. Culiseta melanura (Coquillett), the species generally considered to be the major enzootic EEEV vector, was relatively evenly distributed across all habitat classes, while Aedes vexans (Meigen) and Anopheles crucians Weidemann were most commonly associated with tree plantation habitats.
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Affiliation(s)
- PATRICK T. VANDER KELEN
- Global Health Infectious Disease Research Program, University of South Florida, 3720 Spectrum Blvd., Tampa, FL 33612
| | - JONI A. DOWNS
- Department of Geography, Environment, and Planning, University of South Florida, 4202 E. Fowler Ave., Tampa, FL 33620
| | - NATHAN D. BURKETT-CADENA
- Global Health Infectious Disease Research Program, University of South Florida, 3720 Spectrum Blvd., Tampa, FL 33612
| | - CHRISTY L. OTTENDORFER
- Global Health Infectious Disease Research Program, University of South Florida, 3720 Spectrum Blvd., Tampa, FL 33612
| | - KEVIN HILL
- Global Health Infectious Disease Research Program, University of South Florida, 3720 Spectrum Blvd., Tampa, FL 33612
| | - STEPHEN SICKERMAN
- South Walton County Mosquito Control District, 774 North County Highway 393, Santa Rosa Beach, FL 32459
| | - JOSÉ HERNANDEZ
- South Walton County Mosquito Control District, 774 North County Highway 393, Santa Rosa Beach, FL 32459
| | - JOSEPH JINRIGHT
- South Walton County Mosquito Control District, 774 North County Highway 393, Santa Rosa Beach, FL 32459
| | - BRENDA HUNT
- North Walton Mosquito Control District, 129 Montgomery Circle, DeFuniak Springs, FL 32435
| | - JOHN LUSK
- North Walton Mosquito Control District, 129 Montgomery Circle, DeFuniak Springs, FL 32435
| | - VICTOR HOOVER
- North Walton Mosquito Control District, 129 Montgomery Circle, DeFuniak Springs, FL 32435
| | - KEITH ARMSTRONG
- North Walton Mosquito Control District, 129 Montgomery Circle, DeFuniak Springs, FL 32435
| | | | - LILLIAN M. STARK
- Florida Department of Health, Bureau of Laboratories-Tampa, 3602 Spectrum Blvd., Tampa, FL 33612
| | - THOMAS R. UNNASCH
- Global Health Infectious Disease Research Program, University of South Florida, 3720 Spectrum Blvd., Tampa, FL 33612
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