Characterization of enzootic foci of Venezuelan equine encephalitis virus in western Venezuela.

R. Barrera, N. Torres, J. E. Freier, J. C. Navarro, C. Z. García, R. Salas, C. Vasquez, Scott Weaver

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

The distribution of the sylvatic subtype ID Venezuelan equine encephalitis (VEE) viruses in the lowland tropical forests of western Venezuela was investigated using remote sensing and geographic information system technologies. Landsat 5 Thematic Mapper satellite imagery was used to study the reflectance patterns of VEE endemic foci and to identify other locations with similar reflectance patterns. Enzootic VEE virus variants isolated during this study are the closest genetic relatives of the epizootic viruses that emerged in western Venezuela during 1992-1993. VEE virus surveillance was conducted by exposing sentinel hamsters to mosquito bites and trapping wild vertebrates in seven forests identified and located by means of the satellite image. We isolated VEE viruses from 48 of a total of 1,363 sentinel hamsters in two of the forests on six occasions, in both dry and wet seasons. None of the 12 small vertebrates captured in 8,190 trap-nights showed signs of previous VEE virus infection. The satellite image was classified into 13 validated classes of land use/vegetation using unsupervised and supervised techniques. Data derived from the image consisted of the raw digital values of near- and mid-infrared bands 4, 5, and 7, derived Tasseled Cap indices of wetness, greenness, and brightness, and the Normalized Difference Vegetation Index. Digitized maps provided ancillary data of elevation and soil geomorphology. Image enhancement was applied using Principal Component Analysis. A digital layer of roads together with georeferenced images was used to locate the study sites. A cluster analysis using the above data revealed two main groups of dense forests separated by spectral properties, altitude, and soil geomorphology. Virus was isolated more frequently from the forest type identified on flat flood plains of main rivers rather than the forest type found on the rolling hills of the study area. The spatial analysis suggests that mosquitoes carrying the enzootic viruses would reach 82-97% of the total land area by flying only 1-3 km from forests. We hypothesize that humans within that area are at risk of severe disease caused by enzootic ID VEE viruses. By contrast, equines could actually become naturally vaccinated, thus preventing the local emergence of epizootic IC VEE virus strains and protecting humans indirectly.

Original languageEnglish (US)
Pages (from-to)219-230
Number of pages12
JournalVector Borne Zoonotic Dis
Volume1
Issue number3
StatePublished - Sep 2001
Externally publishedYes

Fingerprint

Venezuelan Equine Encephalitis Viruses
Venezuela
Viruses
Culicidae
Cricetinae
Vertebrates
Venezuelan Equine Encephalomyelitides
Satellite Imagery
Soil
Image Enhancement
Geographic Information Systems
Spatial Analysis
Virus Diseases
Bites and Stings
Forests
Principal Component Analysis
Rivers
Cluster Analysis
Technology

ASJC Scopus subject areas

  • Infectious Diseases
  • Parasitology

Cite this

Barrera, R., Torres, N., Freier, J. E., Navarro, J. C., García, C. Z., Salas, R., ... Weaver, S. (2001). Characterization of enzootic foci of Venezuelan equine encephalitis virus in western Venezuela. Vector Borne Zoonotic Dis, 1(3), 219-230.

Characterization of enzootic foci of Venezuelan equine encephalitis virus in western Venezuela. / Barrera, R.; Torres, N.; Freier, J. E.; Navarro, J. C.; García, C. Z.; Salas, R.; Vasquez, C.; Weaver, Scott.

In: Vector Borne Zoonotic Dis, Vol. 1, No. 3, 09.2001, p. 219-230.

Research output: Contribution to journalArticle

Barrera, R, Torres, N, Freier, JE, Navarro, JC, García, CZ, Salas, R, Vasquez, C & Weaver, S 2001, 'Characterization of enzootic foci of Venezuelan equine encephalitis virus in western Venezuela.', Vector Borne Zoonotic Dis, vol. 1, no. 3, pp. 219-230.
Barrera R, Torres N, Freier JE, Navarro JC, García CZ, Salas R et al. Characterization of enzootic foci of Venezuelan equine encephalitis virus in western Venezuela. Vector Borne Zoonotic Dis. 2001 Sep;1(3):219-230.
Barrera, R. ; Torres, N. ; Freier, J. E. ; Navarro, J. C. ; García, C. Z. ; Salas, R. ; Vasquez, C. ; Weaver, Scott. / Characterization of enzootic foci of Venezuelan equine encephalitis virus in western Venezuela. In: Vector Borne Zoonotic Dis. 2001 ; Vol. 1, No. 3. pp. 219-230.
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