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Volume 11, Number 9—September 2005
Letter

West Nile Virus Antibodies in Colombian Horses

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To the Editor: West Nile Virus (WNV) is rapidly spreading in the Western Hemisphere (1). We report the first evidence for WNV transmission in South America.

WNV is serologically related to the Japanese encephalitis complex of flaviviruses (Flaviviridae), which includes Saint Louis encephalitis virus (SLEV) (in North and South America), Japanese encephalitis virus (Asia), and Murray Valley encephalitis virus (Australia) (2). Because of antigenic cross-reactivity within this complex, WNV serologic diagnosis requires highly specific assays, such as the plaque-reduction neutralization test (PRNT) (3). We used PRNT to evaluate serum collected from 130 healthy equines (horses and donkeys) in Colombia, where WNV had not been previously reported. These equines were sampled between September 15 and October 29, 2004, in the northern departments of Córdoba and Sucre in the Caribbean region of Colombia. Samples were heat-inactivated and titrated by PRNT for antibodies to WNV, SLEV, and 3 other South American flaviviruses: Rocio, Ilhéus, and Bussuquara. Twelve specimens (9%) from 10 different premises tested positive for WNV (Table). None of these animals had been vaccinated against WNV or had traveled outside of the region. An equine immunoglobulin (Ig) M-capture enzyme-linked immunosorbent assay (ELISA) that used WNV antigen detected anti-WNV IgM in 2 of the 12 specimens, which indicated that some of these infections were relatively recent (probably within 3 months of sampling). The positive findings in both Córdoba and Sucre were corroborated by a WNV-specific blocking ELISA (4). Numerous other samples exhibited flavivirus reactivity in the neutralization and blocking ELISA assays, mostly because of SLEV. Complete test results from these horses, as well as from Colombian cattle and chickens, will be presented elsewhere.

These serologic data should be considered indirect evidence of WNV activity in Colombia. We encourage Colombian human and animal health authorities to enhance surveillance for human, equine, and avian disease attributable to WNV. Efforts are needed to isolate the virus or detect specific viral RNA to confirm this finding and to identify vectors and vertebrate hosts involved in WNV transmission in Colombia.

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Acknowledgment

We thank Robert Lanciotti, Janeen Laven, Jason Velez, and Vanesa Otero for technical assistance.

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Salim Mattar*, Eric Edwards†, Jose Laguado*, Marco González*, Jaime Alvarez*, and Nicholas Komar†Comments to Author 
Author affiliations: *University of Córdoba, Montería, Córdoba, Colombia; †Centers for Disease Control and Prevention, Fort Collins, Colorado, USA

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References

  1. Komar  N. West Nile virus: epidemiology and ecology in North America. Adv Virus Res. 2003;61:185234. DOIPubMedGoogle Scholar
  2. Calisher  CH, Karabatsos  N, Dalrymple  JM, Shope  RE, Porterfield  JS, Westaway  EG, Antigenic relationships between flaviviruses as determined by cross-neutralization tests with polyclonal antisera. J Gen Virol. 1989;70:3743. DOIPubMedGoogle Scholar
  3. Beaty  BJ, Calisher  CH, Shope  RE. Arboviruses. In: Lennette EH, Lennette DA, Lennette ET, editors. Diagnostic procedures for viral, rickettsial, and chlamydial infections. 7th ed. Washington: American Public Health Association; 1995. p. 189–212.
  4. Blitvich  BJ, Marlenee  NL, Hall  RA, Calisher  CH, Bowen  RA, Roehrig  JT, Epitope-blocking enzyme-linked immunosorbent assays for the detection of serum antibodies to West Nile virus in multiple avian species. J Clin Microbiol. 2003;41:10417. DOIPubMedGoogle Scholar

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DOI: 10.3201/eid1109.050426

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Table of Contents – Volume 11, Number 9—September 2005

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Please use the form below to submit correspondence to the authors or contact them at the following address:

Nicholas Komar, Centers for Disease Control and Prevention, PO Box 2087, Fort Collins, CO 80522, USA; fax: 970-221-6476

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Page created: April 23, 2012
Page updated: April 23, 2012
Page reviewed: April 23, 2012
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.
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