Putative New Lineage of West Nile Virus, Spain | CDC EID

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Volume 16, Number 3–March 2010
Dispatch
Putative New Lineage of West Nile Virus, Spain
Ana Vázquez, María Paz Sánchez-Seco, Santiago Ruiz, Francisca Molero, Lourdes Hernández, Juana Moreno, Antonio Magallanes, Concepción Gómez Tejedor, and Antonio Tenorio
Author affiliations Centro Nacional de Microbiología–Instituto de Salud Carlos III, Majadahonda, Spain (A. Vázquez, M.P. Sánchez-Seco, F. Molero, L. Hernández, A. Tenorio); Diputación Provincial de Huelva, Huelva, Spain (S. Ruiz, J. Moreno, A. Magallanes); and Laboratorio Central de Veterinaria, Algete, Spain (C. Gómez Tejedor)

Suggested citation for this article

Abstract
To ascertain the presence of West Nile virus (WNV), we sampled mosquitoes in 2006 in locations in southern Spain where humans had been infected. WNV genomic RNA was detected in 1 pool from unfed female Culex pipiens mosquitoes. Phylogenetic analysis demonstrated that this sequence cannot be assigned to previously described lineages of WNV.
West Nile virus (WNV) has been described in Africa, Europe, the Middle East, Asia, Australia, and, most recently, the Americas. Over the last few years, many reports about WNV have been published after the outbreaks in Romania, Morocco, Italy, Russia, and Israel, but especially with the introduction and spread of the virus in the Americas. Currently, the virus has a wide geographic distribution, and WNV infection is considered an emerging zoonosis (1).

Although only WNV lineage 1 is present in the Americas, >5 lineages of the virus seem to circulate in the Old World (2). In 2008, several countries in Europe reported WNV activity due to different lineages. WNV lineage 1 was isolated from horses and birds in northern Italy, and WNV infection was described in 6 persons (3). The Austrian veterinary authorities reported 2 outbreaks of WNV in wild birds, 1 in northern Austria, and 1 in the region of Vienna. The virus isolated from these birds, sparrow hawks, was WNV lineage 2 and was very homologous to 2 strains previously found in goshawks in Hungary in 2004 and 2005. These reports represented the emergence of a WNV lineage 2 strain outside Africa for the first time (4). Migratory birds that overwintered in central Africa may have recently introduced this exotic strain in the wetlands of different eastern European countries. Consequently, this neurotropic, exotic WNV strain may become a resident pathogen in Europe with public health consequences.

A new lineage of WNV (named Rabensburg virus), of as yet unknown human pathogenicity, was isolated from Culex pipiens mosquitoes in 1997 and 1999 on the Czech Republic–Austria border, only a few hundred kilometers from the region where WNV emerged in Hungary (5). The Rabensburg isolate 97–103, obtained from Cx. pipiens mosquitoes (1997) in Czech Republic (6), and LEIVKrnd88–190, isolated from Dermacentor marginatus ticks in a valley in the northwestern Caucasus Mountains in 1998 (7), have been proposed to be novel variants of WNV. These isolates are genetically different from viruses of lineage 1 and 2 and have been proposed as members of lineages 3 and 4, respectively. Moreover, 2 other related viruses show no clear relationships with WNV, the strain KUN MP502–66 from Malaysia, and Koutango (KOUV), an African virus, with poor statistical support for clustering with either of the WNVs, which suggests that they represent 2 single-isolate lineages (8).

Previous serologic surveys conducted with small rodents and humans in different areas of Spain have shown evidence of WNV circulation (9). Although no neurologic illness outbreaks have been documented in Spain, recent studies indicate that WNV is circulating in the southern part of the country, close to the areas of the recent foci in Portugal and Morocco. This part of Spain contains several wetlands, which have high densities of migratory birds and mosquitoes. WNV activity has been reported in this region on the basis of serologic surveys in birds, horses, and humans (10–12). Moreover, the first clinical case of WNV infection in Spain was reported in 2004 in a patient visiting southwestern Spain (13), and WNV lineage 1 was detected and further isolated in free-living and captive Spanish golden eagles in south-central Spain (14). Following up these results, we collected mosquito samples especially from areas from which positive serum samples had been obtained to look for WNV in its vector.

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Suggested Citation for this Article
Vázquez A, Sánchez-Seco MP, Ruiz S, Molero F, Hernández L, Moreno J, et al. Putative new lineage of West Nile virus, Spain. Emerg Infect Dis [serial on the Internet]. 2010 Mar [date cited]. http://www.cdc.gov/EID/content/16/3/549.htm

DOI: 10.3201/eid1603.091033