Isolation of usutu virus in Germany

Abstract

Usutu virus (USUV) is a mosquito-borne flavivirus that emerged 2001 in Austria and caused deaths in wild birds. In Germany, 70,378 female mosquitoes were captured in 2009 and 2010 and assayed for USUV. Virus was isolated in cell culture from one pool of Culex pipiens pipiens mosquitoes trapped exclusively in August 2010 in Weinheim, Germany. Subsequent phylogenetic analysis demonstrated a close relationship between the isolated USUV strain from Germany and a USUV strain from Austria, which was detected in a dead blackbird in 2004.

Figure 1.

Locations of study sites in Germany and phylogenetic analysis of Usutu virus (USUV) strains. For each trapping site, proportions and number of collected mosquitoes are given as a pie chart. Mosquitoes in the pool that were positive for USUV were trapped at Weinheim (underlined). The Bayesian phylogenetic tree was inferred with MrBayes and is based on partial protein envelope nucleotide sequences (length = 1,215 nucleotides) of USUV. For each sequence, the GenBank accession number, strain designation, and strain origin are shown. Posterior probabilities are shown on each node, if higher than 0.50. Scale bar indicates number of nucleotide substitutions per site.