Serological evidence of continuing high Usutu virus (Flaviviridae) activity and establishment of herd immunity in wild birds in Austria

Tanja Meister, Helga Lussy, Tamás Bakonyi, Silvie Šikutová, Ivo Rudolf, Wolfgang Vogl, Hans Winkler, Hans Frey, Zdeněk Hubálek, Norbert Nowotny, Herbert Weissenböck*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

67 Citations (Scopus)


Usutu virus (USUV), family Flaviviridae, has been responsible for avian mortality in Austria from 2001 to 2006. The proportion of USUV-positive individuals among the investigated dead birds decreased dramatically after 2004. To test the hypothesis that establishment of herd immunity might be responsible, serological examinations of susceptible wild birds were performed. Blood samples of 442 wild birds of 55 species were collected in 4 consecutive years (2003-2006). In addition, 86 individuals from a birds of prey rehabilitation centre were bled before, at the peak, and after the 2005 USUV transmission season in order to identify titre dynamics and seroconversions. The haemagglutination inhibition test was used for screening and the plaque reduction neutralization test for confirmation. While in the years 2003 and 2004 the proportion of seropositive wild birds was <10%, the percentage of seroreactors raised to >50% in 2005 and 2006. At the birds of prey centre, almost three quarters of the owls and raptors exhibited antibodies before the 2005 transmission season; this percentage dropped to less than half at the peak of USUV transmission and raised again to almost two thirds after the transmission season. These data show a from year to year continuously increasing proportion of seropositive wild birds. The owl and raptor data indicate significant viral exposure in the previous season(s), but also a number of new infections during the current season, despite the presence of antibodies in some of these birds. Herd immunity is a possible explanation for the significant decrease in USUV-associated bird mortalities in Austria during the recent years.

Original languageEnglish
Pages (from-to)237-248
Number of pages12
JournalVeterinary Microbiology
Issue number3-4
Publication statusPublished - Mar 18 2008


  • Herd immunity
  • Serology
  • USUV
  • Usutu virus
  • Wild birds

ASJC Scopus subject areas

  • Microbiology
  • veterinary(all)


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