[1] Univ Zurich, Vetsuisse Fac, Natl Reference Ctr Poultry & Rabbit Dis, Inst Vet Bacteriol, CH-8057 Zurich, Switzerland
[2] Univ Zurich, Vetsuisse Fac, Inst Virol, CH-8057 Zurich, Switzerland
[3] Zytohisto Diagnost, Freienstein, Switzerland
[4] Ist Zooprofilattt Sperimentale Venezie, OIE FAO Reference Lab Avian Influenza & Newcastle, Padua, Italy
[5] Free Univ Berlin, Inst Poultry Dis, Berlin, Germany
[6] AFRC, Inst Anim Hlth, Compton Lab, Newbury RG16 0NN, Berks, England