[1] INST HYG & EPIDEMIOL,B-1050 BRUSSELS,BELGIUM
[2] UNIV PERUGIA,I-06100 PERUGIA,ITALY
[3] MAFF,CENT VET LAB,WEYBRIDGE KT15 3NB,SURREY,ENGLAND
[4] STATE VET SERUM LAB,DK-1870 COPENHAGEN S,DENMARK
[5] BUNDESGESUNDHEITSAMTES,INST VET MED,BERLIN,FED REP GER
[6] STATENS VET MED ANSTALT,STOCKHOLM,SWEDEN
[7] LAB CENT RECH VET,MAISONS ALFORT,FRANCE
[8] DEPT AGR,VET RES LAB,DUBLIN,IRELAND
[9] VET RES LABS,BELFAST,NORTH IRELAND
[10] LAB MED VET,LUXEMBOURG,LUXEMBOURG
[11] ROYAL VET & AGR UNIV,INST HYG & MICROBIOL,DK-1870 COPENHAGEN V,DENMARK