1. Department of Molecular Microbiology, Institute for Bee Research, Friedrich-Engels-Str. 32, D-16540 Hohen Neuendorf, Germany
2. Department of Entomology, Swedish University of Agricultural Sciences, Box 7044, SE-75007 Uppsala, Sweden
3. National Veterinary and Food Research Institute, PL 92, FIN-70701 Kuopio, Finland
4. Staatliches Veterinäruntersuchungsamt Arnsberg, Zur Taubeneiche 10-12, D-59821 Arnsberg, Germany