Draper, Jenny, Ministry for Primary Industries, Investigation and Diagnostic Centre, Animal Health Laboratory, 66 Ward Street, Wallaceville, Upper Hutt, New Zealand Present address: Institute of Environmental Science and Research Limited (ESR), Kenepuru Science Centre, 34 Kenepuru Drive, Kenepuru, Porirua 5022, PO Box 50348, Porirua 5240, New Zealand