 Bumblebees are parasitised by tracheal mites , <unk> <unk> ; protozoans including <unk> bombi and <unk> bombi ; and microsporidians including Nosema bombi and Nosema ceranae . The tree bumblebee B. <unk> has spread into the United Kingdom despite hosting high levels of a nematode that normally interferes with queen bees ' attempts to establish colonies . <unk> wing virus has been found to affect 11 % of bumblebees in Great Britain . 
