Scientists agree that the parasitic mite Varroa is one of the main threats facing honey bees worldwide. It has been known for some time that the mite kills bees by transmitting virus diseases in much the same way as a mosquito transmits malaria. Now scientists have identified a virulent strain of virus associated with those bee colonies which die.

Dr Stephen Martin of the University of Sheffield who led the work says: “Just 2,000 mites can cause a colony containing 30,000 bees to die. The mite is the biggest problem worldwide for bee keepers; it is responsible for millions of colonies being killed. Understanding the changing viral landscape that honey bees and other pollinators face will help beekeepers and conservationists worldwide protect these important insects. We have discovered what happens at the start of an infection. The goal is to understand how the infection comes about so that we can control it."

Working in Hawaii, where the mite has only recently become established, the scientists showed how the Varroa mite caused deformed wing virus (DWV), a known viral pathogen, to increase its frequency amongst honey bee colonies from 10 per cent to 100 per cent. This change was accompanied by a million-fold increase in the number of virus particles infecting each honey bee and a massive reduction in viral strain diversity leading to the emergence of a single virulent DWV strain.

IBRA Science Director and JAR Senior Editor Norman Carreck says: “This is important work which uses cutting edge molecular techniques to improve our understanding of how the mite kills honey bee colonies. Only by fully understanding the biology of the mite and the viruses that it transmits can we develop effective strategies for its control”.