The last century has seen dramatic changes in the management and distribution of honey bees, bringing along a cocktail of novel stressors such as pesticides and diseases. Chief among these is the ectoparasitic mite, Varroa destructor. The emergence and global spread of Varroa has had a major impact on the health of honey bee populations worldwide. One of the most striking observations is the concurrent increase in levels of Deformed wing virus (DWV), a previously innocuous virus of honey bees, now considered to be the ultimate cause of colony loss once Varroa becomes established in a population. But the link between colony losses, Varroa and the viruses that it spreads remains correlational.
The novel association between honey bees and Varroa has led to many instances of rapid co-evolution, where isolated populations have developed mechanisms to overcome the parasitic burden of mites. However, if honey bee deaths are due to particular viruses, we might expect Varroa-resistant bee populations to exhibit different viral landscapes compared to sensitive bees. Here, I show that virus diversity in Varroa-tolerant honey bees is complex; in some cases involving extreme virus levels, strain recombination and novel virus species. I show that transmission route, RNAi immune response and viral strains may all contribute to the complex host-parasite interaction between bees and mites, leaving us with the question: are viruses the true culprit behind bee declines?
Dr Emily Remnant is a Lecturer and Academic Fellow in the Behaviour and Genetics of Social Insect lab, from the School of Life and Environmental Sciences at the University of Sydney. Her research investigates evolution in action, using genomics to explore how insects respond to strong selective pressures like parasites and pesticides. She is particularly interested in investigating novel ways to improve the health of beneficial insects like honey bees by examining host-parasite interactions, virus discovery and honey bee responses to viral disease.