The emergence and spillover of bumblebee parasites

Pollinators and in particular, bumblebees are currently experiencing significant declines. In Britain, bumblebee populations have been declining since the industrial revolution. Modern farming now requires large, monoculture fields to be effectively pollinated, yet the very nature of such large, homogeneous environments prevents many wild pollinators to thrive there. Since the mid-1980s bumblebees have been reared and imported on an industrial scale to aid the pollination of many valuable crops such as tomatoes and raspberry. There is great concern that the intensive rearing and importation of these bumblebees may permit the introduction of exotic parasites to native bumblebees. These concerns follow suggestions that parasite spillover from commercially reared bumblebees may be occurring; with declines of wild bumblebees in North and South America correlated with commercial bumblebee use. It’s believed that around 50, 000 bumblebee hives are imported into the UK every year and whilst they are purported to be disease free, no independent testing is carried out. Here, I assess what risk the use of commercial bumblebees has on native bees. By screening commercially reared and imported bumblebee colonies for a range of bumblebee and honey bee parasites, I identified the majority have infections. The parasites detected include the emerging diseases Apicystis bombi and Nosema ceranae which are found to be lethal to infected bumblebees. Shared flowers between bumblebees and honey bees are shown to be platforms for the dispersal of many of these parasites. The frequent mixing between domesticated and wild bumblebees allows potential transmission of these parasites. The deployment of commercial bumblebees was shown to increase parasite prevalence within local populations of wild bumblebees and when bumblebees have increased competition in the form of domesticated honey bees, they once again have higher parasite prevalence. Here I show that not only are current import regulation inadequate to avoid introducing infected bumblebees into England, but that there are clear opportunities and evidence that transmission is occurring.