While the prevalence of pests and diseases in managed bee colonies has been widely analyzed in the UK, no studies to date have considered the wider pathogen burden in wild swarms, mainly because of the difficulty in locating and sampling colonies which often nest in inaccessible locations such as church spires and tree tops.
A research team around Catherine E. Thompson from the University of Leeds has now published the results of their pioneer study conducted in 2010, to compare feral pathogen levels with those of local managed honey bee colonies.
They conclude that the prevalence and quantity for the majority of pathogens is similar in the two groups, but that feral honey bees contain a significantly higher level of the Deformed Wing Virus (DWV) than managed colonies. These extremely high values of Deformed Wing Virus would be expected to lead to colony mortality, say the scientists, adding that it is not clear whether feral colonies have novel mechanisms to resist such high levels of DWV.
The researchers suggest that these findings might explain the large fall in the feral population since the arrival of the Varroa mite in 1992.
They also underline the importance of feral colonies as potential pathogen reservoirs for infection of managed colonies, urging UK beekeepers not to abandon Varroa control, particularly in areas of high beekeeping density.