Interspecific transfers of viruses between the western honey bee (Apis mellifera) and the eastern honey bee (Apis cerana) are rare, even if honey bees are kept in close proximity, new research reveals.

Elevated global losses of managed western honey bee colonies have worried beekeepers, scientists, and the general public in recent years. Viruses play a key role in western honey bee health but few studies have investigated virus transfer between bee species. In contrast to some parts of Asia, where many bee species live concomitantly, the western honey bee had been isolated for millions of years and adapted to a range of endemic pathogens and parasites. The introduction of the western bee into Asia, enabling beekeepers to benefit from its high honey yields, exposed Asian bee species to the risk of obtaining new viruses or viral strains and vice versa.

A new study published in Journal of Apicultural Research monitored single and mixed-species apiaries, hosting western bees and the native Asiatic bees, over three years to investigate virus prevalence, and the potential for transmission between species.

Deformed wing virus (DWV), Israeli acute paralysis virus (IAPV), black queen cell virus, (BQCV) and sacbrood virus (SBV) were found among the bees in the Zhejiang Province of China; virus infections and prevalence were generally lower in eastern bees compared to western bees. The sequence data provided evidence for possible interspecific transfer of DWV, IAPV and BQCV, but SBV strains were species-specific. However, given the low prevalence of these viruses, researchers were not able to detect evidence of recent or frequent transfers within the mixed-species apiaries screened. This suggests that such exchanges are infrequent and that the proximity of colonies does not necessarily imply interspecies virus transfer.

Thus, the researchers conclude, interspecific transfers of viruses among honey bees are rare, even if bees are kept in close proximity. Vincent Dietemann, one of the authors of the study, states that “this is surprising: given the labile nature of viruses one could expect easy transmission between the closely related honey bee species. However, the apparent rarity of such transfers is certainly a good news for global apiculture given the already too numerous foreign pathogens spreading due to trade”.