Microsporidia: An Emerging Threat to Bumblebees?

Microsporidia may cause emerging infectious diseases (EIDs) in bumblebees. Two drivers - commercial bumblebees and managed honey bees - have been identified as possible sources of pathogen spillover. In addition, declines in bumblebee populations may have led to lower genetic diversity and subsequent higher susceptibility to infection, enabling microsporidia to increase in prevalence. There is strong evidence for relatively recent increases in the prevalence of Nosema bombi in North America. However, the lack of definitive data on spillover by microsporidia, in North America or elsewhere, makes it difficult to identify the causes of such increases. Phylogenomic studies are urgently needed to identify the global population structure of microsporidia in bumblebees, and thus identify the source of current and future epidemics.