The Prevalence of Parasites and Pathogens in Asian Honeybees Apis cerana in China

Pathogens and parasites represent significant threats to the health and well-being of honeybee species that are key pollinators of agricultural crops and flowers worldwide. We conducted a nationwide survey to determine the occurrence and prevalence of pathogens and parasites in Asian honeybees, Apis cerana, in China. Our study provides evidence of infections of A. cerana by pathogenic Deformed wing virus (DWV), Black queen cell virus (BQCV), Nosema ceranae, and C. bombi species that have been linked to population declines of European honeybees, A. mellifera, and bumble bees. However, the prevalence of DWV, a virus that causes widespread infection in A. mellifera, was low, arguably a result of the greater ability of A. cerana to resist the ectoprasitic mite Varroa destructor, an efficient vector of DWV. Analyses of microbial communities from the A. cerana digestive tract showed that Nosema infection could have detrimental effects on the gut microbiota. Workers infected by N. ceranae tended to have lower bacterial quantities, with these differences being significant for the Bifidobacterium and Pasteurellaceae bacteria groups. The results of this nationwide screen show that parasites and pathogens that have caused serious problems in European honeybees can be found in native honeybee species kept in Asia. Environmental changes due to new agricultural practices and globalization may facilitate the spread of pathogens into new geographic areas. The foraging behavior of pollinators that are in close geographic proximity likely have played an important role in spreading of parasites and pathogens over to new hosts. Phylogenetic analyses provide insights into the movement and population structure of these parasites, suggesting a bidirectional flow of parasites among pollinators. The presence of these parasites and pathogens may have considerable implications for an observed population decline of Asian honeybees.