Detection of honey bee pathogenic viruses in Argentine ants Linepithema humile (Hymenoptera: Formicidae) invading Japan

The spillover and spillback of pathogens caused by invasive alien species represent a cryptic and significant risk. Honey bees, vital ecological and economic pollinators, face threats from numerous pathogens. Recently, honey bee pathogenic viruses have been identified in various arthropods, including ants, which are phylogenetically close to honey bees, raising concerns about non-honey bee insects transmitting these viruses. Argentine ants Linepithema humile Mayr (Hymenoptera: Formicidae), a globally invasive species, have been expanding their range in Japan since their first detection in 1993. This study attempted to detect four pathogenic viruses frequently detected in and may cause serious damage to the western honey bees Apis mellifera Linnaeus (Hymenoptera: Apidae) in Japan from Argentine ants invading managed hives of the honey bees. Quantitative PCR targeting four honey bee pathogenic DNA and RNA viruses detected Apis mellifera filamentous virus (AmFV) and black queen cell virus (BQCV) in Argentine ants attacking hives, with copy numbers ranging from 10¹–10² and 10³–10⁴, respectively. The copy number of deformed wing virus and sacbrood virus was below the detection limit. Homology searches of capsid protein-encoding genes and phylogenetic analysis revealed that all BQCV sequences from this study were most homologous to those previously identified in managed honey bees in Japan. However, AmFV sequences could not be obtained, likely due to the low copy number. These findings suggest that Argentine ants may act as a vector of AmFV and BQCV, raising concerns about their potential impact on the beekeeping industry.