Honey bee stocks exhibit high levels of intra-colony variation in viral loads

Colonies of the western honey bee, Apis mellifera L., are comprised of tens of thousands of genetically related individuals that can easily share and spread pathogens. Honey bee colonies exhibit variations in disease susceptibility that can translate into highly variable pathogen replication among individuals within a colony, between colonies, and between stocks. Here, we investigate the degree of variation in viral titers of common honey bee viruses (DWV-A, DWV-B, IAPV, LSV2, BQCV) within colonies and between colonies of five honey bee stocks in the United States. Our results showed high intra-colony variation in DWV-A, DWV-B, IAPV, and LSV2, but not in BQCV titers. However, the level of variation was not consistent across stocks. Here, we empirically demonstrate that there is significant intra-colony variation in viral titers and that some stocks are more prone to this variability. Our results highlight the need for further studies comparing virus susceptibility among stocks.