Temporal and spatial distributions of pathogens in managed Florida honey bee (Apis mellifera) colonies

Western honey bee (Apis mellifera) pathogens are a major concern for beekeepers and pose a significant threat to colony health. From January - December 2024, adult honey bees were sampled monthly by beekeepers in twenty counties distributed throughout Florida. Honey bees from each colony sample were analyzed using PCR (all pathogens) and microscopy (Nosema spp. only) to determine the temporal and spatial distribution of the following honey bee pathogens: Ascosphaera apis, Crithidia mellificae, Melissococcus plutonius, Malpighamoeba mellificae, Lotmaria passim, Nosema apis, Nosema ceranae, and Apis mellifera filamentous virus (AmFV). In total, 710 samples were collected, of which 4.4% were positive for A. apis, 65.5% were positive for L. passim, 25.5% were positive for M. plutonius, 85.5% were positive for N. ceranae, <0.01% were positive for M. mellificae, and 97.4% were positive for AmFV. Crithidia mellificae and N. apis were not detected in any of the samples. There were significant differences in the prevalence of L. passim, M. plutonius, and N. ceranae pathogen load based on the time of year and location of the colony, with pathogens trending towards higher abundance in summer. These data highlight the need to augment monitoring efforts to determine the geographic and seasonal distribution of pathogens that infect honey bees.