A thirty-two-year (1984–2015) longitudinal analysis of honey bee disease and pathogen prevalence in the USA

From 1984 to 2015, the Bee Disease Diagnostic Lab at the USDA-ARS Beltsville Bee Research Laboratory (MD, USA) analyzed 66,056 samples submitted for disease diagnosis, comprising 35,883 adult bees and 30,173 brood samples collected from symptomatic colonies nationwide. This dataset provided valuable insights into honey bee disease dynamics over three decades. Adult bee samples were screened for Nosema spp. and tracheal mite (Acarapis woodi). Brood samples were microscopically analyzed for the presence of both Paenibacillus larvae and Melissococcus plutonius, the causative agents of American foulbrood (AFB) and European foulbrood (EFB) diseases, respectively. Antibiotic resistance was tested in AFB-positive samples (n = 6,785) for tetracycline and tylosin. Longitudinal analysis revealed significant (p < 0.001) inter-state and seasonal differences in disease prevalence. AFB was significantly more prevalent nationwide (44.71%) compared to EFB (10.01%), with a negative correlation between the two diseases (R = -0.4, p < 0.01). P. larvae resistance to tetracycline and tylosin declined significantly (p < 0.001) in later years, with national resistance averages of 42.52% and 27.78%, respectively. Additionally, positive correlations were recorded between AFB prevalence and P. larvae resistance to both antibiotics. Nosema spp. prevalence ranged from 0% to 77.9% across states, with a national average of 24.09% and significant seasonal variations (p < 0.001). From 2008 to 2015, Nosema infection rates increased significantly, contrasting with a marked decline in tracheal mite prevalence since 2007 (national average of 12.48%), which was negatively correlated with Nosema infection (R = -0.3, p < 0.05). This study provides unprecedented longitudinal insights into honey bee disease dynamics in the United States, highlighting the significant emergence of EFB and Nosema as threats from 2008 to 2015 and a drastic reduction in tracheal mite prevalence. These findings underscore the need for continued monitoring and adaptive management strategies to protect honey bee health and ensure sustainable pollination services.