A progressive honey bee population decline has been reported worldwide during the last decades, and it could be attributed to several causes, in particular to the presence of pathogens and parasites that can act individually or in synergy. The health status of nine apiaries located in different areas of the Veneto region (northeast of Italy) was assessed for two consecutive years (2020 and 2021) in spring, during the resumption of honey bee activity, for determining the presence of known (Nosema spp., Varroa mite and viruses) and less known or emerging pathogens (Lotmaria passim and Crithidia mellificae) in honey bees. After honey bees sampling from each of the nine apiaries, Nosema apis, Nosema ceranae, L. passim, C. mellificae, ABPV, CBPV, IAPV, KBV, BQCV, SBV, DWV-A, DWV-B and V. destructor were investigated either by microscopic observation or PCR protocols. The viruses BQCV, SBV, CBPV followed by N. ceranae and L. passim were the most prevalent pathogens, and many of the investigated hives, despite asymptomatic, had different degrees of co-infection. This study aimed to highlight, during the resumption of honey bee activity in spring, the prevalence and spreading in the regional territory of different honey bee pathogens, which could alone or synergistically alter the homeostasis of bees colonies. The information gathered would increase our knowledge about the presence of these microorganisms and parasites in the territory and could contribute to improve beekeepers practice.

In recent years, honey bee colony losses in the Republic of Kosovo remained largely unknown. From 2019 to 2021, 81 apiaries with different disease suspicions were investigated in the framework of honey bee disease passive surveillance. Fifty-nine of the eighty-one apiaries were tested for Vairimorpha ceranae, Vairimorpha apis, trypanosomatids Lotmaria passim, and Crithidia mellificae. All samples were positive for V. ceranae (100%) whereas L. passim was found with a lower frequency (11.9%). V. apis and C. mellificae were not found. Thirteen of the eighty-one apiaries were tested for seven viruses (ABPV, CBPV, DWV, BQCV, SBV, IAPV, KBV) and five of them were found (ABPV, CBPV, DWV, BQCV, SBV). The most frequently detected viruses in honey bees and Varroa mites were DWV (100%) followed by BQCV, ABPV, SBV, and CBPV (92.3%, 69.2%, 30.8%, and 7.7%, respectively). Varroa mite samples had different degrees of co-infection by viruses. Nine of the eighty-one apiaries consisted of brood combs with larvae, eight of them were AFB positive, ERIC I genotype, and one EFB positive. This paper represents the first molecular investigation (PCR) and detection of the honey bee viruses ABPV, CBPV, DWV, BQCV, and SBV as well as V. ceranae, L. passim, and M. plutonius in the Republic of Kosovo.

Honey bees are valuable bioindicators of environmental contamination due to their wide foraging range and exposure to diverse biotic and abiotic stressors. This study evaluates the use of honey bees as bioindicators for detecting per- and polyfluoroalkyl substances (PFASs) in areas with varying levels of exposure risk (high-, intermediate-, and low-), as well as their potential effects on gut-microbial communities. Analytical chemistry to detect PFASs and pesticide residues were combined with molecular and metagenomic analyses to identify common honey bee pathogens and characterize gut-microbial communities. Short-chain PFASs were predominated over long-chain compounds, particularly in high-risk areas, while pesticide residues occurred in only a few apiaries. Molecular analyses revealed several widespread pathogens, while metagenomics showed a stable gut microbiome mainly composed of the genera Lactobacillus, Bartonella, Bombilactobacillus, Snodgrassella, Gilliamella, Bifidobacterium, and Gluconacetobacter. However, microbial-community composition differed significantly between apiaries with high- versus low-risk PFAS exposure. These results support honey bees as effective bioindicators for environmental PFAS monitoring and suggest that PFAS exposure may be associated with alterations in their gut-microbial communities. Further research is needed to elucidate the impact of PFASs on honey bee toxicity, gut-microbiota composition, and overall health.