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Melissococcus plutonius is a bacterial pathogen that causes epidemic outbreaks of European foulbrood (EFB) in honey bee populations. The pathogenicity of a bacterium depends on its virulence, and understanding the mechanisms influencing virulence may allow for improved disease control and containment. Using a standardized in vitro assay, we demonstrate that virulence varies greatly among sixteen M. plutonius isolates from five European countries. Additionally, we explore the causes of this variation. In this study, virulence was independent of the multilocus sequence type of the tested pathogen, and was not affected by experimental coinfection with Paenibacillus alvei, a bacterium often associated with EFB outbreaks. Virulence in vitro was correlated with the growth dynamics of M. plutonius isolates in artificial medium, and with the presence of a plasmid carrying a gene coding for the putative toxin melissotoxin A. Our results suggest that some M. plutonius strains showed an increased virulence due to the acquisition of a toxin-carrying mobile genetic element. We discuss whether strains with increased virulence play a role in recent EFB outbreaks.

-Apilife VAR®, with thymol as its main active ingredient, is registered for use against Varroa jacobsoni Oudemans in Switzerland. After Apilife VAR® treatment in autumn of 1992, the residues in honey and comb were examined the following spring. Only thymol residues were found in honey, whereas in comb the residues consisted of 99 % thymol and 1 % menthol. The thymol residues in honey did not increase with an increasing number of treatments and varied between 0.02 to 0.48 mg·kg -1 with an average of 0.15 mg·kg -1 (n = 29). The taste threshold of thymol in acacia and rape honey was between 1.1 and 1.6 mg·kg -1 . The brood comb in two apiaries, where Apilife VAR® was used for, on average, 4 consecutive years, had a mean content of 574 mg·kg -1 and this did not increase with an increasing number of treatments. The thymol residues in honey comb were on average 21.6 mg·kg -1 . Thymol did not evaporate during comb melting, but decreased rapidly when comb and foundation were exposed to the air during storage. © Inra/DIB/AGIB/Elsevier, Paris honey / wax / residue / thymol / Apilife VAR®

Various studies have shown that bee-collected pollen sold as nutritional supplements may contain toxic pyrrolizidine alkaloids (PAs) and, thus, pose a potential health risk for consumers. The level of contamination may vary according to its geographical and botanical origin. Here, the PA content of pollen produced in Switzerland was studied and 32 commercially available bee-collected pollen supplements produced between 2010 and 2014 were analysed. In addition, at what time period bees collect PA-containing pollen was investigated. Hence, this study looked into the occurrence of PAs in pollen samples collected daily during two-to-three consecutive seasons. Furthermore, the PA spectrum in pollen was compared to the spectrum found in flower heads of PA-plants to unambiguously identify plants responsible for PA contamination of pollen. The PA concentration of commercial and daily collected pollen was determined by target analysis using an HPLC-MS/MS system, allowing the detection of 18 different PAs and PA N-oxides found in the genera Echium, Eupatorium and Senecio, while the comparison of the PA spectrum in pollen and flower heads was performed by LC-HR-MS, allowing the detection of all PA types in a sample, including saturated, non-carcinogenic PAs. Of the commercially available pollen, 31% contained PAs with a mean concentration of 319 ng/g, mainly Echium- and Eupatorium-type PAs, while the PA concentrations were below the limit of quantitation (LOQ) in 69% of the pollen samples. Bees collected pollen containing Echium-type PAs mainly in June and July, while they gathered pollen containing Eupatorium-type PAs from mid-July to August. Senecio-type PAs appeared from June to September. Comparison of the PA array in pollen and plants identified E. vulgare and E. cannabinum as the main plants responsible for PA contamination of Swiss bee-collected pollen, and to a lesser extent also identified plants belonging to the genus Senecio.

Summary — Forty stingless-bee and 21 Apis mellifera honeys from Venezuela were analysed for their essential composition. The stingless bees comprised 3 Melipona and 5 Trigona species. The moisture content of the honeys from the different stingless-bee species was significantly higher than that of the A mellifera honeys. Generally, the stingless-bee honeys had a higher acidity than the A mellifera honeys. The honeys from the Melipona species had lower diastase activity than the Trigona species. There were also differences in the acidity and the ash and nitrogen content of the honeys of the different stingless-bee species, but these differences might also be due to a different floral origin. While the A mellifera honeys fulfilled the quality requirements set by the Codex Alimentarius, the honeys from the stingless bees failed to do so for several parameters, especially the quality factors such as water content, reducing sugars, acidity, and ash content.

-Formic acid and oxalic acid field trials for control of Varroa destructor were carried out in autumn according to the Swiss prescriptions during three successive years in different apiaries in Switzerland. The following parameters were determined in honey that was harvested the year after treatment: formic acid, oxalic acid and free acidity. The following range of values were found in honeys of untreated colonies: formic acid, from 17 to 284 mg/kg, n = 34; oxalic acid, from 11 to 119 mg/kg, n = 33. There was a small, but unproblematic increase in formic acid levels in comparison to the levels in the controls; average: 46 mg/kg, maximum: 139 mg/kg. No increase in formic acid was found with increasing number of treatment years. If emergency formic acid treatments were carried out in spring, the residue levels were much higher: average increase of 193 mg/kg, maximum 417 mg/kg. The oxalic acid content remained unchanged, even after two successive treatments during the same autumn. No rise of free acidity was encountered after a combined treatment with formic and oxalic acid during the three trial years.honey/residue/formic acid/oxalic acid/free acidity/Varroa destructor

BACKGROUND A national survey on pesticides in recycled beeswax originating from beekeeping has been conducted in Switzerland for almost three decades. It allowed obtaining a good overview of the lipophilic products used for beekeeping within the last 30 years. RESULTS The use of the veterinary drugs containing bromopropylate or tau‐fluvalinate two decades ago led to substantial residues in commercial beeswax. These contaminants are still detectable although in Switzerland the corresponding products have been out of use for many years. The level of coumaphos substantially increased in 2015 up to an annual value of 3.25 mg·kg−1, suggesting that at least a few beekeepers used coumaphos‐containing products. Consequently, an information campaign was launched, and the annual value decreased again. Maximal levels of thymol up to an annual value of 87.5 mg·kg−1 were measured in 2009. Since that time, a steady decrease of thymol residues suggests that beekeepers less frequently use thymol‐containing products. Twenty‐five years ago, 1,4‐dichlorobenzene (PDCB) was widely used for the control of the wax moth, resulting in residues in beeswax up to an annual value of 10.9 mg·kg−1 whereas nowadays, PDCB residues are rarely detected in Swiss beeswax. CONCLUSIONS Our survey illustrates that several beekeeping‐associated pesticides persist in recycled beeswax for many years. Most recent analyses show lower residue levels in Swiss beeswax as compared to previous years. Nowadays Swiss beekeepers mostly use hydrophilic substances for treatment against the Varroa destructor that do not accumulate in beeswax, thus reducing exposure of the honey bees to lipophilic contaminants.