The degree of fungal contamination, presence of mycotoxins in beehive elements, and vulnerability of healthy beehives in environments subjected and not subjected to the disease were investigated. From the contaminating fungal load, species that are mycotoxin producers and pathogenic causing mortality in the bees have been isolated. Bee bread showed the highest correlation between substrate and fungal contamination.

Studies have shown that fungal growth in the beehive, especially on the bee bread, occurs under intense water shortage. Most microorganisms responsible for the breakdown of food do not develop under low limits of Aw [water activity], a situation that favors and selects the presence of xerophilic fungal species. 

High colonization by a diversified fungal microbiota was observed with the presence of the three main mycotoxin-producing genera, namely Aspergillus, Penicillium, and Fusarium. Thus, the most commonly identified species were potential mycotoxin producing fungi. 

The rapid onset of contamination (2 weeks) is enough time for the emergence and propagation of opportunistic fungi such as Aspergillus niger aggregates and Aspergillus flavus, which are bee pathogens (Gliński and Buczek, 2003). The presence of different fungal species may create competition between the fungi and the organism, thus, unleashing pathogenicity by mycosis in the beehive.

The presence of aflatoxins in the diet of bees may cause high mortality even at concentrations below 5µg g-1. Aflatoxins act directly on the central nervous system, affect the endocrine system, and compromise the internal defense system of bees, while reducing resistance to mycotic infection (Gliński and Buczek, 2003). Hilldrup et al. (1977) verified the production of aflatoxins in low levels in samples of pollen, honeycomb (nest), larvae, and adult bees, except in unprocessed honey.

The release of mycotoxin-producing species of aflatoxins and ochratoxin A, was verified, and strains of Aspergillus flavus, which produced aflatoxin B1, were isolated. According to Hilldrup and Llewellyn (1979), Apis mellifera is the most sensitive to aflatoxin B1; however, identifying its susceptibility to other mycotoxins requires further research. 

Keller, K. M., et al. "Fungi infection in honeybee hives in regions affected by Brazilian sac brood." Arquivo Brasileiro de Medicina Veterinária e Zootecnia 66.5 (2014): 1471-1478.

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