2.1. Introduction

Stonebrood is a very rare honey bee brood disease caused by several fungi from the genus Aspergillus. The disease was first described by Massen (1906) and has since then been found worldwide. Aspergillus flavus has most frequently been reported, followed by Asp. fumigatus, but also Asp. niger and other species can kill honey bees (Gilliam and Vandenberg, 1997). Aspergillus is able to infect the host through the gut if the spores are ingested, but also through the cuticle. Therefore, adults as well as larvae and pupae can become infected. In addition, most species of Aspergillus produce aflatoxins that have been suggested to be the primary cause of death in stonebrood infected honey bees (Burnside, 1930). However, a non-aflatoxin producing Asp. flavus strain has been observed to induce stonebrood symptoms equally well in in vitro reared honey bee larvae as afaltoxin producing strains (Vojvodic, unpublished).

Aspergillus spp. are cosmopolitan filamentous fungi often found in soil, where they thrive as saprophytes, but occasionally they do infect living hosts including, plants, insects and mammals. Aspergillus can infect human lungs, eyes, pharynx, skin and open wounds, but most commonly this has been observed in immune deprived individuals (Gefter, 1992; Germaud and Tuchais, 1995; Denning, 1998; Galimberti et al., 1998; Garret et al., 1999). In addition, the alfatoxins are carcinogenic if inhaled or ingested; therefore precautions need to be taken when stonebrood disease occurs in honey bees principally to protect beekeepers and consumers. In several countries stonebrood is a notifiable disease that has to be reported to the authorities if it occurs.