3. Future perspectives

Chalkbrood and stonebrood diseases have been recognized for more than a century, but there is still much that remains to be discovered regarding these diseases and their impact on the general health status of honey bees. The numbers of studies of the two diseases reflects their frequency and abundance, with a magnitude difference in favour of chalkbrood.

The genome of A. apis was published in 2006 (Qin et al., 2006), and although the full annotation is still lacking, it will be useful for future research investigations on the expression of genes important for the infection and virulence of A. apis. Chalkbrood is a stress related disease and a recent longitudinal cohort study based on monitoring data collected over six years indicated that colonies with high numbers of varroa mites in the same season or Nosema ceranae infection in the spring had significantly higher chances of chalkbrood outbreaks (Hedtke et al., 2011). Such a correlation needs experimental confirmation, but it elucidates the complexity of the host-pathogen-interaction in honey bee colonies. Research on the interaction with other pathogens and stressors, such as sublethal concentration of various chemicals, is also warranted.

Aspergillus research is mostly focused on human health and food spoilage due to aflatoxin contamination of grains. Stonebrood outbreaks are rarely observed in honey bee colonies, but should not be underestimated. Their rarity could be a result of honey bees removing the stonebrood infected individuals very quickly, an area of research that has not been previously investigated. Furthermore, the basic biology of stonebrood is still poorly understood, and several studies elucidating stonebrood etiology are still to be performed. Aspergillus spp. spores are present everywhere and a high virulence towards honey bee larvae have been shown. Even though stonebrood is rarely reported, it would be interesting to understand which factors and mechanisms might play a role in the establishment and resistance of this disease.