Honeybee health in Africa—a review

Honey bees (Apis mellifera) play a critical role in global food production as pollinators of numerous crops. Recently, honey bee populations in the United States, Canada, and Europe have suffered an unexplained increase in annual losses due to a phenomenon known as Colony Collapse Disorder (CCD). Epidemiological analysis of CCD is confounded by a relative dearth of bee pathogen field studies. To identify what constitutes an abnormal pathophysiological condition in a honey bee colony, it is critical to have characterized the spectrum of exogenous infectious agents in healthy hives over time. We conducted a prospective study of a large scale migratory bee keeping operation using high-frequency sampling paired with comprehensive molecular detection methods, including a custom microarray, qPCR, and ultra deep sequencing. We established seasonal incidence and abundance of known viruses, Nosema sp., Crithidia mellificae, and bacteria. Ultra deep sequence analysis further identified four novel RNA viruses, two of which were the most abundant observed components of the honey bee microbiome (∼1011 viruses per honey bee). Our results demonstrate episodic viral incidence and distinct pathogen patterns between summer and winter time-points. Peak infection of common honey bee viruses and Nosema occurred in the summer, whereas levels of the trypanosomatid Crithidia mellificae and Lake Sinai virus 2, a novel virus, peaked in January.

Viruses are significant threats to the health and well-being of the honey bee, Apis mellifera. To alleviate the threats posed by these invasive organisms, a better understanding of bee viral infections will be of crucial importance in developing effective and environmentally benign disease control strategies. Although knowledge of honey bee viruses has been accumulated considerably in the past three decades, a comprehensive review to compile the various aspects of bee viruses at the molecular level has not been reported. This chapter summarizes recent progress in the understanding of the morphology, genome organization, transmission, epidemiology, and pathogenesis of honey bee viruses as well as their interactions with their honey bee hosts. The future prospects of research of honey bee viruses are also discussed in detail. The chapter has been designed to provide researchers in the field with updated information about honey bee viruses and to serve as a starting point for future research.