Sacbrood Virus: The First Honey Bee Virus Discovered

Thursday 12 August 2021

Continuing our series of varroa-related honey bee viruses that kicked off last week, this week we take a closer look at a virus which attacks honey bees in the larval stage. Sacbrood virus (SBV) is another honey bee virus that is associated with varroa mite infestations. As we better our understanding of these viruses, including how they are vectored and what they are associated with, we can work to also better our beekeeping habits and management practices. This will ensure we are keeping our honey bee colonies as healthy and strong as possible.

Announcement: A new ATTTA beekeeping podcast episode is out. Keep reading to get a sneak peek into what topics are included this time on our conversational tour of all things honey bees and beekeeping!

We are also excited to announce that we are a part of Perennia's Virtual Field Days online event this year! We have prepared a short video, titled 'Honey Bees as Pollinators: Importance and Determination of Colony Strength', that will be featured on Tuesday August 17thThere is no charge to participate in this event, but registration is required. Full details and registration can be found HERE.

Sacbrood Virus: The First Honey Bee Virus Discovered

Sacbrood virus (SBV) was the first honey bee virus to be detected. It was first discovered in 1913 and has since been dispersed globally, with perhaps the most expansive distribution of all honey bee viruses. Symptoms of this honey bee virus are most prevalent in the spring before the first nectar flow or during a long period of dearth and typically disappear later in the spring or with the onset of a nectar flow. Viral particles of SBV have been observed in honey bees of all castes and all life stages, in honey bee foods both gathered (i.e., nectar and pollen) and produced (i.e., hypopharyngeal glands of nurse bees feeding brood), and in varroa mites. Knowing these hosts and locations that can harbor SBV particles highlights the wide range of transmission routes this virus can take in the infection of a honey bee colony.

Once a larva becomes infected by SBV, its skin turns leathery and sac-like, making the larva unable to pupate and continue its development. Instead, the larva dies and degrades over time until it is a sac-like container filled with fluid containing millions of infectious virus particles. Then, the honey bees responsible for keeping the hive tidy and taking care of brood step in to remove the failed larva from its cell to prepare the cell for its next use. During this removal and cleaning process, depending on the degradation stage of the larva, the adult bee may become a harbor for SBV particles through accidental ingestion of virus particles from accumulation of fluid in the ‘larva sac’. There are no obvious signs of infection in adult bees, however, SBV particles accumulate in the hypopharyngeal gland within the bee’s head and the bee’s lifespan may be shortened. From here, the SBV-harboring adult bees can infect other larvae with SBV particles through feeding and infect other adult bees through the exchange of food. Foraging bees can also harbor SBV particles and act as a route of transmission as they mix glandular secretions to collected pollen that will ultimately be fed to and infect more developing larvae.

Figure 1: Sacbrood infected pupa. Photo: Michael E. Wilson

In addition to these transmission routes, varroa mites are often associated with and may be a vector of SBV. In a past study, researchers observed a positive correlation between SBV levels(?) in varroa mites and adult bees, but no definite causal relationship has been discovered (Tantillo et al, 2015). In addition to mites being a potential route of SBV transmission, a varroa mite infestation can weaken a colony substantially and allow a more detrimental impact to occur with the onset of a SBV infection. More research is required to better understand the association between SBV and varroa mites.

Tantillo,G., M. Bottaro, A. Di Pinto, V. Martella, P. Di Pinto, V. Terio (2015) Virus infections of honeybees Apis Mellifera, Italian journal of food safety., 4. Available ONLINE.

What’s the Buzz with ATTTA Beekeeping Podcast: Episode 7

If a person could be labelled as a honey scientist that person would be Dr. Peter Awram. Peter is a second-generation beekeeper, originally from Alberta but now living in the Fraser Valley area of British Columbia. From this location, Peter continues his family beekeeping operation and runs a food authenticity business. With a background in microbiology and knowledge of beekeeping, Peter has a unique skill set that has allowed him to develop the use of Nuclear Magnetic Resonance for the identification of fraudulent honey. This work uses cutting-edge technology to profile Canadian honey, creating a database to determine the authenticity, floral sources and regionality of our honey. To find out how you could be part of Peter’s research related to honey fraud preventions, listen to this episode of the What’s the Buzz with ATTTA Beekeeping Podcast. Available ONLINE.

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