Deformed wing virus in imported honey: Reducing the risk to our bees

Deformed wing virus (DWV) is one of the most damaging honey bee viruses internationally, especially in countries with varroa mite (Varroa destructor), which acts as a vector. While DWV is yet to be detected in Australian honey bee colonies, researchers investigated whether imported honey could provide another pathway for the virus to reach Australian bees. Understanding this risk pathway and prevention options is especially important now that varroa is established in Australia.

The research project, led by Dr John Roberts (CSIRO) and funded by the AgriFutures Honey Bee & Pollination Program , found the transmission risk of DWV via imported honey to be low, but not impossible, reinforcing its continued threat to the industry.

“With varroa now established in Australia, an incursion of DWV could have serious consequences for colony health and industry productivity. Our findings give us a clearer picture of the risk and where our biosecurity efforts should be focused,” John said.

Australia imports more than 8,000 tonnes of honey each year. While biosecurity measures such as heat treatment are used to limit the introduction of bee diseases to Australia through imported honey, bee viruses are not routinely considered in honey import regulations, despite their importance to colony health, and especially now that varroa is established in Australia.

To understand the risks of DWV entering Australia via honey imports, the research team tested commercial imported honeys, purchased from Australian supermarkets and online. The samples originated from New Zealand, the United States, Brazil, Greece and India and included both raw and processed honey. The team also tested Australian honey, which produced negative results for DWV.

The imported honey was first screened for the virus using qPCR methods, which found that most raw or minimally processed samples contained virus levels that may be near or below the level required for DWV infection.

To determine whether bees consuming the contaminated honey could become infected, researchers conducted feeding trials under strict quarantine conditions. In the trials, researchers injected infected honey into bee pupae and fed it to adult bees to test whether the virus could be detected in the bees afterwards.

The trials did not result in infection in bee pupae. In adult bees, one trial produced a weak positive result with the virus level detected being extremely low, and the result could not be reproduced in a second trial. The results suggest that while DWV can be present in imported raw honey, transmission through feeding may be unlikely under real-world conditions.

The research also found no DWV in the processed honey samples tested. This indicates that heat treatment and filtration can effectively reduce the risk of DWV contamination in honey.

Keeping bee viruses at bay

Whilst the risk of transmission of DWV through imported honey is low, the establishment of DWV in Australia could have severe consequences for colony health and industry productivity. A risk-based approach to biosecurity measures for honey imports, with a particular focus on raw and minimally processed honey products, was recommended by the researchers. This should include reviewing current honey import pathways and policies through a bee virus lens, alongside ongoing surveillance and testing of imported and domestic honey to help detect any change in risk early. Quarantine regulations in Western Australia currently prevent import of raw honey into the state, however none of the eastern states have this regulation.

“Ongoing virus surveillance of imported and domestic honey would further strengthen biosecurity confidence,” John explained. “Monitoring virus prevalence and levels in imported honey would provide early warning of any change in risk, while also offering opportunities to integrate virus screening into honey authenticity and quality testing programs.”