Virus transmission put under the microscope to improve beekeepers’ access to oversees genetics

Experiments look to improve beekeepers’ ability to import desirable genetics, by understanding how deformed wing virus is transmitted from queen bees to eggs through drone semen.

New insights into the transmission of a significant honey bee virus could pave the way for safer access to imported genetics that could help Australia’s honey bee and pollination industry adapt to varroa mite.

Breeding varroa-resistant bees using imported genetics is one approach in the suite of promising methods to manage Varroa destructor. Genetics can be imported from overseas in the form of drone (male honey bee) semen or queen bees. Desirable genetics can improve honey production and influence a range of other attributes. However, ensuring the best-possible genetics are safe from damaging viruses is critical.

Honey bee viruses, including deformed wing virus (DWV), can be transmitted to queens and their offspring through infected drone semen, which can devastate colonies. Fortunately, DWV has not been detected in Australia.

Dr John Roberts of CSIRO, co-researcher Dr Jody Gerdts of Bee Scientifics and their collaborative team are working to understand the transmission process of DWV so that beekeepers can be confident in the use of imported beneficial genetics, such as drone semen.

“DWV is common around the world. A challenge that our industry faces in trying to access overseas genetics is finding source material that is virus-free,” John explained.

“This project is looking at ways we can reduce the risk of DWV from imported overseas genetics by better understanding the transmission process.”

The researchers are interested in understanding the transmission threshold – the amount of virus that needs to be present for transmission to take place.

“We know that DWV can be transmitted vertically – from the queen bee to the offspring – through semen. But we know this doesn’t happen every time,” John said.

“We want to explore whether there is an acceptable low virus level in semen where vertical transmission won’t occur.”

A second objective is to assess the feasibility of treating drone semen with virus-targeting agents to reduce transmission risk. These agents might be specific antibodies or molecules with virus-fighting effects. This aspect will be undertaken in collaboration with Prof. Phillip Lester of Victoria University of Wellington, Dr Biko Muita of CSIRO and Dr Emily Remnant of The University of Sydney.

“If we can have a few extra approaches – including treatment options that reduce that risk of transmitting DWV – that would be a really positive outcome,” John said.

Getting on the front foot of varroa and viruses

DWV is one of the most common honey bee viruses around the world and is primarily spread through varroa mite. The virus can impact all life stages of the honey bee but one of the main symptoms is wing deformities in adult bees, which is the most obvious indicator of the virus. DWV can also result in the mass death of bee colonies.

Varroa has the potential to worsen the spread and impact of viruses like DWV, as the double threat to a colony increases the likelihood of collapse.

“Varroa causes its own damage through feeding on developing bees and weakening them, but it is much worse when there’s the spread of viruses as well,” John explained.

“DWV in particular has formed a close relationship with varroa and virus levels get very high in infected colonies.”

Varroa acts as a vector, helping to spread viruses to uninfected bees and colonies. Varroa carries DWV without any symptoms and transmits the virus to honey bees as they feed. DWV can also multiply within the body of varroa mites, further increasing the risk of infecting honey bees.

Pathogenic viruses represent a significant biosecurity threat to the industry, and as a result strict import requirements and virus testing are in place. This research aims to provide industry with more information to help overcome the barriers encountered when importing semen presented by virus testing, while still maintaining this important biosecurity measure.

This project is expected to finish in July 2026.

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