A team of scientists has identified 27 new viruses that infect European honeybees (Apis mellifera) and other bee species.

“Populations of bees around the world are declining, and viruses are known to contribute to these declines. Despite the importance of bees as pollinators of flowering plants in agricultural and natural landscapes and the importance of viruses to bee health, our understanding of bee viruses is surprisingly limited,” said Dr. David Galbraith, a researcher at Pennsylvania State University.

To improve their ability to detect bee viruses, Dr. Galbraith and co-authors developed a new high-throughput sequencing technique.

“Typically, we would have to develop labor-intensive molecular assays to test for the presence of specific viruses,” said Dr. Zachary Fuller, a postdoctoral researcher at Columbia University.

“With our new method, we can sequence all the viruses present in a sample without having any prior knowledge about what might be there.”

In the new study, the researchers collected samples of DNA and RNA — which is responsible for the synthesis of proteins — in populations of 12 bee species from nine countries, across four continents and Oceania.

“Although our study nearly doubles the number of described bee-associated viruses, there are undoubtedly many more viruses yet to be uncovered, both in well-studied regions and in understudied countries,” Dr. Fuller said.

Among the new viruses they identified was one that is similar to a virus that infects plants.

“It is possible that bees may acquire viruses from plants, and could then spread these viruses to other plants, posing a risk to agricultural crops,” said Pennsylvania State University’s Professor Christina Grozinger.

“We need to do more experiments to see if the viruses are actively infecting the bees — because the viruses could be on the pollen they eat, but not directly infecting the bees — and then determine if they are having negative effects on the bees and crops.”

“Some viruses may not cause symptoms or only cause symptoms if the bees are stressed in other ways.”

To identify viruses that may be circulating among co-foraging bee populations, the team exclusively sampled foraging bees in the landscapes in the summer months.

“Beyond identifying the new viruses, we also found that some of the viruses exist in multiple bee species — such as in honeybees and in bumblebees — suggesting that these viruses may freely circulate within different bee populations,” the study authors explained.

“This finding highlights the importance of monitoring bee populations brought into the United States due to the potential for these species to transmit viruses to local pollinator populations,” Dr. Galbraith said.

The results were published in the journal Scientific Reports.

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David A. Galbraith et al. 2018. Investigating the viral ecology of global bee communities with high-throughput metagenomics. Scientific Reports 8, article number: 8879; doi: 10.1038/s41598-018-27164-z