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Plant compound may help diseased honeybees find their way home

Honeybees can be infected by a virus that makes their wings develop in an abnormal manner and causes them to fly poorly, or even lose their ability to fly altogether. The infection has also been shown to affect the ability of bees to learn and remember, which means that they may lose their way and not return home after a foraging trip. Bees that do not return to the hive at night are likely to die.

Bee colonies have been declining in number globally, and this has serious consequences for the pollination of important food crops. Scientists suggest this decline is due, in part, to the effects of the numerous different pathogens that infect bees. 

The results of a recent study, published in the journal iScience, indicate that a cheap, naturally occurring compound can prevent and even reverse the effects of Deformed Wing Virus (DWV) on infected honeybees. 

“Pathogens are definitely a stressor for bees,” said study first author Cheng-Kang Tang at National Taiwan University. “But the beekeepers don’t want to use pesticides because of food safety concerns. So, we set out to find some compounds that can increase the strength of bees.”

The scientists found that DWV suppresses the expression of genes associated with nerve impulse transmission and other processes related to learning and memory in bees. Past research has shown that feeding aged mice with sodium butyrate (NaB), a common compound found in plants and in human intestines, can significantly improve their memories. Furthermore, NaB is known to increase the expression of genes in a range of different animals. 

A previous study by the same authors demonstrated that including NaB in the diet of honeybees resulted in a significant increase in the expression of genes involved in immunity as well as in learning and memory. NaB also restored learning ability in bees that had been treated with neonicotinoid, an ingredient in some pesticides. Therefore, the researchers set out to test whether adding NaB to the diet of honeybees would improve their ability to resist the effects of infection with DWV. 

A team led by Yueh-Lung Wu at National Taiwan University initially fed bees with NaB-laced sugar water for a week before infecting them with DWV. More than 90 percent of these bees remained alive after five days, while 90 percent of the infected bees that didn’t get NaB died over the same period.

“Our findings show that feeding the insects with NaB before virus exposure can counteract the negative impacts of the pathogen,” said Wu. “We also found previously that NaB can upregulate some immune response genes in bees, and this can help suppress viral replication and improve bees’ chances at survival.”

After finding this result, Wu’s team monitored the numbers of bees leaving and returning to several different beehives on a bee farm. The data, collected over a month, showed that in hives infected with DWV, only half of the foraging bees managed to return to the hive, while more than 80 percent of the bees fed with NaB sugar water were able to return.  

“It is a really interesting study because we tested the effect of NaB on bees across different scales, from the genetic level, to behaviors in the lab, then in the field under a natural scenario,” said Wu. 

“Sodium butyrate is really cheap. So, if we can prove its benefits, it would be an easy and affordable approach for beekeepers to keep their bees. Honeybees are important pollinators of myriad fruits and vegetables with economic importance worldwide and therefore are crucial for maintaining the balance of the ecosystem”

By Alison Bosman, Staff Writer

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