Two non-threatening viral infections in adult honeybees are surprisingly covert and might disrupt their flying ability. One virus enhances speed, while the other acts as a brake.

Bees face a continual fight against infectious fungi, bacteria, mites, and viruses, many of which pose a threat to entire colonies. However, not all pathogens are equally harmful. For instance, both the deformed wing virus (DWV) and the sacbrood virus (SBV) can lead to severe symptoms if they infect honeybees during their early development. Despite being linked to increased mortality and a decrease in colony size, infection in adult honeybees is often viewed as asymptomatic. Michelle Flenniken from Montana State University and her team questioned whether these viruses were truly harmless.

The researchers studied bee health through their flight capabilities and infected bees with either DWV or SBV. After three days, the bees were tethered to a device resembling a set of small balls, forcing them to fly in circles. A total of 240 bees were observed, and the team measured their flight speed, duration, and distance.

Flenniken and her colleagues found that bees infected with DWV flew at slower speeds compared to uninfected counterparts. Conversely, those infected with SBV exhibited enhanced flight performance. The team predicts that bees with high DWV levels will cover 49% shorter distances than healthy honeybees. In contrast, severely infected SBV bees could experience a flight range increase of up to 53%. “SBV infections are detrimental to larvae and typically harm overall colony health,” says Flenniken.

This research reshapes our understanding of the subtle and odd impacts stealth infections can have on honeybee behavior. Other pathogens are known to influence bee actions. For instance, the Kako virus, a distinct variant of DWV, may provoke more aggressive behavior in bees, as noted by Eugene Riabov, who was not part of this research at the James Hutton Institute in the UK.

“It’s fascinating to observe how members of both DWV and SBV, which are closely related, exhibit such contrasting effects on honeybee aerodynamics,” remarks Riabov.

By disrupting bees’ ability to fly and collect nectar, viruses like DWV could negatively affect their pollination of nearby plants, complicating their foraging efforts. Consequently, as bees struggle, the implications reverberate throughout the entire ecosystem.