Inapparent virus infections differentially affect honey bee flight

Honey bee colony deaths are associated with viruses, which frequently do not cause morphological symptoms in adult bees. To assess the impact of these inapparent infections, we measured flight performance as a proxy for honey bee health. We hypothesized that deformed wing virus (DWV) and/or sacbrood virus (SBV) would reduce flight performance and that coinfections would have compounding, negative impacts. We identified virus-specific effects; bees with DWV flew shorter distances at slower speeds, whereas bees with SBV flew greater distances at higher speeds. Bees with high virus loads expressed more heat shock protein 90, and SBV-infected bees expressed more octopamine β-2 receptor (Oβ-2R). Oβ-2R binds octopamine, a "fight or flight" molecule, stimulating metabolic activity, neuromuscular transmission, and movement. To examine relationships between virus infection, octopamine, and flight, we compared the flight performance of DWV-infected bees with octopamine treatment and demonstrated that octopamine negated DWV-associated flight impairment. These findings have organismal-, colony-, and ecosystem-level implications.