Ameliorative Effects of Phytochemical Ingestion on Viral Infection in Honey Bees

Abstract

Honey bee viruses are capable of causing a wide variety of devastating effects, but effective treatments have yet to be discovered. Phytochemicals represent a broad range of substances that honey bees frequently encounter and consume, many of which have been shown to improve honey bee health. However, their effect on bee viruses is largely unknown. Here, we tested the therapeutic effectiveness of carvacrol, thymol, p-coumaric acid, quercetin, and caffeine on viral infection by measuring their ability to improve survivorship in honey bees inoculated with Israeli acute paralysis virus (IAPV) using high-throughput cage bioassays. Among these candidates, caffeine was the only phytochemical capable of significantly improving survivorship, with initial screening showing that naturally occurring concentrations of caffeine (25 ppm) were sufficient to produce an ameliorative effect on IAPV infection. Consequently, we measured the scope of caffeine effectiveness in bees inoculated and uninoculated with IAPV by performing the same type of high-throughput bioassay across a wider range of caffeine concentrations. Our results indicate that caffeine may provide benefits that scale with concentration, though the exact mechanism by which caffeine ingestion improves survivorship remains uncertain. Caffeine therefore has the potential to act as an accessible and inexpensive method of treating viral infections, while also serving as a tool to further understanding of honey bee–virus interactions at a physiological and molecular level.

Agri-environment scheme nectar chemistry can suppress the social epidemiology of parasites in an important pollinator

“…Exposure to such compounds depends upon the duration of flowering and density of flowers, both of which can be high in AES schemes [ 20 ]. Caffeine is well known for its biological activity [ 56 , 57 , 61 , 62 ], and its impacts on N. bombi infection may be through reducing spore germination and subsequent infection success. This is likely to be enhanced in bumblebee larvae, whose blind gut may lead to an increase in caffeine concentration during the exposure period, resulting in a greater impact on the parasite and contributing to the reduction of infection prevalence and intensity recorded in adult bumblebees following eclosure.…”

Agri-environment nectar chemistry suppresses parasite social epidemiology in an important pollinator

“…Exposure to such compounds depends upon the duration of flowering and density of flowers, both of which can be high in AES schemes [20]. Caffeine is well known for its biological activity [59, 60], and its impacts on N. bombi infection may be through reducing spore germination and subsequent infection success. This is likely to be enhanced in bumblebee larvae, whose blind gut may lead to an increase in caffeine concentration during the exposure period, resulting in a greater impact on the parasite and contributing to the reduction of infection prevalence and intensity recorded in adult bumblebees following eclosure.…”

“…The alkaloid caffeine was identified at a concentration of 200μM in the nectar of sainfoin ( Onobrychis viciifolia ) using a retention time (rt) of 6.11 and a mass-to-charge ratio ( m/z ) of 195.09 from a pooled sample taken in 2017. Caffeine has been reported previously to have biological activity against microbes [59], including reducing mortality in honeybees infected with Israeli acute paralysis virus [60]. Consequently, caffeine was an ideal compound to investigate the potential impact of AES phytochemicals on N. bombi epidemiology in B. terrestris .…”

Butenolide Insecticide Flupyradifurone Affects Honey Bee Worker Antiviral Immunity and Survival

“…A 7-day trial duration was chosen because virus-induced mortality peaks 24 -48 hr after inoculation before survival levels off after, and we are focused on how pesticides affect virus-induced mortality during this time span. Previous studies have also found that IAPV-induced mortality or persistent IAPV infection can be observed well in 7 or fewer days (7,47,48,50,54). Throughout the experiments, bee mortality was monitored daily and dead bees were removed.…”

“…IAPV can cause a debilitating disease that can be lethal to all honey bee castes and development stages (49)(50)(51)(52), and has been implicated in colony failure (53). Further, it can be used for repeatable assays on survivorship that have been shown to be affected by different dietary treatments (7,47,54). Thus, we used IAPV treatments to assess the interaction of virus infection with flupyradifurone and clothianidin, and measured treatmentdependent mortality in both the spring and the fall to look for any seasonal effects.…”