Special Issue: “Infection in Honey Bees: Host–Pathogen Interaction and Spillover”

Honey bee health is a very important topic that has recently raised the interest of researchers [...]

Effects of Planted Pollinator Habitat On Bee Health And Interspecific Pathogen Detection

Shared resources can instigate pathogen spread due to large congregations of individuals in both natural and human modified resources. Of concern is the addition of pollinator habitat in conservation efforts as it attracts bees of various species, potentially instigating interspecific sharing of pathogens. Common pathogens have been documented across a wide variety of pollinators with shared floral resources instigating their spread in some, but not all, cases. To evaluate the impact of augmented pollinator habitat on bee health, we screened samples from eight bee species across three families against a panel of 9 pathogens using RT-qPCR. While we found that some habitat characteristics influenced pathogen detection, we found no evidence that pathogen detection in one bee species was correlated with pathogen detection in another. These findings suggest factors other than the habitat itself may be more critical in the dissemination of diseases among bee species. However, we found high levels of gut parasites in some bee species which may be of concern, such as Bombus pensylvanicus. Future monitoring of bee health at augmented pollinator habitat is needed to ensure pathogens do not build up over time to then spread within their communities.

Phylogenomic analyses of Snodgrassella isolates from honeybees and bumblebees reveals taxonomic and functional diversity

Snodgrassella is a Betaproteobacteria genus found in the gut of honeybees (Apis spp.) and bumblebees (Bombus spp). It is part of a conserved microbiome that is composed of few core phylotypes and is essential for bee health and metabolism. Phylogenomic analyses using whole genome sequences of 75 Snodgrassella strains from 4 species of honey bees and 14 species of bumblebees showed that these strains formed a monophyletic lineage within the Neisseriaceae family, that Snodgrassella isolates from Asian honeybees diverged early on from the other species in their evolution, that isolates from honeybees and bumblebees were well separated and that this genus consists of at least seven species. We propose to formally name two new Snodgrassella species that were isolated from bumblebees, i.e. Snodgrassella gandavensis sp. nov. and Snodgrassella communis sp. nov. Possible evolutionary scenarios for 107 species or group specific genes revealed very limited evidence for horizontal gene transfer. Functional analyses revealed the importance of small proteins, defense mechanisms, amino acid transport and metabolism, inorganic ion transport and metabolism and carbohydrate transport and metabolism among these 107 specific genes.ImportanceThe microbiome of honeybees (Apis spp.) and bumblebees (Bombus spp.) is highly conserved and represented by few phylotypes. This simplicity in taxon composition makes the bee’s microbiome an emergent model organism for the study of gut microbial communities. Since the description of the Snodgrassella genus, which was isolated from the gut of honeybees and bumblebees in 2013, a single species, i.e. Snodgrassella alvi, has been named. Here we demonstrate that this genus is actually composed of at least seven species, two of them (Snodgrassella gandavensis sp. nov. and Snodgrassella communis sp. nov.) being formally described in the present publication. We also report the presence of 107 genes specific to Snodgrassella species, showing notably the importance of small proteins and defense mechanisms in this genus.Data summaryCornet L and Vandamme P, European Nucleotide Archive (ENA), Project accession: PRJEB47378Cornet L and Vandamme P, European Nucleotide Archive (ENA), Reads accessions: SAMEA9570070 - SAMEA9570078Cornet L and Vandamme P, European Nucleotide Archive (ENA), Genome accessions: GCA_914768015, GCA_914768025, GCA_914768035, GCA_914768045, GCA_914768055, GCA_914768065, GCA_914768075, GCA_914768085, GCA_914768095.

Sub-lethal pesticide exposure erases colour vision memory and affects flower constancy in foraging honey bees

Neonicotinoid pesticide use has increased around the world despite accumulating evidence of their potential detrimental sub-lethal effects on the behaviour and physiology of bees, and its contribution to the global decline in bee health. Whilst flower colour is considered as one of the most important signals for foraging honey bees, the effects of pesticides on colour vision and memory retention remain unknown. We trained free flying foragers to an unscented artificial flower patch presenting yellow flower stimuli to investigate if sub-lethal levels of imidacloprid would disrupt the acquired association made between flower colour and food reward. We found that for concentrations higher than 4% of LD50 foraging honey bees no longer preferentially visited the yellow flowers and bees reverted back to baseline foraging preferences for blue flowers, with a complete loss of flower constancy. Higher pesticide dosages also resulted in a significant decrease in CaMKII and CREB gene expression, revealing a plausible mechanism to explain the disruption of bee foraging performance. Within important bee pollinators, colour vision is highly conserved and essential for efficient nutrition collection and survival. We thus show that to maintain efficient pollination services bees require environments free from neonicotinoid pesticides.

Loss and Gain of Gut Bacterial Phylotype Symbionts in Afrotropical Stingless Bee Species (Apidae: Meliponinae)

Stingless bees (Apidae: Meliponini) are the most diverse group of corbiculate bees and are important managed and wild pollinators distributed in the tropical and subtropical regions of the globe. However, little is known about their associated beneficial microbes that play major roles in host nutrition, detoxification, growth, activation of immune responses, and protection against pathogens in their sister groups, honeybees and bumble bees. Here, we provide an initial characterization of the gut bacterial microbiota of eight stingless bee species from sub-Saharan Africa using 16S rRNA amplicon sequencing. Our findings revealed that Firmicutes, Actinobacteria, and Proteobacteria were the dominant and conserved phyla across the eight stingless bee species. Additionally, we found significant geographical and host intra-species-specific bacterial diversity. Notably, African strains showed significant phylogenetic clustering when compared with strains from other continents, and each stingless bee species has its own microbial composition with its own dominant bacterial genus. Our results suggest host selective mechanisms maintain distinct gut communities among sympatric species and thus constitute an important resource for future studies on bee health management and host-microbe co-evolution and adaptation.

Screening of Honey Bee Pathogens in the Czech Republic and Their Prevalence in Various Habitats

Western honey bee (Apis mellifera) is one of the most important pollinators in the world. Thus, a recent honey bee health decline and frequent honey bee mass losses have drawn attention and concern. Honey bee fitness is primarily reduced by pathogens, parasites, and viral load, exposure to pesticides and their residues, and inadequate nutrition from both the quality and amount of food resources. This study evaluated the prevalence of the most common honey bee pathogens and viruses in different habitats across the Czech Republic. The agroecosystems, urban ecosystems, and national park were chosen for sampling from 250 colonies in 50 apiaries. Surprisingly, the most prevalent honey bee pathogens belong to the family Trypanosomatidae including Lotmaria passim and Crithidia mellificae. As expected, the most prevalent viruses were DWV, followed by ABPV. Additionally, the occurrence of DWV-B and DWV-C were correlated with honey bee colony mortality. From the habitat point of view, most pathogens occurred in the town habitat, less in the agroecosystem and least in the national park. The opposite trend was observed in the occurrence of viruses. However, the prevalence of viruses was not affected by habitat.

No evidence of effects or interaction between the widely used herbicide, glyphosate, and a common parasite in bumble bees

Background Glyphosate is the world’s most used pesticide and it is used without the mitigation measures that could reduce the exposure of pollinators to it. However, studies are starting to suggest negative impacts of this pesticide on bees, an essential group of pollinators. Accordingly, whether glyphosate, alone or alongside other stressors, is detrimental to bee health is a vital question. Bees are suffering declines across the globe, and pesticides, including glyphosate, have been suggested as being factors in these declines. Methods Here we test, across a range of experimental paradigms, whether glyphosate impacts a wild bumble bee species, Bombus terrestris. In addition, we build upon existing work with honey bees testing glyphosate-parasite interactions by conducting fully crossed experiments with glyphosate and a common bumble bee trypanosome gut parasite, Crithidia bombi. We utilised regulatory acute toxicity testing protocols, modified to allow for exposure to multiple stressors. These protocols are expanded upon to test for effects on long term survival (20 days). Microcolony testing, using unmated workers, was employed to measure the impacts of either stressor on a proxy of reproductive success. This microcolony testing was conducted with both acute and chronic exposure to cover a range of exposure scenarios. Results We found no effects of acute or chronic exposure to glyphosate, over a range of timespans post-exposure, on mortality or a range of sublethal metrics. We also found no interaction between glyphosate and Crithidia bombi in any metric, although there was conflicting evidence of increased parasite intensity after an acute exposure to glyphosate. In contrast to published literature, we found no direct impacts of this parasite on bee health. Our testing focussed on mortality and worker reproduction, so impacts of either or both of these stressors on other sublethal metrics could still exist. Conclusions Our results expand the current knowledge on glyphosate by testing a previously untested species, Bombus terrestris, using acute exposure, and by incorporating a parasite never before tested alongside glyphosate. In conclusion our results find that glyphosate, as an active ingredient, is unlikely to be harmful to bumble bees either alone, or alongside Crithidia bombi.

Impacts of Diverse Natural Products on Honey Bee Viral Loads and Health

Western honey bees (Apis mellifera), a cornerstone to crop pollination in the U.S., are faced with an onslaught of challenges from diseases caused by parasites, pathogens, and pests that affect this economically valuable pollinator. Natural products (NPs), produced by living organisms, including plants and microorganisms, can support health and combat disease in animals. NPs include both native extracts and individual compounds that can reduce disease impacts by supporting immunity or directly inhibiting pathogens, pests, and parasites. Herein, we describe the screening of NPs in laboratory cage studies for their effects on honey bee disease prevention and control. Depending on the expected activity of compounds, we measured varied responses, including viral levels, honey bee immune responses, and symbiotic bacteria loads. Of the NPs screened, several compounds demonstrated beneficial activities in honey bees by reducing levels of the critical honey bee virus deformed wing virus (DWV-A and-B), positively impacting the gut microbiome or stimulating honey bee immune responses. Investigations of the medicinal properties of NPs in honey bees will contribute to a better understanding of their potential to support honey bee immunity to fight off pests and pathogens and promote increased overall honey bee health. These investigations will also shed light on the ecological interactions between pollinators and specific floral food sources.

Identifying the climatic drivers of honey bee disease in England and Wales

Honey bee colony health has received considerable attention in recent years, with many studies highlighting multifactorial issues contributing to colony losses. Disease and weather are consistently highlighted as primary drivers of colony loss, yet little is understood about how they interact. Here, we combined disease records from government honey bee health inspections with meteorological data from the CEDA to identify how weather impacts EFB, AFB, CBP, varroosis, chalkbrood and sacbrood. Using R-INLA, we determined how different meteorological variables influenced disease prevalence and disease risk. Temperature caused an increase in the risk of both varroosis and sacbrood, but overall, the weather had a varying effect on the six honey bee diseases. The risk of disease was also spatially varied and was impacted by the meteorological variables. These results are an important step in identifying the impacts of climate change on honey bees and honey bee diseases.