Honey Bee Health Research Articles

A Monitoring System for Carbon Dioxide in Honeybee Hives: An Indicator of Colony Health

Non-dispersive infra-red (NDIR) detectors have become the dominant method for measuring atmospheric CO2, which is thought to be an important gas for honeybee colony health. In this work we describe a microcontroller-based system used to collect data from Senserion SCD41 NDIR sensors placed in the crown boards and queen excluders of honeybee colonies. The same sensors also provide relative humidity and temperature data. Several months of data have been recorded from four different hives. The mass change measurements, from hive scales, when foragers leave the hive were compared with the data from the gas sensors. Our data suggest that it is possible to estimate the colony size from the change in measured CO2, however no such link with the humidity is observed. Data are presented showing the CO2 decreasing over many weeks as a colony dies.

Native vegetation embedded in landscapes dominated by corn and soybean improves honey bee health and productivity

Abstract Balancing demand for food while supporting biodiversity and ecosystem services in landscapes committed to crop production may require integrating conservation with agriculture. Adding strips of diverse, native, perennial vegetation, through the recently created prairie strips practice of the U.S. Conservation Reserve Program, into annual cropland reduces soil and nutrient loss, and supports more diverse and abundant communities of birds and insects, including native pollinators. It remains unclear if prairie strips can reverse declines in the health and productivity of the exotic honey bee in the U.S. This study determined if prairie strips provide floral resources to honey bees and support colony vigour, in a highly farmed landscape with limited perennial habitat. We hypothesized that honey bee health and productivity would be improved if given access to prairie strips, and this hypothesis was tested in a multi‐year, replicated, longitudinal study on commercial, conventional farms committed to corn and soybean production with and without prairie strips. We predicted that prairie strips would have more diverse flowering plants, and colonies located in these strips would be healthier and more productive than colonies kept at farms without purposefully established native vegetation (i.e. control fields). We found that prairie strips had more diverse flowering plants and abundant floral resources than control fields. Colonies kept at fields with prairie strips collected 50% more pollen during the growing season (June–September), had a 24% larger end‐of‐season worker bee populations, and 20% higher overwinter survival than colonies kept at control fields. Furthermore, colonies kept at prairie strips were 24% heavier when they reached their peak‐weight in August, an indicator of honey production. Honey bees collected pollen from flowering plants found in prairie strips, revealing the potential for interactions with wild pollinators. However, this was limited to 50% of the taxa in prairie strips, suggesting honey bees may not deplete all of the food resources simultaneously used by wild pollinators. Synthesis and applications. Our results suggest that efforts to enhance habitat diversity within croplands with native plants increase honey bee health and productivity while providing multiple additional ecosystem services important to agriculture.

Honeybee (Apis spp.) (Hymenoptera: Apidae) Colony Monitoring Using Acoustic Signals from the Beehive: An Assessment by Global Experts and Our Feedback

Because the sounds emitted by a managed honeybee colony embrace a wealth of information about the status within and outside the beehive, researchers are interested in developing a beehive sound-based assessment of the colony situation. However, how the global experts rank this approach is unclear. We assessed the importance of beehive sound-based colony monitoring using formal expert elicitation. Our results indicate that policy-making bodies should focus on a non-invasive acoustic approach to monitor swarming, honeybee health, pesticides, and environmental pollution at apiaries, as these were considered very important factors with high confidence by global experts. Moreover, all other factors (pests and pathogens, weather conditions, predators, food availability, and spatiotemporal patterns) are rated as important, but experts’ confidence in acoustically monitoring a few of the factors differs. Because experienced forager bees emit bursting sounds during the waggle dance (particularly during the waggle-run phase) at a specific angle on a vertical comb within the hive, we propose an acoustics-based recording setup using a Raspberry Pi and a QuadMic Array to investigate how this sound can predict the spatial and temporal information of the available food sources. In this article, we highlight how the factors falling into the inconclusive category of confidence have the potential to be acoustically monitored. Besides, this paper suggests new and unexplored directions for opening a window for future research in beehive acoustics.

Epizootic monitoring of contagious diseases of bees in Rivne region for the period of 2018–2022

The important role of honey bees has been known for a long time, as the successful work of Apis mellifera helps to maintain natural biogeocenoses and provides humanity with food and medicinal production. The massive loss of honeybee colonies in the southern and eastern border regions of Ukraine is putting a strain on beekeeping production in the north-western regions of Ukraine. To intensify apiaries, there is a need for systematic and regular monitoring research. Epizootic monitoring provides data on the health of honey bees in a specific geographical region that can be scientifically substantiated. To analyse the epizootic situation with contagious bee diseases in the Rivne region in 2017–2022, we used official data from the State Service of Ukraine on Food Safety and Consumer Protection in the Rivne region. In addition to epizootic monitoring, the aim of our study was to identify the most common bee diseases in this region. The analysis of the results shows that diagnostic tests for varroosis and nosema, acarapidosis, American and European foulbroods, and amoebiasis are planned and carried out systematically. From 2017 to 2021, the number of diagnostic tests for bacterial diseases of bees was increased. At the same time, in 2022, the activity of such research decreased by 6.4% in comparison to 2021. A different pattern was registered for parasitic diseases of bees. For example, there was an increase in the number of such studies from 2019 (1678 studies) to 2022 (3184 studies). It was found that the Rivne region has been safe from American and European foulbroods, acarapidosis, braulosis and amoebiasis for the last 6 years. Varoosis and nosema are registered annually in 2017–2022, with the infection rate for these diseases set at 11.06 % (2020) – 14.82 % (2022), respectively. This data is likely to indicate a change in the economic situation of beekeepers, which makes it impossible to prevent hives from being treated for certain diseases in a timely manner. Thus, the analysis of laboratory tests for contagious diseases of bees helps to detail the epizootic state of a particular region, which allows to determine the direction for veterinary and sanitary measures for a specific apiary.

Spermidine dietary supplementation and polyamines level in reference to survival and lifespan of honey bees

Honey bee health has been an important and ongoing topic in recent years. Honey bee is also an important model organism for aging studies. Polyamines, putrescine, spermidine and spermine, are ubiquitous polycations, involved in a wide range of cellular processes such as cell growth, gene regulation, immunity, and regulation of lifespan. Spermidine, named longevity elixir, has been most analysed in the context of aging. One of the several proposed mechanisms behind spermidine actions is antioxidative activity. In present study we showed that dietary spermidine supplementation: (a) improved survival, (b) increased the average lifespan, (c) influenced the content of endogenous polyamines by increasing the level of putrescine and spermidine and decreasing the level of spermine, (d) reduced oxidative stress (MDA level), (e) increased the antioxidant capacity of the organism (FRAP), (f) increased relative gene expression of five genes involved in polyamine metabolism, and (g) upregulated vitellogenin gene in honey bees. To our knowledge, this is the first study on honey bee polyamine levels in reference to their longevity. These results provide important information on possible strategies for improving honey bee health by introducing spermidine into their diet. Here, we offer spermidine concentrations that could be considered for that purpose.

A four-decade profile of apicultural demographics and production in New Zealand, 1980-2020.

The demand for honey and pollination services has continued to grow in many countries worldwide, including New Zealand. This has influenced changes in the demographics of the managed population of honey bees (Apis mellifera). We examined historical data to describe how the apicultural demographics in New Zealand have changed temporally and geographically in the four decades to 2020. We also describe trends in honey production and the economic value of pure honey exported from New Zealand between 2000 and 2020. Our findings suggest that commercial apiculture has been key to the intensification of beekeeping in New Zealand during the study period. This is supported by evidence showing pronounced expansion of beekeeping operations among those with more than 1,000 colonies. The intensification has resulted in the density of apiaries increasing threefold across New Zealand during the four decades. While higher numbers of colonies per area produced higher volumes of honey, there was no corresponding improvement in production efficiency. Honey yields per apiary or colony, as indicators of production efficiency, appear to decline from the mid-2000s. The volume of pure honey export increased over 40-fold, a magnitude approximately ten times higher than that of production increase. This reflects a substantial increase in returns from honey exports, mostly driven by the price of mānuka honey. Our findings add to a pool of information to support evidence-based decision making to enhance honey bee health and develop the apicultural industry in New Zealand.

Modeling disruption of Apis mellifera (honey bee) odorant-binding protein function with high-affinity binders.

Chemical toxins pose a great threat to honey bee health because they affect memory and cognition, diminish immunity, and increase susceptibility to infection, resulting in decreased colony performance, reproduction, and survival. Although the behavioral effects of sub-lethal chemical exposure on honey bees have been intensively studied, how xenobiotics affect olfaction, at the molecular level, still needs to be elucidated. In the present work, in silico tools, such as molecular docking, binding free energy calculations, and molecular dynamics simulations are used to predict if environmental chemicals have stronger binding affinities to honey bee antennal odorant-binding protein 14 (OBP14) than the representative floral odors citralva, eugenol, and the fluorescent probe 1-N-phenylnaphthylamine. Based on structural analysis, 21 chemicals from crop pesticides, household appliances, cosmetics, food, public health-related products, and other sources, many of which are pervasive in the hive environment, have higher binding affinities than the floral odors. These results suggest that chemical exposures are likely to interfere with the honey bee's sense of smell and this disruptive mechanism may be responsible for the lower associative learning and memory based on olfaction found in bees exposed to pesticides. Moreover, bees mainly rely on olfactory cues to perceive their environment and orient themselves as well as to discriminate and identify their food, predators, nestmates, and diseased individuals that need to be removed with hygienic behavior. In summary, sub-lethal exposure to environmental toxins can contribute to colony collapse in several ways from the disruption of proper olfaction functioning.

Effect of bee bread on Africanized honey bees infected with spores of Nosema spp.

Floral diversity allows honey bees, Apis mellifera L. (including its hybrids between subspecies) (Hymenoptera: Apidae), to meet their nutritional requirements. However, infection by Nosema spp. (Microsporidia: Nosematidae) destroys a bee's digestive epithelium, hindering the ability to absorb nutrients. In some subtropical regions, such as the Yucatan Peninsula, Mexico, nosemosis is one of the most widespread diseases in commercial apiaries. To date, there have been no reports of colony deaths attributable to the disease. It is possible that the naturally occurring diet in the Yucatan Peninsula sustains honey bee health. We tested this hypothesis by evaluating the effect of four diets – bee bread collected in the Yucatan's rainy and dry seasons, sucrose syrup, and a pollen substitute – on the response of caged Africanized honey bees (A. m. scutellata × A. m. adansonii × A. mellifera) to nosemosis infection (treatment with spores of Nosema apis Zander and Nosema ceranae Fries). We found that infected and uninfected bees consumed food in similar amounts regardless of the diet, although, overall, they fed at significantly lower rates when provided the pollen-substitute diet. Bees fed either of the bee bread diets had relatively low fat-body weight and expression of Vg, proPO, and GOx genes, three genes related to immune function. Bees fed sucrose syrup had low fat-body weight but relatively high gene expression. Infection from Nosema spores only reduced the individual survival probability for bees fed the bee bread collected in the dry season, yet bees fed the dry-season bee bread had the lowest infection rates. Our results indicate that natural stored bee bread in honey bee colonies from the Yucatan Peninsula could be one of the main factors influencing their survival and reducing Nosema spp. spore load.

Prospects, challenges and perspectives in harnessing natural selection to solve the 'varroa problem' of honey bees.

Honey bees, Apis mellifera, of European origin are major pollinators of crops and wild flora. Their endemic and exported populations are threatened by a variety of abiotic and biotic factors. Among the latter, the ectoparasitic mite Varroa destructor is the most important single cause behind colony mortality. The selection of mite resistance in honey bee populations has been deemed a more sustainable solution to its control than varroacidal treatments. Because natural selection has led to the survival of some European and African honey bee populations to V. destructor infestations, harnessing its principles has recently been highlighted as a more efficient way to provide honey bee lineages that survive infestations when compared with conventional selection on resistance traits against the parasite. However, the challenges and drawbacks of harnessing natural selection to solve the varroa problem have only been minimally addressed. We argue that failing to consider these issues could lead to counterproductive results, such as increased mite virulence, loss of genetic diversity reducing host resilience, population collapses or poor acceptance by beekeepers. Therefore, it appears timely to evaluate the prospects for the success of such programmes and the qualities of the populations obtained. After reviewing the approaches proposed in the literature and their outcomes, we consider their advantages and drawbacks and propose perspectives to overcome their limitations. In these considerations, we not only reflect on the theoretical aspects of host-parasite relationships but also on the currently largely neglected practical constraints, that is, the requirements for productive beekeeping, conservation or rewilding objectives. To optimize natural selection-based programmes towards these objectives, we suggest designs based on a combination of nature-driven phenotypic differentiation and human-directed selection of traits. Such a dual strategy aims at allowing field-realistic evolutionary approaches towards the survival of V. destructor infestations and the improvement of honey bee health.

Colonization of Honey Bee Digestive Tracts by Environmental Yeast Lachancea thermotolerans Is Naturally Occurring, Temperature Dependent, and Impacts the Microbiome of Newly Emerged Bees.

Honey bees are critical pollinators in both agricultural and ecological settings. Recent declines in honey bee colonies in the United States have put increased strain on agricultural pollination. Although there are many environmental stressors implicated in honey bee disease, there has been intensifying focus on the role of microbial attacks on honey bee health. Despite the long-standing appreciation for the association of fungi of various groups with honey bees and their broader environment, the effects of these interactions on honey bee health are incompletely understood. Here, we report the discovery of colonization of the honey bee digestive tract by the environmental yeast Lachancea thermotolerans. Experimental colonization of honey bee digestive tracts by L. thermotolerans revealed that this yeast species maintains high levels in the honey bee midgut only at temperatures below the typical colony temperature. In newly eclosed bees, L. thermotolerans colonization alters the microbiome, suggesting that environmental yeasts can impact its composition. Future studies should be undertaken to better understand the role of L. thermotolerans and other environmental yeasts in honey bee health. IMPORTANCE Although many fungal species are found in association with honey bees and their broader environment, the effects of these interactions on honey bee health are largely unknown. Here, we report the discovery that a yeast commonly found in the environment can be found at high levels in honey bee digestive tracts. Experimentally feeding this yeast to honey bees showed that the yeast's ability to maintain high levels in the digestive tract is influenced by temperature and can lead to alterations of the microbiome in young bees. These studies provide a foundation for future studies to better understand the role of environmental yeasts in honey bee health.

Correction to: Global honeybee health decline factors and potential conservation techniques

Correction to: Global honeybee health decline factors and potential conservation techniques

Imidacloprid Pesticide Causes Unexpectedly Severe Bioelement Deficiencies and Imbalance in Honey Bees Even at Sublethal Doses.

Pesticides impair honeybee health in many ways. Imidacloprid (IMD) is a pesticide used worldwide. No information exists on how IMD impact the bees' body bioelement balance, which is essential for bee health. We hypothesized that IMD disturbs this balance and fed the bees (in field conditions) with diets containing 0 ppb (control), 5 ppb (sublethal considered field-relevant), and 200 ppb (adverse) doses of IMD. IMD severely reduced the levels of K, Na, Ca, and Mg (electrolytic) and of Fe, Mo, Mn, Co, Cu, Ni, Se, and Zn, while those of Sn, V, and Cr (enzymatic) were increased. Levels of P, S, Ti, Al, Li, and Sr were also decreased, while only the B content (physiologically essential) was increased. The increase in Tl, Pb, and As levels (toxic) was alarming. Generally, IMD, even in sublethal doses, unexpectedly led to severe bioelement malnutrition in 69% of bioelements and to a stoichiometric mismatch in the remaining ones. This points to the IMD-dependent bioelement disturbance as another, yet unaccounted for, essential metabolic element which can interfere with apian health. Consequently, there is a need for developing methods of bioelement supplementation of the honey bee diet for better preventing bee colony decline and protecting apian health status when faced with pesticides.

Genetics of tolerance in honeybees to the neonicotinoid clothianidin

The effects of neonicotinoid insecticides (NNIs) on honeybee health are intensely debated, with numerous studies showing negative effects of exposure, while others report no such effects. We carried out experiments to study the genetic and molecular basis of NNI tolerance in honeybees, which may underlie the discrepancies observed in the literature. We discovered that worker survival post-exposure to an acute oral dose of clothianidin is heritable (H 2= 37.8%). Tolerance to clothianidin was not associated with differences in the expression of detoxification enzymes in our experiments. Instead, mutations in the primary neonicotinoid detoxification genes CYP9Q1 and CYP9Q3 were strongly associated with worker survival post-clothianidin exposure. In some instances, the strong association betweenCYP9Q haplotypes and worker survival was associated with the protein's predicted binding affinity for clothianidin. Our findings have implications regarding future toxicological studies utilizing honeybees as a model pollinator.

In Vitro and Predictive Computational Toxicology Methods for the Neurotoxic Pesticide Amitraz and Its Metabolites

The Varroa destructor parasite is responsible for varroasis in honeybees worldwide, the most destructive disease among parasitic diseases. Thus, different insecticides/acaricides have been widely used within beehives to control these parasitic diseases. Namely, amitraz is the most used acaricide due to its high efficacy shown against Varroa destructor. However, pesticides used for beehive treatments could be incorporated into the honey and accumulate in other hive products. Hence, honeybee health and the impairment of the quality of honey caused by pesticides have gained more attention. Amitraz and its main metabolites, N-(2,4-dimethylphenyl) formamide (2,4-DMF) and 2,4-dimethylaniline (2,4-DMA), are known to be potent neurotoxicants. In this research, the cytotoxicity of amitraz and its metabolites has been assessed by MTT and PC assays in HepG2 cells. In addition, possible target receptors by in silico strategies have been surveyed. Results showed that amitraz was more cytotoxic than its metabolites. According to the in silico ADMEt assays, amitraz and its metabolites were predicted to be compounds that are able to pass the blood-brain barrier (BBB) and induce toxicity in the central and peripheral nervous systems. The main target class predicted for amitraz was the family of A G protein-coupled receptors that comprises responses to hormones and neurotransmitters. This affects, among other things, reproduction, development, locomotion, and feeding. Furthermore, amitraz and its metabolites were predicted as active compounds interacting with diverse receptors of the Tox21-nuclear receptor signaling and stress response pathways.

The promise of probiotics in honeybee health and disease management

Over the last decades, losses of bee populations have been observed worldwide. A panoply of biotic and abiotic factors, as well as the interplay among them, has been suggested to be responsible for bee declines, but definitive causes have not yet been identified. Among pollinators, the honeybee Apis mellifera is threatened by various diseases and environmental stresses, which have been shown to impact the insect gut microbiota that is known to be fundamental for host metabolism, development and immunity. Aimed at preserving the gut homeostasis, many researches are currently focusing on improving the honeybee health through the administration of probiotics e.g., by boosting the innate immune response against microbial infections. Here, we review the knowledge available on the characterization of the microbial diversity associated to honeybees and the use of probiotic symbionts as a promising approach to maintain honeybee fitness, sustaining a healthy gut microbiota and enhancing its crucial relationship with the host immune system.

All together now: Geographically coordinated miticide treatment benefits honey bee health.

Deformed wing virus (DWV) is a pathogenic virus of honey bees transmitted by the ectoparasitic mite Varroa destructor. Annual overwintering colony losses, accounting for ~25% of all colonies, are associated with high levels of Varroa-DWV infestation. Effective miticide treatments are available to control Varroa. However, the absence of coordinated treatment means environmental transmission of mites continues unchecked. We aimed to determine whether rational, coordinated treatment is beneficial, and characterized the DWV population as an indicator of colony health.This study uses coordinated treatment of Varroa in a geographically isolated environment (Isle of Arran, Scotland) over 3 years. The study area contained 50-84 colonies managed by ~20 amateur beekeepers. Sampling and virus analysis to assess strain diversity and viral loads were conducted before and after treatments, and changes in population diversity were quantified by sequence analysis.Over the 3 years analysis of the virus population revealed that the dominant DWV variant shifted from Type A to Type B in all apiaries, regardless of mite levels or proximity to other colonies. During this period the number of managed colonies increased by 47% (57-84 colonies), but despite this, we estimate total mite numbers decreased by 58%. Synthesis and applications. In this study, the beekeepers in Arran significantly improved the number of colonies they managed, without importing any bees onto the island, indicating that an improved focus on management techniques, through the combination of a coordinated miticide programme and an improved understanding of bee diseases, could yield positive results for bee health and sustainability.

First detection of Nosema ceranae in honey bees (Apis mellifera L.) of the Macaronesian archipelago of Madeira

The Microsporidia Nosema ceranae is an invasive pathogen affecting honey bee health, particularly in warm climates. In this study, N. ceranae was detected for the first time in honey bees (Apis mellifera L.) of the Madeira archipelago, indicating that this pathogen is now spreading across the entire Macaronesia. Nosema apis was not detected, and the high prevalence (67.7%) of N. ceranae indicates its dominance over N. apis.

Chronic Exposure to Polystyrene Microplastic Fragments Has No Effect on Honey Bee Survival, but Reduces Feeding Rate and Body Weight

Microplastics (MPs), in the form of fragments and fibers, were recently found in honey samples collected in Ecuador as well as in honey bees collected from Denmark and China. However, little is known about how MPs impact bee health. To fill this knowledge gap, we investigated the potential toxicity of irregularly shaped polystyrene (PS)-MP fragments on honey bee health. In the first experiment of its kind with honey bees, we chronically exposed bees with a well-established gut microbiome to small (27 ± 17 µm) or large (93 ± 25 µm) PS-MP fragments at varying concentrations (1, 10, 100 µg mL-1) for 14 days. Bee mortality, food consumption, and body weight were all studied. We found that chronic exposure to PS-MP fragments has no effect on honey bee survival, but reduced the feeding rate and body weight, particularly at 10 µg PS-MP fragments per mL, which may have long-term consequences for honey bee health. The findings of this study could assist in the risk assessment of MPs on pollinator health.

Mixture toxic effects of thiacloprid and cyproconazole on honey bees (Apis mellifera L.)

Pesticide exposure remains one of the main factors in the population decline of insect pollinators. It is urgently necessary to assess the effects of mixtures on pollinator risk assessments because they are often exposed to numerous agrochemicals. In the present study, we explored the mixture toxic effects of thiacloprid (THI) and cyproconazole (CYP) on honey bees (Apis mellifera L.). Our findings revealed that THI possessed higher acute toxicity to A. mellifera (96-h LC50 value of 216.3 mg a.i. L−1) than CYP (96-h LC50 value of 601.4 mg a.i. L−1). It's worth noting that the mixture of THI and CYP exerted an acute synergistic effect on honey bees. At the same time, the activities of detoxification enzyme cytochrome P450s (CYP450s) and neuro target enzyme Acetylcholinesterase (AChE), as well as the expressions of seven genes (CRBXase, CYP306A1, CYP6AS14, apidaecin, defensing-2, vtg, and gp-93) associated with detoxification metabolism, immune response, development, and endoplasmic reticulum stress, were significantly altered in the combined treatment compared with the corresponding individual exposures of THI or CYP. These data indicated that a mixture of THI and CYP could disturb the physiological homeostasis of honey bees. Our study provides a theoretical basis for in-depth studies on the impacts of pesticide mixtures on the health of honey bees. Our study also provides important guidance for the rational application of pesticide mixtures to protect pollinators in agricultural production effectively.

Global honeybee health decline factors and potential conservation techniques

Global honeybee health decline factors and potential conservation techniques