Infection timelines and co-infection effects of Israeli acute paralysis virus and deformed wing virus in the honey bee (Apis mellifera).

Survival mechanisms of preselected breeder honeybee (Apis mellifera) colonies under Varroa-infestation: Selective breeding of natural selection.

Emerging infectious diseases (EIDs) threaten biodiversity, yet identifying key host species in complex ecological communities remains a major challenge. Here, we develop a quantitative framework combining field data, epidemiological modelling, simulations, and Bayesian inference to pinpoint key viral hosts in multispecies bee communities. Using flower-visitor interaction data and molecular virus screening, we estimate species-specific basic reproduction numbers (R0) and assess the role of both key hosts and community metrics in virus transmission and persistence. We show that, while honeybees often act as primary reservoirs for deformed wing virus and black queen cell virus, others, such as the bumblebee Bombus lapidarius, can drive the spread of acute bee paralysis virus. Viral dynamics are primarily explained by exposure to key hosts, while community effects are not as pronounced. Identification of non-honeybee key hosts challenges existing assumptions and highlights drivers of transmission and pathogen persistence in complex host-pathogen networks.

Landscape-scale virome analysis uncovers endemic and emerging honey bee viruses in the Silk-Road hub of Uzbekistan.

The ectoparasitic mite Varroa destructor and the viruses it transmits pose a significant threat to honey bee health ( Apis mellifera ), contributing to colony collapse disorder. In this study, a metatranscriptomic analysis of V. destructor from six regions in South Korea was conducted to characterize its viral communities. Using high-throughput sequencing (HTS), we identified 16 known viruses and classified them into three groups: honey bee-pathogenic, Varroa destructor viruses (VDVs), and viruses with unknown hosts. Reverse transcription polymerase chain reaction (RT-PCR) was used to validate the HTS results, revealing only two discrepancies out of 96 comparisons. This emphasizes the importance of integrating both methods for comprehensive virome analysis. Deformed wing virus was the most prevalent and abundant virus, comprising 75%–99% of viral reads in five out of six farms. One farm showed a high abundance of VDVs (3 and 9). Notably, two previously unreported viruses with unknown hosts, Hubei partiti-like virus 34 and Lilac leaf chlorosis virus (LLCV), were identified. For LLCV, the detection of all ribonucleic acid segments highlighted the critical impact of sequencing depth on viral genome analysis. To our knowledge, this study provides the first virome characterization of V. destructor in South Korea, revealing diverse viral communities. It also proposes an integrated analytical approach using RT-PCR and HTS, emphasizing the importance of sequencing depth. This analysis provides valuable insights into the potential impacts of viral infections on honey bee colony health and the epidemiology of viral transmission.

This study aimed to determine the presence of relevant infectious and parasitic agents (IPAs) in managed honeybees from Central Italy and the Republic of Kosovo and Albania to assess the overall health status of local apiaries by determining the contamination levels and co-occurrence. Therefore, pathogens and parasites such as Paenibacillus larvae, Melissococcus plutonius, Vairimorpha apis, V. ceranae, the acute bee paralysis virus (ABPV), black queen cell virus (BQCV), chronic bee paralysis virus (CBPV), deformed wing virus variants DWV-A and DWV-B, and the parasitoid flies Megaselia scalaris and Senotainia tricuspis were detected by quantitative polymerase chain reaction (qPCR) and reverse transcriptase qPCR (RT-qPCR) in clinically healthy adult honeybees collected from 187 apiaries in the Abruzzo and Molise regions of Central Italy, 206 apiaries in the Republic of Kosovo in 2022 and 2023 and 18 apiaries in Albania in 2022. The percentages of positive samples and contamination for V. ceranae, P. larvae and DWV-B were significantly higher in the Republic of Kosovo and Albania, while the percentages of samples positive for M. plutonius, CBPV, DWV-A, and the parasitoid flies were higher in Central Italy. Additionally, P. larvae and some viruses showed significantly different occurrence rates between the two years in Italy and the Republic of Kosovo. The co-occurrence of IPAs also differed between the two geographic areas. Their varying distribution could depend on epidemiological dynamics, climatic factors, and management practices specific to each country, whose relative impact should be defined to guide targeted interventions to reduce honeybee mortality.

Deformed Wing Virus infection induces immunosuppression and gut dysbiosis in honey bees.

Viruses can impact individual host fitness and host population dynamics, especially following host shifts. Thus, the decline of wild solitary bee populations over the last few decades may be linked to viruses or other pathogens. However, evidence for the impact of viruses-transmitted from other genera or resident in solitary bees-on their fitness remains scarce. Here, by assessing solitary bee (Osmia cornuta) foraging, offspring sex ratio, survival and body mass across seven locations in northern Switzerland, we show that resident viruses-but not honeybee-associated viruses-can impact fitness proxies in the field. Loads of Osmia-resident viruses (Ganda bee virus-GABV; Scaldis River bee virus-SRBV) and honeybee-associated viruses (black queen cell virus-BQCV; deformed wing virus B-DWV-B) were quantified in foraging females. Prevalence and loads of GABV and SRBV were higher than BQCV and DWV-B. Females with high SRBV or GABV loads had reduced offspring survival or lower male offspring body mass, respectively. Honeybee-associated viruses had no impact on O. cornuta fitness proxies. We demonstrate that viruses can affect solitary bee fitness negatively, but the degree of impact varies with viral species and provenance. Further research is needed to unravel the dynamics of multi-host pathogens in pollinator communities.

This study aimed to investigate the presence of known bee viruses in the European hornet (Vespa crabro, Linnaeus, 1758), a species recognized as a bee predator in Hungary. Several viruses affecting honeybees (Apis mellifera, Linnaeus, 1758), such as deformed wing virus (DWV), sacbrood virus (SBV), chronic bee paralysis virus (CBPV), and acute bee paralysis virus (ABPV), have been documented in various wasp species. For instance, DWV has been frequently isolated in Vespa orientalis (Linnaeus, 1761), and ABPV has been detected in V. orientalis. Additionally, viruses like Kashmir bee virus (KBV) and Black queen cell virus (BQCV) have been confirmed in other wasp species such as Vespula germanica and Vespa velutina. Despite this, data on virus presence in V. crabro remain limited. Between August and October 2023, we tested 40 adult V. crabro workers, collected from Kiskunlacháza and Vácduka, for viral infections using polymerase chain reaction (PCR). Our results confirmed the presence of genetic material from DWV and ABPV infection in adult workers of the European hornet, which showed no morphological alterations. This study provides the first detection of DWV (in Hungary) and ABPV in V. crabro, contributing to our understanding of virus transmission pathways in wasp species and their potential impact on bee populations.

Deformed wing virus (DWV) is a major driver of honeybee colony losses, yet its sublethal effects on adult foraging behaviour remain underexplored. Building on evidence that covert DWV infections impair sucrose responsiveness and associative learning, we tested whether infection changes foraging success and specialization in worker bees. Using a controlled experiment, we marked 1,000 newly emerged workers that were either inoculated with DWV lysate or injected with an RNA-interference control that suppressed viral replication. Foraging activity, success, and specialization were recorded. Our results show that DWV-infected bees began foraging earlier (“precocious foraging”) and had higher mortality, reducing their lifespan as foragers. Furthermore, infected nectar foragers were significantly less likely to return with nectar, and when they did, it contained markedly lower sugar concentrations compared to control bees. Conversely, infected bees were slightly more likely to return with pollen and showed greater specialization in pollen foraging, although pollen load weights were similar between treatments. These findings indicate that DWV disrupts multiple aspects of foraging ecology by accelerating behavioural maturation, shortening forager lifespan, reducing nectar yield and quality, and shifting resource preference towards pollen. Such changes may reflect a compensatory response to impaired nectar collection, but nonetheless could compromise colony nutrition, particularly when high-quality nectar is scarce. Our results align with previous work linking DWV to impaired foraging efficiency, and altered foraging specialization, and reduced honeybee survival, underscoring DWV’s substantial sublethal costs. By reducing nectar foraging while leaving pollen loads unaffected, DWV may limit honey stores and brood rearing during high demand periods, contributing to seasonal losses. Even moderate declines in nectar-foraging can undermine colony resilience, highlighting the need to address DWV’s role in the pollinator crisis.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-31753-0.

ABSTRACTHoney bees (Apis mellifera) provide important ecosystem services to both natural and human-managed environments, but are increasingly threatened by a variety of pathogens, the most common of which is deformed wing virus (DWV). DWV is known to replicate in the honey bee brain and has been documented as both improving and impairing olfactory learning and memory. We examined the transcriptomic response of the honey bee mushroom bodies – an area of the insect brain associated with higher cognitive functions – in bees with naturally occurring DWV infections, which varied in their ability to perform an associative learning task. RNA-sequencing analysis detected increased expression of genes involved in the immune response, including important antimicrobial peptides such as hymenoptaecin, apidaecin, and abaecin, and the downregulation of lysozyme, prophenoloxidase, and other genes associated with responses to a range of stressors. Additionally, gene ontology enrichment analysis revealed overrepresentation of key biological processes that form part of the immune response. We also noted significant differential expression of long non-coding RNAs (lncRNAs) presumed to be acting in a regulatory manner, and used these lncRNAs to construct gene regulatory networks. Strikingly, in contrast to previous studies on bees with artificially induced infections that have examined viral loads in the abdomen and non-specific areas of the brain, no correlation between DWV load in the mushroom bodies and cognitive function was noted. This highlights the complexity of host-pathogen interactions in honey bee neural tissues and the benefits of a spatially refined approach to brain transcriptomics in naturally occurring infections.

Apis mellifera multi-omics responses to ectoparasitic mites: unveiling biomarkers for Tropilaelaps mercedesae and Varroa destructor in honeybee hemolymph through hemolymph peptide and proteome analysis using MALDI-MS and LC-ESI-MS/MS.

Efforts to improve honey bee colony health continue due to persistent high loss rates. A major focus in this area is Deformed wing virus (DWV), a key driver of colony loss. The application of modern molecular techniques has characterized the DWV genome and its high mutational rate that enables the formation of diverse quasi-species populations capable of evading host immune responses, while other work has led to the development of DWV clones suitable for sequence-specific tracking of viral dynamics. In this work we combine knowledge of these efforts to track the mutational progression in a DWV clone surrounding an area of low nucleotide diversity and compare it to its wild-type source. We achieve this through amplicon sequencing of the structural viral protein, VP2, after incubation across three generations and multiple host genetic sources. Inocula were injected into pupae, allowed to replicate, then extracted for a further two generations of injections. For the final injection generation, recipient pupae were injected with preparations from either the same genetic source or cross-fostered from other colonies. Overall, we compared the mean number and type of mutations, their proportional abundance in the read pool, and specific locations across strains. Sequencing results indicate a limited number of mutational hotspots, which were driven by silent mutations in the final injection generation of the wild-type strains. No significant differences were found among other mutation types, cross-fostering status, or interactions with host genetics. This work is an initial attempt at examining viral dynamics in a cloned system across multiple generations and treatment groups. The results provide valuable insights, which may further enhance our understanding of viral dynamics and potentially improve future honey bee therapeutics.

Efforts to improve honey bee colony health continue due to persistent high loss rates. A major focus in this area is Deformed wing virus (DWV), a key driver of colony loss. The application of modern molecular techniques has characterized the DWV genome and its high mutational rate that enables the formation of diverse quasi-species populations capable of evading host immune responses, while other work has led to the development of DWV clones suitable for sequence-specific tracking of viral dynamics. In this work we combine knowledge of these efforts to track the mutational progression in a DWV clone surrounding an area of low nucleotide diversity and compare it to its wild-type source. We achieve this through amplicon sequencing of the structural viral protein, VP2, after incubation across three generations and multiple host genetic sources. Inocula were injected into pupae, allowed to replicate, then extracted for a further two generations of injections. For the final injection generation, recipient pupae were injected with preparations from either the same genetic source or cross-fostered from other colonies. Overall, we compared the mean number and type of mutations, their proportional abundance in the read pool, and specific locations across strains. Sequencing results indicate a limited number of mutational hotspots, which were driven by silent mutations in the final injection generation of the wild-type strains. No significant differences were found among other mutation types, cross-fostering status, or interactions with host genetics. This work is an initial attempt at examining viral dynamics in a cloned system across multiple generations and treatment groups. The results provide valuable insights, which may further enhance our understanding of viral dynamics and potentially improve future honey bee therapeutics.

Honey bee populations have experienced alarming declines, often associated with the presence of pathogens such as deformed wing virus (DWV). In this context, pollen is essential for the health and survival of bees. The biodiversity of Chilean native plants offers a unique opportunity to find natural resources with antiviral properties. In this sense, the effect of diets based on pollen of different botanical compositions on the reduction of viral load, the increase in survival and immune response of bees inoculated with the DWV-A was evaluated. Phenolic profiles and antioxidant properties were also studied. The results indicated that in honey bees treated with native Eucryphia cordifolia pollen significantly reduced the DWV-A load from 1.0 × 1013 to 1.0 × 105 copy number per bee, meanwhile, that polyfloral and monofloral Rubus ulmifolius pollen reduced DVW-A load from 1.0 × 1013 to 1.0 × 106 copy number per bee. The highest survival rate (91%) corresponded to bees that consumed E. cordifolia pollen; however, there were no significant differences detected with other pollen sources. Pollen diets modulated the expression of four immune-related genes, reducing Cactus expression while up-regulating Dorsal, Relish, and Dicer-like. Native E. cordifolia pollen showed high concentrations of gallic acid, vanillic acid, 3,4-dimethoxybenzyl, vanillin, chlorogenic acid, caffeic acid, quercetin, and kaempferol. Principal component analysis (PCA) revealed a separation between pollens according to their botanical composition, with greater distinction between non-native polyfloral and monofloral pollen of R. ulmifolius compared to native monofloral pollen of E. cordifolia. These findings highlight the antiviral value of pollens.

Bees are important pollinators that are increasingly threatened by viruses. In this study, we investigated the viruses in honey bees in Bangladesh, focusing on western (Apis mellifera) and native bee species (A. cerana, A. dorsata, A. florea, and Trigona sp.). Using high-throughput poly(A)-selected RNA sequencing, we observed that viruses of the order Picornavirales are frequently detected in both western and native bees. However, this pattern may reflect both true biological abundance and methodological bias, as this approach inherently enriches for polyadenylated RNA viruses. Deformed wing virus (DWV), black queen cell virus (BQCV), and sacbrood virus (SBV) were commonly found in western bees, while native bees exhibited a high diversity of viral communities rather than dominance of specific viruses. The common bee viruses also showed high read abundances in western bees. Notably, the study identified unreported viruses in bees belonging to the Iflaviridae and Dicistroviridae families, expanding the known diversity of honey bee pathogens. In addition, plant-associated viruses were identified, suggesting a potential role for honey bees as vectors of plant viruses and highlighting the interactions between bees, plants, and their pathogens. The results of the diversity analysis demonstrated significant differences in the composition of virus populations between western and native bees in our studied samples. These results reveal the occurrence of bee viruses in Bangladesh and highlight the potential interspecific transmission of viruses, which may pose a significant threat to local bee populations. Our study emphasizes the importance of monitoring known viruses and novel viruses, as well as plant pathogens, and implementing sustainable management practices to reduce the spread of pathogens and protect both native and western bees.IMPORTANCEPollinators face increasing threats from viral pathogens, yet data on their viromes remain limited in many parts of the world, including South Asia. This study provides insights into the viral communities of both native and non-native bee species in Bangladesh using RNA sequencing. While Apis mellifera showed higher viral loads of known honey bee viruses, native bee species exhibited a broader diversity of viral sequences, including several uncharacterized viruses. Although based on a limited sample set, these findings contribute to a growing understanding of viral diversity in pollinators and underscore the value of continued surveillance to better understand virus-host associations and potential cross-species transmission in regions undergoing rapid apicultural expansion.

American foulbrood (AFB) and European foulbrood (EFB), caused by Paenibacillus larvae and Melissococcus plutonius, respectively, are severe bacterial diseases that significantly affect honey bee health and productivity worldwide. Rapid and accurate diagnosis is essential for effective disease management in apiaries. We developed and validated a multiplex point-of-care (POC) quantitative real-time PCR (qPCR) assay that enables simultaneous and rapid detection of P. larvae and M. plutonius directly in apiaries. Our POC qPCR assay, using the XQ station (Postbio), had diagnostic sensitivity and specificity comparable to laboratory-based qPCR assays. For P. larvae detection, the POC qPCR assay had a sensitivity of 93% (56 of 60 samples) and specificity of 97% (97 of 100 samples). Similarly, for M. plutonius, sensitivity was 95% (59 of 62 samples) and specificity was 97% (97 of 100 samples). Our POC qPCR assay had analytical sensitivity comparable to that of laboratory-based qPCR assays, with a limit of detection of ~102 copies/reaction for both pathogens. Additionally, the assay had high analytical specificity, with no cross-reactivity against other common honey bee pathogens, including deformed wing virus (DWV), black queen cell virus (BQCV), and Vairimorpha ceranae. Our POC qPCR assay consistently had lower cycle quantification values than the laboratory-based qPCR on the same samples, indicating robust detection capability even at low pathogen concentrations. Although not compared to a gold standard, our POC qPCR assay had reliable diagnostic performance. Our multiplex POC qPCR assay enables rapid, accurate pathogen detection in apiaries, thereby enhancing disease management and supporting sustainable, productive apiculture.

Honey bees provide essential pollination services in the ecosystem. The high annual loss of honey bees has raised concerns about global food security and the agricultural economy. As a primary stressor causing colony failure, the mite Varroa destructor feeds on the hemolymph and the bee’s fat body tissue. The Varroa mite-associated deformed wing virus has been extensively studied because it can be found in each individual mite and causes bee mortality. A recent study shows that the Varroa mite can transmit pathogenic bacteria, while the transmission route remains unclear. In this study, we isolated and assembled a previously uncultured bacterium, Morganella morganii, from the mites Varroa destructor. This pathogenic bacterium exhibited a high case fatality rate, as evidenced by 215 cells causing over 30% mortality in pupae and adult bees. Using a fluorescent protein-tagged strain, we provide evidence that M. morganii can not be transmitted among bees through social contacts, while it can be transmitted from mites to bees, and vice versa. The cumulative incidence of transmitting M. morganii from infected bees to mites is 92.1%, and 68.49% from infected mites to naïve bees. Our data aligns with the honey bee colony collapse in winter, when the mite population expands, accelerating the honey bees to tap into a reservoir of this lethal bacterium.

ABSTRACTDeformed wing virus (DWV) is an important pathogen for honeybee colonies, whose infections are linked to those caused by the ectoparasitic mite Varroa destructor. The current study concerns DWV's molecular detection and phylogenetic characterization in Iranian honeybee populations originating from Mazandaran, Hormozgan, Kurdistan and Khorasan Razavi provinces. DWV was detected using RT‐PCR targeting the structural polyprotein gene region, followed by sequencing and phylogenetic analysis. Among the 89 apiary samples tested, 16 (17.97%) were infected with DWV, although it was not detected in Mazandaran Province. The phylogenetic analysis showed three different groups of DWV isolates, some of which had a high similarity to strains from Syria and Yemen. These findings suggest possible relations between virus distribution and regional trade or ecological factors. The current study emphasizes the importance of geographic and molecular surveys in DWV management and insists on a more effective approach to controlling Varroa infections and reducing the incidence of viral diseases that would contribute to the health and productivity of honeybee colonies. Controlling honeybee pathogens such as mites and viruses, especially through biological control methods, will lead to better bee health and ultimately help to produce a variety of higher quality and organic honeybee products.

Pathogenic threats to reproductive individuals pose a profound challenge to the stability of insect societies. In honey bees (Apis mellifera L.), severe virus infections in queens can trigger worker-initiated supersedure, a socially coordinated replacement of the queen that, while risky, is essential when her reproductive competence is compromised. How viruses impact the physiology of queen hosts, who bear unique reproductive burdens within their colonies, and how this perturbs colony social order remains poorly understood. We hypothesized that the supersedure response is mediated by pathogen-induced, intensity-dependent changes in queen pheromonal signaling. Laboratory infection experiments revealed that queens challenged with deformed wing virus B and black queen cell virus infections demonstrated a reduction in methyl oleate, a key component of the queen retinue pheromone, and field data corroborated this association. Lipidomics analysis demonstrated that infection coincides with a systemic lipid deficiency, especially in triacylglycerides (major energy reserves), providing a physiological link among viral stress, ovarian atrophy, and altered pheromone output. Notably, artificial suppression of ovary investment via restricted laying also caused methyl oleate production to decline; therefore, high virus infection likely indirectly suppresses methyl oleate production by reducing ovary mass. In field trials, we further show that synthetic pheromone blends containing methyl oleate significantly suppressed queen cell rearing compared to no-pheromone controls, whereas blends lacking this compound yielded an intermediate effect. These results demonstrate that virus-induced reproductive decline disrupts pheromone signaling, revealing a plausible mechanistic pathway by which pathogens can erode social cohesion.