scholarly journals Dead or Alive: Deformed Wing Virus and Varroa destructor Reduce the Life Span of Winter Honeybees

2011 ◽  
Vol 78 (4) ◽  
pp. 981-987 ◽  
Author(s):  
Benjamin Dainat ◽  
Jay D. Evans ◽  
Yan Ping Chen ◽  
Laurent Gauthier ◽  
Peter Neumann
Keyword(s):  
Life Expectancy ◽  
Life Span ◽  
Varroa Destructor ◽  
Colony Losses ◽  
Deformed Wing Virus ◽  
Content Type ◽  
Parasitic Mite ◽  
Honeybee Colony ◽  
Underlying Mechanisms ◽  
Acute Bee Paralysis Virus

ABSTRACTElevated winter losses of managed honeybee colonies are a major concern, but the underlying mechanisms remain controversial. Among the suspects are the parasitic miteVarroa destructor, the microsporidianNosema ceranae, and associated viruses. Here we hypothesize that pathogens reduce the life expectancy of winter bees, thereby constituting a proximate mechanism for colony losses. A monitoring of colonies was performed over 6 months in Switzerland from summer 2007 to winter 2007/2008. Individual dead workers were collected daily and quantitatively analyzed for deformed wing virus (DWV), acute bee paralysis virus (ABPV),N. ceranae, and expression levels of thevitellogeningene as a biomarker for honeybee longevity. Workers from colonies that failed to survive winter had a reduced life span beginning in late fall, were more likely to be infected with DWV, and had higher DWV loads. Colony levels of infection with the parasitic miteVarroa destructorand individual infections with DWV were also associated with reduced honeybee life expectancy. In sharp contrast, the level ofN. ceranaeinfection was not correlated with longevity. In addition,vitellogeningene expression was significantly positively correlated with ABPV andN. ceranaeloads. The findings strongly suggest thatV. destructorand DWV (but neitherN. ceranaenor ABPV) reduce the life span of winter bees, thereby constituting a parsimonious possible mechanism for honeybee colony losses.

scholarly journals Haemolymph removal by Varroa mite destabilizes the dynamical interaction between immune effectors and virus in bees, as predicted by Volterra's model

2019 ◽  
Vol 286 (1901) ◽  
pp. 20190331 ◽  
Author(s):  
Desiderato Annoscia ◽  
Sam P. Brown ◽  
Gennaro Di Prisco ◽  
Emanuele De Paoli ◽  
Simone Del Fabbro ◽  
...  
Keyword(s):  
Viral Evolution ◽  
Colony Losses ◽  
Viral Pathogen ◽  
Dynamical Interaction ◽  
Deformed Wing Virus ◽  
Pathogen Virulence ◽  
Mite Feeding ◽  
Parasitic Mite ◽  
Honeybee Colony ◽  
Honeybee Health

The association between the deformed wing virus and the parasitic mite Varroa destructor has been identified as a major cause of worldwide honeybee colony losses. The mite acts as a vector of the viral pathogen and can trigger its replication in infected bees. However, the mechanistic details underlying this tripartite interaction are still poorly defined, and, particularly, the causes of viral proliferation in mite-infested bees. Here, we develop and test a novel hypothesis that mite feeding destabilizes viral immune control through the removal of both virus and immune effectors, triggering uncontrolled viral replication. Our hypothesis is grounded on the predator–prey theory developed by Volterra, which predicts prey proliferation when both predators and preys are constantly removed from the system. Consistent with this hypothesis, we show that the experimental removal of increasing volumes of haemolymph from individual bees results in increasing viral densities. By contrast, we do not find consistent support for alternative proposed mechanisms of viral expansion via mite immune suppression or within-host viral evolution. Our results suggest that haemolymph removal plays an important role in the enhanced pathogen virulence observed in the presence of feeding Varroa mites. Overall, these results provide a new model for the mechanisms driving pathogen–parasite interactions in bees, which ultimately underpin honeybee health decline and colony losses.

scholarly journals Neonicotinoid Clothianidin reduces honey bee immune response and contributes to Varroa mite proliferation

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Desiderato Annoscia ◽  
Gennaro Di Prisco ◽  
Andrea Becchimanzi ◽  
Emilio Caprio ◽  
Davide Frizzera ◽  
...  
Keyword(s):  
Immune Responses ◽  
Honey Bee ◽  
Honey Bees ◽  
Varroa Destructor ◽  
Negative Impact ◽  
Asymptomatic Infection ◽  
Varroa Mite ◽  
Deformed Wing Virus ◽  
Synergistic Interactions ◽  
Parasitic Mite

AbstractThe neonicotinoid Clothianidin has a negative impact on NF-κB signaling and on immune responses controlled by this transcription factor, which can boost the proliferation of honey bee parasites and pathogens. This effect has been well documented for the replication of deformed wing virus (DWV) induced by Clothianidin in honey bees bearing an asymptomatic infection. Here, we conduct infestation experiments of treated bees to show that the immune-suppression exerted by Clothianidin is associated with an enhanced fertility of the parasitic mite Varroa destructor, as a possible consequence of a higher feeding efficiency. A conceptual model is proposed to describe the synergistic interactions among different stress agents acting on honey bees.

scholarly journals Advances and perspectives in selecting resistance traits against the parasitic mite Varroa destructor in honey bees

2020 ◽  
Vol 52 (1) ◽  
Author(s):  
Matthieu Guichard ◽  
Vincent Dietemann ◽  
Markus Neuditschko ◽  
Benjamin Dainat
Keyword(s):  
Honey Bee ◽  
Environmental Effects ◽  
Honey Bees ◽  
Varroa Destructor ◽  
Selection Strategy ◽  
Pollination Services ◽  
Colony Losses ◽  
New Host ◽  
Parasitic Mite ◽  
Resistance Traits

Abstract Background In spite of the implementation of control strategies in honey bee (Apis mellifera) keeping, the invasive parasitic mite Varroa destructor remains one of the main causes of colony losses in numerous countries. Therefore, this parasite represents a serious threat to beekeeping and agro-ecosystems that benefit from the pollination services provided by honey bees. To maintain their stocks, beekeepers have to treat their colonies with acaricides every year. Selecting lineages that are resistant to infestations is deemed to be a more sustainable approach. Review Over the last three decades, numerous selection programs have been initiated to improve the host–parasite relationship and to support honey bee survival in the presence of the parasite without the need for acaricide treatments. Although resistance traits have been included in the selection strategy of honey bees, it has not been possible to globally solve the V. destructor problem. In this study, we review the literature on the reasons that have potentially limited the success of such selection programs. We compile the available information to assess the relevance of selected traits and the potential environmental effects that distort trait expression and colony survival. Limitations to the implementation of these traits in the field are also discussed. Conclusions Improving our knowledge of the mechanisms underlying resistance to V. destructor to increase trait relevance, optimizing selection programs to reduce environmental effects, and communicating selection outcomes are all crucial to efforts aiming at establishing a balanced relationship between the invasive parasite and its new host.

scholarly journals A Diverse Range of Novel RNA Viruses in Geographically Distinct Honey Bee Populations

2017 ◽  
Vol 91 (16) ◽  
Author(s):  
Emily J. Remnant ◽  
Mang Shi ◽  
Gabriele Buchmann ◽  
Tjeerd Blacquière ◽  
Edward C. Holmes ◽  
...  
Keyword(s):  
Disease Management ◽  
Honey Bee ◽  
Small Rna ◽  
Honey Bees ◽  
Rna Viruses ◽  
Viral Diversity ◽  
Colony Losses ◽  
Diverse Range ◽  
Deformed Wing Virus ◽  
Content Type

ABSTRACT Understanding the diversity and consequences of viruses present in honey bees is critical for maintaining pollinator health and managing the spread of disease. The viral landscape of honey bees (Apis mellifera) has changed dramatically since the emergence of the parasitic mite Varroa destructor, which increased the spread of virulent variants of viruses such as deformed wing virus. Previous genomic studies have focused on colonies suffering from infections by Varroa and virulent viruses, which could mask other viral species present in honey bees, resulting in a distorted view of viral diversity. To capture the viral diversity within colonies that are exposed to mites but do not suffer the ultimate consequences of the infestation, we examined populations of honey bees that have evolved naturally or have been selected for resistance to Varroa. This analysis revealed seven novel viruses isolated from honey bees sampled globally, including the first identification of negative-sense RNA viruses in honey bees. Notably, two rhabdoviruses were present in three geographically diverse locations and were also present in Varroa mites parasitizing the bees. To characterize the antiviral response, we performed deep sequencing of small RNA populations in honey bees and mites. This provided evidence of a Dicer-mediated immune response in honey bees, while the viral small RNA profile in Varroa mites was novel and distinct from the response observed in bees. Overall, we show that viral diversity in honey bee colonies is greater than previously thought, which encourages additional studies of the bee virome on a global scale and which may ultimately improve disease management. IMPORTANCE Honey bee populations have become increasingly susceptible to colony losses due to pathogenic viruses spread by parasitic Varroa mites. To date, 24 viruses have been described in honey bees, with most belonging to the order Picornavirales. Collapsing Varroa-infected colonies are often overwhelmed with high levels of picornaviruses. To examine the underlying viral diversity in honey bees, we employed viral metatranscriptomics analyses on three geographically diverse Varroa-resistant populations from Europe, Africa, and the Pacific. We describe seven novel viruses from a range of diverse viral families, including two viruses that are present in all three locations. In honey bees, small RNA sequences indicate that these viruses are processed by Dicer and the RNA interference pathway, whereas Varroa mites produce strikingly novel small RNA patterns. This work increases the number and diversity of known honey bee viruses and will ultimately contribute to improved disease management in our most important agricultural pollinator.

scholarly journals A mutualistic symbiosis between a parasitic mite and a pathogenic virus undermines honey bee immunity and health

2016 ◽  
Vol 113 (12) ◽  
pp. 3203-3208 ◽  
Author(s):  
Gennaro Di Prisco ◽  
Desiderato Annoscia ◽  
Marina Margiotta ◽  
Rosalba Ferrara ◽  
Paola Varricchio ◽  
...  
Keyword(s):  
Honey Bee ◽  
Stress Factors ◽  
Colony Losses ◽  
Viral Pathogen ◽  
Deformed Wing Virus ◽  
Mutualistic Symbiosis ◽  
Bee Colony ◽  
Parasitic Mite ◽  
Honey Bee Colony ◽  
Honey Bee Colony Losses

Honey bee colony losses are triggered by interacting stress factors consistently associated with high loads of parasites and/or pathogens. A wealth of biotic and abiotic stressors are involved in the induction of this complex multifactorial syndrome, with the parasitic mite Varroa destructor and the associated deformed wing virus (DWV) apparently playing key roles. The mechanistic basis underpinning this association and the evolutionary implications remain largely obscure. Here we narrow this research gap by demonstrating that DWV, vectored by the Varroa mite, adversely affects humoral and cellular immune responses by interfering with NF-κB signaling. This immunosuppressive effect of the viral pathogen enhances reproduction of the parasitic mite. Our experimental data uncover an unrecognized mutualistic symbiosis between Varroa and DWV, which perpetuates a loop of reciprocal stimulation with escalating negative effects on honey bee immunity and health. These results largely account for the remarkable importance of this mite–virus interaction in the induction of honey bee colony losses. The discovery of this mutualistic association and the elucidation of the underlying regulatory mechanisms sets the stage for a more insightful analysis of how synergistic stress factors contribute to colony collapse, and for the development of new strategies to alleviate this problem.

scholarly journals Acaricide Treatment Affects Viral Dynamics in Varroa destructor-Infested Honey Bee Colonies via both Host Physiology and Mite Control

2011 ◽  
Vol 78 (1) ◽  
pp. 227-235 ◽  
Author(s):  
Barbara Locke ◽  
Eva Forsgren ◽  
Ingemar Fries ◽  
Joachim R. de Miranda
Keyword(s):  
Honey Bee ◽  
Varroa Destructor ◽  
Synergistic Effects ◽  
Physiological Effect ◽  
Mite Infestation ◽  
Initial Increase ◽  
Virus Infections ◽  
Deformed Wing Virus ◽  
Content Type ◽  
Honey Bee Health

ABSTRACTHoney bee (Apis mellifera) colonies are declining, and a number of stressors have been identified that affect, alone or in combination, the health of honey bees. The ectoparasitic miteVarroa destructor, honey bee viruses that are often closely associated with the mite, and pesticides used to control the mite population form a complex system of stressors that may affect honey bee health in different ways. During an acaricide treatment using Apistan (plastic strips coated with tau-fluvalinate), we analyzed the infection dynamics of deformed wing virus (DWV), sacbrood virus (SBV), and black queen cell virus (BQCV) in adult bees, mite-infested pupae, their associatedVarroamites, and uninfested pupae, comparing these to similar samples from untreated control colonies. Titers of DWV increased initially with the onset of the acaricide application and then slightly decreased progressively coinciding with the removal of theVarroamite infestation. This initial increase in DWV titers suggests a physiological effect of tau-fluvalinate on the host's susceptibility to viral infection. DWV titers in adult bees and uninfested pupae remained higher in treated colonies than in untreated colonies. The titers of SBV and BQCV did not show any direct relationship with mite infestation and showed a variety of possible effects of the acaricide treatment. The results indicate that other factors besidesVarroamite infestation may be important to the development and maintenance of damaging DWV titers in colonies. Possible biochemical explanations for the observed synergistic effects between tau-fluvalinate and virus infections are discussed.

scholarly journals Can colony size of honeybees (Apis mellifera) be used as predictor for colony losses due to Varroa destructor during winter?

2020 ◽  
Author(s):  
Coby van Dooremalen ◽  
Frank van Langevelde
Keyword(s):  
Apis Mellifera ◽  
Colony Size ◽  
Varroa Destructor ◽  
Warning Signs ◽  
Colony Losses ◽  
Early Warning Signs ◽  
Parasitic Mite ◽  
Almost All ◽  
Early Predictor

AbstractFor more than three decades, honeybee colonies (Apis mellifera) experience high losses during winter, and these losses are still continuing. It is crucial that beekeepers monitor their colonies closely and anticipate losses early enough to apply mitigating actions. We tested whether colony size can be used as early predictor for potential colony losses, in particular due to the parasitic mite Varroa destructor. V. destructor is one of the most important causes for these losses. Such early predictor for potential V. destructor induced losses is especially relevant as measuring V. destructor load in colonies is difficult and cumbersome. During three years, we monitored colonies with high and low V. destructor load from July until March of the next year. We found that differences in colony size were only visible after November, even though we lost almost all colonies every winter in the group with high V. destructor load. In the Northern hemisphere, November is considered to be too late for beekeepers to strengthen colonies in preparation for winter. We therefore argue that early-warning signs for potential colony losses due to V. destructor are urgently needed to allow beekeepers preventing winter losses. We discuss the role of precision apiculture to monitor the health and productivity of honeybee colonies.

scholarly journals Direct Evidence for Infection of Varroa destructor Mites with the Bee-Pathogenic Deformed Wing Virus Variant B - but Not Variant A - via Fluorescence-in situ-Hybridization Analysis.

2020 ◽  
Author(s):  
Sebastian Gisder ◽  
Elke Genersch
Keyword(s):  
Salivary Glands ◽  
Honey Bees ◽  
Varroa Destructor ◽  
Direct Evidence ◽  
Rna Virus ◽  
Colony Losses ◽  
Deformed Wing Virus ◽  
Brain Infection ◽  
Biological Vector

Deformed wing virus (DWV) is a bee pathogenic, single- and positive-stranded RNA virus that has been involved in severe honey bee colony losses worldwide. DWV, when transmitted horizontally or vertically from bee to bee, causes mainly covert infections not associated with any visible symptoms or damage. Overt infections occur after vectorial transmission of DWV to the developing bee pupae through the ectoparasitic mite Varroa destructor. Symptoms of overt infections are pupal death, bees emerging with deformed wings and shortened abdomens, or cognitive impairment due to brain infection. So far, three variants of DWV, DWV-A, DWV-B, and DWV-C, have been described. While it is widely accepted that V. destructor acts as vector of DWV, the question of whether the mite only functions as a mechanical vector or whether DWV can infect the mite thus using it as a biological vector is hotly debated, because in the literature data can be found that support both hypotheses. In order to settle this scientific dispute, we analyzed putatively DWV-infected mites with a newly established protocol for fluorescence-in situ-hybridization of mites and demonstrated DWV-specific signals inside mite cells. We provide compelling and direct evidence that DWV-B infects the intestinal epithelium and the salivary glands of V. destructor. In contrast, no evidence for DWV-A infecting mite cells was found. Our data are key to understanding the pathobiology of DWV, the mite’s role as a biological DWV vector and the quasispecies dynamics of this RNA virus when switching between insect and arachnid host species. IMPORTANCE Deformed wing virus (DWV) is a bee pathogenic, originally rather benign, single- and positive-stranded RNA virus. Only the vectorial transmission of this virus to honey bees by the ectoparasitic mite Varroa destructor leads to fatal or symptomatic infections of individuals, usually followed by collapse of the entire colony. Studies on whether the mite only acts as a mechanical virus vector or whether DWV can infect the mite and thus use it as a biological vector have led to disparate results. In our study using fluorescence-in situ-hybridization we provide compelling and direct evidence that at least the DWV-B variant infects the gut epithelium and the salivary glands of V. destructor. Hence, the host range of DWV includes both, bees (Insecta) and mites (Arachnida). Our data contribute to a better understanding of the triangular relationship between honey bees, V. destructor and DWV and the evolution of virulence in this viral bee pathogen.

scholarly journals Interaction between Varroa destructor and imidacloprid reduces flight capacity of honeybees

2015 ◽  
Vol 282 (1820) ◽  
pp. 20151738 ◽  
Author(s):  
Lisa J. Blanken ◽  
Frank van Langevelde ◽  
Coby van Dooremalen
Keyword(s):  
Varroa Destructor ◽  
Lethal Dose ◽  
Interactive Effects ◽  
Colony Losses ◽  
Cascading Effects ◽  
Flight Capacity ◽  
Colony Collapse ◽  
Flight Mills ◽  
Neonicotinoid Insecticide ◽  
Parasitic Mite

Current high losses of honeybees seriously threaten crop pollination. Whereas parasite exposure is acknowledged as an important cause of these losses, the role of insecticides is controversial. Parasites and neonicotinoid insecticides reduce homing success of foragers (e.g. by reduced orientation), but it is unknown whether they negatively affect flight capacity. We investigated how exposing colonies to the parasitic mite Varroa destructor and the neonicotinoid insecticide imidacloprid affect flight capacity of foragers. Flight distance, time and speed of foragers were measured in flight mills to assess the relative and interactive effects of high V. destructor load and a field-realistic, chronic sub-lethal dose of imidacloprid. Foragers from colonies exposed to high levels of V. destructor flew shorter distances, with a larger effect when also exposed to imidacloprid. Bee body mass partly explained our results as bees were heavier when exposed to these stressors, possibly due to an earlier onset of foraging. Our findings contribute to understanding of interacting stressors that can explain colony losses. Reduced flight capacity decreases the food-collecting ability of honeybees and may hamper the use of precocious foraging as a coping mechanism during colony (nutritional) stress. Ineffective coping mechanisms may lead to destructive cascading effects and subsequent colony collapse.

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