scholarly journals Outcomes of honeybee pupae inoculated with deformed wing virus genotypes A and B

Apidologie ◽  
2019 ◽  
Vol 51 (1) ◽  
pp. 18-34 ◽  
Author(s):  
Eric Dubois ◽  
Marine Dardouri ◽  
Frank Schurr ◽  
Nicolas Cougoule ◽  
Fabrice Sircoulomb ◽  
...  
Keyword(s):  
Quantitative Pcr ◽  
Varroa Destructor ◽  
Mortality Rates ◽  
Virus Genotype ◽  
Colony Losses ◽  
Deformed Wing Virus ◽  
Viral Loads ◽  
Virus Genotypes ◽  
Pcr Targeting ◽  
Genotype A

AbstractDeformed wing virus and Varroa destructor virus-1 have a high percentage of nucleotide identity and might be considered as closely related viruses: DWV genotype A (DWV-A) and DWV genotype B (DWV-B) respectively. They have been implicated in overwinter colony losses in association with Varroa destructor infestations that vectored both DWV variants. In this study, we performed experimental inoculations of honeybee pupae with viral suspensions prepared from honeybee heads naturally infected by either DWV-A or DWV-B. Two outcomes were observed: the inoculated pupae exhibited either higher rates of bees with deformed wings or higher mortality rates than control bees. For both DWV variants, the viral loads quantified in the head of inoculated bees were significantly greater than those in control bees (p < 0.01). These outcomes were not correlated to the virus genotype (DWV-A or DWV-B) detected in the inocula by RT-quantitative PCR targeting the VP3 coding sequence (RT-qPCR). However, the highest mortality rates found in our study were correlated with an increase in sacbrood virus (SBV) load. Despite the fact that only either DWV-A or DWV-B was expected to be inoculated, we observed increased mortality in honeybees that were infected with both DWV and SBV.

scholarly journals New Viruses from the Ectoparasite Mite Varroa destructor Infesting Apis mellifera and Apis cerana

Viruses ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 94 ◽  
Author(s):  
Sofia Levin ◽  
Noa Sela ◽  
Tal Erez ◽  
David Nestel ◽  
Jeffery Pettis ◽  
...  
Keyword(s):  
Apis Mellifera ◽  
Varroa Destructor ◽  
Rna Virus ◽  
Apis Cerana ◽  
Virus Genome ◽  
Deformed Wing Virus ◽  
Viral Loads ◽  
Short Period ◽  
Honeybee Subspecies ◽  
Colony Survival

Varroa destructor is an ectoparasitic mite of Asian or Eastern honeybees Apis cerana (A. cerana) which has become a serious threat to European subspecies of Western honeybees Apis mellifera (A. mellifera) within the last century. V. destructor and its vectored honeybee viruses became serious threats for colony survival. This is a short period for pathogen- and host-populations to adapt. To look for possible variation in the composition of viral populations we performed RNA metagenomic analysis of the Western honeybee subspecies A. m. ligustica, A. m. syriaca, A. m. intermissa, and A. cerana and their respective V. destructor mites. The analysis revealed two novel viruses: Varroa orthomyxovirus-1 (VOV-1) in A. mellifera and V. destructor and a Hubei like-virga virus-14 homolog in V. destructor. VOV-1 was more prevalent in V. destructor than in A. mellifera and we found evidence for viral replication in both hosts. Interestingly, we found differences in viral loads of A. cerana and their V. destructor, A. m. intermissa, and its V. destructor showed partial similarity, while A. m. ligustica and A. m. syriaca and their varroa where very similar. Deformed wing virus exhibited 82.20%, 99.20%, 97.90%, and 0.76% of total viral reads in A. m. ligustica, A. m. syriaca, A. m. intermissa, and A. cerana, respectively. This is the first report of a complete segmented-single-stranded negative-sense RNA virus genome in honeybees and V. destructor mites.

scholarly journals Deformed wing virus type A, a major honey bee pathogen, is vectored by the mite Varroa destructor in a non-propagative manner

2019 ◽  
Author(s):  
Francisco Posada-Florez ◽  
Anna K. Childers ◽  
Matthew C. Heerman ◽  
Noble I. Egekwu ◽  
Steven C. Cook ◽  
...  
Keyword(s):  
Honey Bee ◽  
Honey Bees ◽  
Varroa Destructor ◽  
Rna Virus ◽  
Fold Increase ◽  
Type A ◽  
Deformed Wing Virus ◽  
Negative Strand ◽  
Viral Loads ◽  
Insect Pollinator

AbstractHoney bees, the primary managed insect pollinator, suffer considerable losses due to Deformed wing virus (DWV), an RNA virus vectored by the mite Varroa destructor. Mite vectoring has resulted in the emergence of virulent DWV variants. The basis for such changes in DWV is poorly understood. Most importantly, it remains unclear whether replication of DWV occurs in the mite. In this study, we exposed Varroa mites to DWV type A via feeding on artificially infected honey bees. A significant, 357-fold increase in DWV load was observed in these mites after 2 days. However, after 8 additional days of passage on honey bee pupae with low viral loads, the DWV load dropped by 29-fold. This decrease significantly reduced the mites’ ability to transmit DWV to honey bees. Notably, negative-strand DWV RNA, which could indicate viral replication, was detected only in mites collected from pupae with high DWV levels but not in the passaged mites. We also found that Varroa mites contain honey bee mRNAs, consistent with the acquisition of honey bee cells which would additionally contain DWV replication complexes with negative-strand DWV RNA. We propose that transmission of DWV type A by Varroa mites occurs in a non-propagative manner.

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 Haemolymph removal by the parasite Varroa destructor can trigger the proliferation of the Deformed Wing Virus in mite infested bees (Apis mellifera), contributing to enhanced pathogen virulence

2018 ◽  
Author(s):  
Desiderato Annoscia ◽  
Sam P. Brown ◽  
Gennaro Di Prisco ◽  
Emanuele De Paoli ◽  
Simone Del Fabbro ◽  
...  
Keyword(s):  
Honey Bee ◽  
Varroa Destructor ◽  
Viral Evolution ◽  
Colony Losses ◽  
Viral Pathogen ◽  
Deformed Wing Virus ◽  
Bee Colony ◽  
Bee Health ◽  
Honey Bee Health ◽  
Mite Feeding

AbstractThe association between the Deformed Wing Virus and the parasitic mite Varroa destructor has been identified as a major cause of worldwide honey bee 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, in particular, the causes of viral proliferation in mite infested bees.Here we develop and test a novel hypothesis - grounded in ecological predator-prey theory - that mite feeding destabilizes viral immune control through the removal of both viral ‘prey’ and immune ‘predators’, triggering uncontrolled viral replication. Consistent with this hypothesis, we show that experimental removal of increasing volumes of haemolymph from individual bees results in increasing viral densities. In contrast, we find no support for alternative proposed mechanisms of viral expansion via mite immune-suppression or within-host viral evolution.Overall, these results provide a new model for the mechanisms driving pathogen-parasite interactions in bees, which ultimately underpin honey bee health decline and colony losses.

scholarly journals Comb Irradiation Has Limited, Interactive Effects on Colony Performance or Pathogens in Bees, Varroa destructor and Wax Based on Two Honey Bee Stocks

Insects ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 15 ◽  
Author(s):  
Lilia I. De Guzman ◽  
Michael Simone-Finstrom ◽  
Amanda M. Frake ◽  
Philip Tokarz
Keyword(s):  
Honey Bee ◽  
Honey Bees ◽  
Varroa Destructor ◽  
Adult Population ◽  
Interactive Effects ◽  
Colony Losses ◽  
Deformed Wing Virus ◽  
Bee Health ◽  
Honey Bee Health ◽  
Russian Honey Bees

Parasitic mites and pathogens compromise honey bee health. Development of sustainable and integrative methods of managing these problems will minimize their detrimental impact on honey bees. Here, we aimed to determine if the combination of using mite-resistant stocks along with gamma-irradiated combs influences colony health and productivity. The major finding concerned honey bee genotype confirming that Russian honey bees are more resistant to Varroa destructor than Italian honey bees. The effect of comb irradiation was inconsistent showing a significant increase in adult bee population and amount of stored pollen in 2015, but not in 2016. The increased amount of stored pollen was probably associated with larger adult population in colonies with irradiated combs in September 2015 regardless of honey bee stock. Nevertheless, the ability of bees to collect and store more pollen in the irradiated group does not appear to compensate the negative impacts of mite parasitism on honey bees especially in the Italian bees, which consistently suffered significant colony losses during both years. Results of viral analyses of wax, newly emerged bees, and Varroa and their pupal hosts showed common detections of Deformed wing virus (DWV), Varroa destructor virus (VDV-1), Chronic bee paralysis virus (CBPV), and Black queen cell virus (BQCV). Wax samples had on average ~4 viruses or pathogens detected in both irradiated and non-irradiated combs. Although pathogen levels varied by month, some interesting effects of honey bee stock and irradiation treatment were notable, indicating how traits of mite resistance and alternative treatments may have additive effects. Further, this study indicates that wax may be a transmission route of viral infection. In addition, pupae and their infesting mites from Italian colonies exhibited higher levels of DWV than those from Russian colonies suggesting potential DWV resistance by Russian honey bees. CBPV levels were also reduced in mites from Russian colonies in general and in mites, mite-infested pupae, and newly emerged bees that were collected from irradiated combs. However, BQCV levels were not reduced by comb irradiation. Overall, the contribution of irradiating comb in improving honey bee health and colony survival appears to be subtle, but may be useful as part of an integrated pest management strategy with the addition of using mite-resistant stocks.

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 Exposure to Inactivated Deformed Wing Virus Leads to Trans-Generational Costs but Not Immune Priming in Honeybees (Apis mellifera)

2021 ◽  
Vol 9 ◽  
Author(s):  
Matti Leponiemi ◽  
Gro V. Amdam ◽  
Dalial Freitak
Keyword(s):  
Immune System ◽  
Priming Effect ◽  
Immune Challenge ◽  
Colony Losses ◽  
Viral Pathogen ◽  
Deformed Wing Virus ◽  
Immune Priming ◽  
Viral Loads ◽  
Honeybee Colony ◽  
Pupal Mortality

Pathogens are identified as one of the major drivers behind the honeybee colony losses, as well as one of the reasons for the reported declines in terrestrial insect abundances in recent decades. To fight infections, animals rely on their immune system. The immune system of many invertebrates can be primed by exposure to a pathogen, so that upon further exposure the animal is better protected. The protective priming effect can even extend to the next generation, but the species capable of priming the immune system of their offspring are still being investigated. Here we studied whether honeybees could prime their offspring against a viral pathogen, by challenging honeybee queens orally with an inactivated deformed wing virus (DWV), one of the most devastating honeybee viruses. The offspring were then infected by viral injection. The effects of immune priming were assayed by measuring viral loads and two typical symptoms of the virus, pupal mortality, and abnormal wing phenotype. We saw a low amount of wing deformities and low pupal mortality. While no clear priming effect against the virus was seen, we found that the maternal immune challenge, when combined with the stress caused by an injection during development, manifested in costs in the offspring, leading to an increased number of deformed wings.

scholarly journals Effects of Deformed Wing Virus Infection on Expressions of Immune- and Apoptosis-Related Genes in Western Honeybees (Apis mellifera)

Insects ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 82
Author(s):  
Wannapha Mookhploy ◽  
Sasiprapa Krongdang ◽  
Panuwan Chantawannakul
Keyword(s):  
Apis Mellifera ◽  
Mortality Rate ◽  
Virus Infection ◽  
Treatment Method ◽  
Positive Control ◽  
Control Groups ◽  
Gene Expressions ◽  
Deformed Wing Virus ◽  
Immune Genes ◽  
Viral Loads

Honeybees are globally threatened by several pathogens, especially deformed wing virus (DWV), as the presence of DWV in western honeybees is indicative of colony loss. The high mortality rate is further exacerbated by the lack of effective treatment, and therefore understanding the immune and apoptosis responses could pave an avenue for the treatment method. In this study, DWV was directly injected into the white-eyed pupae stage of western honeybees (Apis mellifera). The DWV loads and selected gene responses were monitored using the real-time PCR technique. The results showed that honeybee pupae that were injected with the highest concentration of viral loads showed a significantly higher mortality rate than the control groups. Deformed wings could be observed in newly emerged adult bees when the infected bees harbored high levels of viral loads. However, the numbers of viral loads in both normal and crippled wing groups were not significantly different. DWV-injected honeybee pupae with 104 and 107 copy numbers per bee groups showed similar viral loads after 48 h until newly emerged adult bees. Levels of gene expression including immune genes (defensin, abaecin, and hymenoptaecin) and apoptosis genes (buffy, p53, Apaf1, caspase3-like, caspase8-like, and caspase9-like) were analyzed after DWV infection. The expressions of immune and apoptosis genes were significantly different in infected bees compared to those of the control groups. In the pupae stage, the immune genes were activated by injecting DWV (defensin and hymenoptaecin) or Escherichia coli (defensin, abaecin, and hymenoptaecin), a positive control. On the contrary, the expression of apoptosis-related genes (buffy, caspase3-like, caspase8-like, and caspase9-like genes) was suppressed at 96 h post-infection. In DWV-infected newly emerged adult bees, abaecin, hymenoptaecin, Apaf1, and caspase8-like genes were upregulated. However, these genes were not significantly different between the normal and crippled wing bees. Our results suggested that DWV could activate the humoral immunity in honeybees and that honeybee hosts may be able to protect themselves from the virus infection through immune responses. Apoptosis gene expressions were upregulated in newly emerged adult bees by the virus, however, they were downregulated during the initial phase of viral infection.

scholarly journals Pupal cannibalism by worker honey bees contributes to the spread of deformed wing virus

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Francisco Posada-Florez ◽  
Zachary S. Lamas ◽  
David J. Hawthorne ◽  
Yanping Chen ◽  
Jay D. Evans ◽  
...  
Keyword(s):  
Honey Bees ◽  
Control Strategies ◽  
Virus Transmission ◽  
Experimental Conditions ◽  
Colony Losses ◽  
Viral Pathogen ◽  
Deformed Wing Virus ◽  
Hygienic Behaviour ◽  
Pathogen Virulence ◽  
Comprehensive Knowledge

AbstractTransmission routes impact pathogen virulence and genetics, therefore comprehensive knowledge of these routes and their contribution to pathogen circulation is essential for understanding host–pathogen interactions and designing control strategies. Deformed wing virus (DWV), a principal viral pathogen of honey bees associated with increased honey bee mortality and colony losses, became highly virulent with the spread of its vector, the ectoparasitic mite Varroa destructor. Reproduction of Varroa mites occurs in capped brood cells and mite-infested pupae from these cells usually have high levels of DWV. The removal of mite-infested pupae by worker bees, Varroa Sensitive Hygiene (VSH), leads to cannibalization of pupae with high DWV loads, thereby offering an alternative route for virus transmission. We used genetically tagged DWV to investigate virus transmission to and between worker bees following pupal cannibalisation under experimental conditions. We demonstrated that cannibalization of DWV-infected pupae resulted in high levels of this virus in worker bees and that the acquired virus was then transmitted between bees via trophallaxis, allowing circulation of Varroa-vectored DWV variants without the mites. Despite the known benefits of hygienic behaviour, it is possible that higher levels of VSH activity may result in increased transmission of DWV via cannibalism and trophallaxis.

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