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Cook SC, Ryabov EV, Becker C, Rogers CW, Posada-Florez F, Evans JD, Chen YP. Deformed wing virus of honey bees is inactivated by cold plasma ionized hydrogen peroxide. Front Insect Sci 2023; 3:1216291. [PMID: 38469475 PMCID: PMC10926414 DOI: 10.3389/finsc.2023.1216291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Accepted: 07/18/2023] [Indexed: 03/13/2024]
Abstract
Deformed wing virus (DWV) is a widespread pathogen of Apis mellifera honey bees, and is considered a major causative factor for the collapse of infected honey bee colonies. DWV can be horizontally transmitted among bees through various oral routes, including via food sharing and by interactions of bees with viral-contaminated solid hive substrates. Cold plasma ionized hydrogen peroxide (iHP) is used extensively by the food production, processing and medical industries to clean surfaces of microbial contaminants. In this study, we investigated the use of iHP to inactivate DWV particles in situ on a solid substrate. iHP-treated DWV sources were ~105-fold less infectious when injected into naïve honey bee pupae compared to DWV receiving no iHP treatment, matching injected controls containing no DWV. iHP treatment also greatly reduced the incidence of overt DWV infections (i.e., pupae having >109 copies of DWV). The level of DWV inactivation achieved with iHP treatment was higher than other means of viral inactivation such as gamma irradiation, and iHP treatment is likely simpler and safer. Treatment of DWV contaminated hive substrates with iHP, even with honey bees present, may be an effective way to decrease the impacts of DWV infection on honey bees.
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Affiliation(s)
- Steven C. Cook
- United States Department of Agriculture - Agricultural Research (USDA-ARS) Service, Bee Research Laboratory, Beltsville, MD, United States
| | - Eugene V. Ryabov
- United States Department of Agriculture - Agricultural Research (USDA-ARS) Service, Bee Research Laboratory, Beltsville, MD, United States
- Department of Entomology, University of Maryland, College Park, MD, United States
| | | | - Curtis W. Rogers
- United States Department of Agriculture - Agricultural Research (USDA-ARS) Service, Bee Research Laboratory, Beltsville, MD, United States
| | - Francisco Posada-Florez
- United States Department of Agriculture - Agricultural Research (USDA-ARS) Service, Bee Research Laboratory, Beltsville, MD, United States
| | - Jay D. Evans
- United States Department of Agriculture - Agricultural Research (USDA-ARS) Service, Bee Research Laboratory, Beltsville, MD, United States
| | - Yan Ping Chen
- United States Department of Agriculture - Agricultural Research (USDA-ARS) Service, Bee Research Laboratory, Beltsville, MD, United States
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Huang Q, Sim SB, Geib SM, Childers A, Liu J, Wei X, Han W, Posada-Florez F, Xue AZ, Li Z, Evans JD. Identification of sex chromosomes and primary sex ratio in the small hive beetle, a worldwide parasite of honey bees. Gigascience 2022; 12:giad056. [PMID: 37489752 PMCID: PMC10367126 DOI: 10.1093/gigascience/giad056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 04/20/2023] [Accepted: 07/03/2023] [Indexed: 07/26/2023] Open
Abstract
BACKGROUND The small hive beetle (SHB), Aethina tumida, has emerged as a worldwide threat to honey bees in the past two decades. These beetles harvest nest resources, feed on larval bees, and ultimately spoil nest resources with gelatinous slime together with the fungal symbiont Kodamaea ohmeri. RESULTS Here, we present the first chromosome-level genome assembly for the SHB. With a 99.1% representation of conserved (BUSCO) arthropod genes, this resource enables the study of chemosensory, digestive, and detoxification traits critical for SHB success and possible control. We use this annotated assembly to characterize features of SHB sex chromosomes and a female-skewed primary sex ratio. We also found chromosome fusion and a lower recombination rate in sex chromosomes than in autosomes. CONCLUSIONS Genome-enabled insights will clarify the traits that allowed this beetle to exploit hive resources successfully and will be critical for determining the causes of observed sex ratio asymmetries.
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Affiliation(s)
- Qiang Huang
- Honeybee Research Institute, Jiangxi Agricultural University, 330045, Nanchang, China
- Department of Integrative Biology, The University of Texas at Austin, Austin, TX 78712, USA
| | - Sheina B Sim
- Daniel K. Inouye US Pacific Basin Agricultural Research Center Tropical Pest Genetics and Molecular Biology Research, USDA, Agricultural Research Service, Hilo, HI 96720, USA
| | - Scott M Geib
- Daniel K. Inouye US Pacific Basin Agricultural Research Center Tropical Pest Genetics and Molecular Biology Research, USDA, Agricultural Research Service, Hilo, HI 96720, USA
| | - Anna Childers
- Beltsville Agricultural Research Center, Bee Research Laboratory, USDA, Agricultural Research Service, Beltsville, MD 20705, USA
| | - Junfeng Liu
- Periodicals Agency, Jiangxi Agricultural University, 330045, Nanchang, China
| | - Xiuxiu Wei
- Honeybee Research Institute, Jiangxi Agricultural University, 330045, Nanchang, China
| | - Wensu Han
- Environment and Plant Protection Institute, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, China
| | - Francisco Posada-Florez
- Beltsville Agricultural Research Center, Bee Research Laboratory, USDA, Agricultural Research Service, Beltsville, MD 20705, USA
| | - Allen Z Xue
- Department of Integrative Biology, The University of Texas at Austin, Austin, TX 78712, USA
| | - Zheng Li
- Department of Integrative Biology, The University of Texas at Austin, Austin, TX 78712, USA
| | - Jay D Evans
- Beltsville Agricultural Research Center, Bee Research Laboratory, USDA, Agricultural Research Service, Beltsville, MD 20705, USA
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Ryabov EV, Posada-Florez F, Rogers C, Lamas ZS, Evans JD, Chen Y, Cook SC. The vectoring competence of the mite Varroa destructor for deformed wing virus of honey bees is dynamic and affects survival of the mite. Front Insect Sci 2022; 2:931352. [PMID: 38468796 PMCID: PMC10926515 DOI: 10.3389/finsc.2022.931352] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 09/12/2022] [Indexed: 03/13/2024]
Abstract
The ectoparasitic mite, Varroa destructor and the viruses it vectors, including types A and B of Deformed wing virus (DWV), pose a major threat to honey bees, Apis mellifera. Analysis of 256 mites collected from the same set of field colonies on five occasions from May to October 2021 showed that less than a half of them, 39.8% (95% confidence interval (CI): 34.0 - 46.0%), were able to induce a high (overt) level DWV infection with more than 109 viral genomes per bee in the pupa after 6 days of feeding, with both DWV-A and DWV-B being vectored at similar rates. To investigate the effect of the phoretic (or dispersal) stage on adult bees on the mites' ability to vector DWV, the mites from two collection events were divided into two groups, one of which was tested immediately for their infectiveness, and the other was kept with adult worker bees in cages for 12 days prior to testing their infectiveness. We found that while 39.2% (95% CI: 30.0 - 49.1%) of the immediately tested mites induced overt-level infections, 12-day passage on adult bees significantly increased the infectiousness to 89.8% (95% CI: 79.2 - 95.6%). It is likely that Varroa mites that survive brood interruptions in field colonies are increasingly infectious. The mite lifespan was affected by the DWV type it transmitted to pupae. The mites, which induced high DWV-B but not DWV-A infection had an average lifespan of 15.5 days (95% CI: 11.8 - 19.2 days), which was significantly shorter than those of the mites which induced high DWV-A but not DWV-B infection, with an average lifespan of 24.3 days (95% CI: 20.2 - 28.5), or the mites which did not induce high levels of DWV-A or DWV-B, with an average survival of 21.2 days (95% CI: 19.0 - 23.5 days). The mites which transmitted high levels of both DWV-A and DWV-B had an intermediate average survival of 20.5 days (95% CI: 15.1 - 25.9 days). The negative impact of DWV-B on mite survival could be a consequence of the ability of DWV-B, but not DWV-A to replicate in Varroa.
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Affiliation(s)
- Eugene V. Ryabov
- United States Department of Agriculture - Agricultural Research Service, Bee Research Laboratory, Beltsville, MD, United States
- Department of Entomology, University of Maryland, College Park, MD, United States
| | - Francisco Posada-Florez
- United States Department of Agriculture - Agricultural Research Service, Bee Research Laboratory, Beltsville, MD, United States
| | - Curtis Rogers
- United States Department of Agriculture - Agricultural Research Service, Bee Research Laboratory, Beltsville, MD, United States
| | - Zachary S. Lamas
- Department of Entomology, University of Maryland, College Park, MD, United States
| | - Jay D. Evans
- United States Department of Agriculture - Agricultural Research Service, Bee Research Laboratory, Beltsville, MD, United States
| | - Yanping Chen
- United States Department of Agriculture - Agricultural Research Service, Bee Research Laboratory, Beltsville, MD, United States
| | - Steven C. Cook
- United States Department of Agriculture - Agricultural Research Service, Bee Research Laboratory, Beltsville, MD, United States
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Posada-Florez F, Lamas ZS, Hawthorne DJ, Chen Y, Evans JD, Ryabov EV. Pupal cannibalism by worker honey bees contributes to the spread of deformed wing virus. Sci Rep 2021; 11:8989. [PMID: 33903723 PMCID: PMC8076318 DOI: 10.1038/s41598-021-88649-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Accepted: 04/12/2021] [Indexed: 11/30/2022] Open
Abstract
Transmission 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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Affiliation(s)
- Francisco Posada-Florez
- USDA, Agricultural Research Service, Bee Research Lab, BARC-East Bldg. 306, 10300 Baltimore Ave., Beltsville, MD, 20705, USA.
| | - Zachary S Lamas
- USDA, Agricultural Research Service, Bee Research Lab, BARC-East Bldg. 306, 10300 Baltimore Ave., Beltsville, MD, 20705, USA.,Department of Entomology, University of Maryland, College Park, MD, USA
| | - David J Hawthorne
- Department of Entomology, University of Maryland, College Park, MD, USA
| | - Yanping Chen
- USDA, Agricultural Research Service, Bee Research Lab, BARC-East Bldg. 306, 10300 Baltimore Ave., Beltsville, MD, 20705, USA
| | - Jay D Evans
- USDA, Agricultural Research Service, Bee Research Lab, BARC-East Bldg. 306, 10300 Baltimore Ave., Beltsville, MD, 20705, USA.
| | - Eugene V Ryabov
- USDA, Agricultural Research Service, Bee Research Lab, BARC-East Bldg. 306, 10300 Baltimore Ave., Beltsville, MD, 20705, USA.
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Ryabov EV, Christmon K, Heerman MC, Posada-Florez F, Harrison RL, Chen Y, Evans JD. Development of a Honey Bee RNA Virus Vector Based on the Genome of a Deformed Wing Virus. Viruses 2020; 12:E374. [PMID: 32231059 PMCID: PMC7232236 DOI: 10.3390/v12040374] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 03/24/2020] [Accepted: 03/26/2020] [Indexed: 12/22/2022] Open
Abstract
We developed a honey bee RNA-virus vector based on the genome of a picorna-like Deformed wing virus (DWV), the main viral pathogen of the honey bee (Apis mellifera). To test the potential of DWV to be utilized as a vector, the 717 nt sequence coding for the enhanced green fluorescent protein (eGFP), flanked by the peptides targeted by viral protease, was inserted into an infectious cDNA clone of DWV in-frame between the leader protein and the virus structural protein VP2 genes. The in vitro RNA transcripts from egfp-tagged DWV cDNA clones were infectious when injected into honey bee pupae. Stable DWV particles containing genomic RNA of the recovered DWV with egfp inserts were produced, as evidenced by cesium chloride density gradient centrifugation. These particles were infectious to honey bee pupae when injected intra-abdominally. Fluorescent microscopy showed GFP expression in the infected cells and Western blot analysis demonstrated accumulation of free eGFP rather than its fusions with DWV leader protein (LP) and/or viral protein (VP) 2. Analysis of the progeny egfp-tagged DWV showed gradual accumulation of genome deletions for egfp, providing estimates for the rate of loss of a non-essential gene an insect RNA virus genome during natural infection.
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Affiliation(s)
- Eugene V. Ryabov
- USDA, Agricultural Research Service, Bee Research Lab, Beltsville, MD 20705, USA; (K.C.); (M.C.H.); (F.P.-F.); (Y.C.); (J.D.E.)
| | - Krisztina Christmon
- USDA, Agricultural Research Service, Bee Research Lab, Beltsville, MD 20705, USA; (K.C.); (M.C.H.); (F.P.-F.); (Y.C.); (J.D.E.)
- Department of Entomology, University of Maryland, College Park, MD 20742, USA
| | - Matthew C. Heerman
- USDA, Agricultural Research Service, Bee Research Lab, Beltsville, MD 20705, USA; (K.C.); (M.C.H.); (F.P.-F.); (Y.C.); (J.D.E.)
| | - Francisco Posada-Florez
- USDA, Agricultural Research Service, Bee Research Lab, Beltsville, MD 20705, USA; (K.C.); (M.C.H.); (F.P.-F.); (Y.C.); (J.D.E.)
| | - Robert L. Harrison
- USDA, Agricultural Research Service, Invasive Insect Biocontrol and Behavior Laboratory, Beltsville, MD 20705, USA;
| | - Yanping Chen
- USDA, Agricultural Research Service, Bee Research Lab, Beltsville, MD 20705, USA; (K.C.); (M.C.H.); (F.P.-F.); (Y.C.); (J.D.E.)
| | - Jay D. Evans
- USDA, Agricultural Research Service, Bee Research Lab, Beltsville, MD 20705, USA; (K.C.); (M.C.H.); (F.P.-F.); (Y.C.); (J.D.E.)
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Li AY, Cook SC, Sonenshine DE, Posada-Florez F, Noble NII, Mowery J, Gulbronson CJ, Bauchan GR. Insights into the feeding behaviors and biomechanics of Varroa destructor mites on honey bee pupae using electropenetrography and histology. J Insect Physiol 2019; 119:103950. [PMID: 31562841 DOI: 10.1016/j.jinsphys.2019.103950] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Revised: 09/24/2019] [Accepted: 09/25/2019] [Indexed: 06/10/2023]
Abstract
Feeding behaviors and biomechanics of female Varroa destructor mites are revealed from AC-DC electropenetrography (EPG) recordings of mites feeding from Apis mellifera honey bee pupae and histology of mite internal ingestion apparatus. EPG signals characteristic of arthropod suction feeding (ingestion) were identified for mites that fed on pupae during overnight recordings. Ingestion by these mites was confirmed afterwards by observing internally fluorescent microbeads previously injected into their hosts. Micrographs of internal ingestion apparatus illustrate the connection between a gnathosomal tube and a pharyngeal lumen, which is surrounded by alternating dilator and constrictor muscles. Inspection of EPG signals showed the muscularized mite pharyngeal pump operates at a mean repetition rate of 4.5 cycles/s to ingest host fluids. Separate feeding events observed for mites numbered between 23 and 33 over approximately 16 h of recording, with each event lasting ~10 s. Feeding events were each separated by ~2 min. Consecutive feeding events separated by either locomotion or prolonged periods of quiescence were grouped into feeding bouts, which ranged in number from one to six. Statistical analyses of EPG data revealed that feeding events were prolonged for mites having lower pharyngeal pump frequencies, and mites having prolonged feeding events went unfed for significantly more time between feeding events. These results suggest that mites may adjust behaviors to meet limitations of their feeding apparatus to acquire similar amounts of food. Data reported here help to provide a more robust view of Varroa mite feeding than those previously reported and are both reminiscent of, as well as distinct from, some other acarines and fluid-feeding insects.
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Affiliation(s)
- Andrew Y Li
- Invasive Insect Biocontrol & Behavior Laboratory, Agricultural Research Service, UDSA, Beltsville, MD 20705, United States
| | - Steven C Cook
- Bee Research Laboratory, Agricultural Research Service, UDSA, Beltsville, MD 20705, United States.
| | - Daniel E Sonenshine
- Bee Research Laboratory, Agricultural Research Service, UDSA, Beltsville, MD 20705, United States; Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529, United States
| | - Francisco Posada-Florez
- Bee Research Laboratory, Agricultural Research Service, UDSA, Beltsville, MD 20705, United States
| | - Noble I I Noble
- Bee Research Laboratory, Agricultural Research Service, UDSA, Beltsville, MD 20705, United States
| | - Joseph Mowery
- Electron and Confocal Microscopy Unit, Agricultural Research Service, USDA, Beltsville, MD 20705, United States
| | - Connor J Gulbronson
- Floral and Nursery Plant Research Unit, Agricultural Research Service, USDA, Beltsville, MD 20705, United States
| | - Gary R Bauchan
- Electron and Confocal Microscopy Unit, Agricultural Research Service, USDA, Beltsville, MD 20705, United States
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Ryabov EV, Childers AK, Lopez D, Grubbs K, Posada-Florez F, Weaver D, Girten W, vanEngelsdorp D, Chen Y, Evans JD. Dynamic evolution in the key honey bee pathogen deformed wing virus: Novel insights into virulence and competition using reverse genetics. PLoS Biol 2019; 17:e3000502. [PMID: 31600204 PMCID: PMC6805011 DOI: 10.1371/journal.pbio.3000502] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 10/22/2019] [Accepted: 09/20/2019] [Indexed: 12/23/2022] Open
Abstract
The impacts of invertebrate RNA virus population dynamics on virulence and infection outcomes are poorly understood. Deformed wing virus (DWV), the main viral pathogen of honey bees, negatively impacts bee health, which can lead to colony death. Despite previous reports on the reduction of DWV diversity following the arrival of the parasitic mite Varroa destructor, the key DWV vector, we found high genetic diversity of DWV in infested United States honey bee colonies. Phylogenetic analysis showed that divergent US DWV genotypes are of monophyletic origin and were likely generated as a result of diversification after a genetic bottleneck. To investigate the population dynamics of this divergent DWV, we designed a series of novel infectious cDNA clones corresponding to coexisting DWV genotypes, thereby devising a reverse-genetics system for an invertebrate RNA virus quasispecies. Equal replication rates were observed for all clone-derived DWV variants in single infections. Surprisingly, individual clones replicated to the same high levels as their mixtures and even the parental highly diverse natural DWV population, suggesting that complementation between genotypes was not required to replicate to high levels. Mixed clone–derived infections showed a lack of strong competitive exclusion, suggesting that the DWV genotypes were adapted to coexist. Mutational and recombination events were observed across clone progeny, providing new insights into the forces that drive and constrain virus diversification. Accordingly, our results suggest that Varroa influences DWV dynamics by causing an initial selective sweep, which is followed by virus diversification fueled by negative frequency-dependent selection for new genotypes. We suggest that this selection might reflect the ability of rare lineages to evade host defenses, specifically antiviral RNA interference (RNAi). In support of this hypothesis, we show that RNAi induced against one DWV strain is less effective against an alternate strain from the same population. Deformed wing virus, a key pathogen of honey bees, shows rapid diversification after genetic bottlenecks; a novel reverse-genetic system provides insights into the forces that shape virus diversity, suggesting that virus quasi-species diversification may be driven by selection of genotypes capable of evading host RNAi defences.
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Affiliation(s)
- Eugene V. Ryabov
- Bee Research Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, USDA, Beltsville, Maryland, United States of America
- * E-mail: ,
| | - Anna K. Childers
- Bee Research Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, USDA, Beltsville, Maryland, United States of America
| | - Dawn Lopez
- Bee Research Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, USDA, Beltsville, Maryland, United States of America
| | - Kyle Grubbs
- Bee Research Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, USDA, Beltsville, Maryland, United States of America
| | - Francisco Posada-Florez
- Bee Research Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, USDA, Beltsville, Maryland, United States of America
| | - Daniel Weaver
- Bee Research Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, USDA, Beltsville, Maryland, United States of America
- Beeweaver Apiaries, Navasota, Texas, United States of America
| | - William Girten
- Bee Research Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, USDA, Beltsville, Maryland, United States of America
- Department of Chemistry, Fort Lewis College, Durango, Colorado, United States of America
| | - Dennis vanEngelsdorp
- Department of Entomology, University of Maryland, College Park, Maryland, United States of America
| | - Yanping Chen
- Bee Research Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, USDA, Beltsville, Maryland, United States of America
| | - Jay D. Evans
- Bee Research Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, USDA, Beltsville, Maryland, United States of America
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Posada-Florez F, Childers AK, Heerman MC, Egekwu NI, Cook SC, Chen Y, Evans JD, Ryabov EV. Deformed wing virus type A, a major honey bee pathogen, is vectored by the mite Varroa destructor in a non-propagative manner. Sci Rep 2019; 9:12445. [PMID: 31455863 PMCID: PMC6712216 DOI: 10.1038/s41598-019-47447-3] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 07/09/2019] [Indexed: 12/22/2022] Open
Abstract
Honey 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.
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Affiliation(s)
| | - Anna K Childers
- USDA, Agricultural Research Service, Bee Research Lab, Beltsville, MD, USA
| | - Matthew C Heerman
- USDA, Agricultural Research Service, Bee Research Lab, Beltsville, MD, USA
| | - Noble I Egekwu
- USDA, Agricultural Research Service, Bee Research Lab, Beltsville, MD, USA
| | - Steven C Cook
- USDA, Agricultural Research Service, Bee Research Lab, Beltsville, MD, USA
| | - Yanping Chen
- USDA, Agricultural Research Service, Bee Research Lab, Beltsville, MD, USA
| | - Jay D Evans
- USDA, Agricultural Research Service, Bee Research Lab, Beltsville, MD, USA
| | - Eugene V Ryabov
- USDA, Agricultural Research Service, Bee Research Lab, Beltsville, MD, USA.
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