Bees | Colony Collapse Disorder | Tobacco Ring Spot Virus | Pesticides Not the Cause
Dr Gilbert Ross.
Enviornmental Group theories Sketchy at the least
A rapidly mutating virus has leaped from plants to honeybees, where it is reproducing and contributing to the collapse of colonies vital to the multibillion-US-dollar agricultural industry, according to a new study.
Tobacco ringspot virus (TRSV), a pollen-borne pathogen that causes blight in soy crops, was found during routine screening of commercial honeybees at a US Department of Agriculture laboratory, where further study revealed the RNA virus was replicating inside its Apis mellifera hosts and spreading to mites that travelled from bee to bee, according to the study published online on Tuesday in the journal mBio.
The discovery is the first report of honeybees becoming infected by a pollen-born RNA virus that spread systematically through the bees and hives. Traces of the virus were detected in every part of the bee examined, except its eyes, according to the study.
Systemic Spread and Propagation of a Plant-Pathogenic Virus in European Honeybees, Apis mellifera
- Ji Lian Lia,
- R. Scott Cornmanb,
- Jay D. Evansb,
- Jeffery S. Pettisb,
- Yan Zhaoc,
- Charles Murphyd,
- Wen Jun Penga,
- Jie Wua,
- Michele Hamiltonb,
- Humberto F. Boncristiani Jr.e,
- Liang Zhouf,
- John Hammondg,
- Yan Ping Chenb
+ Author Affiliations
aKey Laboratory of Pollinating Insect Biology of the Ministry of Agriculture, Institute of Apicultural Research, Chinese Academy of Agricultural Science, Beijing, China
bDepartment of Agriculture, ARS, Bee Research Laboratory, Beltsville, Maryland, USA
cDepartment of Agriculture, ARS Molecular Plant Pathology Laboratory, Beltsville, Maryland, USA
dDepartment of Agriculture, ARS, Soybean Genomic & Improvement Laboratory, Beltsville, Maryland, USA
eDepartment of Biology, University North Carolina at Greensboro, Greensboro, North Carolina, USA
fDepartment of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA
gDepartment of Agriculture, ARS, Floral and Nursery Plants Research Unit, Beltsville, Maryland, USA
- Address correspondence to Yan Ping Chen, Judy.Chen@ars.usda.gov.
Editor Anne Vidaver, University of Nebraska
Emerging and reemerging diseases that result from pathogen host shifts are a threat to the health of humans and their domesticates. RNA viruses have extremely high mutation rates and thus represent a significant source of these infectious diseases. In the present study, we showed that a plant-pathogenic RNA virus, tobacco ringspot virus (TRSV), could replicate and produce virions in honeybees, Apis mellifera, resulting in infections that were found throughout the entire body. Additionally, we showed that TRSV-infected individuals were continually present in some monitored colonies. While intracellular life cycle, species-level genetic variation, and pathogenesis of the virus in honeybee hosts remain to be determined, the increasing prevalence of TRSV in conjunction with other bee viruses from spring toward winter in infected colonies was associated with gradual decline of host populations and winter colony collapse, suggesting the negative impact of the virus on colony survival. Furthermore, we showed that TRSV was also found in ectoparasitic Varroa mites that feed on bee hemolymph, but in those instances the virus was restricted to the gastric cecum of Varroa mites, suggesting that Varroa mites may facilitate the spread of TRSV in bees but do not experience systemic invasion. Finally, our phylogenetic analysis revealed that TRSV isolates from bees, bee pollen, and Varroa mites clustered together, forming a monophyletic clade. The tree topology indicated that the TRSVs from arthropod hosts shared a common ancestor with those from plant hosts and subsequently evolved as a distinct lineage after transkingdom host alteration. This study represents a unique example of viruses with host ranges spanning both the plant and animal kingdoms.
IMPORTANCE Pathogen host shifts represent a major source of new infectious diseases. Here we provide evidence that a pollen-borne plant virus, tobacco ringspot virus (TRSV), also replicates in honeybees and that the virus systemically invades and replicates in different body parts. In addition, the virus was detected inside the body of parasitic Varroa mites, which consume bee hemolymph, suggesting that Varroa mites may play a role in facilitating the spread of the virus in bee colonies. This study represents the first evidence that honeybees exposed to virus-contaminated pollen could also be infected and raises awareness of potential risks of new viral disease emergence due to host shift events. About 5% of known plant viruses are pollen transmitted, and these are potential sources of future host-jumping viruses. The findings from this study showcase the need for increased surveillance for potential host-jumping events as an integrated part of insect pollinator management programs.
Citation Lian JL, Cornman RS, Evans JD, Pettis JS, Zhao Y, Murphy C, Peng WJ, Wu J, Hamilton M, Boncristiani HF, Jr., Zhou L, Hammond J, Chen YP. 2014. Systemic spread and propagation of a plant-pathogenic virus in European honeybees, Apis mellifera. mBio 5(1):e00898-13. doi:10.1128/mBio.00898-13.
- Received 20 October 2013
- Accepted 13 December 2013
- Published 21 January 2014