Systemic spread and propagation of a plant-pathogenic virus in European honeybees, Apis mellifera.
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.


OBJECTIVE
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.
Ji Lian
JL
Li
R Scott
RS
Cornman
Jay D
JD
Evans
Jeffery S
JS
Pettis
Yan
Y
Zhao
Charles
C
Murphy
Wen Jun
WJ
Peng
Jie
J
Wu
Michele
M
Hamilton
Humberto F
HF
Boncristiani
Liang
L
Zhou
John
J
Hammond
Yan Ping
YP
Chen
D000825:Animal Structures / Q000821:virology; D000818:Animals; D001516:Bees / Q000821:virology*; D016000:Cluster Analysis; D005838:Genotype; D008969:Molecular Sequence Data; D017860:Nepovirus / Q000254:growth & development* / Q000302:isolation & purification / Q000502:physiology; D010802:Phylogeny; D011058:Pollen / Q000821:virology; D012367:RNA, Viral / Q000235:genetics; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D057077:Varroidae / Q000821:virology; D014779:Virus Replication
D012367:RNA, Viral