Pathogenic plant virus jumps to honeybees
by Staff Writers
Washington DC (SPX) Jan 24, 2014
Toxic viral cocktails appear to have a strong link with honey bee Colony Collapse Disorder (CCD), a mysterious malady that abruptly wiped out entire hives across the United States and was first reported in 2006. Israel Acute Paralysis Virus (IAPV), Acute Bee Paralysis Virus (ABPV), Chronic Paralysis Virus (CPV), Kashmir Bee Virus (KBV), Deformed Wing Bee Virus (DWV), Black Queen Cell Virus (BQCV) and Sacbrood Virus (SBV) are other known causes of honeybee viral disease.
Researchers working in the U.S. and Beijing, China report their findings in mBio, the online open-access journal of the American Society for Microbiology.
The routine screening of bees for frequent and rare viruses “resulted in the serendipitous detection of Tobacco Ringspot Virus, or TRSV, and prompted an investigation into whether this plant-infecting virus could also cause systemic infection in the bees,” says Yan Ping Chen from the U.S. Department of Agriculture’s Agricultural Research Service (ARS) laboratory in Beltsville, Maryland, an author on the study.
“The results of our study provide the first evidence that honeybees exposed to virus-contaminated pollen can also be infected and that the infection becomes widespread in their bodies,” says lead author Ji Lian Li, at the Chinese Academy of Agricultural Science in Beijing.
“We already know that honeybees, Apis melllifera, can transmit TRSV when they move from flower to flower, likely spreading the virus from one plant to another,” Chen adds.
Notably, about 5% of known plant viruses are pollen-transmitted and thus potential sources of host-jumping viruses. RNA viruses tend to be particularly dangerous because they lack the 3′-5′ proofreading function which edits out errors in replicated genomes. As a result, viruses such as TRSV generate a flood of variant copies with differing infective properties.
One consequence of such high replication rates are populations of RNA viruses thought to exist as “quasispecies,” clouds of genetically related variants that appear to work together to determine the pathology of their hosts. These sources of genetic diversity, coupled with large population sizes, further facilitate the adaption of RNA viruses to new selective conditions such as those imposed by novel hosts. “Thus, RNA viruses are a likely source of emerging and reemerging infectious diseases,” explain these researchers.
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Bee Deaths May Stem From Virus, Study Says
The mysterious mass die-offs of honeybees that have wiped out roughly a third of commercial colonies each year since 2006 may be linked to a rapidly mutating virus that jumped from tobacco plants to soy plants to bees, according to a new study.
The research, reported Tuesday in the online version of the academic journal mBio, found that the increase in honeybee deaths that generally starts in autumn and peaks in winter was correlated with increasing infections by a variant of the tobacco ringspot virus.
The virus is found in pollen that bees pick up while foraging, and it may be spread as the bees mix saliva and nectar with pollen to make “bee bread” for larvae to eat. Mites that feed on the bees may also be involved in transmitting the virus, the researchers said.
Among the study’s authors are leading researchers investigating the bee deaths at the Agriculture Department’s laboratories in Beltsville, Md., as well as experts at American universities and at the Chinese Academy of Agricultural Sciences in Beijing.
Their research offers one explanation for the phenomenon known as colony collapse disorder, in which bees have died at more than twice the usual rate since it was identified seven years ago. But most researchers, including the study’s authors, suspect that a host of viruses, parasites and, perhaps, other factors like pesticides are working in combination to weaken colonies and increase the death rate.
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