Bee Disease still A Mystery
Pastor Dale Morgan
Bee Disease still A Mystery*
Deformed wing virus has been linked to the collapse of honey bee
colonies in Britain.
by Staff Writers
London, UK (SPX) Jun 30, 2008
Scientists are one step closer to understanding the recent demise of
billions of honey bees after making an important discovery about the
transmission of a common bee virus. Deformed wing virus (DWV) is passed
between adult bees and to their developing brood by a parasitic mite
called Varroa destructor when it feeds.
However, research published in the July issue of the Journal of General
Virology suggests that the virus does not replicate in Varroa,
highlighting the need for further investigation.
Deformed wing virus has been linked to the collapse of honey bee
colonies in Britain. In recent years the prevalence of the virus has
increased globally in colonies infested with Varroa. It is widely
accepted that the virus replicates in the mite and is then transmitted
to bees when it bites.
However, researchers at Rothamsted Research and the University of
Nottingham have found that the virus does not replicate in the mite,
suggesting an alternative means of transmission.
"Experiments and field observations have shown that V. destructor is
able to transmit several different unrelated honey bee viruses, like
acute bee paralysis virus and Kashmir bee virus as well as deformed wing
virus," said Professor Teresa Santillan-Galicia from Rothamsted
Research. "But we still don't know exactly how these viruses are passed
from the mite to the bee."
The researchers wanted to find out whether the virus replicates in the
mite and if so where this occurs, to understand how the virus is
transmitted.
They used a process called immunohistochemistry which involves using
antibodies which bind to specific surface proteins, enabling the virus
particles to be located. There was no evidence of virus replication
within the cells of the mite; the virus was found only in the lumen of
the gut, suggesting it was merely eaten.
"The presence of deformed wing virus in large amounts in mite faeces
suggests it is picked up during feeding on an infected bee," said
Professor Santillan-Galicia. "However, one important question remains -
how is the virus transmitted to bees?"
One possibility is that the mouthparts of the mite could become
contaminated with the virus during feeding, but this is an unlikely
answer. Varroa mites cannot regurgitate their gut contents as there is a
membrane in the oesophagus that acts as a non-return valve, so they
could not pass the virus on this way either.
Unfortunately, not enough is known about the anatomy of the mite, or
their feeding mechanism, to suggest other routes of transmission.
"It is likely that the amount of virus acquired by the mite plays an
important role in the interaction between deformed wing virus and the
Varroa mite," said Professor Santillan-Galicia.
"Full understanding of the interaction between deformed wing virus and
the Varroa mite will provide basic information for the future
development of more sustainable control strategies against the mite and
the virus. Our work provides elements of understanding but further
research in this area is needed."