http://www.cornucopia.org/2013/12/neonicotinoids-let-virus-thrive-bees/
Neonicotinoids Let Virus Thrive in BeesDecember 31st, 2013
*Chemistry World
<http://www.rsc.org/chemistryworld/2013/10/neonicotinoids-let-virus-thrive-bees-colony-collapse-disorder>By
Simon Hadlington*
[image: Honey_Bee]<http://www.cornucopia.org/wp-content/uploads/2013/06/Honey_Bee.jpg>Scientists
in Italy believe they have found a molecular trigger by which neonicotinoid
pesticides may harm colonies of
honeybees<http://dx.doi.org/10.1073/pnas.1314923110>.
The team's experiments suggest that exposure to neonicotinoids results in
increased levels of a particular protein in bees that inhibits a key
molecule involved in the immune response, making the insects more
susceptible to attack by harmful viruses.
Francesco Pennacchio <http://www.docenti.unina.it/francesco.pennacchio>, of
the University of Naples Federico II, and colleagues identified a gene in
insects that codes for a protein family similar to that found in other
animals that is known to regulate the immune response. This leucine-rich
repeat protein family, or LRR, has been shown to suppress the activity of a
key protein involved in immune signalling, called NF-ęB.
When the researchers exposed bees to sub-lethal doses of the neonicotinoid
clothianidin<http://www.chemspider.com/Chemical-Structure.184723.html?rid=86780c6f-cbc5-4ea3-ae23-fa1f3ce3b7f6>
they
saw a significant increase in the expression of the gene encoding the LRR
protein, and a concomitant suppression of the NF-ęB signalling pathway.
These effects were not seen when bees were exposed to the organophosphate
insecticide chlorpyriphos<http://www.chemspider.com/Chemical-Structure.2629.html?rid=44ed5f63-8654-4612-89c1-266dc0a1467e>
.
When the team infected bees with a common pathogen - deformed wing virus -
and exposed them to clothianidin and another neonicotinoid,
imidacloprid<http://www.rsc.org/chemistryworld/2013/07/imidacloprid-neonicitinoids-bee-pesticide-podcast>,
at concentrations similar to those that would be found in the field, there
was significantly increased replication of the virus, which was not seen
either in untreated bees, or those exposed to chlorpyriphos.
The virus is common in bees and usually remains inactive - kept in check by
the bees' immune system. The results suggest that insecticide-induced
suppression of bees' immune systems lets the virus replicate unchecked.
'The reported effect on immunity exerted by neonicotinoids will allow
additional toxicological tests to be defined to assess if chronic exposure
of bees to sub-lethal doses of agrochemicals can adversely affect their
immune system and health conditions,' says team member Francesco
Nazzi<http://www.uniud.it/ricerca/strutture/dipartimenti_scientifica/dipi/sezione-di-entomologia/personale-afferente-alla-sezione/francesco-nazzi>
of
the University of Udine. 'Moreover, our data indicate the possible
occurrence in insects, as in vertebrates, of a neural modulation of the
immune response. This sets the stage for future studies in this research
area, and poses the question on how neurotoxic substances may affect the
immune response.'
Susan Kegley <http://www.pesticideresearch.com/site/> runs the Pesticide
Research Institute, an independent consultancy in the US. She tells *Chemistry
World*: 'The EU has already implemented a minimumtwo-year
suspension<http://www.rsc.org/chemistryworld/2013/04/europe-ban-controversial-neonicotinoid-pesticides>
of
the use of the most toxic neonicotinoid insecticides - clothianidin,
imidacloprid and
thiamethoxam<http://www.chemspider.com/Chemical-Structure.96828.html?rid=828a206f-17ea-4cf4-b0e8-9d85a57053ec>
-
on bee-attractive crops, to take effect December 1, 2013.
The US EPA [Environmental Protection Agency] remains unconvinced that
neonicotinoids could be a primary factor in recent pollinator population
declines. This new study, in conjunction with other observational studies
showing enhanced susceptibility to pathogens caused by exposure to
neonicotinoids, should prompt US EPA to re-evaluate the science.'
References
G Di Prisco *et al*, *Proc. Natl. Acad. Sci. USA*, DOI:
10.1073/pnas.1314923110. <http://dx.doi.org/10.1073/pnas.1314923110>
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