[Pollinator] Kim Flottum's CATCH THE BUZZ - Neonicotinoids let virus in bees thrive

[Matthew Shepherd]

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CATCH THE BUZZ

Neonicotinoids let virus thrive in bees - Another nail in the Neonic Coffin?

>From Chemistry World

Scientists in Italy believe they have found a molecular trigger by which
<http://dx.doi.org/10.1073/pnas.1314923110> neonicotinoid pesticides may
harm colonies of honey bees. 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. 

 <http://www.docenti.unina.it/francesco.pennacchio> 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 signaling, called NF-κB. When the researchers
exposed bees to sub-lethal doses of the neonicotinoid
<http://www.chemspider.com/Chemical-Structure.184723.html?rid=86780c6f-cbc5-
4ea3-ae23-fa1f3ce3b7f6> clothianidin they saw a significant increase in the
expression of the gene encoding the LRR protein, and a concomitant
suppression of the NF-κB signalling pathway. These effects were not seen
when bees were exposed to the organophosphate insecticide
<http://www.chemspider.com/Chemical-Structure.2629.html?rid=44ed5f63-8654-46
12-89c1-266dc0a1467e> chlorpyriphos.

When the team infected bees with a common pathogen - deformed wing virus -
and exposed them to clothianidin and another neonicotinoid,
<http://www.rsc.org/chemistryworld/2013/07/imidacloprid-neonicitinoids-bee-p
esticide-podcast> imidacloprid, 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
<http://www.uniud.it/ricerca/strutture/dipartimenti_scientifica/dipi/sezione
-di-entomologia/personale-afferente-alla-sezione/francesco-nazzi> 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.'

 <http://www.pesticideresearch.com/site/> Susan Kegley runs the Pesticide
Research Institute, an independent consultancy in the US. She tells
Chemistry World: 'The EU has already implemented a minimum
<http://www.rsc.org/chemistryworld/2013/04/europe-ban-controversial-neonicot
inoid-pesticides> two-year suspension of the use of the most toxic
neonicotinoid insecticides - clothianidin, imidacloprid and
<http://www.chemspider.com/Chemical-Structure.96828.html?rid=828a206f-17ea-4
cf4-b0e8-9d85a57053ec> thiamethoxam - 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.'

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