The researchers used a method developed by the military called mass spectrometry-based proteomics (MSP), a tool that identifies peptide sequences which are screened against a database to identify pathogens. Two previously unidentified RNA viruses were found in the studied bee populations; a variety of RNA viruses thus far have been the main culprits in CCD. However, the real surprise was the identification of a co-occurrence of a DNA virus, an invertebrate iridescent virus (IIV), and a Nosema fungus. Nosema had been pinpointed previously in some collapsing populations, but the finding of an IIV is going to shift new research away from RNA viruses. The exact identity of the IIV is still unknown because not all known types in the virus family have been peptide sequenced.
The virus-fungus correlation is very strong, as the researchers found their co-occurrence in sampled US apiaries from 2006-2007, an observation colony that demonstrated collapse over the time of the study, and separate colonies in Florida experiencing CCD. As an illustration, the peptides of the pathogen pairing were shown to increase in the observation colony as bee forager flights decreased.
Bees sampled from a Montana colony and also bees shipped from Australia with no history of CCD did not contain the lethal pairing. Laboratory inoculations also supported the field studies' findings.
A major question, however, is if this virus-fungus pairing is the true cause of CCD. Are collapsing colonies just more susceptible due to something else, and the two pathogens together burn down the house? The lead researcher from the University of Montana, Dr. Jerry Bromenshenk, cautions, "We truly don't know if these two pathogens cause CCD or whether the colonies with CCD are more likely to succumb to these two pathogens."
Excellent update post, Caitlin. Thank you!
ReplyDeleteAndy