In colony collapse disorder, honey bee colonies inexplicably lose all of their worker bees. CCD has resulted in a loss of 50-90% of colonies in beekeeping operations across the U.S. The consortium of scientists who have been studying the role of infection in this phenomenon includes Diana Cox-Foster, professor in the Department of Entomology at Pennsylvania State University, Ian Lipkin, director of the Center for Infection and Immunity at Columbia University Mailman School of Public Health, Jeffery Pettis, research leader of the ARS Bee Research Laboratory, and Nancy Moran, Professor at the University of Arizona, Tucson.
Ian Lipkin, MD, professor of Epidemiology, Neurology, and Pathology at Columbia, and his team at the Mailman School's Center for Infection and Immunity, together with a team at 454 Life Sciences, used revolutionary genetic technologies, to survey microflora of CCD hives, normal hives, and imported royal jelly. Candidate pathogens were screened for significance of association with CCD by examining samples collected by the USDA and Penn State from several sites over a period of three years.
Using the 454 Life Sciences high-throughput DNA sequencing platform, and analytical methods developed at Columbia, Dr. Lipkin's team searched for footprints of viruses, bacteria, fungi, and parasites in thousands of sequences. Candidates were further characterized by more detailed sequence analysis to ascertain their specificity for CCD and relationship to known and unknown pathogens.
IAPV, an unclassified dicistrovirus not previously reported in the U.S. that is transmitted by the varroa mite, and Kasmir bee virus were only found in CCD hives. The researchers report that IAPV was found in all four affected operations sampled, in two of four royal jelly samples, and in the Australian sample. KBV was present in three of four CCD operations, but not in the royal jelly. One organism was significantly correlated with CCD: finding IAPV in a bee sample correctly distinguished CCD from non-CCD status 96.1 percent of the time.
"This is a powerful new strategy for looking at outbreaks of infectious disease and finding cause. Dr. Cox-Foster recruited us into this project, making a persuasive case for applying our state-of-the-art methods for differential diagnosis of infectious disease in humans, to this challenge in agricultural epidemiology," said Dr. Lipkin. "The profound synergy within the group—bringing entomology, microbiology, and bioinformatics together—enabled us to work toward a solution to this extraordinarily complex problem."
This is the first report of IAPV in the United States. IAPV was first described in 2004 in Israel where infected bees presented with shivering wings, progressed to paralysis and then died just outside the hive. Importation to the U.S. of bees from Australia began in 2004, coinciding with early reports of unusual colony declines.
IAPV was found in non-CCD hives in some cases, which could reflect strain variation, co-infection, or the presence of other stressors, such as pesticides or poor nutrition. The varroa mite, for example, absent in Australia, immunosuppresses bees making them more susceptible to infection by other organisms, including viruses. Other stressors may include chemical pesticides used on plants pollinated by bees and in hives to control pests.
"Our results indicate that IAPV is a significant marker for CCD. This discovery may be helpful in identifying hives at risk for disease. The next step is to ascertain whether IAPV, alone or in concert with other factors, can induce CCD in healthy bees," added Dr. Lipkin.
Bees play an integral role in the world food supply, and are essential for the pollination of over 90 fruit and vegetable crops worldwide, with the economic value of these agricultural products placed at more than $14.6 billion in the U.S.
In addition to agricultural crops, honey bees also pollinate many native plants within the ecosystem. Recently, the increased deaths in bee colonies due to CCD seriously threaten the ability of the bee industry to meet the pollination needs of fruit and vegetable producers in the U.S.