On the eve of National Honey Bee Day, PLOS’s Jose Mendez interviews researcher Dr. Michelle Flenniken, Ph.D of Montana State University to discuss the role of viruses on honey bee health and the importance of honey bee colony losses in her new PLOS Pathogens Pearls Article, The Buzz About Honey Bee Viruses.
How did you get interested in studying honey bees?
My interests in viruses began as a graduate student at Montana State University, where I worked on repurposing plant viruses and nanometer-scale protein cage architectures from hyperthermophilic organisms for anticancer and imaging agent delivery. To further pursue my interests in virology, I joined Raul Andino’s lab at UCSF as a postdoc. I became interested in honey bee host-virus interactions in 2008, shortly after the initial reports of high colony losses and Colony Collapse Disorder. At the time, we knew that RNA-inference (RNAi) played a major role in fruit fly and mosquito antiviral defense, so I investigated the role of RNAi in honey bee antiviral defense (PLoS ONE 8(10): e77263). At the same time, Joseph DeRisi at UCSF was sent some honey bee samples to analyze for both known and yet-to-be discovered honey bee pathogens. Since research at UCSF is primarily centered on human health, it didn’t take long for the two people working on bee viruses to be united, with help from grad student Charles Runckel. Together, we initiated a longitudinal honey bee colony monitoring project aimed at characterizing and identifying the pathogens associated with honey bee colonies throughout the course of the year (PLoS ONE 6(6): e20656). This study was one of the first to examine the dynamics of honey bee pathogens in commercially managed colonies, and served as an important baseline for investigating the factors that most correlate with colony deaths.
What are you working on now that you are most excited about?
In 2012, I joined the faculty at Montana State University and transferred my honey bee research program to Bozeman, Montana. Montana is an important beekeeping state that ranked 2nd in honey production in 2013, and MSU, which is a land-grant university, is an excellent institution for my research program. Our recently established Pollinator Research Group includes colleagues with expertise in wild pollinators, such as Laura Burkle, and my research program is fortunate to have first-rate graduate (Laura Brutscher, Alex McMenamin, and Will Glenny) and undergraduate students carrying out several lines research important to honey bee health. I’m really excited about our work on dsRNA-triggered antiviral defense mechanisms; our results indicate that honey bee antiviral defense involves a non-sequence-specific, general, dsRNA-triggered immune response (akin to the mammalian interferon response), in addition to the sequence-specific RNAi-mediated antiviral response that plays a major role in antiviral defense in solitary insects, including fruit flies and mosquitoes.
One of the biggest challenges to maintaining healthy bee colonies is mitigating mite (Varroa destructor) infestations. What can beekeepers do to reduce mite infestations?
Mites feed on developing bees as well as transmit viruses; together these effects often result in the death of the honey bee colony. Beekeepers reduce mite infestation by monitoring mite levels and either removing heavily infested colonies from apiaries or using mite control strategies, which include both organic and synthetic chemical treatments, when necessary. Recently, the Honey Bee Health Coalition developed a guide to effective Varroa sampling and control (see: http://honeybeehealthcoalition.org/varroa/).
You note in your Pearls article that honey bees and bumble bees harbor similar virus strains. Have researchers seen the same kind of decline in bumble bees that they do in honey bees? If so, what are the primary reasons for bumble bee decline?
In general, insect viruses can infect a broader range of hosts than mammalian viruses, so it’s not surprising that honey bees and bumble bees can be infected by similar viruses. Bee viruses can be transmitted inter- and intra- species via shared floral resources (nectar and pollen). Scientists are currently examining the pathogenesis of specific viruses and viral strains in both honey bee and bumble bees to better understand their potential role in bee losses. Both honey bees (Apis mellifera) and wild pollinators, including some bumble bee species, have experienced high losses. There are multiple factors that influence bee losses, including lack of adequate habitat, lack of quality forage, chemical exposure, weather/climate, management, and pathogens. The impact of these factors varies with time, geographic location, and bee species; better understanding of the role of these factors on bee health is an active area of research. The health of bees and other pollinators is enhanced by bee forage enhancement projects (including Conservation Research Protection lands and bee gardens) and reduced chemical (particularly insecticide) use in both home and agricultural settings. So conscientious members of the community can play a role in mitigating pollinator losses.
What are some of the challenges of working on honey bee viruses, and your work in particular?
Although this line of research is important and timely, there are some challenges associated with investigating honey bee host-pathogen interactions. Honey bees are eusocial insects and important model for behavioral studies, however there are few available cellular or molecular biology tools. For example, immortalized honey bee cell lines aren’t available (though primary cells can be used for in vitro studies) and we can’t order bee lines with particular genes knocked-out, like you can for fruit fly studies, so we become amateur beekeepers and maintain colonies with variable genetic backgrounds and use RNAi-mediated gene knockdown to investigate gene function. In spite of the challenges, it’s really exciting to study such a fascinating organism that’s important to global health.
Michelle Flenniken is an Assistant Professor in the Plant Sciences Department at Montana State University. She is a microbiologist investigating honey bee host –pathogen interactions. Michelle received a B.S. in Biology from the University of Iowa, then was a Peace Corps volunteer in Ghana, before obtaining her Ph.D. in Microbiology from Montana State University. She did postdoctoral research at the University of California, San Francisco prior to becoming a faculty member at MSU.
Featured Image Credit: Flickr user Heather Smithers