Thursday, January 30, 2014

Zombie bees

These days our honey bee colonies (and other bees) are subject to numerous pathogens and parasites. The interaction among multiple pathogens and parasites is the proposed cause for the so called Colony Collapse Disorder (CCD), a syndrome characterized by worker bees abandoning their hive. 

As if this wasn't enough about a year ago colleagues from San Francisco and Los Angeles provided the first documentation that the phorid fly Apocephalus borealis, previously known to parasitize bumble bees and wasps, also infects and eventually kills honey bees and may pose an emerging threat to North American apiculture.

The way the fly kills the bee isn't pretty. The female Apocephalus pierces the bee's abdomen with a sword-like tube and deposits her eggs. The developing larvae attack the bee's brains, disorienting it into flying at night; hence the name, "zombie bee". Usually the poor victim dies within a few hours of exhibiting the aberrant behavior — fortunate because, about seven days later, up to 13 mature Apocephalus borealis will emerge at where the bee's thorax meets its head, decapitating the bee in the process; hence the name, Apocephalus.  

The colleagues used DNA Barcoding to confirm that the phorid flies that emerged from honey bees and bumble bees belong to the same species. Additional microarray analyses of honey bees from infected hives revealed that these animals are often infected with pathogens that are also associated with CCD, implicating the fly as a potential vector or reservoir of these honey bee pathogens. The researchers found that 77 % of the hives they sampled in the San Francisco Bay Area had been infected by the parasite. They also found the parasites in commercial hives in California's Central Valley and South Dakota. 

As a consequence the researchers started ZomBee Watch, a citizen science project sponsored by the San Francisco State University Department of Biology, the San Francisco State University Center for Computing for Life Sciences and the Natural History Museum of LA County. ZomBee Watch has three main goals:

- To determine where in North America the Zombie Fly Apocephalus borealis is parasitizing honey bees.
- To determine how often honey bees leave their hives at night, even if they are not parasitized by the Zombie Fly.
- To engage citizen scientists in making a significant contribution to knowledge about honey bees and to become better observers of nature.

ZomBee Watch already lists two confirmed infections outside California, one in South Dakota and another one discovered only recently, in Vermont. It is certainly too early to say if the parasite has established in the East. The discovery was made in October 2013 and authorities and researchers are now waiting to see if it survives the winter which - in this case fortunately - has been harsh so far. I am willing to freeze a little longer if it helps the bees.

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