CCD - Colony Collapse Disorder - the drastic disappearance of most of honey bees from hives...
         accounted for a loss of  22% of the U.S. bee colonies during the winter of 2007-2008
         large bee losses were reported in Australia, Brazil, Canada, China, & Europe. 
         world's agricultural production depends upon
Apis mellifera - European honeybee -
         for armies crop pollinators at almost any time of the year.  

   Several potential causes, working together may be the cause of colony collapse including:
varroa mites - a parasite that sucks hemolymph
nosema apis - a single celled fungal parasite that causes bee dysentery
          new synthetic poison - as acaricides (neonicotinoids: act like nicotine) used to kill mites
             tobacco plants deploy nicotine against leaf-eating pests & could enter pollen.
             subsequent analyses have discovered over 170 different chemicals (some 35 in pollen).
             poor nutrition - fewer natural food sources could lead to diseases of honey bees
           all these are opportunistic infections possible caused by a weakened bee immune system.
    Using metagenomics (all nucleic acids of environ are collected and sequenced): the organisms 
             present are then identified - revealing a never before identified virus in U.S. bees -
                            IAPV - Israeli acute paralysis virus (1st identified in 2004).
            Healthy bees exposed to IAPV mimicked the CCD symptoms and dies away from hives.

honey bee Protection against the virus by RNA interference may block viral reproduction in bees.
   Consensus is that multiple factors - poor nutrition, pesticide exposure, & parasites-
   weaken colonies and make them susceptible to virus mediated collapse.