New Insights into the Disappearance of the Honeybee

Since 2006 when the depopulation of the honey bee (Apis mellifera) hives was first documented 25% of American       beekeepers have been affected by what has been termed Colony Collapse Disorder or CCD.  The number of bee colonies in the US dropped 31.8% in the 2006-2007 winter season and 35.8% in the winter of 2007-2008 and there was a 28.6 % loss in 2008-2009. A 30% loss of colonies was recorded for 2009-2010. These are general statistics of bee loss and not necessarily all the bee loss was due to CCD.  Bees succumb to pesticides, mites, malnutrition, insect diseases and other factors. In 2007-2008 60% of the losses were attributed to CCD while only 15% appeared to be from this cause in 2008-2009. While the rates appear to be declining the losses are still too great to sustain a population large enough to do what bees do best, pollinate our crops.

In Colony Collapse Disorder bees do not return to the hive. They simply disappear, something that is very unusual in the highly socialized bee community. The adults disappear over a very short period of time and no dead bees are found in or around the hive. A live and laying queen is left behind with a small retinue of attendants. Pollen and honey stores are intact. Larval bees are present but without adults to care for them. The lack of dead bees makes it difficult to trace the source of the problem.

There has been considerable speculation among beekeeper and the scientific community, as to what is causing the disappearance of the honey bee. Guesses range from stress due to environmental factors to a fungi or viral disease. A single celled parasite Nosema ceranae and infestations of the Varroa mite are suggested possible causes. Israeli acute paralysis virus is present in almost all of the affected colonies but, while it is considered a marker, there is no proof that it is causative of the colony collapse.   Some experts believe that lack of genetic diversity among American bee colonies is a contributing factor. Bees that are raised for honey production are often artificially inseminated to produce colonies that achieve high production rates. It is speculated that lack of genetic diversity makes the bees more susceptible to disease. What has come out of the ongoing research is that there is probably more than one dynamic causing the problem. Speculation is running in the direction of attributing CCD to a syndrome.

The University of Montana is heavily into honeybee research including investigations into Colony Collapse Disorder. Their latest findings suggest that both a fungus and a virus might be involved. The virus is insect iridescent virus. This virus invades the abdomens of the bees and turns them a bluish green or purple color. The fungus is Nosema ceranae. The ingestion of the spores of this fungus causes the bees to sicken. One of the symptoms of Nosema Ceranae is what is referred to as “bee diarrhea” These two pathogens were found only in hives affected with CCD. Researchers at the University of Montana are not prepared to say that these two culprits actually cause CCD. An alternate possibility is that colonies weakened by the actual cause are more likely to succumb to these two pathogens.  Robert Cramer, pathologist at Montana State University in Bozeman states that, “There seems to be a correlation between the presences of these two pathogens together. We envision the bee gets an infection from one or the other, and this causes the bees to become stressed, which then allows the second infection to come in and more effectively cause disease.

A similar report was given at American Society for Microbiology in May of this year. Jay Evans of the United States Department of Agriculture’s Agricultural Research Service in Beltsville, Maryland suggested that Nosema ceranae “is a precursor to infectious diseases” and that these diseases are the direct cause of CCD. This group of researchers has been looking at Nosema ceranae in conjunction with a group of RNA viruses and the mites that spread the viruses. They are seemingly suggesting that only when multiple factors are present is the collapse of a colony actually triggered.

While Nosema ceranae is treatable with an antibiotic the spores are nearly impossible to kill. Viruses are also treatable but are difficult to eradicate completely. It is suggested that what is causing the decline of CCD in the last year is more cleanliness in the hives. Simply not cross contaminating hives by using the same cleaning equipment can reduce the spread of CCD. Joanna Gress, a doctoral student at Montana State University did some testing and found that a 10% solution of bleach was very effective in killing Nosema ceranae.

CCD may be one of those things that just burns itself out. If its cause is indeed a number of interlocking factors that have overstressed the bee population, a change in one of those factors may stem the problem. Nosema ceranae is a relatively new import virtually replacing Norema apis, which also caused bee diarrhea but less death. Ongoing research will analyze how the bee immunological systems react to each species. Perhaps bees can be bred to be more resistant or perhaps Mother Nature will take care of that on her own. Never underestimate Mother Nature!