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International Society for Infectious Diseases
[1]
Date: Wed 29 Jul 2009
Source: Environment News Service (ENS) [edited]
Scientists untangle multiple causes of bee colony disorder
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A microscopic pathogen and pesticides embedded in old honeycombs are
2 major contributors to the bee disease known as colony collapse
disorder [CCD], which has wiped out thousands of beehives throughout
the United States and Europe over the past 3 years, new research at
Washington State University (WSU) has confirmed.
Working on the project funded in part by regional beekeepers and
WSU's Agricultural Research Center, entomology professor Steve
Sheppard and his team have narrowed the list of potential causes for
colony collapse disorder. "One of the 1st things we looked at was the
pesticide levels in the wax of older honeycombs," Sheppard said.
Using combs contributed by US Department of Agriculture, Sheppard
found "fairly high levels of pesticide residue." Bees raised in those
hives "had significantly reduced longevity," he said. One easy
solution is for beekeepers to change honeycombs more often. In
Europe, for example, apiarists change combs every 3 years. "In the
US, we haven't emphasized this practice and there's no real consensus
about how often beekeepers should make the change," said Sheppard.
"Now we know that it needs to be more often."
Many researchers are investigating colony collapse disorder because
domestic honeybees are essential for a variety of agricultural crops
in the United States. Beekeepers truck their hives cross country to
pollinate almond groves in California, field crops and forages in the
Midwest, apples and blueberries in the Northeast, and citrus in
Florida. Unlike other diseases that have plagued bees in the past,
colony collapse disorder does not kill bees within the hive. It
leaves a hive with a few newly hatched adults, a queen, and plenty of food.
Another aspect of Sheppard's work, which is being conducted by
graduate student Matthew Smart, focuses on the impact of a
microsporidian pathogen known as _Nosema ceranae_, which attacks
bees' ability to process food. Beekeepers have considered it to be
"the smoking gun" behind colony collapse disorder. "_N. ceranae_ was
only recently described in the US, the 1st time in 2007," Sheppard
said. "But while no one really noticed, it has spread throughout the country."
But in a 2007 study, Jeffery Pettis, who heads the US Agriculture
Department's Bee Research Laboratory, and colleagues reported that
_N. ceranae_ had been in the United States for at least 10 years.
Smart surveyed numerous bee colonies in both the Pacific Northwest
and in California, and found _N. ceranae_ to be very widespread.
Sheppard's earlier research found _N. ceranae_ to be a tough bug to
battle. Of 24 hives checked in early 2008, _Nosema_ build-up was high
in a majority of the bees sampled.
Beekeeper Eric Olson of Yakima, Washington said he treated a hive
with a mega-dose of the antibiotic fumagillin. "That should have
caused the _Nosema_ to either disappear or at least go down," he
said, "but the levels went up." "What it basically does is it causes
bees to get immune-deficiency disorder. So it's actually causing the
bees to almost get a version of HIV," said Mark Pitcher, president of
Babe's Honey and the biggest beekeeper in Saanich on Canada's
Vancouver Island. Pitcher told the "Saanich News" that once the bees'
immune systems are compromised, they become susceptible to dying from
a wide range of causes, including chemicals once used to protect the
bees from parasites such as _Varroa_ mites.
Last summer [2008], researchers at Pennsylvania State University
found unprecedented levels of fluvalinate and coumaphos -- pesticides
used in the hives to combat varroa mites -- in all honeycomb and
foundation wax samples. They also found lower levels of 70 other
pesticides and metabolites of those pesticides in pollen and bees.
The Penn State researchers worked with the National Science
Laboratory of the US Department of Agricultural Marketing Service
that already tests commodities such as milk and fruits and vegetables.
"When we began doing this work, honey was not regularly analyzed, and
bee pollen was not a commodity and so was not analyzed," says Mullin.
"We decided to go with the types of screening the lab does for milk
and apples which look at over 170 pesticides. Now, honey is included
in the commodities to be analyzed." All of the bees tested showed at
least one pesticide and pollen averaged 6 pesticides with as many as
31 in a sample."
"We do not know that these chemicals have anything to do with colony
collapse disorder, but they are definitely stressors in the home and
in the food sources," says Penn State's Dr Maryann Frazier.
"Pesticides alone have not shown they are the cause of CCD. We
believe that it is a combination of a variety of factors, possibly
including mites, viruses, and pesticides."
While beekeepers will have a difficult time controlling pesticide
exposure outside the hive, the Penn State researchers tested a method
for reducing the chemical load in beeswax. Using gamma radiation from
a cobalt 60 source housed at Penn State's Breazeale Reactor, they
irradiated the sheets of beeswax that beekeepers use as the
structural foundation for the bees to build their combs. They used
radiation levels at the high end of that used to irradiate foods and
found that in the wax, irradiation broke down about 50 percent of the
acaricides, pesticides that kill mites.
--
Communicated by:
ProMED-mail
******
[2]
Date: Thu 30 Jul 2009
From: Jose and Sandy Villa
Re: multiple causes of bee colony disorder
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The thought has crossed my mind on a number of occasions that a
trained epidemiologist, an outsider to the small club of researchers
and beekeepers in the US, would find the issue of CCD quite a dream
to try to sort out from a 'history of science' and politics
perspective. Here are some summary thoughts to captivate your
intellect (assuming you have some interest): [Now that is a
challenge! - Mod.MHJ]
First of all, CCD is poorly identified as a real syndrome. A
committee tried to come up with a list of symptoms to describe what
some first saw or heard reported in the fall of 2006. Later, some of
the members of the committee changed the definition to make it more
expansive (which to me sounds like making the syndrome fit the
evidence). Even worst, the definition of distribution and impact is
based on self-reporting. No one at our lab has ever seen it and we
are perhaps the most field oriented group in the country.
Second, CCD in my view is still idiopathic (although a group in
Montana has been claiming for months that they are about to describe
a single causative new organism). Despite a good amount of research
from a number of teams, a paper in Science, a lot of analytical
chemistry work, the best approximation is that "it" is likely a
combination of factors (assuming CCD is a unique syndrome). No one
has found a single cause; no one has followed Koch's postulates.
Third, beekeepers lose colonies in variable but significant numbers
nationwide and make up for it by "divisions." Some years are worse
than others. Unusual "disappearances" of colonies have been reported
through the decades and no single cause has been found. In my view,
the main explanations for the current spikes in colony mortality are
the parasitic varroa mite, poor weather, and nutrition, in that order
(with the possibility of pesticide poisoning for the most unusually
high mortalities).
In terms of what the report from the Sheppard lab in Washington State
claims, the issue of pesticides (particularly illegally applied
miticides) could explain the spotty but very high mortalities that
some claim to have experienced the fall of 2006. The pictures of
colonies with CCD with a handful of live adult workers, a queen, and
very large areas of immature bees fit a pesticide poisoning more than
anything else. One of the symptoms, the lack of interest by
opportunistic lepidopterans and coleopterans in the remains of CCD
"deadouts" also jumps at me as an overdose of a miticide/insecticide
rather than a pathogen. In terms of _N. ceranae_, the timing of CCD
does not coincide with the appearance of _N. ceranae_.
What makes the nationwide fascination with CCD even more bizarre is
the fact that beekeepers are reporting colonies in better shape this
year (2009) than in a long time......
This is a very quick overview of what I see from an unofficial
perspective. You can find a lot of the reports, press releases, and a
few papers archived at a site at Penn State with the acronym MAAREC
[Mid-Atlantic Apiculture Research & Extension Consortium at
would gladly clarify or discuss any of the above if you are interested.
--
Jose Villa
Baton Rouge, LA
USA
[Our thanks to my apiarist friend, neighbour, and colleague, Jose
Villa for his valuable insights and the challenge he has set us
epidemiologists ... a very fair one. Pragmatically I test for "causal
factors," which when corrected result in a decrease in disease
incidence, whatever the statistical significance, and Koch not
withstanding. Apropos, many years ago I discovered that any r-square
association had to be greater than 0.1 to be worth investigation
because I routinely found that, for example in the 1967-68 FMD
epidemic 10 percent of farms on the Welsh Border had "black & white
dogs" (that is, Border Collies) and FMD, ditto FMD and well water as
opposed to piped water. These '10 percenters' come up all the time.
Plus it is rarely cost-effective to correct them even when they are
real. - Mod.MHJ]
[see also
2008
----
Colony collapse disorder, apis - Germany: chemical ban 20080613.1868
2007
----
Colony collapse disorder, apis - USA: (FL) 20071026.3490]
...................................mpp/mhj/mj/mpp
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