2010年10月23日土曜日

日米蜂群崩壊症候群の解明

日米蜂群崩壊症候群が解明されたようだ。

ニホンミツバチ
 佐世保市や平戸市等で飼育していた110群いたニホンミツバチは、
 1年間で3群になった。
セイヨウミツバチ
 約900群の大量死を報告。
カメムシ退治にネオニコチノイド系の農薬「ダントツ」を散布。
農薬が散布された本土地域のほとんどのミツバチが壊滅状態。
散布されなかった離島地域では繁殖数を伸ばしていた。
農薬と大量失踪・死の科学的な因果関係は解明されていない。

米メリーランド州の米陸軍エッジウッド化学生物センターとモンタナ州
の各大学の昆虫学者らが共同研究した結果
 真犯人は真菌N. ceranae(ノゼマ病微胞子虫)とウイルスの組合せ。
 ウイルスと真菌はミツバチ腸で働き、栄養分を吸収するらしい。

米国ノゼマ病微胞子虫とウイルスによる説は、一部には該当するかも
知れないが、すべてではないと言う説もある。

ミツバチヘギイタダニと羽変形病ウィルス、バクテリアが共謀して免疫を
抑制する説もあった。

研究が遅れているため、日本の一部では農薬説を説くが、研究が進む
米国では、菌とウィルスによる説に絞り込んでいるようだ。一部は
農薬説を説く人もいる。

世界的にミツバチは増加し始めたのだろうか。


Rooftop Remedy: Colony Collapse Disorder


Where Are The Bees?


Nob Hill's five star honeybees fight Colony Collapse Disorder

気分転換

Cute Bumble Bee Look


---ミツバチ激減問題提起 県内研究者ら「農薬影響か」---
2010年10月19日 読売新聞
http://www.yomiuri.co.jp/e-japan/nagasaki/news/20101018-OYT8T01140.htm

 昨年、全国的にミツバチが大量失踪(しっそう)、大量死した問題で、県内でも在来種の「ニホンミツバチ」が激減している実態が、研究者らでつくる「ミツバチたすけ隊」の調査で明らかになった。農薬の散布時期と合致していることから、同隊は「農薬が影響した可能性が高い」として、名古屋市で開催中の「生物多様性条約第10回締約国会議」(COP10)の関連イベントで問題提起している。
 同隊によると、リーダーの久志冨士男さん(75)が佐世保市や平戸市などで飼っていたニホンミツバチが、昨夏頃を境に激減。巣箱に蜜を残したまま失踪したり、死んだりした。110群いたニホンミツバチは、この1年間で3群になったという。また、県養蜂協会が昨年9月、セイヨウミツバチ約900群の大量死を県に報告した。
 久志さんらは昨年11月、原因を突き止めようと、研究仲間らと共に「たすけ隊」を結成した。
 県によると、イネの害虫である外来種のカメムシが昨年、大量発生。県内のJA7団体のうち離島地域を除く3団体が夏頃、ネオニコチノイド系の農薬「ダントツ」を散布した。同隊が養蜂家ら約50人に聞き取り調査を行った結果、農薬が散布された本土地域のほとんどが壊滅状態だった一方、散布されなかった離島地域では繁殖数を伸ばしていたことがわかった。
 だが、農薬と大量失踪・死の科学的な因果関係は解明されていない。同隊は29日までのイベント期間中、写真や映像資料などを使って壱岐や五島など離島地域でのニホンミツバチの繁殖事例を紹介するなどし、科学者らに本格的な調査の実施を求める予定だ。
 久志さんは「ミツバチは自然環境の現状を示すバロメーター。虫がいなくなれば、農業や森林もダメになり、人間の生活にも影響が及ぶ。多くの人に身近な問題として考えてほしい」と話している。


---ミツバチはなぜ大量死するのか? 謎ついに解明---
2010.10.15 11:00
http://www.gizmodo.jp/2010/10/post_7810.html

 ミツバチが忽然と姿を消す怪現象「蜂群崩壊症候群(CCD:colony collapse disorder)」。
 5年ぐらい前から世界各地で起こり、アメリカ国内ではコロニーの2割から4割が被害に遭っており、原因をめぐっては殺虫剤から遺伝子組換え農作物まで諸説乱立、研究者たちも頭を抱えています。
 結局あれは携帯電話が原因だったの? いやいや。
 メリーランド州の米陸軍エッジウッド化学生物センターとモンタナ州の各大学の昆虫学者らが共同研究した結果、なんと真犯人は菌とウイルスの組み合わせであることがわかったのです。崩壊したコロニーを調べてみたら、どのコロニーでも菌とウイルスの2段階攻撃でミツバチ8件をノックダウンした形跡が見つかったって言うんですね。
 菌とウイルスどちらか片方ならまだOKなんだけど、このふたつがタッグを組むとたちまちキラーカクテルに変身! ミツバチは百発百中の確率で死んじゃうのですよ。
 どんな仕組みで作用するかは分かりません。一方で弱ったところでもう一方がトドメ...なのか、それとも複合作用で互いに破壊力を高めてしまうのか、その辺は今後の研究課題。でも、菌とウイルスはどちらも冷たく湿り気の多い気候で増殖しますし、どちらも蜂のお腹の中で悪さしますから、それで栄養摂取が困難になるみたいですよ。
 これまでにも疑わしい菌とウイルスの名は無数に出てますけど、一体どれなのか? 
 特定に使ったのは、軍がタンパク質解析用に開発した新ソフトウェアシステムです。ミツバチ8件調べるために作ったものじゃないので最初は出し渋ったようですが、民間にないものだからと頼み込んで使わせてもらいました。ミツバチの体をペースト状にして調べるんですけど、これはいいろいろ試した結果、コーヒーの豆挽き機が一番とわかったそう。
...ともあれ調べてみたら、DNAベースの新型ウイルスがどんぴしゃ検出され、菌の「N. ceranae(ノゼマ病微胞子虫)」との関連も実証されたのです。前々から怪しいと言われていたノゼマ病原菌ですが、まさかウイルスの共犯者がいたとは!
 それにしてもこのCCD。ゾッとするのは蜂の死に様ですよね。

蜂群崩壊には、謎の解明を困難にする厄介な特徴がある。蜂がただ死ぬのではなく、巣から四方八方に飛び去って、ひとりぼっちで死んで、消散することだ。

 なぜ巣から飛び去るのか? こちらのミステリーは謎のままです。この研究率いるモンタナ大Jerry Bromenshenk博士は、きっとウイルスと菌のコンビで記憶や方向感覚が壊れて単に道に迷っているか、あるいは「insect insanity(昆虫の精神錯乱)」のようなものではないか、と話してますよ。んー人間に起こったら怖いな...。


---Scientists and Soldiers Solve a Bee Mystery---
By KIRK JOHNSON
Published: October 6, 2010
http://www.nytimes.com/2010/10/07/science/07bees.html?_r=4

DENVER - It has been one of the great murder mysteries of the garden: what is killing off the honeybees?

Since 2006, 20 to 40 percent of the bee colonies in the United States alone have suffered “colony collapse.” Suspected culprits ranged from pesticides to genetically modified food.

Now, a unique partnership - of military scientists and entomologists - appears to have achieved a major breakthrough: identifying a new suspect, or two.

A fungus tag-teaming with a virus have apparently interacted to cause the problem, according to a paper by Army scientists in Maryland and bee experts in Montana in the online science journal PLoS One.

Exactly how that combination kills bees remains uncertain, the scientists said - a subject for the next round of research. But there are solid clues: both the virus and the fungus proliferate in cool, damp weather, and both do their dirty work in the bee gut, suggesting that insect nutrition is somehow compromised.

Liaisons between the military and academia are nothing new, of course. World War II, perhaps the most profound example, ended in an atomic strike on Japan in 1945 largely on the shoulders of scientist-soldiers in the Manhattan Project. And a group of scientists led by Jerry Bromenshenk of the University of Montana in Missoula has researched bee-related applications for the military in the past - developing, for example, a way to use honeybees in detecting land mines.

But researchers on both sides say that colony collapse may be the first time that the defense machinery of the post-Sept. 11 Homeland Security Department and academia have teamed up to address a problem that both sides say they might never have solved on their own.

“Together we could look at things nobody else was looking at,” said Colin Henderson, an associate professor at the University of Montana’s College of Technology and a member of Dr. Bromenshenk’s “Bee Alert” team.

Human nature and bee nature were interconnected in how the puzzle pieces came together. Two brothers helped foster communication across disciplines. A chance meeting and a saved business card proved pivotal. Even learning how to mash dead bees for analysis - a skill not taught at West Point - became a factor.

One perverse twist of colony collapse that has compounded the difficulty of solving it is that the bees do not just die - they fly off in every direction from the hive, then die alone and dispersed. That makes large numbers of bee autopsies - and yes, entomologists actually do those - problematic.

Dr. Bromenshenk’s team at the University of Montana and Montana State University in Bozeman, working with the Army’s Edgewood Chemical Biological Center northeast of Baltimore, said in their jointly written paper that the virus-fungus one-two punch was found in every killed colony the group studied. Neither agent alone seems able to devastate; together, the research suggests, they are 100 percent fatal.

“It’s chicken and egg in a sense - we don’t know which came first,” Dr. Bromenshenk said of the virus-fungus combo - nor is it clear, he added, whether one malady weakens the bees enough to be finished off by the second, or whether they somehow compound the other’s destructive power. “They’re co-factors, that’s all we can say at the moment,” he said. “They’re both present in all these collapsed colonies.”

Research at the University of California, San Francisco, had already identified the fungus as part of the problem. And several RNA-based viruses had been detected as well. But the Army/Montana team, using a new software system developed by the military for analyzing proteins, uncovered a new DNA-based virus, and established a linkage to the fungus, called N. ceranae.

“Our mission is to have detection capability to protect the people in the field from anything biological,” said Charles H. Wick, a microbiologist at Edgewood. Bees, Dr. Wick said, proved to be a perfect opportunity to see what the Army’s analytic software tool could do. “We brought it to bear on this bee question, which is how we field-tested it,” he said.

The Army software system - an advance itself in the growing field of protein research, or proteomics - is designed to test and identify biological agents in circumstances where commanders might have no idea what sort of threat they face. The system searches out the unique proteins in a sample, then identifies a virus or other microscopic life form based on the proteins it is known to contain. The power of that idea in military or bee defense is immense, researchers say, in that it allows them to use what they already know to find something they did not even know they were looking for.

But it took a family connection - through David Wick, Charles’s brother - to really connect the dots. When colony collapse became news a few years ago, Mr. Wick, a tech entrepreneur who moved to Montana in the 1990s for the outdoor lifestyle, saw a television interview with Dr. Bromenshenk about bees.

Mr. Wick knew of his brother’s work in Maryland, and remembered meeting Dr. Bromenshenk at a business conference. A retained business card and a telephone call put the Army and the Bee Alert team buzzing around the same blossom.

The first steps were awkward, partly because the Army lab was not used to testing bees, or more specifically, to extracting bee proteins. “I’m guessing it was January 2007, a meeting in Bethesda, we got a bag of bees and just started smashing them on the desk,” Charles Wick said. “It was very complicated.”

The process eventually was refined. A mortar and pestle worked better than the desktop, and a coffee grinder worked best of all for making good bee paste.

Scientists in the project emphasize that their conclusions are not the final word. The pattern, they say, seems clear, but more research is needed to determine, for example, how further outbreaks might be prevented, and how much environmental factors like heat, cold or drought might play a role.

They said that combination attacks in nature, like the virus and fungus involved in bee deaths, are quite common, and that one answer in protecting bee colonies might be to focus on the fungus - controllable with antifungal agents - especially when the virus is detected.

Still unsolved is what makes the bees fly off into the wild yonder at the point of death. One theory, Dr. Bromenshenk said, is that the viral-fungal combination disrupts memory or navigating skills and the bees simply get lost. Another possibility, he said, is a kind of insect insanity.

In any event, the university’s bee operation itself proved vulnerable just last year, when nearly every bee disappeared over the course of the winter.


---Iridovirus and Microsporidian Linked to Honey Bee Colony Decline---
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0013181

Abstract
Background

In 2010 Colony Collapse Disorder (CCD), again devastated honey bee colonies in the USA, indicating that the problem is neither diminishing nor has it been resolved. Many CCD investigations, using sensitive genome-based methods, have found small RNA bee viruses and the microsporidia, Nosema apis and N. ceranae in healthy and collapsing colonies alike with no single pathogen firmly linked to honey bee losses.
Methodology/Principal Findings

We used Mass spectrometry-based proteomics (MSP) to identify and quantify thousands of proteins from healthy and collapsing bee colonies. MSP revealed two unreported RNA viruses in North American honey bees, Varroa destructor-1 virus and Kakugo virus, and identified an invertebrate iridescent virus (IIV) (Iridoviridae) associated with CCD colonies. Prevalence of IIV significantly discriminated among strong, failing, and collapsed colonies. In addition, bees in failing colonies contained not only IIV, but also Nosema. Co-occurrence of these microbes consistently marked CCD in (1) bees from commercial apiaries sampled across the U.S. in 2006-2007, (2) bees sequentially sampled as the disorder progressed in an observation hive colony in 2008, and (3) bees from a recurrence of CCD in Florida in 2009. The pathogen pairing was not observed in samples from colonies with no history of CCD, namely bees from Australia and a large, non-migratory beekeeping business in Montana. Laboratory cage trials with a strain of IIV type 6 and Nosema ceranae confirmed that co-infection with these two pathogens was more lethal to bees than either pathogen alone.
Conclusions/Significance

These findings implicate co-infection by IIV and Nosema with honey bee colony decline, giving credence to older research pointing to IIV, interacting with Nosema and mites, as probable cause of bee losses in the USA, Europe, and Asia. We next need to characterize the IIV and Nosema that we detected and develop management practices to reduce honey bee losses.

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