受取日時：2001.11.26
発信者：神谷正男
電子住所：
電話番号:
保存場所：http://ac-net.org/home/hokudai/doc/011128-kamiya.shtml

環境動物フォーラムのご案内


テーマ「新しい革袋にお酒（＝エキノコックス：感染源対策技術）はあるの？」

とき：2001年11月28日　午後5時30分〜7時45分　

ところ：北海道大学・遠友学舎（北18西7）

　入場無料

このところの肉骨粉や牛乳などの事件は、環境に毒が撒かれていたり、食品に異物 や病原体が混じり込んでいたら、商品は売れない、地域の経済は成り立たないこと を明解に示しています。かつて、７０年代、日本で自治意識の高まりの中から世界 に先駆けて公害を押さえこんだ実績があります。ダイオキシンでは後れをとりまし たが、日本の４大公害訴 訟とその後の公害規制、処理技術は世界のお手本になった と思います。病気の原因になるものを取り除くことが、重要です。公害物質、ある いは、肉骨粉に混入するプリオンをエキノコックスに置き換えればわかりやすいと 思うのです。

地域の大学や役所が５０年前から本気で考えなければならならなかったテーマかも しれません。今年も本州から若いエキノコックス症重症患者もみつかっています。 ４〜５歳の間、北海道に住んでいた人です。この人の場合、感染ルートを特定はで きませんが、北海道で感染した可能性が大きいでしょう。北海道の高レベルの流行 を抑えれば本州への新たな流行地の形成は、いまなら防げると考えています。プリ オン病やエイズの顛末に酷似しています。北海道では、プリオン病やエイズよりも 問題は大きいのです。

北海道内の患者の動向は役所：協議会（専門委員、医師で構成）が把握しています が、表には出てきません。通常、住民が覚悟を決めようにも判断材料が、一般市民 にはありません。役所の病気から市民の病気にシフトさせ、自分のことは自分で守 る姿勢から始めなければならない等々と考えております。 大学は大きく変わっています。「新しい革袋は、次々できるが、中身はどうなの？ 」と問われると苦しいところもありますが、エキノコックス：感染源対策技術につ いては、「新しいお酒」ができました。ぜひ、聴いていただき、討論にご参加くだ さいますよう、お友達と、あるいはご家族と一緒に、気軽にご来場をお待ちしてい ます。

神谷正男
〒０６０0818　札幌市北区北１８西９
北海道大学大学院獣医学研究科寄生虫学教室　
（略称：北大・獣医・寄生虫）
TEL & FAX +81-11-706-5198, FAX +81-11-706-5190
kamiya@vetmed.hokudai.ac.jp
http://www.hokudai.ac.jp/veteri/organization/dis-cont/parasitol/index.html

During the mid-twentieth century, there was an expression of“This Wormy World(Stoll , 1947: J. Parasitol.)”to describe the abundance of parasitic worms in our society. However, with the widespread use of antihelmintics, roundworms and the related helminths had been almost eradicated in Japan. Nevertheless, with the increase of garbage from kitchens and from agricultural and fisheries waste materials as food for wildlife such as the red fox, the epidemiology of certain parasites had changed greatly.

In August 1999, Echinococcus multilocularis metacestodes were found in pigs in Aomori prefecture, on the mainland of Japan. Thus, the endemic area for this cestode, which had been hitherto confined to Hokkaido has been extended to the mainland of Japan. When this parasite infects the human body, it causes clinical signs similar to that of hepatic tumor for more than a decade. Since there is no effective antihelmintic for this alveolar hydatid disease, therapy is difficult when the patient starts to show clinical signs. In Hokkaido, ca. 400 people had been confirmed as having the lesions caused by this parasite and most cases of the disease had been reported fatal.

Echinoccocus multilocularis has skillfully adapted its life cycle to the predator-prey(foxes-voles) relationship. Humans are infected by ingestion of the parasite ova excreted from the predator. Human to human, or pig to human transmission of the parasite does not occur.

In April 1999, with the enactment of the“New Infectious Disease Ordinance”, human echinococcosis, as diagnosed by detection of the parasite or the antibody against it, must be reported to the authorities within 7 days. Although such regulation had been highly regarded, much more needs to be done. The most important measure is to eradicate the source of infection of this disease. There is a need to identify and control the animal hosts that disperse the parasite eggs and also to set up a systematic program for controlling and containing the spread of the parasite.

Until the 1970's it was thought that echinococcosis in Hokkaido could be controlled by cutting one third of all foxes on the island, but such a measure proved to be fruitless. Studies on fox behavior had shown that they inhabit a defined territory or domain and that if a certain fox had been killed in a certain area, other foxes from the surrounding territory would move into the culled fox domain. Thus, the culling of foxes is thought to be counterproductive and has resulted in the migration of infected foxes and an increased infection rate among the animals, leading to further spread of the disease.

Presently, the prevalence of echinococcosis in Hokkaido foxes is about 60％ and the parasite has also been detected in pet dogs and cats. If no actions are taken to control the source of infection of this parasite, then its spread to Honshu on the main land of Japan, will become a matter of time.

Several years ago, our research group at Hokkaido University developed a diagnostic method for fox detecting antigen in the feces of the infected fox, whereby it is not necessary to kill the animal in order to diagnose the infection.

In 1998, a deworming program to eradicate echinococcosis in wild foxes, involving more than 10,000 hours per year was carried out by our research group, in a pilot area facing the Sea of Okhotsk in northern-eastern Hokkaido, covering 200 Km2. The wild foxes were fed meat and fish sausage containing the antihelmintic, Praziquantel. Using the coproantigen detecting method and fecal examination, it was observed that the number of foxes excreting the Echinococcus eggs had been reduced to almost zero despite the fact that some foxes were still positive for the coproantigen test which indicates there are still infected intermediate voles in the area. Thus, it is thought that if the deworming program were carried out more extensively, there is a possibility of eradicating the source of infection of the parasite from all foxes.

In an echinococcosis control pilot program that was carried out in southern Germany about 10 years ago, wild foxes were fed antihelmintic and then killed to evaluate the effectiveness of the deworming program. In the peripheral pilot area, the effectiveness of the deworming program was quite low due to the movement of other infected foxes into the test area following the culling of foxes there. However, the prevalence of echinococcosis among foxes in the center of the pilot area had been completely eradicated. Thus, both Japanese and German researchers had shown that it is possible to clean up our environment contaminated by infected foxes.

In 1994, the Parasitology Department of the Faculty of Veterinary Medicine, Hokkaido University, was designated as a reference center for echinococcosis by OIE. Since then, the aforementioned department has been collaborating with researchers from other endemic areas such as Uruguay, France and China, as well as with officials from international organizations such as FAO and WHO, in attempts to control the source of infection of the echinococcosis. Collaborative networks were also forged with researchers in EU countries in the form of exchange of scientific information as well as diagnostic reagents and antihelmintics used in sylvatic control programs.

A measure to control echinococcosis had not been taken by the Japanese government authority. In this context, I would like to propose 3 points, which will not only help solve the echinococcosis problem domestically but also contribute to international cooperation.

The first is to add to the “New Infectious Disease Ordinance” the duty to authorities the authority the prevalence of Echinococcus infected 径animals which serve as the source of infection to humans, as well as the establishment of the diagnosis and quarantine of these animals.

The second is to establish a specialize research organization with facilities and human resources to handle infected animals and the ability to response to the needs of each individual local situation. For example, using the local agricultural and fisheries waste products to develop antihelmintic-laced baits for the deworming program of the infected foxes, development of a parasite vaccine for the foxes and training of experts and technicians to educate the public on prevention of the disease.

The third is to establish a network among international researchers where information exchange and scientific collaboration can transcend the borders of their countries in order to establish and perfecting the disease control program. This includes the free flow of information on the sources of infection, on techniques regarding the prevention of infection, and on the extension of technical cooperation to the endemic areas. These proposals are in line with the policy on the International Control of Parasitic Diseases (the so-called "Hashimoto Initiative")as proposed by Japan in the 1998 summit meeting in Birmingham, England.

北大先端研ニュース「研究プロジェクト：寄生虫・エキノコックスの生態解析と汚
染環境の修復」、　　　２００１年７号
日本瞭望、「消滅棘球条虫」１９９９年８月号１３
LOOK JAPAN 「OUTFOXING ECHINOCOCCUS」AUGUST 1999, 29
「DETENER AL EQUINOCOCO」AGOSTO 1999, 13
北海道大学広報誌　季刊　リテラ・ポプリ、「旅をする寄生虫：WANDERING
PARASITE,消滅棘球条虫」
　　　　　　　２０００年４号

朝日新聞、論壇　エキノコックス感染源対策を、２０００年２月２５日