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ProMED翻訳情報(266回) ~台湾におけるイタチアナグマの狂犬病ウイルス保持に関する意見~


狂犬病:台湾(02) イタチアナグマ、古い侵入ウイルス
Date: Thu 1 May 2014  Source: Taiwan Today/United Daily News [edited]

A team led by Victor Fei Pang, professor at the School of Veterinary Medicine of Taipei City-based National Taiwan University, found that the rabies outbreak last year [2013] among Taiwan ferret badgers was caused by a cryptically circulating endemic strain of the virus rather than animals from mainland China as previously thought. The results were published on 1 May 2014 in the journal Emerging Infectious Diseases, produced by U.S. Centers for Disease Control and Prevention.
台北市にある国立台湾大学獣医学部のVictor Fei Pang教授率いる研究チームは、昨年(2013年)台湾イタチアナグマの間で流行している狂犬病は、以前考えられていた中国本土からの動物によってもたらされたというより、ウイルスの流行株の密かな循環によってもたらされたことを発見した。その結果は、アメリカ疾病管理予防センター(CDC)が発行しているジャーナル「Emerging Infectious Diseases(EID)」で2014年5月1日に発表された。

Between the beginning of the outbreak in July last year [2013] and the end of August 2013, 105 ferret badgers, or _Melogale moschata_ subaurantiaca, were found with rabies. But the research by Pang shows that the disease was already present in Taiwan between 2002 and 2014.
昨年(2013年)7月の流行開始から2013年8月いっぱいまでの間に、105頭のイタチアナグマ(Melogale moschata_ subaurantiaca)が狂犬病で見つかっていた。しかし、Pang教授の研究は、狂犬病がすでに2002年から2014年の間に台湾国内にすでに存在していたことを示している。

The ROC Council of Agriculture announced on 16 Jul 2013 that 3 dead ferret badgers from Nantou and Pingtung counties in central and southern Taiwan, respectively, tested positive for rabies. These were the 1st recorded cases since 1961. The next month [August 2013], the COA said tests showed high similarity between the rabies strains found in local ferret badgers and those from mainland China.

After 5 months of investigation, Pang’s team concluded their investigation and submitted the paper to EID. According to their findings, the Taiwan ferret badger rabies strain diverged from strains in mainland Chinese ferret badgers, Chinese dogs, and Philippines dogs between 158 and 210 years ago, and already appeared in Taiwan more than a century ago. It did not come from mainland China, nor did it come from dogs, the study showed.

As to why the disease had cryptically circulated for more than 52 years and only ferret badgers were affected, Pang said successful conservation efforts may have allowed the ferret badger population to expand to the level where disease transmission became possible. “But further research is needed to determine the exact cause,” he added.

According to Pang, an infected shrew and puppy have been found since the outbreak began, suggesting that the strain can jump the species barrier. If this is the case, the question becomes why it has remained hidden until now. Pang’s team is working on clarifying these issues.

According to Tsai Hsiang-jung, director general of Animal Health Research Institute under the COA, experiments on mice will start within the next couple of weeks, followed by work on 5-month-old healthy badgers and then beagles. As for the spread of known cases, he said, there have been none north of Miaoli in northern Taiwan, nor in Kaohsiung City in the south of the country.
農業委員会配下の動物衛生研究所所長Tsai Hsiang-jung氏によるとネズミを用いた実験は2週間以内に開始し、引き続き5ヶ月令の健常なイタチアナグマを用いた実験、その次にはビーグルを用いた実験に取り組む予定である。Tsai Hsiang-jung氏は、発生地域の拡大に関して、台湾北部の苗栗県北部にも台湾南部の高雄市にも全く報告されてない、と述べた。

Communicated by: Merritt Clifton  

Date: May 2014   Source: Emerging Infectious Disease Journal [edited]

Molecular Characterization of Cryptically Circulating Rabies Virus from Ferret Badgers, Taiwan

Hue-Ying Chiou, Chia-Hung Hsieh, Chian-Ren Jeng, Fang-Tse Chan, Hurng-Yi Wang, and Victor Fei Pang


After the last reported cases of rabies in a human in 1959 and a nonhuman animal in 1961, Taiwan was considered free from rabies. However, during 2012-2013, an outbreak occurred among ferret badgers in Taiwan. To examine the origin of this virus strain, we sequenced 3 complete genomes and acquired multiple rabies virus (RABV) nucleoprotein and glycoprotein sequences.

Phylogeographic analyses demonstrated that the RABV affecting the Taiwan ferret badgers (RABV-TWFB) is a distinct lineage within the group of lineages from Asia and that it has been differentiated from its closest lineages, China I (including isolates from Chinese ferret badgers) and the Philippines, 158-210 years ago. The most recent common ancestor of RABV-TWFB originated 91-113 years ago. Our findings indicate that RABV could be cryptically circulating in the environment. An understanding of the underlying mechanism might shed light on the complex interaction between RABV and its host.

[I strongly recommend that subscribers read the full EID J script. But all this leaves a big question standing in the room: Where has this virus been in the past 50-100 years? Saying it has been cryptically circulating merely describes the situation but not how it hid. Logically, if the ferret-badger population was minimal, the chances of anyone stumbling upon a sick ferret and submitting it for necropsy is slight to absent. As the population has latterly blossomed, this would no longer be the case. And if the rabies virus can aesitivate in bats, there may be a seasonal hibernation in ferret-badgers. And what about congenital infections in utero such as we see with _Leptospira_ and _Brucella_? A stretch maybe. An interesting puzzle. – Mod.MHJ
私は、購読者はEID J原稿の全文を読まれることを強く勧める。しかし、この論文には立ちはだかる大きな疑問が残る。すなわち、過去50〜10年の間このウイルスはどこにいたのだろうか?そのウイルスは単に密かに循環していたと状態を表現しているが、どの様に隠れていたのか述べていない。論理的に、もしイタチアナグマの個体数が(流行を維持するための)最小限であれば、罹患したイタチアナグマが誰かの目に止まる機会や剖検をする機会が非常に少なかったかなかったのである。個体数が最近増加したので、その事例ではないのだろう。また、もしそのウイルスがコウモリの体内で夏眠できれば、イタチアナグマの体内で季節的な冬眠状態となるかもしれない。それから、レプトスピラ症やブルセラ症で見られるような子宮内での先天的な感染についてはどうだろうか。この問題は継続するだろう・興味深い難問である。