狂犬病

Rabies

Ⅰ．狂犬病について

　「イヌが狂躁状態になり市民を咬み，咬まれた市民が同じく狂躁状態となり死亡した場合は，そのイヌの飼い主は銀3分の2を支払うこと」と紀元前2，300年のエシュンナ法典に記されているごとく，狂犬病の存在とその恐ろしさは古くから知られてきた。この病が人類を脅かすものとして登場するのは，18～19世紀に都市が形成され，それまで野獣（オオカミやキツネ）などの間に流行していたこの病気が，都市の畜犬の間に入り込み，都市から都市へと全ヨーロッパに拡がるに及んで，人類は直接的に狂犬病の恐怖にさらされることになった。

　Pasteurは，狂犬病の臨床的観察から，その原因は神経系にあり，狂犬の脳を乳剤として健康犬または家兎の脳内に直接接種するという方法でその推定を実証した。これが近代狂犬病学の出発点である^1）。

Abstract

　Rabies is a fetal viral encephalitis caused by the rabies virus,that is mainly transmitted through the saliva of infected domestic or wild animals.　Rabies remains an important public health issue worldwide due to the prevalence of endemic dog rabies in developing countries.　The epidemiological impact is particularly still high in Asian and African countries.　In contrast,in the developed countries,including Japan,rabies is a re-emerging disease.　The Lyssaviruses (types EBLV and ABL) and rabies virus infections via bats have recently emerged in Europe and the United States.　Although the incubation period averages 1-3 months,there is no known treatment once the symptoms of rabies appear.　On the basis of clinical manifestations,rabies can be classified into 2 types: furious and paralytic rabies.　The former is characterized by the well-known symptoms of hydrophobia,aerophobia,and hypersalivation.　However the latter type is likely to be misdiagnosed because of its similarity to Guillian-Barre syndrome and neuropsychiatric illnesses.　Therefore,post-exposure treatment (PET) using a tissue-culture vaccine is the only way to prevent the disease.　In the case of exposure to severe bites (WHO category III),rabies immunoglobulin (RIG) is essential for PET.　Although the mechanism underlying the pathogenesis of rabies remains poorly understood,the recent technique of reverse genetics can be a useful tool for understanding rabies pathogenesis at a genetic level.　Japan has been free of rabies for over 50 years because of the proper registration of domestic animals and control over their vaccinations.　However,it is necessary to always remember that rabies is still a global burden as a representative of a re-emerging disease.