Epidemic typhus

Japanese: 発疹チフス - ほっしんチフス（英語表記）Epidemic typhus
Epidemic typhus

What kind of infection is it?

It is an acute febrile infectious disease caused by Rickettsia typhus. The Rickettsia multiplies in the intestines of body lice that have sucked the patient's blood and are excreted in the feces. If you scratch your skin due to the itching caused by the louse bites, the skin wounds and Bite ( Shiko ) Lice are transmitted by rubbing into the area, or by inhaling dust contaminated with lice faeces.

There have been no cases in Japan since 1957. Overseas, there are localized epidemics in high altitude areas such as Africa, Mexico, and the Andes region of South America. In a November 2003 revision to the Infectious Diseases Control Law, it was classified as a new Category 4 infectious disease that requires animal control. It is designated as a disease requiring international surveillance, and outbreaks are reported to the WHO.

How symptoms manifest

The incubation period is 1 to 2 weeks. Symptoms include chills, headache, back pain, and muscle pain in the limbs. A high fever develops suddenly and continues. In severe cases, the patient may suffer from severe headaches and loss of consciousness. coma ( Today ) This leads to:

A rash appears on the trunk about 4 days after the onset of fever, and spreads to the whole body except the face. Millet ( Dragon ) They range in size from large to the size of a red bean, and rarely merge. At first, they are pale pink and disappear with acupressure, but eventually they turn dark red and do not disappear with acupressure.

The fever subsides rapidly in about two weeks, but after the initial infection, the rickettsiae remain dormant in the body and the infection may recur several years later.

Testing and diagnosis

If your fever lasts for more than three days or you experience severe headache or muscle pain, please see a doctor.

It would be certain if Rickettsia could be identified from the blood of a patient during the fever phase, but since isolating Rickettsia requires a laboratory with a safety level of 3 or higher, diagnosis is mainly based on antibodies. It is necessary to distinguish from typhus, typhoid fever, paratyphoid fever, scrub typhus, etc.

Treatment methods

Tetracycline antibiotics are effective, and fever usually subsides within 3 days of starting administration. The drug should be taken for at least 1 week. If appropriate antibiotics are used, death will not occur, but if antibiotics are not used, the fatality rate is 10-60%.

Prevention

Generally, lice do not infect people directly, so the first step in prevention is to get rid of them. Clothes and bedding should be disinfected with heat. Generally, lice will die if exposed to 70°C heat for 30 minutes.

The vaccine is not commercially available in Japan, but inactivated and live vaccines are available.

Yuko Sagara

Source: Houken “Sixth Edition Family Medicine Encyclopedia” Information about the Sixth Edition Family Medicine Encyclopedia

Japanese:

どんな感染症か

　発疹チフスリケッチアによる急性熱性感染症です。患者さんの血液を吸ったコロモジラミの腸管内でリケッチアが増殖し、糞中に排泄されます。シラミに刺されたかゆみで皮膚をかくと、皮膚の傷や刺咬(しこう)部位から擦り込まれて感染します。シラミの糞便で汚染されたほこりの吸引による感染もあります。

　日本では1957年以降の発生はありません。海外ではアフリカ、メキシコ、南米アンデス地域などの高地で局地的に流行しています。感染症法の2003年11月の改正で、動物対策が必要な新4類感染症に分類されました。国際的監視が必要な疾患に指定され、発生時にはWHOに報告されます。

症状の現れ方

　潜伏期は1～2週間です。寒気、頭痛、背部痛、四肢の筋肉痛を伴って突然発熱し、高熱が続きます。激しい頭痛や意識障害を伴い、重症例では昏睡(こんすい)に陥ります。

　発熱から4日前後に発疹が体幹にみられ、顔面を除く全身に拡大します。大きさは粟粒(ぞくりゅう)大から小豆大で、融合することはまれです。初めは淡紅色で指圧により消退しますが、やがて暗赤色となり指圧では消退しなくなります。

　およそ2週間で急速に解熱しますが、初感染後、体内にリケッチアが潜伏し、数年後に再発することがあります。

検査と診断

　発熱が3日以上続いたり、頭痛や筋肉痛が強い場合は受診してください。

　発熱期の患者さんの血液からリケッチアを証明すれば確実ですが、リケッチアの分離には安全度レベル3以上の実験室が必要とされるため、実際には抗体による診断が中心となります。発疹熱、腸チフス、パラチフス、ツツガムシ病などとの区別が必要です。

治療の方法

　抗菌薬としてはテトラサイクリン系薬が有効で、通常、投与開始から3日以内に解熱します。少なくとも1週間は服薬します。適切な抗菌薬が用いられれば死亡することはありませんが、抗菌薬が使用されない場合、致命率は10～60％です。

予防のために

　一般的には、シラミの媒介なしに直接ヒトからヒトへ感染することはないので、シラミの駆除が予防の第一です。衣類や寝具は加熱消毒を行います。一般に70℃の熱気に30分通せば死滅します。

　ワクチンは国内では市販されていませんが、不活化ワクチンと生ワクチンがあります。

相楽　裕子

出典　法研「六訂版 家庭医学大全科」六訂版 家庭医学大全科について　情報

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