Rat-bite disease

Japanese: 鼠咬症 - そこうしょう（英語表記）Rat-bite disease

What kind of infection is it?

Rat-bite fever is an infectious disease caused by the bite of a rodent, especially a rat. It is a very rare disease, and the causative agent is Moniliforme. Streptobacillus ( Rensa Kankin ) There are two types of bacteria:

Moniliforme streptobacillus-induced rat-bite disease can occur in mice, squirrels, or other animals other than rats. rodent ( Ghastly ) It can also be caused by being bitten by a dog or cat that preys on rats. In most cases of rat-bite fever, the cause is rats.

Although rare, outbreaks have occurred through contaminated water or milk.

How symptoms manifest

In the case of infection with Streptobacillus moniliforme, the infection usually develops suddenly after an incubation period of 3 to 5 days. Chills ( Mom ) It begins with flu-like symptoms such as relapsing fever (which rises and falls repeatedly), headache, vomiting, and muscle pain.

More than 90% of patients have dark black measles ( Machine ) A measles-like rash appears on the insides of the limbs and joints, but disappears within a few days. Patients also develop painful polyarthritis. Complications include endocarditis, abscess ( Use ) formation of pneumonia, hepatitis, nephritis, Meningitis ( Zuimakuen ) And more.

The symptoms are similar in rat-bite spirillum, but arthritis is rarely involved.

Testing and diagnosis

Clinical diagnosis is difficult, so we must rely on laboratory diagnosis. Diagnosis is made by proving the pathogen in the affected area or in body fluids such as blood. Streptobacillus moniliforme can be cultured in artificial media, but in recent years, PCR (polymerase chain reaction) has made it possible to diagnose at the genetic level. In a survey conducted in our laboratory, 92% of brown rats and 58% of brown rats captured in Japan were positive.

On the other hand, since it has not been possible to successfully cultivate S. spirillum on artificial media, the bacterium is identified by inoculating it into an animal and then observing it under a microscope.

Plague, Tularemia ( Yato Hospital ) , tuberculosis, cat scratch disease, pasteurellosis, relapsing fever, brucellosis, leptospirosis, Gonorrhea ( Physician's Office ) It is necessary to distinguish it from malaria, etc.

Treatment methods

Penicillin is the drug of first choice, but tetracycline and doxycycline are also effective.

What to do if you notice an illness

If you are bitten by a rat or other rodent, you must disinfect the wound immediately. Visit a medical institution, tell them you have been bitten by a rat or other rodent, and receive appropriate treatment.

Akio Yamada

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

Japanese:

どんな感染症か

　鼠咬症はネズミ、とくにラットに咬まれることで起こる感染症です。非常にまれな病気で、病原体はモニリホルム連鎖桿菌(れんさかんきん)と鼠咬症スピリルムという2種類の細菌です。

　モニリホルム連鎖桿菌による鼠咬症は、ラット以外にもマウスやリス、あるいはこれらの齧歯類(げっしるい)を補食するイヌやネコに咬まれて発症することもあります。鼠咬症スピリルムの場合は、ほとんどはラットが原因です。

　ごくまれですが、汚染された水やミルクを介した集団発生もあります。

症状の現れ方

　モニリホルム連鎖桿菌の感染の場合は、通常3～5日の潜伏期ののち、突然の悪寒(おかん)、回帰性を示す発熱（上がり下がりを繰り返す）、頭痛、嘔吐、筋肉痛などインフルエンザのような症状で発症します。

　90％以上の患者さんに、暗黒色の麻疹(ましん)（はしか）のような発疹が四肢の内側や関節の部位に現れますが、数日で消えます。また、痛みを伴う多発性関節炎を起こします。合併症としては心内膜炎、膿瘍(のうよう)の形成、肺炎、肝炎、腎炎、髄膜炎(ずいまくえん)などがあります。

　鼠咬症スピリルムでもほぼ同様ですが、関節炎を伴うことはほとんどありません。

検査と診断

　臨床的には診断は困難なので、実験室診断に頼らざるをえません。患部あるいは血液などの体液から、病原菌を証明することで診断します。モニリホルム連鎖桿菌は人工培地で培養できますが、近年はPCR（ポリメラーゼ連鎖反応）法で遺伝子レベルの診断も可能になってきています。私たちの研究室で行った調査では、国内で捕獲されたドブネズミの92％、クマネズミの58％が陽性でした。

　一方、鼠咬症スピリルムは人工培地での培養は成功していないので、動物へ接種したのち顕微鏡観察で菌の証明をします。

　ペスト、野兎病(やとびょう)、結核、猫ひっかき病、パスツレラ症、回帰熱、ブルセラ症、レプトスピラ症、淋病(りんびょう)、マラリアなどとの区別が必要です。