Typhus: Scrub Typhus

Scrub typhus is the commonest type of typhus in men. Scrub typhus is caused by O. tsutsugamushi. It is maintained by transovarian transmission in trombiculid mites. After hatching, infected larval mites known as chigger, which is the only stage that feeds on a host, inoculate organisms into the skin. Scrub typhus is endemic in eastern and southern Asia, northern Australia, and islands of the western Pacific and Indian Oceans.

The mode of transmission is as follows:


Mite to Rats & mice to Mite to  Rats & mice




Signs & Symptoms: The symptoms can be from mild self limiting disease to fatal. Incubation period of scrub typhus is 6–21 days. Fever, headache, cough, myalgia, and gastrointestinal symptoms are common. The classic symptom includes an eschar where the chigger feeds, regional lymphadenopathy, and a maculopapular rash, but only rarely seen. Severe cases include encephalitis and interstitial pneumonia which are due to vascular injury. The case-fatality rate for untreated classic cases is 7%.

Diagnosis:  Diagnosis is mainly by clinical symptoms. IFA (immuno fluorescent assay), indirect immunoperoxidase, and enzyme immunoassays are the laboratory diagnosis techniques.

Treatment: Doxycycline 100 mg twice a day for 7 -15 days or chloramphenicol 500 mg four times a day orally for 7–15 days is the treatment of choice.

Some cases of scrub typhus as seen in Thailand are caused by doxycycline or chloramphenicol resistant strains. These doxycycline or chloramphenicol resistant cases of scrub typhus are treated with rifampin, azithromycin or clarithromycin.

Prevention: Good personal hygiene is required for prevention. Clearing of vegetation where rats and mice live and application of insecticides like lindane, chlordane to ground and vegetation to control the mite. No vaccine is available at present.

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