Deadly scrub typhus on the rise in Chennai; do not ignore fever with black patch on the skin

There is a sudden spurt in the number of cases in Chennai with patients presenting with fever not responding to conventional antibiotics for three weeks and associated with brown mark in the skin.

Scrub typhus spreads when chiggers – mites found in forests and, more recently, in urban shrubs – bite the person and inject a microorganism Rickettsia tsutsugamushi into the blood. The bite area turns black, the major symptom of the disease. The fatality rate is 8%. The disease shows symptoms similar to dengue, typhoid and malaria.

• Scrub typhus is a mite-borne infectious disease

• It is caused by Orientia tsutsugamushi (previously called R. tsutsugamushi).

• The reservoir and vector of scrub typhus are larval trombiculid mites of the genus Leptotrombidium.

• Scrub typhus may begin insidiously with headache, anorexia, and malaise, or start abruptly with chills and fever. As the illness evolves, most patients develop high fever, worsening of headache severity and myalgias. An eschar or rash may develop in a subset of patients. The severity of infection can range from mild symptoms and signs to multiorgan failure.

• Diagnostic include serology, biopsy, culture and polymerase chain reaction.

• The indirect fluorescent antibody (IFA) test remains the mainstay of serologic diagnosis; a 4-fold rise in titers over a 14-day period is conclusive.

• The differential diagnosis of scrub typhus includes malaria, dengue, leptospirosis and other rickettsial diseases.

• Doxycycline is the drug of choice.

• Scrub typhus may cause spontaneous abortions in pregnant women.

• Azithromycin is an alternative drug to treat scrub typhus in pregnancy.

• Several studies have demonstrated that chemoprophylaxis with a long-acting tetracycline is highly effective when used by nonimmune individuals living or working in areas in which scrub typhus is endemic.

• The use of insect repellants and miticides are highly effective when applied to both clothing and skin.

• Permethrin and benzyl benzoate are also useful agents when applied to clothing and bedding.

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