Scrub Typhus

Scrub typhus


Scrub typhus is an acute, febrile, infectious illness that is caused by Orientia (formerly Rickettsia) tsutsugamushi. It is also known as tsutsugamushi disease or Chigger borne typhus. It is a zoonotic disease, transmitted by arthropod vector trombiculid mite. Humans are accidental hosts in this disease.

Scrub typhus is prevalent in many parts of India. There have been outbreaks in areas located in the sub-Himalayan belt, from Jammu to Nagaland. Outbreaks were also reported from Rajasthan. There were reports of scrub typhus outbreaks in Himanchal Pradesh, Sikkim and Darjeeling (West Bengal) during 2003-2004 and 2007. Outbreak occurs more frequently during the rainy season however in southern India outbreaks are reported during the cooler months of the year. Scrub typhus is a reemerging infectious disease in India.


A Papule develops at the site of bite. Bites are often found on the groin, axillae, genitalia or neck.  The papule ulcerates and eventually heals with development of a black eschar.

Onset is acute with chills and fever (1040-1050 F), severe headache, infection of the mucous membrane lining the eyes (the conjunctiva), and swelling of the lymph nodes.

Approximately one week later, a spotted and then maculopapular rash appears first on the trunk and then on the extremities and blenches within a few days.

Symptoms generally disappear after two weeks even without treatment.

Complications are interstitial pneumonia (30 to 65% of cases), meningoencephalitis and myocarditis. In severe cases with pneumonia and myocarditis, the mortality rate may reach 30%.


Scrub typhus is caused by a bacterium called Orientia tsutsugamushi. Infection is transmitted by the mite Leptotrombidium deliense.

Human beings are infected when they walk into the mite islands (areas in the soil where the microecosystem is favourable for mites) and are bitten by the mite larvae (chiggers). The mite feeds on the serum of warm blooded animals only once during its cycle of development, and adult mites do not feed on man. The microbes are transmitted through ovarian transmission (certain arthropod vectors transmit disease-causing bacteria from parent arthropod to offspring arthropod) in mites.

The larval stage serves both as a reservoir and vector for infecting humans and rodents.

The incubation period of scrub typhus is about 5 to 20 days (mean, 10-12 days) after the initial bite.


Scrub typhus commonly presents as an undifferentiated fever that requires laboratory confirmation for the diagnosis,

Blood test- may reveal early lymphopenia with late lymphocytosis and Thrombocytopenia

Urine test-  Albuminuria

Scrub typhus may be diagnosed in the laboratory by:

(i)            Isolation of the organism

(ii)            Serology

(iii)          Molecular diagnosis (PCR)

Several serological tests available for the diagnosis are Weil-Felix Test (WFT), Indirect Immunoflourescent test (IIF), Enzyme linked Immunosorbent assay (ELISA)


Scrub typhus is treated with antibiotics. Treatment to be given will depend on the age of patient, pregnancy status of female patient.

For further details consult the physician.



Complications are interstitial pneumonia (30 to 65% of cases), meningoencephalitis and myocarditis. In severe cases with pneumonia and myocarditis, the mortality rate may reach 30%.

There is no vaccine for scrub typhus.

In endemic areas, certain precautions should be taken-

  •        Wear protective clothing.
  •        Insect repellents containing dibutyl phthalate, benzyl benzoate, diethyl toluamide, and other substances can be applied to the skin and clothing to prevent chigger bites.
  •        Do not sit or lie on bare ground or grass; use a suitable ground sheet or other ground cover.
  •        Clearing of vegetation and chemical treatment of the soil, rodent control may help to break up the cycle of transmission.

  • PUBLISHED DATE : Oct 23, 2015
  • PUBLISHED BY : Zahid
  • CREATED / VALIDATED BY : Dr. Aruna Rastogi
  • LAST UPDATED ON : Nov 23, 2015


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