eMedicine Specialties > Dermatology > Bacterial Infections

Scrub Typhus

Author: Robert A Schwartz, MD, MPH, Professor and Head of Dermatology, Professor of Medicine, Professor of Pediatrics, Professor of Pathology, Professor of Preventive Medicine and Community Health, UMDNJ-New Jersey Medical School
Coauthor(s): Cris Jagar, MD, Staff Physician, Department of Psychiatry, Saint Vincent Catholic Medical Centers
Contributor Information and Disclosures

Updated: Apr 22, 2008

Introduction

Background

Scrub typhus typically occurs in Southeast Asia and Japan, where the disease was first described in 1899. During World War II, scrub typhus killed or incapacitated thousands of troops who were stationed in rural or jungle areas of the Pacific theatre. The disease is called scrub typhus because it generally occurs after exposure to areas with scrub vegetation because this is where the rodents predominantly live. It has recently been found that the disease can also be prevalent in areas, such as sandy beaches, mountain deserts, and equatorial rain forests.

Rickettsial diseases such as scrub typhus have forced the American military to continue work on countermeasures to control the arthropod vectors and participate in the development of rapid, accurate diagnostic tests, vaccines, and improved surveillance methods.1

The eMedicine Pediatrics article Scrub Typhus may be helpful. Additionally, the Medscape Emerging and Reemerging Infectious Diseases Resource Center may be of interest.

Pathophysiology

Scrub typhus is caused by Rickettsia tsutsugamushi (Orientia tsutsugamushi). It is a tiny intracellular parasite that lives primarily in mites (the primary reservoir) belonging to the species Leptotrombidium (Trombicula) akamushi and Leptotrombidium deliense. The Rickettsia organisms are found throughout the mite's body, but the highest number is present in the salivary glands. When the mite feeds on rodents (eg, rats, moles, and field mice, which are the secondary reservoirs) or humans, the parasites are transmitted to the host. Only larval Leptotrombidium mites (eg, chiggers) transmit the disease. This zoonotic disease may disseminate into multiple organs through endothelial cells and macrophages, resulting in the development of fatal complications.2,3

Frequency

United States

The United States is not affected by scrub typhus. The only cases of scrub typhus in the United States are in travelers who have recently been to one of the endemic areas.

International

The disease is limited to eastern and southeastern Asia, India, and northern Australia and the adjacent islands. The seasonal occurrence of scrub typhus varies with the climate in different countries because the mites are able to thrive as conditions change. The mites prefer the rainy season and certain areas (eg, forest clearings, riverbanks, grassy regions). Areas in which the mites thrive pose a greater risk to humans. The prevalence of scrub typhus in Japan has been rising, and much of the current research has been based in Japan.

Mortality/Morbidity

The mortality rate ranges from 1-60%, depending on the geographic area and the rickettsial strain.

  • Death can occur from the primary infection or from secondary complications (eg, pneumonitis, encephalitis, circulatory failure).
  • Most fatalities occur by the end of the second week of infection.

Race

All races are affected equally.

Sex

Both men and women are affected equally.

Age

People of all ages are affected equally.

Clinical

History

  • Once transmitted to the host, R tsutsugamushi incubates for about 10-12 days (although this can vary from as little as 6 d or as long as 21 d).
  • After incubation, persons may experience headaches, shaking chills, lymphadenopathy, conjunctival infection, fever, anorexia, and general apathy.
  • The fever usually reaches 104-105°F.
  • Diagnosing this disease early in its course can be difficult because many conditions can present with a high fever; however, the presentation of the rash, a history of exposure to endemic areas, and the presentation of the sore caused by the bite can be diagnostic.

Physical

  • The site of infection is marked by a chigger bite.
    • This initial lesion has been said to be most easily discernible in whites. However, the presence or absence of eschar was thoroughly examined among 176 Korean patients with scrub typhus confirmed by immunofluorescent assay4 ; 162 (92%) cases had eschar, with 128 (79.5%) on the front of the body. Eschars were detected in men within 30 cm below the umbilicus (19 patients, 35.8%). Distribution on the lower extremities and the chest above the umbilicus were 22.6% (12 patients) and 20.8% (11 patients), respectively. In women, the most prevalent area was the chest above the umbilicus, which accounted for 40.7% (44 patients) of all the detected eschars.
    • The infection begins as a red indurated lesion that eventually enlarges to 8-12 mm in diameter, vesiculates and ruptures, and becomes dark and necrotic in the center.
    • Scarring may occur.
  • From 5-8 days after infection, a dull red rash may appear all over the body, especially starting on the trunk and extending to the extremities.
    • Additional symptoms at this time include enlargement of the spleen, cough, and delirium.
    • Pneumonitis or encephalitis may develop during the second week.
  • In severe cases, the patient's pulse rate increases and the blood pressure decreases.
    • The patient may become delirious and lose consciousness.
    • Other complications, such as splenomegaly, muscle twitching, or interstitial myocarditis, may develop.
  • If the patient does not receive treatment, symptoms may last for more than 2 weeks; with treatment, the patient recovers within 36 hours.
  • The patient's recovery is usually rapid and without sequelae.

Causes

Scrub typhus is caused by R tsutsugamushi (O tsutsugamushi). It is a tiny parasite that lives primarily in mites belonging to the species L (Trombicula) akamushi and L deliense.

More on Scrub Typhus

Overview: Scrub Typhus
Differential Diagnoses & Workup: Scrub Typhus
Treatment & Medication: Scrub Typhus
Follow-up: Scrub Typhus
References
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References

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Further Reading

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Keywords

tsutsugamushi disease, tsutsugamushi fever, tropical typhus, Rickettsia tsutsugamushi, R tsutsugamushi, Orientia tsutsugamushi, O tsutsugamushi, Leptotrombidium (Trombicula) akamushi, L akamushi, Leptotrombidium deliense, L deliense

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Contributor Information and Disclosures

Author

Robert A Schwartz, MD, MPH, Professor and Head of Dermatology, Professor of Medicine, Professor of Pediatrics, Professor of Pathology, Professor of Preventive Medicine and Community Health, UMDNJ-New Jersey Medical School
Robert A Schwartz, MD, MPH is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American College of Physicians, and Sigma Xi
Disclosure: Nothing to disclose.

Coauthor(s)

Cris Jagar, MD, Staff Physician, Department of Psychiatry, Saint Vincent Catholic Medical Centers
Disclosure: Nothing to disclose.

Medical Editor

Janet Fairley, MD, Professor and Head, Department of Dermatology, University of Iowa
Janet Fairley, MD is a member of the following medical societies: American Academy of Dermatology, American Dermatological Association, American Federation for Medical Research, and Society for Investigative Dermatology
Disclosure: Nothing to disclose.

Pharmacy Editor

David F Butler, MD, Professor of Dermatology, Texas A&M University College of Medicine; Director, Division of Dermatology, Scott and White Clinic; Director Dermatology Residency Training Program, Scott and White Clinic
David F Butler, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American Medical Association, American Society for Dermatologic Surgery, American Society for MOHS Surgery, Association of Military Dermatologists, and Phi Beta Kappa
Disclosure: 3M Pharmaceutical Grant/research funds Other; Graceway Pharmaceuticals Grant/research funds Other

Managing Editor

Rosalie Elenitsas, MD, Associate Professor of Dermatology, University of Pennsylvania School of Medicine; Director, Penn Cutaneous Pathology Services, Department of Dermatology, University of Pennsylvania Health System
Rosalie Elenitsas, MD is a member of the following medical societies: American Society of Dermatopathology
Disclosure: Nothing to disclose.

CME Editor

Glen H Crawford, MD, Assistant Clinical Professor, Department of Dermatology, University of Pennsylvania School of Medicine; Chief, Division of Dermatology, The Pennsylvania Hospital
Glen H Crawford, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American Medical Association, Phi Beta Kappa, and Society of USAF Flight Surgeons
Disclosure: Nothing to disclose.

Chief Editor

William D James, MD, Paul R Gross Professor of Dermatology, University of Pennsylvania School of Medicine; Vice-Chair, Program Director, Department of Dermatology, University of Pennsylvania Health System
William D James, MD is a member of the following medical societies: American Academy of Dermatology and Society for Investigative Dermatology
Disclosure: elsevier Royalty Other; american college of physicians Honoraria Other

 
 
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