eMedicine Specialties > Pediatrics: General Medicine > Infectious Disease

Scrub Typhus

Author: Aracelis D Fernandez, MD, FAAP, Attending Physician, Assistant Professor of Pediatrics, Assistant Professor of Immunology an, Department of Pediatrics, Children's Hospital at Albany Medical Center
Coauthor(s): Rosemary Johann-Liang, MD, Medical Officer, Infectious Diseases and Pediatrics, Division of Special Pathogens and Immunological Drug Products, Center for Drug Evaluation and Research, Food and Drug Administration
Contributor Information and Disclosures

Updated: Jun 29, 2009

Introduction

Background

Scrub typhus is an acute, febrile, infectious illness that was first described by the Chinese about 2000 years ago. This illness is caused by Orientia (formerly Rickettsia) tsutsugamushi, an obligate intracellular gram-negative bacterium, which was first isolated in 1930. Although it is recognized as one of the tropical rickettsioses diseases, O tsutsugamushi has a different cell wall structure and genetic composition than that of the rickettsiae. Guidelines for diagnosis and management of rickettsial diseases have been established.1 Humans are accidental hosts in this zoonotic disease.

A transmission electron micrograph depicting a pe...

A transmission electron micrograph depicting a peritoneal mesothelial cell of a mouse that had been experimentally infected intraperitoneally with Orientia tsutsugamushi rickettsial micro-organisms. In this photomicrograph, several organisms are visible within the mesothelial cell's cytoplasm. O tsutsugamushi is the cause of scrub typhus.

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A transmission electron micrograph depicting a pe...

A transmission electron micrograph depicting a peritoneal mesothelial cell of a mouse that had been experimentally infected intraperitoneally with Orientia tsutsugamushi rickettsial micro-organisms. In this photomicrograph, several organisms are visible within the mesothelial cell's cytoplasm. O tsutsugamushi is the cause of scrub typhus.


The term scrub is used because of the type of vegetation (terrain between woods and clearings) that harbors the vector; however, the name is not entirely correct because certain endemic areas can also be sandy and semiarid. Cases diagnosed in the United States have been imported from regions of the "tsutsugamushi triangle," which extends from northern Japan and far-eastern Russia in the north, to northern Australia in the south, and to Pakistan and Afghanistan in the west, where the disease is endemic.

An estimated one million cases occur annually. Because of reports of O tsutsugamushi strains with reduced susceptibility to antibiotics, as well as reports of interesting interactions between this bacterium and HIV, a renewed interest in this illness has emerged.

Pathophysiology

Humans acquire the disease when an infected chigger, the larval stage of trombiculid mites (Leptotrombidium deliense and others), bites them while feeding and inoculates O tsutsugamushi pathogens. The bacteria multiply at the inoculation site with the formation of a papule that ulcerates and becomes necrotic, evolving into an eschar, with regional lymphadenopathy that progresses to generalized lymphadenopathy within a few days. Before symptoms develop, patients are rickettsemic. As in other rickettsial diseases, perivasculitis of the small blood vessels occurs. The endothelium is involved, however, the basic histopathologic lesions suggest that macrophages might be more affected.2

Frequency

United States

Reported cases are imported by travelers, military personnel, and persons who have emigrated from abroad.3

International

Scrub typhus is endemic in regions of eastern Asia and the southwestern Pacific (Korea to Australia) and from Japan to India and Pakistan.2,4,5,6,7,8

Mortality/Morbidity

Mortality rates in untreated patients range from 0-30%. Complications may include atypical pneumonia, overwhelming pneumonia with adult respiratory distress syndrome (ARDS)–like presentation, myocarditis, and disseminated intravascular coagulation (DIC). No significant morbidity or mortality occurs in patients who receive appropriate treatment.

Clinical

History

  • In suspected cases of scrub typhus, elicit any history of travel to endemic areas.
  • Patients most commonly present with high fever, severe headache, generalized myalgia, and malaise.
  • The incubation period from the mite bite is 5-20 days following inoculation.

Physical

  • Patients experience abrupt onset of high fever (104-105°F), severe headache, myalgia, and eschar (resembling a cigarette burn) with tender regional lymphadenopathy. Less frequently, ocular pain, wet cough, malaise, and injected conjunctiva are present.
  • Toward the end of the first week, approximately 35% of patients develop a centrifugal macular rash on the trunk, which may become papular. By this time, hepatosplenomegaly and generalized lymphadenopathy are present.
  • A small number of patients have CNS involvement, with tremors, nervousness, slurred speech, nuchal rigidity, or deafness during, the second week of the disease; however, results from the cerebrospinal fluid examination either are normal or indicate a low number of monocytes.

Causes

  • O tsutsugamushi
    • This is an obligate intracellular gram-negative bacterium that has a large number of serotypes. Five serotypes, Karp, Gilliam, Kawazaki, Boryon, and Kato, are helpful in serologic diagnosis.
    • This pathogen does not have a vacuolar membrane; thus, it grows freely in the cytoplasm of infected cells.

More on Scrub Typhus

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

  1. [Guideline] Chapman AS, Bakken JS, Folk SM, et al. Diagnosis and management of tickborne rickettsial diseases: Rocky Mountain spotted fever, ehrlichioses, and anaplasmosis--United States: a practical guide for physicians and other health-care and public health professionals. MMWR Recomm Rep. Mar 31 2006;55:1-27. [Medline].

  2. Suputtamongkol Y, Suttinont C, Niwatayakul K, et al. Epidemiology and clinical aspects of rickettsioses in Thailand. Ann N Y Acad Sci. May 2009;1166:172-9. [Medline].

  3. Hendershot EF, Sexton DJ. Scrub typhus and rickettsial diseases in international travelers: a review. Curr Infect Dis Rep. Jan 2009;11(1):66-72. [Medline].

  4. Matsumura Y, Shimizu T. [Case of imported scrub typhus contracted in Myanmar]. Kansenshogaku Zasshi. May 2009;83(3):256-60. [Medline].

  5. Liu Y, Feng D, Suo J, et al. Clinical characteristics of the autumn-winter type scrub typhus cases in south of Shandong province, northern China. BMC Infect Dis. Jun 4 2009;9(1):82. [Medline].

  6. McGready R, Blacksell SD, Luksameetanasan R, Wuthiekanun V, Jedsadapanpong W, Day NP, et al. First Report of an Orientia tsutsugamushi Type TA716-Related Scrub Typhus Infection in Thailand. Vector Borne Zoonotic Dis. Jun 3 2009;[Medline].

  7. Sharma PK, Ramakrishnan R, Hutin YJ, et al. Scrub typhus in Darjeeling, India: opportunities for simple, practical prevention measures. Trans R Soc Trop Med Hyg. Mar 13 2009;[Medline].

  8. Kramme S, An le V, Khoa ND, et al. Orientia tsutsugamushi bacteremia and cytokine levels in Vietnamese scrub typhus patients. J Clin Microbiol. Mar 2009;47(3):586-9. [Medline].

  9. Phetsouvanh R, Blacksell SD, Jenjaroen K, Day NP, Newton PN. Comparison of indirect immunofluorescence assays for diagnosis of scrub typhus and murine typhus using venous blood and finger prick filter paper blood spots. Am J Trop Med Hyg. May 2009;80(5):837-40. [Medline].

  10. Paris DH, Aukkanit N, Jenjaroen K, Blacksell SD, Day NP. A highly sensitive quantitative real-time PCR assay based on the groEL gene of contemporary Thai strains of Orientia tsutsugamushi. Clin Microbiol Infect. May 2009;15(5):488-95. [Medline].

  11. Tsai CC, Lay CJ, Wang CL, Ho YH, Wang LS, Chen LK. Levofloxacin versus tetracycline antibiotics for the treatment of scrub typhus. Int J Infect Dis. Jun 3 2009;[Medline].

  12. Baxter JD. The typhus group. Clin Dermatol. May-Jun 1996;14(3):271-8. [Medline].

  13. Edwards MS, Feigen RD. Rickettsial diseases. In: Textbook of Pediatric Infectious Diseases. Vol 2. 2004:2508-9.

  14. Jensenius M, Fournier PE, Raoult D. Rickettsioses and the international traveler. Clin Infect Dis. Nov 15 2004;39(10):1493-9. [Medline].

  15. Raoult D. Scrub typhus. In: Mandell, Douglas and Bennett's Principles and Practice of Infectious Diseases. Vol 2. 2005:2309-10.

  16. Seong SY, Choi MS, Kim IS. Orientia tsutsugamushi infection: overview and immune responses. Microbes Infect. Jan 2001;3(1):11-21. [Medline].

  17. Sharma PK, Ramakrishnan R, Hutin YJ, et al. Scrub typhus in Darjeeling, India: opportunities for simple, practical prevention measures. Trans R Soc Trop Med Hyg. Mar 13 2009;[Medline].

  18. Watt G, Parola P. Scrub typhus and tropical rickettsioses. Curr Opin Infect Dis. Oct 2003;16(5):429-36. [Medline].

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Keywords

scrub typhus, chigger fever, tsutsugamushi fever, tsutsugamushi disease, akamushi disease, flood fever, inundation fever, island disease, island fever, Japanese river fever, kedani fever, mite typhus, shimamushi disease tropical typhus, Rickettsia tsutsugamushi, R tsutsugamushi, Rickettsia orientalis, R orientalis, Oriental tsutsugamushi, O tsutsugamushi, HIV infection, adult respiratory distress syndrome, ARDS, disseminated intravascular coagulation, DIC, treatment, diagnosis

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Contributor Information and Disclosures

Author

Aracelis D Fernandez, MD, FAAP, Attending Physician, Assistant Professor of Pediatrics, Assistant Professor of Immunology an, Department of Pediatrics, Children's Hospital at Albany Medical Center
Disclosure: Nothing to disclose.

Coauthor(s)

Rosemary Johann-Liang, MD, Medical Officer, Infectious Diseases and Pediatrics, Division of Special Pathogens and Immunological Drug Products, Center for Drug Evaluation and Research, Food and Drug Administration
Rosemary Johann-Liang, MD is a member of the following medical societies: American Academy of Pediatrics, American Medical Association, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Medical Editor

José Rafael Romero, MD, Director of Pediatric Infectious Diseases Fellowship Program, Associate Professor, Department of Pediatrics, Combined Division of Pediatric Infectious Diseases, Creighton University/University of Nebraska Medical Center
José Rafael Romero, MD is a member of the following medical societies: American Academy of Pediatrics, American Society for Microbiology, Infectious Diseases Society of America, New York Academy of Sciences, and Pediatric Infectious Diseases Society
Disclosure: Nothing to disclose.

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner

Managing Editor

Larry I Lutwick, MD, Professor of Medicine, State University of New York, Downstate Medical School; Director, Infectious Diseases, Veterans Affairs New York Harbor Health Care System, Brooklyn Campus
Larry I Lutwick, MD is a member of the following medical societies: American College of Physicians and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

CME Editor

Robert W Tolan Jr, MD, Chief, Division of Allergy, Immunology and Infectious Diseases, The Children's Hospital at Saint Peter's University Hospital; Clinical Associate Professor of Pediatrics, Drexel University College of Medicine
Robert W Tolan Jr, MD is a member of the following medical societies: American Academy of Pediatrics, American Medical Association, American Society for Microbiology, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, Phi Beta Kappa, and Physicians for Social Responsibility
Disclosure: GlaxoSmithKline Honoraria Speaking and teaching; MedImmune Honoraria Speaking and teaching; Merck Honoraria Speaking and teaching; sanofi pasteur Honoraria Speaking and teaching; Baxter Healthcare Honoraria Speaking and teaching

Chief Editor

Russell W Steele, MD, Head, Division of Pediatric Infectious Diseases, Ochsner Children's Health Center; Clinical Professor, Department of Pediatrics, Tulane University School of Medicine
Russell W Steele, MD is a member of the following medical societies: American Academy of Pediatrics, American Association of Immunologists, American Pediatric Society, American Society for Microbiology, Infectious Diseases Society of America, Louisiana State Medical Society, Pediatric Infectious Diseases Society, Society for Pediatric Research, and Southern Medical Association
Disclosure: None None None

 
 
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