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Scrub typhus or Tsutsugamushi fever[1] is a form of typhus caused by the intracellular parasite Orientia tsutsugamushi, a Gram-negative (alpha)-proteobacterium of the family Rickettsiaceae first isolated and identified in 1930 in Japan.[2][3]


Signs and symptoms include fever, headache, muscle pain, cough, and gastrointestinal symptoms; while morbilliform rash, and eschar are also typical presentations. More virulent strains of O. tsutsugamushi can cause hemorrhaging and intravascular coagulation. [4][2]


The etiology is a form of typhus caused by the intracellular parasite Orientia tsutsugamushi, a Gram-negative (alpha)-proteobacterium of family Rickettsiaceae.[2]Scrub typhus is transmitted by some species of trombiculid mites ("chiggers", particularly Leptotrombidium deliense).[5]


Orientia tsutsugamushi initially attacks the myelocytes in the area of inoculation, and then the endothelial cells lining the vasculature. In the blood circulation, it targets phagocytes such as dendritic cells and macrophages in all organs as the secondary targets. The parasite first attaches itself to the target cells using surface proteoglycans present on the host cell and bacterial surface proteins such as type specific protein 56 or type specific antigen, TSA 56 and surface cell antigens Sca A and Sca C, which are membrane transporter proteins.[6][7]


In terms of the evaluation, a blood test is done. However, if a diagnostic laboratory is not readily available; then diagnosis is based on clinical findings and epidemiologic setting.[2]


The drug most commonly used is doxycycline or tetracycline, but chloramphenicol is an alternative. Strains that are resistant to doxycycline and chloramphenicol have been reported in northern Thailand.[8][9]


Severe epidemics of the disease occurred among troops in Burma and Ceylon during World War II.[10]


The first known batch of scrub typhus vaccine actually used to inoculate human subjects was dispatched to India for use by Allied Land Forces, South-East Asia Command in June 1945.[11] The vaccine was produced at Wellcome's laboratory at Ely Grange, Frant, Sussex. An attempt to verify the efficacy of the vaccine by using a placebo group for comparison was vetoed by the military commanders, who objected to the experiment.[12]


  1. "Scrub typhus (Concept Id: C0036472) - MedGen - NCBI". Archived from the original on 30 July 2023. Retrieved 28 July 2023.
  2. 2.0 2.1 2.2 2.3 "Scrub typhus | CDC". Centers for Disease Control and Prevention. 13 November 2020. Archived from the original on 26 March 2017. Retrieved 18 March 2024.
  3. Pediatric Scrub Typhus Archived 2017-10-12 at the Wayback Machine, accessdate: 16 October 2011
  4. Jain P; Prakash S; Tripathi PK; et al. (2018). "Emergence of Orientia tsutsugamushi as an important cause of acute encephalitis syndrome in India". PLOS Negl Trop Dis. 12 (3): e0006346. doi:10.1371/journal.pntd.0006346. PMC 5891077. PMID 29590177.
  5. Pham XD, Otsuka Y, Suzuki H, Takaoka H (2001). "Detection of Orientia tsutsugamushi (Rickettsiales: Rickettsiaceae) in unengorged chiggers (Acari: Trombiculidae) from Oita Prefecture, Japan, by nested polymerase chain reaction". J Med Entomol. 38 (2): 308–311. doi:10.1603/0022-2585-38.2.308. PMID 11296840. S2CID 8133110.
  6. Ge, Y.; Rikihisa, Y. (2011). "Subversion of host cell signaling by Orientia tsutsugamushi". Microbes and Infection. 13 (7): 638–648. doi:10.1016/j.micinf.2011.03.003. PMID 21458586.
  7. Ha, N.Y.; Sharma, P.; Kim, G.; Kim, Y.; Min, C.K.; Choi, M.S.; Kim, I.S.; Cho, N.H. (2015). "Immunization with an autotransporter protein of Orientia tsutsugamushi provides protective immunity against scrub typhus". PLOS Neglected Tropical Diseases. 9 (3): e0003585. doi:10.1371/journal.pntd.0003585. PMC 4359152. PMID 25768004.
  8. Watt G, Chouriyagune C, Ruangweerayud R, et al. (1996). "Scrub typhus infections poorly responsive to antibiotics in northern Thailand". Lancet. 348 (9020): 86–89. doi:10.1016/S0140-6736(96)02501-9. PMID 8676722. S2CID 23316592.
  9. Kollars TM, Bodhidatta D, Phulsuksombati D, et al. (2003). "Short report: variation in the 56-kD type-specific antigen gene of Orientia tsutsugamushi isolated from patients in Thailand". Am J Trop Med Hyg. 68 (3): 299–300. doi:10.4269/ajtmh.2003.68.299. PMID 12685633.
  10. Audy JR (1968). Red mites and typhus. London: University of London, Athlone Press. ISBN 978-0-485-26318-3.
  11. "Scrub Typhus Vaccine, Far East". Hansard. Millbanksystems. April 2, 1946. Archived from the original on March 3, 2016. Retrieved October 16, 2021.
  12. Thomson Walker W (1947). "Scrub Typhus Vaccine". Br Med J. 1 (4501): 484–7. doi:10.1136/bmj.1.4501.484. PMC 2053023. PMID 20248030.