Scrub typhus

Infobox_Disease
Name = PAGENAME


Caption = Orientia tsutsugamushi
DiseasesDB = 31715
ICD10 = ICD10|A|75|3|a|75
ICD9 = ICD9|081.2
ICDO =
OMIM =
MedlinePlus =
eMedicineSubj = derm
eMedicineTopic = 841
eMedicine_mult = eMedicine2|ped|2710 | MeshID = D012612

Scrub typhus is a form of typhus caused by "Orientia tsutsugamushi".cite journal |author=Tseng BY, Yang HH, Liou JH, Chen LK, Hsu YH |title=Immunohistochemical study of scrub typhus: a report of two cases |journal=Kaohsiung J. Med. Sci. |volume=24 |issue=2 |pages=92–8 |year=2008 |month=February |pmid=18281226 |doi= |url=http://ajws.elsevier.com/ajws_pubmed/pubmed_switch.asp?journal_issn=1607-551X&art_pub_year=2008&%20art_pub_month=02&art_pub_vol=24&art_sp=92]

Although it is similar in presentation to other forms of typhus, it is caused by an agent in a different Genus, and is frequently classified separately from the other typhi.

Causes and geographical distribution

Scrub typhus is transmitted by trombiculid mites ("chiggers"), which are found in areas of heavy scrub vegetation. The bite of this mite leaves a characteristic black eschar that is useful to the doctor for making the diagnosis.

Scrub typhus is endemic to a part of the world known as 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. [cite web|author=Fernandez AD, Johann-Liang R|title=Scrub typhus|publisher=eMedicine|url=http://www.emedicine.com/PED/topic2710.htm|accessdate=2008-10-03]

The precise incidence of the disease is unknown, as microbiological facilities are not available in much of its native range. In rural Thailand and in Laos, murine and scrub typhus accounts for around a quarter of all adults presenting to hospital with negative blood cultures. [cite journal|author=Phongmany S, Rolain JM, Phetsouvanh R, "et al."|title=Rickettsial infections and fever, Vientiane, Laos|journal=Emerg Infect Dis|volume=12|pages=256–262] [cite journal|author=Suttinont C, Losuwanaluk K, Nitwatayakul K, "et al."|title=Causes of acute, undifferentiated, febrile illness in rural Thailand: results of a prospective observational study|journal=Ann Trop Med Parasit|volume=100|363–370] The incidence in Japan has fallen over the past few decades, probably due to decreasing exposure, and many prefectures report fewer than 50 cases per year. [cite journal|author=Katayama T, Hara M, Furuya Y, Nikkawa T, Ogasawara H|title=Scrub typhus (Tsutsugamushi disease) in Kanagawa Prefecture in 2001–2005|volume=59|pages=207–208] [cite journal|author=Yamamoto S, Ganmyo H, Iwakiri, Suzuki S|title=Annual incidence of Tsusugamushi disease in Miyazaki Prefecture, Japan in 2001–2005|year=2006|pages=404–405] It affects females more than males in Korea, but not in Japan.cite journal |author=Bang HA, Lee MJ, Lee WC |title=Comparative research on epidemiological aspects of tsutsugamushi disease (scrub typhus) between Korea and Japan |journal=Jpn J Infect Dis|volume=61|pages=148–50 |year=2008 |pmid=18362409 |doi= |url=http://www.nih.go.jp/JJID/61/148.html]

ymptoms

Symptoms include fever, headache, muscle pain, cough, and gastrointestinal symptoms. More virulent strains of "O. tsutsugamushi" can cause hemorrhaging and intravascular coagulation.

Treatment

Without treatment, the disease is often fatal. The clinical trial evidence on which to base treatment is small, but the drug most commonly used is doxycycline; tetracycline and rifampicin are alternatives. [cite journal|author=Panpanich R, Garner P|title=Antibiotics for treating scrub typhus|journal=Cochrane Database of Systematic Reviews 2002|doi=10.1002/14651858.CD002150] Other drugs that may be effective are azithromycin and the fluoroquinolones, but there is no evidence on which to recommend their use. Chloramphenicol and rifampicin may be useful for infection in children (doxycycline is relatively contraindicated in children).

Vaccine

There are currently no licensed vaccines available in the US. [cite book|author=Arguin PM, Kozarsky PE, Reed C (eds.)|chaptertitle=Chapter 4: Rickettsial Infections|title=CDC Health Information for International Travel, 2008|publisher=Mosby|year=2008|url=http://wwwn.cdc.gov/travel/yellowBookCh4-Rickettsial.aspx|isbn=0323048854]

An early attempt to create a scrub typhus vaccine occurred in the United Kingdom in 1937 (with the Wellcome Foundation infecting around 300,000 cotton rats in a classified project called "Operation Tyburn", but the vaccine was not used.cite web |url=http://www.nal.usda.gov/awic/newsletters/v5n2/5n2princ.htm#toc5 |title=AWIC Newsletter: The Cotton Rat In Biomedical Reserach |format= |work= |accessdate=] The first known batch of scrub typhus vaccine actually used to inoculate human subjects was despatched to India for use by Allied Land Forces, South-East Asia Command (A.L.F.S.E.A.) in June, 1945. By December, 1945, 268,000 cc. had been despatched. [cite journal|journal=Hansard|title="Far East Report"|date=2 April 1946|url=http://hansard.millbanksystems.com/written_answers/1946/apr/02/scrub-typhus-vaccine-far-east] 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. [cite journal|author=Thomson Walker W|title=Scrub typhus vaccine: its effect on sixteen cases incubating the disease|journal=Br Med J|year=1947|volume=1|issue=4501|pages=484–487|url=http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2053023]

History

Severe epidemics of the disease occurred among troops in Burma and Ceylon during World War II (WWII).cite book |author=Audy JR|title=Red mites and typhus |publisher=University of London, Athlone Press|location=London|year=1968|pages= |isbn=0-485-26318-1 |oclc= |doi=] Several members of the U.S. Army's 5307th Composite Unit (Merrill's Marauders) died of the disease; and in 1944, there were no effective antibiotics or vaccines available. [Kearny, Cresson H. (Major), "Jungle Snafus...And Remedies", Oregon Institute (1996), p. 309] [Smallman-Raynor, Matthew, and Cliff, Andrew David, "War Epidemics: An Historical Geography of Infectious Diseases in Military Conflict and Civil Strife, 1850-2000", Oxford University Press, 2004ISBN 0198233647, 9780198233640, pp. 489-491] The disease was also a problem for US troops stationed in Japan after WWII, and was variously known as "Shichitou fever" (by troops stationed in the Izu Shichitou islands) or as Hatsuka fever (Chiba prefecture). [cite journal|author=Ogawa M, Hagiwara T, Kishimoto T, "et al."|title=Scrub typhus in Japan: Epidemiology and clinical features of cases reported in 1998|journal=Am J Trop Med Hyg|volume=67|issue=2|pages=162–165]

References