- Case report
- Open Access
Imported scrub typhus: first case in South America and review of the literature
© The Author(s). 2018
- Received: 5 July 2018
- Accepted: 8 August 2018
- Published: 16 August 2018
Scrub typhus is a neglected vector-borne zoonosis causing life-threatening illnesses, endemic in the Asian-Pacific region and, as recently discovered, in southern Chile. Scrub typhus is rarely reported in travelers, most probably due to the lack of clinical experience and diagnostic tests in non-endemic countries. We report the first case of imported scrub typhus in South America.
A 62-year-old tourist from South Korea presented severely ill with fever, rash, and eschar in Santiago, Chile. Laboratory exams showed thrombocytopenia and elevated inflammation parameters, hepatic enzymes, and LDH. With the clinical suspicion of scrub typhus, empirical treatment with doxycycline was initiated and the patient recovered rapidly and without complications. The diagnosis was confirmed by IgM serology and by real-time PCR, which demonstrated infection with Orientia tsutsugamushi (Kawasaki clade).
Only due to the emerging clinical experience with endemic South American scrub typhus and the recent implementation of appropriate diagnostic techniques in Chile, were we able to firstly identify and adequately manage a severe case of imported scrub typhus in South America. Physicians attending febrile travelers need to be aware of this rickettsiosis, since it requires prompt treatment with doxycycline to avoid complications.
- Arthropod-borne diseases
- Scrub typhus
- Orientia tsutsugamushi
- Imported infection
Scrub typhus is a vector-borne zoonosis caused by Orientia species that manifests as an acute febrile disease and has a potentially severe outcome . It is transmitted by the larval stage of trombiculid mites called ‘chiggers’. After the bite of an infective chigger, a characteristic necrotic inoculation lesion termed eschar might develop, which typically contains high bacterial loads. The microorganism then spreads via lymphatics and blood, causing systemic manifestations and laboratory abnormalities such as elevated C-reactive protein (CRP) and liver enzymes . Although widely under-recognized, scrub typhus is considered the most important rickettsial infection worldwide threatening over a billion people and causing more than a million cases per year with substantial mortality . Until recently, scrub typhus was associated with a single species, O. tsutsugamushi, which exclusively occurred within the so-called ‘Tsutsugamushi Triangle’ ranging from Pakistan in the West, far-eastern Russia in the East to northern Australia in the South. However, recent reports of autochthonous cases in the Middle East and southern Chile have reshaped this epidemiological paradigm, suggesting a wider geographical distribution [3, 4].
Scrub typhus is very rarely diagnosed in travelers, with a total of < 40 cases reported in the medical literature. Still, the problem might be under-recognized, since the initial clinical suspicion relies on the physicians’ experience, routine laboratory tests are largely unavailable, and only few reference laboratories permit a definite diagnosis by molecular methods and/or culture. Here we report an Orientia tsutsugamushi infection in a traveler from South Korea visiting Chile, which was confirmed by molecular methods and serology.
Primers and probes used for diagnostic and phylogenetic analysis
First & second
First & second
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With antibiotic treatment, fever subsided within 36 h and the patient was discharged after three days.
Although scrub typhus represents an important public health issue in the Asia-Pacific region and is one of the most severe rickettsial infections, it is almost unrecognized in travelers and poorly covered in web-based information platforms and textbooks of Travel Medicine. A review from 2004 includes ~ 20 cases in travelers ; since then, < 15 additional patients have been published, all as single case reports or small case series [9–19]. The GeoSentinel network reported only five confirmed cases among 47,915 ill travelers between 1996 and 2008 . Most of these patients were diagnosed by serological tests of single (mostly convalescent) samples and only few were molecularly confirmed (mostly in endemic countries) [18, 19]. In contrast, many experts postulate an increased risk of travel-associated scrub typhus due to the emergence of ecotourism (camping, trekking, rafting) in endemic areas [8, 21, 22], which is in accordance with experiences during military operations during World War II and the Vietnam and Korea conflicts, when scrub typhus affected thousands of soldiers . The main reasons for the sustained paucity of reports in Travel Medicine, is most probably the lack of clinical experience and diagnostic tools in many non-endemic countries. In South America, for example, diagnostic tests for scrub typhus were unavailable until recently, and imported cases have never been described. In our case, the emerging clinical experience with endemic South American scrub typhus  and recent implementation of diagnostic techniques in Chile permitted the proper management and rapid diagnostic confirmation of this imported case.
Routinely, scrub typhus is diagnosed by serology, either by positive IgM or IgG seroconversion; though early cases are often seronegative. Definitive diagnosis mostly relies on molecular methods, preferably from eschar material, which stays positive even after initiation of treatment . As in other severe rickettsial infections, empirical treatment should never be delayed due to diagnostic difficulties. In our case, PCR and serology permitted a timely (but also retrospective) diagnosis, proving infection with O. tsutsugamushi Kawasaki strain, which was acquired in the Imsil district, a region of high scrub typhus incidence in South Korea .
Untreated scrub typhus has a high rate of complications and mortality, especially in naïve patients . The immediate start of appropriate antibiotic treatment is therefore the main goal of clinical management and lowers the risk of severe manifestations. For this, the physicians’ clinical experience and judgment is crucial. The most characteristic sign of scrub typhus is a necrotic skin lesion (eschar) at the inoculation site. It appears in 20–90% of patients, but seems to be more frequently present in naïve patients, e.g. travelers [1, 22]. To detect the inconspicuous and painless lesion, a thorough physical exam is essential. If the eschar is not detected or patients do not present the lesion, diagnosis is often delayed and complications more probable. Scrub typhus may also affect domestic travelers. This phenomenon has been recognized in Asian countries such as Taiwan , and is also an emerging problem in Chilean travelers returning to the central metropolitan region from trips to endemic regions in southern Chile (unpublished data). The main differential diagnoses in eschar-positive febrile travelers are spotted fever group rickettsioses. In our patient, those included Japanese spotted fever caused by Rickettsia japonica and other endemic rickettsiae endemic in South Korea such as R. monacensis, R. felis, and R. akari [27, 28]. The centrifugal distribution of the rash, sparing palms and soles, was suggestive for scrub typhus, since rickettsial spotted fevers have a centripetal rash including palms and soles . In comparison to the rash of patients with dengue or other arboviral infections, the rash in scrub typhus has a coarser and more irregular appearance. The presence of atypical lymphocytes might lead to the misdiagnosis of infective mononucleosis, especially in the presence of lymphadenopathy.
This first case of imported scrub typhus in South America highlights the need of physicians attending febrile travelers to be aware of this severe rickettsiosis. This includes knowledge of the endemic regions in Asia, its emergence in South America, and the recognition of the typical clinical manifestations. As in other rickettsial infections, rapid clinical recognition and prompt empirical treatment with doxycycline are crucial for a favorable patient’s prognosis. Diagnostic tools, ideally molecular methods, are useful for retrospective confirmation, but are only available in specialized laboratories. Pre-travel consultations should include information on the risk and prevention of this infection, especially for travelers with outdoor activities such as camping and trekking in endemic regions.
We wish to thank Lorena Porte for her thoughtful manuscript input.
This work was partially supported by the Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT N° 1170810) and the Global Emerging Infectious Diseases Section, work unit # A1402.
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The opinions and assertions contained in this paper are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of the Navy, the Department of Defense nor the United States Government.
A. L. Richards is an employee of the United States Government. This work was prepared as a part of his official duties. Title 17 U.S.C. §105 provides that ‘Copyright protection under this title is not available for any work of the United States Government’. Title 17 U.S.C. §101 defines a U.S. Government work as a work prepared by a military service member or employee of the U.S. Government as part of that person’s official duties.
TW and ALR conceived the report. TW, CM-V, JJ, and ALR drafted the manuscript and contributed to the literature review. TW, MA, JMM, and LT attended the patient. All authors participated in the interpretation of relevant results, provided critical edits, and approved the final manuscript.
Ethics approval and consent to participate
Ethics approval for this case report was not sought as there was no human subjects study in which to participate. The patient consented that his personal and clinical information was used for scientific and teaching reasons.
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The patient consented that information regarding his case was presented in this manuscript.
The authors declare that they have no competing interests.
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