To the Editor:
Scrub typhus (ST) is an infection caused by Orientia tsutsugamushi (genus Rickettsia), which is transmitted by the larvae of trombiculid mites, commonly called chiggers. The disease mainly has been described in Asia in an area known as the Tsutsugamushi Triangle, delineated by Pakistan, eastern Russia, and northern Australia. Although this classic distribution remains, recent reports have documented 1 case in the Arabian Peninsula1 and more than 16 cases in southern Chile.2-4 The first case in Chile was published in 2011 from Chiloé Island.2 To date, no other cases have been reported in the Americas.1-6
We describe a new case of ST from Chiloé Island and compare it to the first case reported in Chile in 2011.2 Both patients showed the typical clinical manifestation, but because ST has become an increasingly suspected disease in southern regions of Chile, new cases are now easily diagnosed. This infection is diagnosed mainly by skin lesions; therefore, dermatologists should be aware of this diagnosis when presented with a febrile rash.
A 67-year-old man from the city of Punta Arenas presented to the emergency department with a dark necrotic lesion on the right foot of 1 week’s duration. The patient later developed a generalized pruritic rash and fever. He also reported muscle pain, headache, cough, night sweats, and odynophagia. He reported recent travel to a rural area in the northern part of Chiloé Island, where he came into contact with firewood and participated in outdoor activities. He had no other relevant medical history.
Physical examination revealed a temperature of 38 °C and a macular rash, with some papules distributed mainly on the face, trunk, and proximal extremities (Figure 1). He had a necrotic eschar on the dorsum of the right foot, with an erythematous halo (tache noire)(Figure 2).
Figure 1. Scrub typhus. A and B, Mainly macular rash distributed centrifugally on the patient’s trunk and extremities.
Figure 2. Tache noire—necrotic eschar on the dorsum of the right foot—with an erythematous halo characteristic of scrub typhus.
A complete blood cell count, urinalysis, and tests of hepatic and renal function were normal. C-reactive protein was elevated 18 times the normal value. Because of high awareness of ST in the region, eschar samples were taken and submitted for serologic testing and polymerase chain reaction (PCR) targeting the 16S rRNA Orientia gene. Empirical treatment with oral doxycycline 100 mg twice daily was started. Polymerase chain reaction analysis showed the presence of Orientia species, confirming the diagnosis of ST. The rash and eschar diminished considerably after 7 days of antibiotic treatment.
Scrub typhus is a high-impact disease in Asia, described mainly in an area known as the Tsutsugamushi Triangle. Recent reports show important epidemiologic changes in the distribution of the disease, with new published reports of cases outside this endemic area—1 in the Arabian peninsula1 and more than 16 in southern Chile.2-4
The disease begins with a painless, erythematous, and usually unnoticed papule at the site of the bite. After 48 to 72 hours, the papule changes to a necrotic form (tache noire), surrounded by a red halo that often is small, similar to a cigarette burn. This lesion is described in 20% to 90% of infected patients in different series.7 Two or 3 days later (1 to 3 weeks after exposure), high fever suddenly develops. Along with fever, a maculopapular rash distributed centrifugally develops, without compromise of the palms or soles. Patients frequently report headache and night sweating. Sometimes, ST is accompanied by muscle or joint pain, red eye, cough, and abdominal pain. Hearing loss and altered mental status less frequently have been reported.5,8