Queensland Tick Typhus (Rickettsia Australis) in a Man After Hiking in Rural Queensland

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Queensland tick typhus (Rickettsia australis) in a man after hiking in rural Queensland

Stephen A Thomas, Jason Wu his rash. Some ongoing minor lethargy survive by feeding off other wildlife persisted. Rickettsial serology was (Figure 4), including marsupials and repeated at this time (four weeks after rodents. likely bite exposure) and showed an CASE elevated R. rickettsii titre. Answer 2 A man aged 51 years presented with a one-week history of fever, lethargy, There is an incubation period of two anorexia and generalised arthralgias, Question 1 to 14 days from the time of bite. Initial with an erythematous eruption (Figure 1) clinical presentation typically includes and a large plaque with eschar noted Where and how do people contract eschar at the bite site, fever, headache on examination (Figure 2). The patient Queensland tick typhus? and a confluent erythematous eruption. was afebrile and haemodynamically If left untreated for more than one to stable, with an otherwise unremarkable Question 2 two weeks, the disease poses some risk examination and no organomegaly or of pneumonitis, encephalitis, septic lymphadenopathy. How does the disease typically present? shock or death.2 Prolonged lethargy Further questioning revealed a history or fatigue, even after rash clearance, of visiting the Bunya Mountains National Question 3 is a common symptom reported with Park, Queensland, for a hiking trip two rickettsial infection. Blood tests may weeks prior to presentation. The patient What testing is done for this disease? reveal an elevated white cell count, was not aware of being bitten by ticks or acute transaminitis and elevated other insects; however, Queensland tick Question 4 C-reactive protein. typhus was suspected clinically, given this is a common presentation in patients What is the treatment for this disease? Answer 3 with tick bites who have visited that area, while Sweet syndrome was considered as Answer 1 Serological R. rickettsii indirect a remote differential. Initial management immunofluorescence assay detects the included doxycycline 100 mg twice daily Rickettsia refers to a group of Gram- infection at 1:128 dilution, with cross- and follow-up. negative bacterial infections. Australian reactivity between R. rickettsii (Rocky Lesional biopsy for histopathology was tick typhus, otherwise known as Mountain spotted fever) and R. australis performed at presentation, confirming a Queensland tick typhus (R. australis), (Queensland tick typhus).3 Positive cases mononuclear vasculitis consistent with is a commonly encountered rickettsial that are detected at 1:128 dilution have rickettsial infection, and no features infection in Australia. The name, repeated titrations of sera, providing a of Sweet syndrome. Initial serology Queensland tick typhus, arose after final titre result.4 immunofluorescence assay was negative soldiers training in Queensland during Serology takes at least six days (<1:128 titre) for Rickettsia rickettsii (the World War II were affected.1 R. australis before obtaining a positive result and is serological test that is cross-reactive for may occur from tick exposure, typically currently the gold standard for testing.4 Rickettsia australis). Other blood tests, along the east coast of Australia (Wilsons Initial negative serological studies do including liver and renal function tests, Promontory in Victoria to tropical north not rule out rickettsial infection and were normal. Queensland; Figure 3). Infection can should not alter treatment completion At review two weeks later, the patient result from the bite of an infected tick or in potentially infected patients. Testing reported that most of his symptoms had from exposure to the faeces of infected could subsequently be repeated in resolved and demonstrated clearing of hosts. Ticks in the affected areas generally more suspicious cases four weeks after

Authors Stephen A Thomas MBBS, Department of R. australis Dermatology, Princess Alexandra Hospital, Brisbane, Qld. [email protected] Jason Wu FACD, Department of Dermatology,

Princess Alexandra Hospital, Brisbane, Qld Competing interests: None. Provenance and peer review: Not commissioned, externally peer reviewed.

References 1. Appuhamy RD, Tent J, Mackenzie JS. Figure 1. Initial clinical presentation of Figure 3. Distribution map of Queensland Tick Toponymous diseases of Australia. Med J Aust non-confluent erythematous plaques on Typhus in Australia.4 2010;193(11−12):642–46. upper back Adapted with permission from Graves S. Update on 2. Expert Group for Antibiotic. Rickettsial infections. Australian rickettsial infections. Surry Hills, NSW: In: eTG complete [Internet]. Melbourne: Australasian Society for Infectious Diseases, 2017 Therapeutic Guidelines Limited, 2014. 3. health.vic. Rickettsial infections. Melbourne: Department of Health and Human Services, 2017. Available at www2.health.vic.gov.au/public-health/ infectious-diseases/disease-information-advice/ rickettsial-infection [Accessed 11 August 2017]. 4. Graves S. Update on Australian rickettsial infections. Surry Hills, NSW: Australasian Society for Infectious Diseases, 2017. Available at www. asid.net.au/documents/item/415 [Accessed 11 August 2017]. 5. Wang JM, Hudson BJ, Watts MR, et al. Diagnosis of Queensland tick typhus and African tick bite fever by PCR of lesion swabs. Emerg Infect Dis 2009;15(6):963–65. doi: 10.3201/eid1506.080855.

Figure 2. Initial clinical presentation of central Figure 4. Photograph of an unfed and fed tick. eschar on broad erythematous plaque on back ‘Tick before and after feeding’ by Bjørn Christian (suggestive of original bite site) Tørrissen, www.pvv.org/~bct/nsw/imagepages/ image53.htm. Licence at https://creativecommons. org/licenses/by-sa/3.0/

suspected exposure but is unlikely to Key points alter management. An alternative diagnostic method • R. australis is an infection typically by polymerase chain reaction (PCR) is presenting with eschar at bite site, available nationally from the Australian fevers, lethargy and arthralgias in Rickettsial Reference Laboratory. PCR patients who have visited endemic areas looks for rickettsial DNA, although this has (typically rural or bush areas along the inferior diagnostic sensitivity. PCR of a eastern seaboard of Australia). skin biopsy or swab from an eschar lesion, • Clinical presentations of rickettsial or from the patient’s blood, may be more infection in the context of recent sensitive during days one to five of the exposure to endemic areas should cause infection.4,5 the physician to have a low threshold for treatment, with or without patient Answer 4 knowledge of a tick bite. • Serological R. rickettsii Initial management of suspected cases immunofluorescence is the current gold should include a seven-day course of oral standard for testing; however, typically, doxycycline 100 mg twice daily. If allergy this will not test positive until at least or contraindications to doxycycline exist, one week following tick bite exposure. oral azithromycin 250 mg may be used PCR is a more appropriate test on days once daily for seven days. Treatment one to five after bite exposure but has response is usually rapid. inferior overall sensitivity. correspondence [email protected]