Case 1

The first case occurred in a 40-year-old woman from Kuranda, Queensland, with a 1-week history of fever, myalgia, headache, and dry cough. She had sustained tick bites to the back and leg while planting trees. She was febrile (temperature 38.1°C). A widespread maculopapular rash with a minor petechial component was present. No eschars were found. Renal dysfunction was evident by blood tests (Table). A provisional diagnosis of leptospirosis was made, and she was treated with intravenous penicillin. Urea and creatinine levels continued to increase over 3 days to 14.8 mmol/L and 300 μmol/L, respectively, despite administration of intravenous fluids. She showed no dehydration or hypotension. Urinalysis showed 1+ proteinuria only. The patient’s clinical condition improved slowly over 7 days. The rash had a more noticeable petechial component at this stage of the disease. The patient was discharged on day 7 and given a 5-day course of oral doxycycline, 100 mg, twice a day. She had fully recovered on subsequent follow-up. A diagnosis of QTT was made retrospectively on the basis of serologic results..

Case 2

The second case occurred in a 69-year-old woman from Innisfail, Queensland, who was hospitalized with a 2-week history of fever, myalgia, neck pain, and confusion. She was febrile (temperature 39.2°C) and had tachycardia (140 beats/min). Multiorgan failure, purpura fulminans, and digital necrosis developed over a 2-day period, and she was transferred to an intensive care unit. Intubation and ventilation were required. She had widespread cutaneous and digital necrosis. There were no eschars or lymphadenopathy. Prothrombin time was 22 s (normal range 8–14 s), activated partial thromboplastin time was 53 s (normal range 25–38 s), and fibrinogen level was 1.6 g/L (normal range 1.5–4.0 g/L). The latex D dimer titer was 8 (normal <1). Results of a PCR for Neisseria meningitidis in blood and an extensive screen for primary vasculitides and prothrombotic disorders were negative. A skin biopsy specimen showed vessel thrombosis and no evidence of vasculitis, which is consistent with purpura fulminans.

Figure 1

Figure 1. Digital gangrene in a patient (case 2) with Rickettsia australis infection.

Treatment included broad-spectrum antimicrobial drugs and doxycycline. Clinical recovery was prolonged, and she required temporary renal dialysis. Fourteen digital amputations were performed on her hands and feet (Figure 1). There was serologic evidence of R. australis infection. She lived in a house that bordered bushland and had received tick bites. However, she could no recall her last exposure. Tissue from the skin biopsy specimen was tested by PCR with primers against the rickettsial 17-kDa gene (2), and immunohistochemical analysis was performed with polyclonal rabbit antisera against spotted fever group (SFG) rickettsiae. Both tests showed negative results.

Case 3

Figure 2

Figure 2. Radiograph showing pneumonia in a patient (case 3) with Rickettsia australis infection.

The third case occurred in a 45-year-old man from Deeral, Queensland, who was seen with headache, malaise, and vomiting 10 days after a tick bite. He also had a cough, dyspnea, and insulin-dependent diabetes. He was employed working on rural roads. He was febrile (temperature 38.2°C) and had tachycardia (145 beats/min) and tachypnea (40 breaths/min). He required 15 L/min oxygen by mask to maintain oxygenation. There was a fine petechial rash and left inguinal lymphadenopathy. A chest radiograph showed bilateral interstitial infiltrates (Figure 2). Over the ensuing hours, respiratory failure developed, and he required intubation and ventilation. Twelve hours after admission, his arterial blood gas results were pH 7.32, pO₂ 59 mmHg, and pCO₂ 55 mmHg on 100% oxygen while ventilated. His creatinine level increased to 180 μmol/L over the first 2 days and then slowly returned to normal. He was given broad-spectrum antimicrobial drugs, including doxycycline, on the day of admission. Treatment with doxycycline continued for 7 days. His recovery was marked by gross generalized edema. Serologic results were diagnostic for infection with R. australis. He was ventilated for 16 days and spent 3 weeks in the intensive care unit. He returned to work 2 months after admission.