ADF Health 2011 - Volume 12 Number 1Clinical QuizA Soldier with Fever and a Rash
In May 2011, a 37 year old male soldier presented with a sudden onset of fever, retro-orbital headache, arthralgia, myalgia, some nausea and fatigue. On examination, the patient had a widespread rash, including the trunk (A, B). There was no history of overseas travel, but the soldier had been in the Cowley Beach Training Area, near Innisfail, North Queensland, and then in Cairns for a few days before returning to Townsville, where he presented unwell.
Clinical Quiz - AnswerA Soldier with Fever and a RashDiagnosis: This patient had probable dengue. Initial Investigations: Full blood count revealed a slightly lowered white cell count (3.8; ref. 4.0-11), a slight lymphocytopenia (0.7; ref. 1.1-4.0), and a thrombocytopenia (66; ref. 150-450). He was also positive on a Dengue NS1 antigen rapid test. Additional history: The soldier had been taking daily doxycycline for prevention of scrub typhus. Discussion: His visit to Cowley Beach certainly raises the possibility of scrub typhus, as this is a known area for previous outbreaks amongst military personnel. 1–3 It could have represented a failure to his prophylaxis and scrub typhus was also investigated as a diagnosis. However, north Queensland is also an area where there are frequent outbreaks of dengue, which is often brought in by travellers and spreads quickly amongst the local population. 4 Outbreaks of all four serotypes of dengue (DEN-1, DEN-2, DEN-3 & DEN-4) has been seen in recent years in northern Queensland, as the vector, Aedes aegypti, is widespread in this region. 4 At the time of presentation, there were three dengue outbreaks declared in north Queensland, namely in Cairns (DEN-4), Innisfail (DEN-4 and DEN-2) and Townsville (DEN-1). 5 These outbreaks are now declared over. 6 Infection with dengue virus can range from no apparent symptoms to a mild to moderate illness (dengue), or sometimes even a potentially fatal condition, i.e. dengue haemorrhagic fever (DHF) or dengue shock syndrome (DSS), 4 which may be related to subsequent infections with a different dengue serotype. The symptoms of dengue usually come on between 4-7 days after exposure, but can be an earlier or later onset, and symptoms can last up to a week. There is sometimes quite a florid macular or maculopapular rash a few days after the onset of fever and other symptoms. 4 The detection and successful typing of dengue virus from patients with suspected dengue is important both for the diagnosis of the disease and also for the implementation of public health control measures. The development of rapid tests to detect the non-structural protein (NS1) has greatly improved early diagnosis of dengue. 7 NS1 is an antigen localized on the surface of cells infected with dengue virus that is common to the four dengue serotypes and is detectable between the first and ninth days after the onset of fever. 7 NS1 rapid tests kits are being increasingly promoted for first-line testing for acute dengue infection in clinical diagnostic laboratories. Its sensitivity is around 89% and it appears to be 100% specific. 8 Definitive dengue tests include dengue serology (acute and convalescent samples to detect antibodies) and serum dengue PCR (particularly used if early in the illness). Treatment and Prevention: Treatment of dengue is symptomatic and supportive and usually involves paracetamol and adequate oral and supplemental intravenous hydration, while carefully following relevant parameters such as the haematocrit, platelet count and tourniquet test for any evidence of DHF/DSS, 9 as was largely the case with this patient. Aspirin and nonsteroidal anti-inflammatory drugs are avoided, because it can aggravate bleeding. 7,9 Public health management is directed at preventing transmission, where suitable vectors are present, which is certainly the case in Townsville. Dengue is a notifiable disease in Queensland and suspected dengue on clinical/ provisional grounds requires notification by clinicians. 10 In north Queensland, there is an ever present risk of importation of dengue from soldiers, which must be well managed. 11 The Australian Defence Force experienced a significant exposure to dengue during its deployments to Timor Leste. 12 Until a suitable dengue vaccine becomes available, where there has been some progress, 12 personal protective measures remain the first line of defence against dengue. 4 References
Lieutenant Colonel Peter Leggat, RAAMC, joined the Australian Regular Army in 1987. He was posted to various units, including the historic 2 Field Ambulance in Townsville. Lieutenant Colonel Leggat is currently serving as a Consultant, Defence Health Service, Army Reserve, Queensland. In 2002, he was awarded the Major General John Pearn Surgeon General’s Medal for outstanding contributions to tropical medicine. He was also President of The Australasian College of Tropical Medicine from 1996 to 1998, from 2002 to 2004 and from 2006-2008. He is currently Deputy National Director of Training for St John. School of Public Health, Tropical Medicine and Rehabilitation Sciences, James Cook University, Townsville, QLD. Peter A Leggat, MD, FAFPHM, Professor. Correspondence: Lieutenant Colonel Peter A Leggat, School of Public Health, Tropical Medicine and Rehabilitation Sciences, James Cook University, Townsville, QLD 4811. peter.leggat@jcu.edu.au |
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