A 28-year-old man is brought to the ED with a 10-day history of fevers, myalgia, headache and malaise. Today he is feeling much worse, is confused and lethargic. He has recently returned from a holiday in South-East Asia; prior to the trip he had all necessary vaccinations and took Malarone (atavaquoneproguanil) as chemoprophylaxis against malaria.
Which ONE of the following is correct regarding malaria?
Answer: D: Patients may develop malaria despite appropriate chemoprophylaxis. Appropriate diagnostic testing includes full blood count, renal function and electrolytes, serum glucose, liver function tests and Coombs’ tests. Results typically show a haemolytic anaemia (normochromic normocytic) with elevated unconjugated hyperbilirubinaemia, reduced serum haptoglobin, raised lactate dehydrogenase (LDH) and a positive direct Coombs’ test. The serum white cell count is usually low rather than elevated, as is the platelet count. Cerebrospinal fluid analysis is undertaken to exclude other causes for a patient’s altered level of consciousness, and is usually relatively normal in cerebral malaria. Thick and thin films are examined to determine the species of parasite and the parasitic load. A negative blood film/ smear may be seen due to sequestration of the mature parasites from the peripheral blood; in this instance antimalarial treatment should still be commenced, since delay can lead to markedly increased morbidity and mortality. Repeat films should be taken at least every 12 hours for 2–3 days to exclude malaria completely.
Falciparum malaria should be assumed to be resistant to chloroquine and treatment should be commenced with artesunate 2.4 mg/kg IV 12-hourly, or quinine IV loading followed by maintenance doses.
References:
A 32-year-old female presents to the ED with a history of fever and malaise. She has recently returned from travelling in Africa for 3 months. She took doxycycline as malaria prophylaxis throughout her trip and had all mandatory vaccinations prior to the trip. Further questioning reveals she has additional symptoms including constipation, abdominal pain and a pale red macular rash.
Which ONE of the following infections is most likely to be causing her symptoms?
Answer: C: Yellow fever is caused by Flavivirus infection transmitted by a mosquito and is endemic in parts of South America and Africa. Vaccination is mandatory prior to entering endemic areas; it is also highly effective, hence the infection is rare in travellers. Symptoms develop after an incubation period of 3–6 days and vary in severity from a flu-like illness to haemorrhagic fever with a 50% mortality rate. Typical symptoms include fever, headaches, myalgia, conjunctival infection, abdominal pain, facial flushing and relative bradycardia; some patients recover at this point while others relapse and develop high fever, vomiting, back pain, shock, multiorgan failure and coagulopathy. Treatment is supportive.
Dengue fever is caused by an Arbovirus prevalent in Asia, Africa and South America and including urban environments; it is transmitted by mosquitoes. The incubation period of 4–7 days is followed by sudden fever, headache, nausea, vomiting, myalgias and a fine pale morbiliform rash that spreads from the trunk to the face and limbs. If a second infection occurs, the patient may develop Dengue haemorrhagic fever, in which there is a bleeding diathesis, fatigue and a mortality of 10%; if untreated this develops into Dengue septic shock. Again, treatment is supportive.
Typhoid is caused by Salmonella typhi or S. paratyphi and is seen in travellers to Asia, Africa, Central and South America. It is spread by food contaminated with faeces or urine from infected persons or asymptomatic carriers. Vaccination is only 75% effective. Typical symptoms include high fever, chills, abdominal distension, constipation (more often than diarrhoea), and a relative bradycardia; after several days a pale red macular rash may appear on the trunk (‘rose spots’). Complications include pneumonia, small bowel ulceration, DIC, anaemia, meningitis and renal failure. Diagnosis is clinical and confirmed by blood, urine, rose spot or stool culture. Treatment is traditionally with chloramphenicol, but in Australasia ceftriaxone or ciprofloxacin is commonly used.
Malaria is caused by Plasmodia species transmitted by infected mosquitoes. The incubation period is variable. Patients typically develop intermittent fevers with myalgia, malaise and headache, and possible chest pain, cough, abdominal pain and diarrhoea. As the illness progresses patients develop high fevers, tachycardia, orthostatic dizziness and extreme weakness; on examination these patients appear ill, and complications include splenomegaly, hepatomegaly, coagulopathy, delirium or reduced level of consciousness. Diagnosis is clinical and confirmed on blood smears (thick and thin films). Treatment will depend on the species of Plasmodium and possible resistance.
Reference:
A 42-year-old man who has human immunodeficiency virus (HIV) is brought to the ED with a 2-day history of increasing headaches and fever; prior to this he had no symptoms. He takes HAART regularly; his last CD4+ count was 150 cells/µl. A contrast-enhanced CT shows multiple ring-enhancing lesions.
What is the most likely pathology causing these findings?
Answer: D: Toxoplasmosis is the most common cause of encephalitis in patients with AIDS. Symptoms include headache, fever, seizures, altered mental status and focal neurological deficits. Diagnostic investigations include the presence of antibodies to Toxoplasma gondii in CSF and multiple ring-enhancing subcortical lesions on CT; these lesions may also be visible on non-contrast CT. Treatment for patients with suspected toxoplasmosis includes pyrimethamine and sulfadiazine, with folinic acid to ameliorate haematological side effects of therapy. Dexamethasone is also given to reduce oedema if necessary.
The differential diagnosis for ring-enhancing lesions in the brain of HIV-infected patients includes:
Patients with cryptococcal meningitis usually have normal neuroimaging. Patients with AIDS dementia complex usually experience a slow and subtle impairment of short-term memory and cognition, followed by more obvious changes in mental status and possible impairment of motor function and speech. Lymphoma presents with neurological deterioration over months.
A staff member presents to the ED shortly after a needlestick exposure. The exposure involved a solid needle, which had just been used to suture the source patient; it entered the staff member’s gloved thumb. The source patient is a 35-year-old injecting drug user who has refused to give consent for serological testing. The staff member has been vaccinated for hepatitis B and is a responder.
Which ONE of the following is CORRECT?
Answer: A: The risk of HIV transmission from percutaneous exposure to HIV infected blood is 0.3%. The risk is higher:
The prevalence of HIV among injecting drug users in Australasia is 1–2%, so the risk of HIV transmission in this case would be ~ 1:300 x 1:100 i.e. 1: 30,000. The use of PEP should be discussed with an infectious diseases clinician, and if prescribed, a 2 or 3 drug regime should be used (e.g. zidovudine plus lamivudine, and lopinavir/ritonavir); single-drug regimes are not indicated.
Hepatitis B immunoglobulin is indicated for PEP in patients who are not hepatitis B immune; patients who have been immunised and have evidence of hepatitis B antibodies at a level of > 10 mIU/mL do not require any HBV prophylaxis after a body fluid exposure, regardless of source status.
The risk of hepatitis C transmission after body fluid exposure is 1.8–10%. Many studies show no role for immunoglobulin or antiviral agents (interferon, ribavirin) in PEP. Management involves early identification of infection since anti-viral treatment of acute HCV infection may increase rates of HCV clearance.
A patient presents to the ED requesting rabies PEP after he woke up to find a bat in the bedroom. The incident occurred 2 days ago; at the time there was a small scratch on the arm which is barely visible today. He has never been immunised for rabies and is fit and well with no allergies.
Answer: C: Rabies is an invariably fatal disease transmitted by many mammals. In Australia, no native animals carry the rabies virus but the related (and also fatal) Australian bat lyssavirus is found in several species of bats. Disease can be transmitted by bites, scratches or mucous membrane contact.
Post-exposure prophylaxis (PEP) is required for all bite, scratch or mucous membrane exposures from bats in Australia and animals abroad, particularly dogs, monkeys and bats. It is preferably initiated within 24 hours; however, if there is a delay it should be administered regardless of the duration of the delay, as evidence exists that the incubation period of rabies can be more than a year. When followed exactly, PEP prevents development of rabies. The wound should be cleansed thoroughly using povidone-iodine (virucidal). Post-exposure prophylaxis should be administered as follows:
HRIG is indicated only once to provide immediate antibodies before the patient responds to the vaccine by producing their own antibodies. There are no contraindications to HRIG or rabies vaccine, since the disease is fatal.
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