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    Malaria – Diagnosis

    Hematological / Oncological, Infections, Neurological, Special Populations

    Last Updated Sep 23, 2020
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    • Parasitic disease transmitted by the Anopheles It is endemic to much of the world and is the leading cause of infectious disease-related death worldwide.
    • Malaria has a broad geographic distribution in South America, Central America, Asia, Africa, and Oceania. Refer to the CDC Yellow Book for region-specific information.
    • Five species responsible for human malaria:
      • Plasmodium falciparum,
      • Plasmodium vivax,
      • Plasmodium ovale,
      • Plasmodium malariae, and
      • Plasmodium knowlesi.
    • The majority of deaths are caused by Plasmodium falciparum.
    • Clinical manifestations determined by species-specific lifecycle patterns, which are varied and complex. In general, the malaria life cycle occurs in red blood cells, resulting in hemolysis.
      • Falciparum malaria causes more acute and severe presentations, with organ dysfunction and death
      • Other types of malaria often cause more subacute and mild presentations
    • Falciparum malaria causes severe organ dysfunction through severe hemolysis causing anemia with intravascular sludging resulting in end-organ ischemia.
    • Most evaluation for malaria will begin with a returning traveller presenting with either fever, anemia, or new end-organ dysfunction without an obvious cause.

    Diagnostic Process

    • All patients with fever in a traveller returning from a malaria endemic area should be evaluated for malaria.
      • Fever is often irregular or cyclic – not sensitive or specific.
      • Most fever presents within 1 month of infection, however, cases of delayed presentation up to 1 year after travel have been reported (typically non-Falciparum malaria).
    • General manifestations include malaise, myalgias, arthralgias, diaphoresis, abdominal pain, diarrhea, headache, cough.
    • Severe malaria is defined as Falciparum parasitemia with one of the following:
      • Hyperparasitemia:
        • >2% for children <5 years old.
        • >5% for non-immune adults and children.
        • >10% for semi-immune adults and children.
      • Impaired consciousness.
      • Severe weakness with inability to sit, stand, or support oneself.
      • Seizures.
      • Severe acidosis (HCO3 <15 mmol/L, lactate >5 mmol/L).
      • Hypoglycemia.
      • Severe anemia (Hb <50g/L).
      • Renal Failure (Cr >265 µmol/L).
      • Jaundice (Bilirubin >50 µmol/L).
      • Pulmonary edema.
      • Bleeding or DIC.
      • Shock.
    • Diagnostic testing for malaria includes:
      • Light microscopy of peripheral blood (i.e. Thick and thin Smear) = Gold standard.
        • Thick smear = gross examination for any parasites.
        • Thin smear = determination of species and parasite burden.
      • Rapid Diagnostic Tests:
        • Can be used if microscopy is unavailable or will be delayed.
        • Some test for Falciparum only, while others can identify multiple species.
        • Reasonable sensitivity and specificity (90-95%).
        • Can be useful to provisionally exclude Falciparum malaria, which requires more urgent treatment.
        • Cannot provide information on parasite burden.
    • A single negative blood smear and/or rapid diagnostic test is insufficient to exclude the diagnosis of malaria.
      • Two additional smears should be obtained at 12-24 hour intervals to exclude the diagnosis
      • Thus, close follow-up is essential to ensure rapid treatment if subsequent testing is positive, and to evaluate other etiologies of patient symptoms.
    • If definitive diagnostic tests are unavailable and there is high clinical suspicion for malaria (especially Falciparum), consult an infectious disease specialist.

    Quality Of Evidence?


    While there are few high quality randomized controlled trials in this area, there is a significant body of longitudinal research and well-establish Canadian and international guidelines supporting malaria diagnosis and treatment recommendations.


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