Microbiology

Malaria

Malaria

MALARIA DIAGNOSTICS

Human malaria is a parasitic infection caused by different species of the Plasmodium parasite:

  • Plasmodium falciparum
  • Non-falciparum
    • Plasmodium vivax
    • Plasmodium malariae
    • Plasmodium ovale
    • others

The malaria parasite is transmitted by the bite of the female Anopheles mosquito. Annually approximately 300-500 million malaria infections occur worldwide with an estimated one million deaths. Once the diagnosis is considered, early detection and effective treatment are key elements in the "ABC" of malaria.

THE "ABC" OF MALARIA

  1. Awareness and assessment of malaria risk
  2. Avoidance of mosquito bites
  3. Compliance with Chemoprophylaxis, when indicated
  4. Early detection of malaria
  5. Effective treatment

DETECTION OF MALARIA

Malaria should always be excluded when a patient who resides in or has travelled to a malaria area presents with a non-specific flu-like illness or other symptoms suggestive of malaria. In babies and toddlers the diagnosis may even be more challenging as malaria may present with very atypical symptoms such as diarrhoea.

LABORATORY DIAGNOSIS

1. Microscopic detection

Thin and thick blood smear

  • This remains the "gold standard" for the diagnosis of malaria, but is dependent on the experience of the microscopy operator and is also time consuming.
  • The thin smear allows for speciation and parasite count.
  • At least three smears at different time intervals should be submitted before the diagnosis can be excluded.

Fig 1. Thin smear showing P. falciparum

Thin smear showing P. falciparum

2. Rapid antigen detection

This test allows for a rapid diagnosis of malaria.

  • Depending on manufacturer most can only detect P. falciparum but non-falciparum species may be also be detected.
  • The rapid test unfortunately does not eliminate the need for microscopy as very low parasitic infections may be missed and microscopy is required to calculate the parasite count.

Fig.2 Rapid Malaria Test

Rapid Malaria Test

3. Fluorescence microscopy

If the thin and thick smears are negative a QBC Malaria Test (fl uorescence microscopy-based) can be performed.

  • The test has superior sensitivity compared to a thick smear.

4. Molecular detection (PCR)

Molecular testing is the latest development in malaria diagnostics.

  • PCR is not currently recommended as a fi rst line test.
  • When malaria is suspected and the initial blood smears are negative or a mixed infection is suspected the PCR may aid in making the diagnosis.
  • The PCR is able to differentiate between the four main Plasmodium species

5. Serological antibody detection

Serology is not used for the acute diagnosis of malaria and is not routinely available. It is mostly used in epidemiological research settings.

Specimens to be submitted to the laboratory
EDTA blood (purple top tube)

Reference: Brunette, GW & Whatley, AD, 2010. CDC Health Information for International Travel. (The Yellow Book.) Oxford Univesity Press, New York. Compiled by Dr Ben Prinsloo.

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