Thick films - parasites and debris

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Recognising parasites on thick malaria films

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Recognising "debris" on thick films
The parasites on a thick film lie within a background of white cells, platelets and various red cell components that have not been fully lysed. It is important to recognise these different features (which may vary a little between films depending on thickness and staining). A film area without parasites is shown below.

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  A

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  B

Normal background elements of a thick malaria film. The neutrophil (A) is recognisable by the characteristic nuclear shape but show artefactual distortion: in this case the chromatin detail is lost and there is no visible membrane outline or granular content. A careful look at the group of structures (B) suggests that they are part of a large group of clumped platelets formed when the film was prepared. Finally, the more amorphous material (C) most likely represents fibrin clot and un-lysed red cell debris.

Precise appearances can vary and additional examples are shown below.

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  C

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  D

In the example C the red cells are incompletely lysed in a less thick area of the film and can be distinguished as separate cells, although with reduced haemoglobin content indicated by their yellow shade. The example D is similar to the previous images (A & B) but with better preservation and granulation of the neutrophil.

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Distinguishing parasites on thick films

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  A

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  B

Subtle single parasite

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  C

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  D

Two parasites with debris

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  A

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  B

3 parasites

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