Microscopic determination of malaria parasite load: role of image analysis

Quantitation of malaria burden provides prognostic and disease monitoring information, vital for proper clinical management of patients. It may also be required to assess response to malaria vaccines or drugs in clinical trials. Accurate microscopic malaria diagnosis requires training and experience, and is therefore an obvious target for automation using digital image processing and analysis systems. Most of the literature in this field has focused on detecting, identifying, and quantifying malaria parasites on thin blood films. To date it is clear that routine automatic microscopy for malaria infection detection and species identification is still a distant prospect, but quantitation of malaria burden is a more realistic target. A method to reliably count malaria parasites on conventional thick blood films, using readily available equipment and software, is described. Good correlation between manual and digital counts was achieved in a proof-of-principle study.