In vivo microscopy of hemozoin: towards a needle free diagnostic for malaria.

Clinical diagnosis of malaria suffers from poor specificity leading to overtreatment with antimalarial medications. Alternatives, like blood smear microscopy or antigen-based tests, require a blood sample. We investigate in vivo microscopy as a needle-free malaria diagnostic. Two optical signatures, birefringence and absorbance, of the endogenous malaria by-product hemozoin were evaluated as in vivo optical biomarkers. Hemozoin birefringence was difficult to detect in highly scattering tissue; however, hemozoin absorbance was observed in increasingly complex biological environments and detectable over a clinically-relevant range of parasitemia in vivo in a P. yoelii-infected mouse model of malaria.