Rapid detection of malaria and other bloodstream parasites by fluorescence microscopy with 4'6 diamidino-2-phenylindole (DAPI).

DAPI is a fluorescent dye which appears to complex specifically with DNA. We have used this probe to detect and identify malarial infections by fluorescence microscopy. Experiments were conducted using Plasmodium berghei yoeli--infected mouse blood, P. lophurae--infected duck blood, and P. vivax--infected human blood. Infected avian blood was used to detect parasites within nucleated erythrocytes. Control blood smears from uninfected hosts revealed fluorescence only in the leukocytes of mammalian blood or in nuclei of leukocytes and erythrocytes of avian blood. Cytoplasmic staining of red blood cells was absent in all controls. In contrast, the cytoplasm of infected red blood cells was stippled with fluorescence centers. Ring forms, trophozoites, segmenters, and merozoites frequently were observed. This simple procedure can be applied directly to routine clinical analysis, as well as experimental procedures, DAPI can also be used to stain other parasites, including nuclei in microfilariae.