The rotating-crystal magneto-optical detection (RMOD) method has been developed for
the rapid and quantitative diagnosis of malaria and tested systematically on various
malaria infection models. Very recently, an extended field trial in a high-transmission
region of Papua New Guinea demonstrated its great potential for detecting malaria
infections, in particular Plasmodium vivax. In the present small-scale field test,
carried out in a low-transmission area of Thailand, RMOD confirmed malaria in all
samples found to be infected with Plasmodium vivax by microscopy, our reference method.
Moreover, the magneto-optical signal for this sample set was typically 1-3 orders
of magnitude higher than the cut-off value of RMOD determined on uninfected samples.
Based on the serial dilution of the original patient samples, we expect that the method
can detect Plasmodium vivax malaria in blood samples with parasite densities as low
as similar to 5-10 parasites per microliter, a limit around the pyrogenic threshold
of the infection. In addition, by investigating the correlation between the magnitude
of the magneto-optical signal, the parasite density and the erythrocytic stage distribution,
we estimate the relative hemozoin production rates of the ring and the trophozoite
stages of in vivo Plasmodium vivax infections.
