Efficient monitoring of blood-stage infection in a malaria rodent model by the rotating-crystal magneto-optical method

Intense research efforts have been focused on the improvement of the efficiency and sensitivity of malaria diagnostics, especially in resource-limited settings for the detection of asymptomatic infections. A recently developed magneto-optical (MO) method allows for the high-sensitivity detection of malaria pigment (hemozoin) crystals in blood via their magnetically induced rotational motion. First evaluations of the method using synthetic βhematin crystals and in vitro P. falciparum cultures imply its potential for in-field diagnosis. To further investigate this potential, here we study the performance of the method in monitoring the in vivo onset and progression of the blood stage infection in a rodent malaria model. We found that the MO method can detect the first generation of intraerythrocytic parasites at the ring stage 61-66 hours after sporozoite injection, demonstrating better sensitivity than light microscopy or flow cytometry. MO measurements performed after the treatment of P. berghei infections show that the clearance period of hemozoin in mice is approx. 5 days, which indicates the feasibility of the detection of later reinfections as well. Being label and reagent-free, cost-effective and rapid, together with the demonstrated sensitivity, we believe that the MO method is ready for in-depth clinical evaluation in endemic settings.