Abstract
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. Our recently developed magneto-optical (MO) method allows the accurate quantification of malaria pigment crystals (hemozoin) in blood by their magnetically induced rotation. First evaluations of the method using β-hematin crystals and in vitro P. falciparum cultures implied its potential for high-sensitivity malaria 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. Our results show that the MO method can detect the first generation of intraerythrocytic P. berghei parasites 66–76 hours after sporozoite injection, demonstrating similar sensitivity to Giesma-stained light microscopy and exceeding that of flow cytometric techniques. Magneto-optical measurements performed during and after the treatment of P. berghei infections revealed that both the follow up under treatment and the detection of later reinfections are feasible with this new technique. The present study demonstrates that the MO method – besides being label and reagent-free, automated and rapid – has a high in vivo sensitivity and is ready for in-field evaluation.
Highlights
Of laboratory experiments or for the primary diagnosis of patient samples due to their high running cost[8,9]
Onset of the blood-stage in P. berghei infections monitored by the MO method, light microscopy, PCR and flow cytometry
In order to evaluate the sensitivity of the MO method in comparison with standard techniques and to determine the time scale of the first positive detections, blood was drawn from mice starting at the end of the liver stage in approx. 5-hour intervals until the fourth day of blood-stage infection
Summary
Of laboratory experiments or for the primary diagnosis of patient samples due to their high running cost[8,9]. The hemozoin-based flow cytometric detection of parasite maturation has been utilized in a novel reagent-free drug sensitivity assay as well[25,26]. In our recent study the sensitivity of the method has been evaluated using ring and schizont stages from P. falciparum in vitro cultures where detection thresholds of 0.0008% and 0.0002% parasitemia have been found, respectively[28]. These results implied that the MO method is suitable for the high-sensitivity detection of the infection as a laboratory tool or, eventually, as an in-field diagnostic technique. The clearance of hemozoin during the treatment of P. berghei infections was followed to establish a time-frame after which the MO signal vanishes in successfully treated mice
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