Research Article published by Malaria Journal
Background: Conventional malaria parasite detection methods, such as rapid diagnostic tests (RDT) and light
microscopy (LM), are not sensitive enough to detect low level parasites and identification of gametocytes in the
peripheral blood. A modified and sensitive laboratory prototype, Magnetic Deposition Microscopy (MDM) was developed
to increase the detection of sub-microscopic parasitaemia and estimation of gametocytes density in asymptomatic
school children.
Methods: Blood samples were collected from 303 asymptomatic school children from seven villages in Bagamoyo
district in Tanzania. Participants were screened for presence of malaria parasites in the field using RDT and MDM
whereas further examination of malaria parasites was done in the laboratory by LM. LM and MDM readings were used
to calculate densities and estimate prevalence of asexual and sexual stages of the parasite.
Results: Plasmodium falciparum parasites (asexual and sexual stages) were detected in 23 (7.6 %), 52 (17.2 %), and 59
(19.5 %) out of 303 samples by LM, RDT and MDM respectively. Gametocytes were detected in 4 (1.3 %) and 12 (4.0 %)
out of the same numbers of samples by LM, and MDM, respectively. Likewise, in vitro results conducted on two laboratory
strains of P. falciparum, 3D7 and NF54 to assess MDM sensitivity on gametocytes detection and its application
on concentrating gametocytes indicated that gametocytes were enriched by MDM by 10-fold higher than LM. Late
stages of the parasite strains, 3D7 and NF54 were enriched by MDM by a factor of 20.5 and 35.6, respectively. MDM
was more specific than LM and RDT by 87.5 % (95 %, CI 71.2–89.6 %) and 89.0 % (95 % CI 82.9–91.4) respectively. It was
also found that MDM sensitivity was 62.5 % (95 % CI 49.5–71.8) when compared with RDT while with LM was 36.5 %
(95 % CI 32.2–60.5).
Conclusions: These findings provide strong evidence that MDM enhanced detection of sub-microscopic P. falciparum
infections and estimation of gametocyte density compared to current malaria diagnostic tools. In addition,
MDM is superior to LM in detecting sub-microscopic gametocytaemia. Therefore, MDM is a potential tool for low-level
parasitaemia identification and quantification with possible application in malaria transmission research.