Detection of malaria parasites after treatment in travelers: A 12-months longitudinal study and statistical modelling analysis

Abstract

The rapid clearance of malaria parasite DNA from circulation has widely been accepted as a fact without being systemically investigated. We assessed the persistence of parasite DNA in travelers treated for Plasmodium falciparum malaria in a malaria-free area. Venous blood was collected at the time of admission and prospectively up to one year. DNA and RNA were extracted and analyzed using species-specific and gametocyte-specific real-time PCR as well as merozoite surface protein 2 (msp2)-PCR. In 31 successfully treated individuals, asexual parasites were seen by microscopy until two days after treatment, whereas parasite DNA was detected by msp2-and species-specific PCR up to days 31 and 42, respectively. Statistical modelling predicted 26% (±0•05 SE) species-specific PCR positivity until day 40 and estimated 48 days for all samples to become PCR negative. Gametocytes were detected by microscopy and PCR latest two days after treatment. C T values correlated well with microscopy-defined parasite densities before but not after treatment started. These results reveal that PCR positivity can persist several weeks after treatment without evidence of viable sexual or asexual parasites, indicating that PCR may overestimate parasite prevalence after treatment.

B cell profiling in malaria reveals expansion and remodeling of CD11c+ B cell subsets

“…In addition to isolation and freezing of PBMCs at each follow-up, samples were also collected for antibody analysis (serum or plasma), blood chemistry and microscopy, and PCR and blood smears for detection of malaria parasites. Part of the cohort has been described previously for telomere dynamics (49) and parasite prevalence after treatment (50). For some time points and study participants, only plasma or cells were available, explaining the different (n) included in the analysis.…”

Can Plasmodium’s tricks for enhancing its transmission be turned against the parasite? New hopes for vector control

“…Only people carrying gametocytes can be infectious to mosquitoes. Recent studies showed that microscopy is insufficiently sensitive to detect low densities of asexual parasites and gametocyte [25,26]. In most endemic settings, a small proportion of infecting parasites are gametocytes [27].…”

Persistence of P. Falciparum Ring-Stage Parasites 42 Days After Artemisinin and Non-Artemisinin Combination Therapy in Naturally Infected Malians

“…Post-treatment detection of parasite DNA may re ect both (remnants of) asexual parasites and gametocytes (6,7), the latter commonly persisting after ACT treatment (8). A study in travelers in Sweden (9) indicated that residual parasite DNA can be detected by qPCR for up to 42 days after successful treatment without evidence of viable asexual parasites or gametocytes. Recently, mRNA transcripts speci c to ring-stage parasites (skeleton binding protein; sbp1) were reported following ACT treatment (6,10).…”