Increasing Malaria Parasite Clearance Time after Chloroquine Therapy, South Korea, 2000-2016

We reviewed the clinical efficacy of chloroquine for Plasmodium vivax malaria, the changing trend of parasite clearance time, and fever clearance time during 2000–2016 in South Korea. Median parasite clearance time and fever clearance time increased significantly over the study period. Chloroquine was mostly underdosed when used to treat P. vivax malaria.

Artemisinin resistance phenotypes and K13 inheritance in a Plasmodium falciparum cross and Aotus model

Concerns about malaria parasite resistance to treatment with artemisinin drugs (ARTs) have grown with findings of prolonged parasite clearance t _1/2s (>5 h) and their association with mutations in Plasmodium falciparum Kelch-propeller protein K13. Here, we describe a P. falciparum laboratory cross of K13 C580Y mutant with C580 wild-type parasites to investigate ART response phenotypes in vitro and in vivo. After genotyping >400 isolated progeny, we evaluated 20 recombinants in vitro: IC₅₀ measurements of dihydroartemisinin were at similar low nanomolar levels for C580Y- and C580-type progeny (mean ratio, 1.00; 95% CI, 0.62-1.61), whereas, in a ring-stage survival assay, the C580Y-type progeny had 19.6-fold (95% CI, 9.76-39.2) higher average counts. In splenectomized Aotus monkeys treated with three daily doses of i.v. artesunate, t _1/2 calculations by three different methods yielded mean differences of 0.01 h (95% CI, -3.66 to 3.67), 0.80 h (95% CI, -0.92 to 2.53), and 2.07 h (95% CI, 0.77-3.36) between C580Y and C580 infections. Incidences of recrudescence were 57% in C580Y (4 of 7) versus 70% in C580 (7 of 10) infections (-13% difference; 95% CI, -58% to 35%). Allelic substitution of C580 in a C580Y-containing progeny clone (76H10) yielded a transformant (76H10^C580Rev) that, in an infected monkey, recrudesced regularly 13 times over 500 d. Frequent recrudescences of ART-treated P. falciparum infections occur with or without K13 mutations and emphasize the need for improved partner drugs to effectively eliminate the parasites that persist through the ART component of combination therapy.

Phenotypic approach artemisinin resistance in malaria rodent as in vivo model

Aim:

The aim of this study is to prove the development of artemisinin resistance phenotypically in malaria rodent as an in vivo resistance development model in humans.

Materials and Methods:

Plasmodium berghei was infected intraperitoneally in mice, then artemisinin was given with “4-day-test” with effective dose (ED) 99% dose for 3 days which begins 48 h after infection (D2, D3, and D4). Parasite development was followed during 5^th until 10^th days of infection. After parasitemia >2% of red blood cell which contains parasites on 1 mice, that mice were used as donor to be passaged on the new 5 mice. After that, parasitemia was calculated. ED₅₀ and ED₉₀ were examined with parasite clearance time (PCT), recrudescence time (RT), and also morphology development examination of intraerythrocytic cycle of P. berghei with transmission electron microscope.

Results:

Among the control group compare with the treatment group showed significant differences at α=0.05 on 5^th day (D5) until 10^th day (D10). The control group of 4^th passage (K4) with passage treatment group of 4^th passage (P4) on the 10^th days (D10) post infection showed no significant differences in the α=0.05. The average percentage of inhibition growth was decreasing which is started from 5^th to 10^th day post infection in P1, P2, P3, and P4. On the development of P. berghei stage, which is given repeated artemisinin and repeated passage, there was a formation of dormant and also vacuoles in Plasmodium that exposed to the drug.

Conclusion:

Exposure to artemisinin with repeated passages in mice increased the value of ED₅₀ and ED₉₀, decreased the PCT and RT and also changes in morphology dormant and vacuole formation.

Therapy of uncomplicated falciparum malaria in Europe: MALTHER - a prospective observational multicentre study

BACKGROUND

Malaria continues to be amongst the most frequent infectious diseases imported to Europe. Whilst European treatment guidelines are based on data from studies carried out in endemic areas, there is a paucity of original prospective treatment data. The objective was to summarize data on treatments to harmonize and optimize treatment for uncomplicated malaria in Europe.

METHODS

A prospective observational multicentre study was conducted, assessing tolerance and efficacy of treatment regimens for imported uncomplicated falciparum malaria in adults amongst European centres of tropical and travel medicine.

RESULTS

Between December 2003 and 2009, 504 patients were included in 16 centres from five European countries. Eighteen treatment regimens were reported, the top three being atovaquone-proguanil, mefloquine, and artemether-lumefantrine. Treatments significantly differed with respect to the occurrence of treatment changes (p = 0.005) and adverse events (p = 0.001), parasite and fever clearance times (p < 0.001), and hospitalization rates (p = 0.0066) and durations (p = 0.001). Four recrudescences and two progressions to severe disease were observed. Compared to other regimens, quinine alone was associated with more frequent switches to second line treatment, more adverse events and longer inpatient stays. Parasite and fever clearance times were shortest with artemether-mefloquine combination treatment. Vomiting was the most frequent cause of treatment change, occurring in 5.5% of all patients but 9% of the atovaquone-proguanil group.

CONCLUSIONS

This study highlights the heterogeneity of standards of care within Europe. A consensus discussion at European level is desirable to foster a standardized management of imported falciparum malaria.