Intervals to Plasmodium falciparum recurrence after anti-malarial treatment in pregnancy: a longitudinal prospective cohort.

BACKGROUND: Plasmodium falciparum infections adversely affect pregnancy. Anti-malarial treatment failure is common. The objective of this study was to examine the duration of persistent parasite carriage following anti-malarial treatment in pregnancy. METHODS: The data presented here are a collation from previous studies carried out since 1994 in the Shoklo Malaria Research Unit (SMRU) on the Thailand-Myanmar border and performed using the same unique methodology detailed in the Materials and Methods section. Screening for malaria by microscopy is a routine part of weekly antenatal care (ANC) visits and therapeutic responses to anti-malarials were assessed in P. falciparum malaria cases. Women with microscopy confirmed P. falciparum malaria had a PCR blood spot from a finger-prick sample collected. Parasite DNA was extracted from the blood-spot samples using saponin lysis/Chelex extraction method and genotyped using polymorphic segments of MSP1, MSP2 and GLURP. Recurrent infections were classified by genotyping as novel, recrudescent or indeterminate. Factors associated with time to microscopy-detected recrudescence were analysed using multivariable regression techniques. RESULTS: From December 1994 to November 2009, 700 women were treated for P. falciparum and there were 909 recurrent episodes (481 novel and 428 recrudescent) confirmed by PCR genotyping. Most of the recurrences, 85% (770/909), occurred after treatment with quinine monotherapy, artesunate monotherapy or artesunate-clindamycin. The geometric mean number of days to recurrence was significantly shorter in women with recrudescent infection, 24.5 (95%: 23.4-25.8), compared to re-infection, 49.7 (95%: 46.9-52.7), P<0.001. The proportion of recrudescent P. falciparum infections that occurred after days 28, 42 and 63 from the start of treatment was 29.1% (124/428), 13.3% (57/428) and 5.6% (24/428). Recrudescent infections≥100 days after treatment occurred with quinine and mefloquine monotherapy, and quinine+clindamycin and artesunate+atovaquone-proguanil combination therapy. Treatments containing an artemisinin derivative or an intercalated Plasmodium vivax infection increased the geometric mean interval to recrudescence by 1.28-fold (95% CI: 1.09-1.51) and 2.19-fold (1.77-2.72), respectively. Intervals to recrudescence were decreased 0.83-fold (0.73-0.95) if treatment was not fully supervised (suggesting incomplete adherence) and 0.98-fold (0.96-0.99) for each doubling in baseline parasitaemia. CONCLUSIONS: Prolonged time to recrudescence may occur in pregnancy, regardless of anti-malarial treatment. Long intervals to recrudescence are more likely with the use of artemisinin-containing treatments and also observed with intercalated P. vivax infections treated with chloroquine. Accurate determination of drug efficacy in pregnancy requires longer duration of follow-up, preferably until delivery or day 63, whichever occurs last.

Pharmacokinetics of dihydroartemisinin and piperaquine in pregnant and nonpregnant women with uncomplicated falciparum malaria.

Dihydroartemisinin-piperaquine is a fixed-dose artemisinin-based combination treatment. Some antimalarials have altered pharmacokinetics in pregnancy. Pregnant women in the 2nd or 3rd trimester and matched nonpregnant women with uncomplicated falciparum malaria were treated with a total of 6.4 mg/kg of body weight dihydroartemisinin and 51.2 mg/kg piperaquine once daily for 3 days. Venous blood samples were drawn at prespecified time points over 9 weeks. Plasma dihydroartemisinin and piperaquine concentrations were analyzed by liquid chromatography-mass spectrometry. Piperaquine and dihydroartemisinin pharmacokinetics were well described. There were no significant differences in total piperaquine exposure (P = 0.80) or drug exposure during the terminal elimination phase (72 h to infinity) (P = 0.64) between the two groups. The apparent volume of distribution of piperaquine was significantly smaller (602 liters/kg versus 877 liters/kg) in pregnant women than in nonpregnant women (P = 0.0057), and the terminal elimination half-life was significantly shorter (17.8 days versus 25.6 days; P = 0.0023). Dihydroartemisinin exposure after the first dose was significantly lower (844 h × ng/ml versus 1,220 h × ng/ml, P = 0.0021) in pregnant women, but there were no significant differences in total dihydroartemisinin exposure or maximum concentrations between the two groups. There were no significant differences in any pharmacokinetic parameters between the second and third trimester. These results obtained through noncompartmental analysis suggest that in the treatment of falciparum malaria, there are no clinically important differences in the pharmacokinetics of dihydroartemisinin or piperaquine between pregnant and nonpregnant women. However, a more detailed analysis using population pharmacokinetic modeling is needed to fully investigate the differences found for some of the pharmacokinetic parameters, such as the terminal half-life.

Considerations on the use of nucleic acid-based amplification for malaria parasite detection.

BACKGROUND: Nucleic acid amplification provides the most sensitive and accurate method to detect and identify pathogens. This is primarily useful for epidemiological investigations of malaria because the infections, often with two or more Plasmodium species present simultaneously, are frequently associated with microscopically sub-patent parasite levels and cryptic mixed infections. Numerous distinct equally adequate amplification-based protocols have been described, but it is unclear which to select for epidemiological surveys. Few comparative studies are available, and none that addresses the issue of inter-laboratory variability. METHODS: Blood samples were collected from patients attending malaria clinics on the Thai-Myanmar border. Frozen aliquots from 413 samples were tested independently in two laboratories by nested PCR assay. Dried blood spots on filter papers from the same patients were also tested by the nested PCR assay in one laboratory and by a multiplex PCR assay in another. The aim was to determine which protocol best detected parasites below the sensitivity level of microscopic examination. RESULTS: As expected PCR-based assays detected a substantial number of infected samples, or mixed infections, missed by microscopy (27 and 42 for the most sensitive assay, respectively). The protocol that was most effective at detecting these, in particular mixed infections, was a nested PCR assay with individual secondary reactions for each of the species initiated with a template directly purified from the blood sample. However, a lesser sensitivity in detection was observed when the same protocol was conducted in another laboratory, and this significantly altered the data obtained on the parasite species distribution. CONCLUSIONS: The sensitivity of a given PCR assay varies between laboratories. Although, the variations are relatively minor, they primarily diminish the ability to detect low-level and mixed infections and are sufficient to obviate the main rationale to use PCR assays rather than microscopy or rapid diagnostic tests. The optimal approach to standardise methodologies is to provide PCR template standards. These will help researchers in different settings to ensure that the nucleic acid amplification protocols they wish to use provide the requisite level of sensitivity, and will permit comparison between sites.

A randomised controlled trial of artemether-lumefantrine versus artesunate for uncomplicated plasmodium falciparum treatment in pregnancy.

BACKGROUND: To date no comparative trials have been done, to our knowledge, of fixed-dose artemisinin combination therapies (ACTs) for the treatment of Plasmodium falciparum malaria in pregnancy. Evidence on the safety and efficacy of ACTs in pregnancy is needed as these drugs are being used increasingly throughout the malaria-affected world. The objective of this study was to compare the efficacy, tolerability, and safety of artemether-lumefantrine, the most widely used fixed ACT, with 7 d artesunate monotherapy in the second and third trimesters of pregnancy. METHODS AND FINDINGS: An open-label randomised controlled trial comparing directly observed treatment with artemether-lumefantrine 3 d (AL) or artesunate monotherapy 7 d (AS7) was conducted in Karen women in the border area of northwestern Thailand who had uncomplicated P. falciparum malaria in the second and third trimesters of pregnancy. The primary endpoint was efficacy defined as the P. falciparum PCR-adjusted cure rates assessed at delivery or by day 42 if this occurred later than delivery, as estimated by Kaplan-Meier survival analysis. Infants were assessed at birth and followed until 1 y of life. Blood sampling was performed to characterise the pharmacokinetics of lumefantrine in pregnancy. Both regimens were very well tolerated. The cure rates (95% confidence interval) for the intention to treat (ITT) population were: AS7 89.2% (82.3%-96.1%) and AL 82.0% (74.8%-89.3%), p = 0.054 (ITT); and AS7 89.7% (82.6%-96.8%) and AL 81.2% (73.6%-88.8%), p = 0.031 (per-protocol population). One-third of the PCR-confirmed recrudescent cases occurred after 42 d of follow-up. Birth outcomes and infant (up to age 1 y) outcomes did not differ significantly between the two groups. The pharmacokinetic study indicated that low concentrations of artemether and lumefantrine were the main contributors to the poor efficacy of AL. CONCLUSION: The current standard six-dose artemether-lumefantrine regimen was well tolerated and safe in pregnant Karen women with uncomplicated falciparum malaria, but efficacy was inferior to 7 d artesunate monotherapy and was unsatisfactory for general deployment in this geographic area. Reduced efficacy probably results from low drug concentrations in later pregnancy. A longer or more frequent AL dose regimen may be needed to treat pregnant women effectively and should now be evaluated. Parasitological endpoints in clinical trials of any antimalarial drug treatment in pregnancy should be extended to delivery or day 42 if it comes later. TRIAL REGISTRATION: Current Controlled Trials ISRCTN86353884.

Malaria in the post-partum period; a prospective cohort study.

BACKGROUND: Several studies have shown a prolonged or increased susceptibility to malaria in the post-partum period. A matched cohort study was conducted to evaluate prospectively the susceptibility to malaria of post-partum women in an area where P.falciparum and P.vivax are prevalent. METHODS: In an area of low seasonal malaria transmission on the Thai-Myanmar border pregnant women attending antenatal clinics were matched to a non-pregnant, non-post-partum control and followed up prospectively until 12 weeks after delivery. RESULTS: Post-partum women (n = 744) experienced significantly less P.falciparum episodes than controls (hazard ratio (HR) 0.39 (95%CI 0.21-0.72) p = 0.003) but significantly more P.vivax (HR 1.34 (1.05-1.72) p = 0.018). The reduced risk of falciparum malaria was accounted for by reduced exposure, whereas a history of P.vivax infection during pregnancy was a strong risk factor for P.vivax in post-partum women (HR 13.98 (9.13-21.41), p<0.001). After controlling for effect modification by history of P.vivax, post-partum women were not more susceptible to P.vivax than controls (HR: 0.33 (0.21-0.51), p<0.001). Genotyping of pre-and post-partum infections [Formula in text] showed that each post-partum P.falciparum was a newly acquired infection. CONCLUSIONS: In this area of low seasonal malaria transmission post-partum women were less likely to develop falciparum malaria but more likely to develop vivax malaria than controls. This was explained by reduced risk of exposure and increased risk of relapse, respectively. There was no evidence for altered susceptibility to malaria in the post-partum period. The treatment of vivax malaria during and immediately after pregnancy needs to be improved.