[Role of primaquine in malaria control and elimination in French-speaking Africa]. / Place de la primaquine dans la lutte contre le paludisme en Afrique francophone.

Primaquine, an 8-aminoquinoline, is a relatively unknown and underutilized drug in French-speaking African countries. It acts against the liver stage parasites of all human malaria species, asexual blood stages of Plasmodium vivax and, to a lesser degree, Plasmodium falciparum; P. falciparum mature gametocytes, and P. vivax and Plasmodium ovale hypnozoites. Gastrointestinal disturbances are its most common side effects. The clinical utility of primaquine is limited due to its hematological side effects in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency and other contraindications (pregnant woman, breastfeeding woman, infants less than 6 months old). In the light of the recent recommendations of the World Health Organization (WHO), we propose to examine how primaquine can be used in French-speaking Africa to improve malaria control and move towards malaria elimination. Two indications supported by the WHO are of relevance in Africa. First, artemisinin-based combination therapies and primaquine given as a single low dose (0.25 mg base/kg) are effective to kill asexual and sexual parasites of P. falciparum, are well-tolerated, and have very little risk even in mild to moderate G6PD-deficient patients. This strategy may be helpful to contain transmission in an area in Africa where P. falciparum malaria incidence has decreased considerably. There is an ethical concern in administering primaquine as a gametocytocide as it does not confer any direct benefit to the treated patient. However, the single low-dose primaquine is most likely associated with very low risk for adverse hematological effects, and WHO recommends its use even without prior G6PD testing. In our opinion, clinical studies including G6PD test should be conducted to assess the safety of low-dose primaquine in African patients. Second, primaquine is effective and necessary for radical treatment of P. vivax and P. ovale, but the standard 14-day treatment (0.25-0.5 mg base/kg/day) is not recommended in patients with G6PD deficiency. Prior G6PD testing is required before prescribing primaquine for radical treatment. The use of primaquine for radical treatment in patients without contraindications does not raise any major ethical problem since the probability of relapse in patients who do not receive anti-hypnozoite treatment can be relatively high and each relapse can cause or aggravate anemia, especially in children. In our opinion, patients with mild or moderate G6PD deficiency should not be treated with primaquine at present. Further clinical studies are necessary to define the role of this drug for radical treatment in G6PD-deficient African patients. Without primaquine, the eventual elimination of P. vivax and P. ovale malaria appears to be very difficult. Updated epidemiological data on G6PD, Duffy antigen, and the current distribution of and burden due to P. vivax and P. ovale are required for a rational use of primaquine in the African continent. Moreover, clinical studies on primaquine are required in Africa.

Efficacy of sulfadoxine-pyrimethamine for the treatment of uncomplicated falciparum malaria in southern Mauritania.

BACKGROUND: Until 2006, the Mauritanian Ministry of Health recommended chloroquine and sulfadoxine-pyrimethamine for first- and second-line treatment of uncomplicated malaria, respectively. This study assessed the clinical efficacy of sulfadoxine-pyrimethamine in Kobeni as first-line treatment. MATERIALS AND METHODS: This study included 55 patients with Plasmodium falciparum infections, who were treated with sulfadoxine-pyrimethamine and followed up for 28 days. Isolates were genotyped to distinguish between recrudescence and reinfection. Treatment success rates and survival were analysed per protocol to evaluate drug efficacy. RESULTS: After inclusion, 2 patients were excluded for protocol violations, and 3 patients were lost to follow-up. Of the remaining 50 patients (per protocol population), 43 (86%) had adequate clinical and parasitological responses. Of the 7 patients with treatment failure, 5 (10%) were early failures, while 2 (4%) had initially responded and had late clinical failure on day 7, associated with recrudescence. With the exception of one adult weighing 91 kg, all treatment failures occurred in children aged from 7 to 12 years. CONCLUSIONS: Sulfadoxine-pyrimethamine monotherapy was moderately effective but insufficiently reliable in view of the relatively high rate of early treatment failure. The high prevalence of chloroquine resistance found in earlier studies and the results of the present study on sulfadoxine-pyrimethamine justify the change in national policy and systematic use of artemisinin-based combination therapy for first-line treatment of P. falciparum malaria in Mauritania.

In vitro susceptibility of Plasmodium falciparum to monodesethylamodiaquine, quinine, mefloquine and halofantrine in Abidjan (Côte d'Ivoire).

BACKGROUND: Malaria is the primary cause of hospitalization in Côte d'Ivoire. Early treatment is one of the strategies to control this illness. However, the spread of resistance of Plasmodium falciparum to antimalarial drugs can seriously compromise this strategy. OBJECTIVES: The aim of this study was to assess the in vitro susceptibility of P. falciparum to monodesethylamodiaquine and aminoalcohols in Abidjan (Côte d'Ivoire). METHODS: We assessed the in vitro susceptibility of isolates collected from patients with uncomplicated malaria by using the WHO optical microtest technique. RESULTS: The proportions of resistance to monodesethylamodiaquine, méfloquine and halofantrine were 12.5%, 15.6% and 25.9%, respectively. For quinine, none of isolates showed evidence of in vitro resistance. However, two isolates (6.1%) had IC(50) values above 300 nM. The IC(50) of each drug was positively and significantly correlated to that of the other three drugs, and the correlation was higher between halofantrine and mefloquine. CONCLUSIONS: Our results showed that the in vitro chloroquine resistance reported in previous studies has been extended to other antimalarial drugs investigated in this study except for quinine. Therefore, it is necessary to implement a long-term monitoring system of antimalarial drug resistance.

In vitro susceptibility of Plasmodium falciparum to Monodesethylamodiaquine; Quinine; Mefloquine and Halofantrine in Abidjan (Cote d'Ivoire)

Background: Malaria is the primary cause of hospitalization in Ctte d'Ivoire. Early treatment is one of the strategies to control this illness. However; the spread of resistance of Plasmodium falciparum to antimalarial drugs can seriously compromise this strategy. Objectives: The aim of this study was to assess the in vitro susceptibility of P. falciparum to monodesethylamodiaquine and aminoalcohols in Abidjan (Ctte d'Ivoire). Methods: We assessed the in vitro susceptibility of isolates collected from patients with uncomplicated malaria by using the WHO optical microtest technique. Results: The proportions of resistance to monodesethylamodiaquine; m?floquine and halofantrine were 12.5; 15.6and 25.9; respectively. For quinine; none of isolates showed evidence of in vitro resistance. However; two isolates (6.1) had IC 50 values above 300 nM. The IC 50 of each drug was positively and significantly correlated to that of the other three drugs; and the correlation was higher between halofantrine and mefloquine. Conclusions: Our results showed that the in vitro chloroquine resistance reported in previous studies has been extended to other antimalarial drugs investigated in this study except for quinine. Therefore; it is necessary to implement a long-term monitoring system of antimalarial drug resistance. 15.6and 25.9; respectively. For quinine; none of isolates showed evidence of in vitro resistance. However; two isolates (6.1) had IC 50 values above 300 nM. The IC 50 of each drug was positively and significantly correlated to that of the other three drugs; and the correlation was higher between halofantrine and mefloquine. Conclusions: Our results showed that the in vitro chloroquine resistance reported in previous studies has been extended to other antimalarial drugs investigated in this study except for quinine. Therefore; it is necessary to implement a long-term monitoring system of antimalarial drug resistance

Molecular Epidemiology of Malaria in Cameroon XXIX. Characterization of DHFR and Drug Resistance Markers and Efficacy of Sulfadoxine-Pyrimethamine Monotherapy in Children in Niete(HEVECAM)

In most African countries ; sulfadoxine-pyrimethamine ( Sp) had been the second-line drug to treat chloraquine in resistant Plasmodium falciparum infections in the 1990s and early 2000s . Although its use a monotherapy has been restricted in recent years ; SP has become important for intermittent preventive treatement (IPT) in pregnant women in Africa ; and some countries have been resorting to the combination artesunate -SP for the treatement of uncomplicated malaria .Therefore ; the evaluation of its efficacy remains relevant.In this study ; 58 symptomatic children were treated with SP according to the standard World Health Organization protocol and followed for 14 days .The sequences of P.Falciparum dihydrofolate reductase (dhfr)and dihydropteroate synthase (dhps) genes were determined to correlate these genetic markers and clinical outcome .In addition; blood samples form patients who did not satisfy the inclusion criteria were analysed for the presence of the key dhfr mutation .Results do not suggest any correlation between the observed mutations and SP treatement failure but show a high prevalence of mutations associated with resistance to antifolate drugs and sulfa drugs .However ; it will be important to pursue clinical studie on SP efficacy and epidemiological surveys using these molecular markers ; in particular because in Cameroon the major markers proposed to be highly associated with SP failure elsewhere in the world ; i.e.dhfr mutant codon Glu-540; have not yet been repoted

[Malaria in health centres in the southern districts of Brazzaville, Congo]. / Le paludisme dans deux centres de santé au sud de Brazzaville, Congo.

During the surveys on antimalarial drug efficacy carried out from 2003 to 2006, we systematically checked the presence of Plasmodium falciparum in patients consulting in two health centres located in the south of Brazzaville. The first centre is situated in the urban zone; the second, in the semi rural area. The objective of this survey was to determine the prevalence of malaria-infected patients among the consulting patients and the prevalence of symptomatic patients with acute malaria attacks based on the parasitic density. Patients with parasites were assigned to one of the 5 following classifications: <2000, > or =2000, <5000, > or =5000 and > or =10,000 asexual parasites/microl of blood. Based on the threshold of parasite density 10,000 asexual parasites/microl, 10% and 24% of febrile patients in Tenrikyo and Madibou health centres were diagnosed as cases of malaria, respectively; 13.6% and 26.8% of patients under 5 years old consulting in these two health centres had malaria attacks. If the threshold of parasite density is lowered to 2000 asexual parasites/microl for patients > or =15 years old, 8% and 14% of adults in Tenrikyo and Madibou had malaria attacks, respectively The malaria burden was higher in the periphery of the city of Brazzaville than in the urbanized central districts. The Madibou health centre located in semi rural zone receives twice as many malaria cases for consultation than Tenrikyo located in the urban zone.

[In vivo evaluation of sulfadoxine-pyrimethamine efficacy during uncomplicated falciparum malaria in children of Yopougon (Abidjan, Côte d'Ivoire)]. / Evaluation in vivo de l'efficacité thérapeutique de l'association sulfadoxine-pyriméthamine au cours du paludisme non compliqué chez les enfants de Yopougon (Abidjan, Côte d'Ivoire).

The malaria, deadly parasite infection in its severe form, is widely spread in tropical zone where it rages in an endemic way. The emergence and the extension of Plasmodium resistance contributed to increase the morbidity and the mortality of this pathology in children under 5 years old. Facing the extend of this phenomenon, a monitoring of the expansion of the chemosensitivity proves to be necessary. The goal of the present study was to assess the sulfadoxine-pyrimethamine (S-P) efficacy according to the in vivo test WHO protocol of 14 days-follow-up. Children are treated to the S-P at the rate of 1/2 tablet per 10 kg of body weight in unique dose, then controls are done days 3, 7 and 14. At the end of this work, 179 on 475 subjects were effectively carriers of asexual parasites. So, the general plasmodic index and Plasmodium falciparum rate infection were respectively 37.7% and 100%. Among the 89 children followed until J14, those aged of 13 to 24 months represented 38% of the population of children suffering from Plasmodium malaria, against 7% of those aged between 49 and 59 months. In terms of therapeutic efficacy, 76.4% of adequate clinical and parasitological response (ACR) have been reached against 23.6% of therapeutic failure (TF).

Point mutations in the Plasmodium falciparum cg2 gene, polymorphism of the kappa repeat region, and their relationship with chloroquine resistance.

Based on the available DNA sequence data of the Plasmodium falciparum cg2 gene, we have hypothesized that 3 amino-acid substitutions, His275Gln, Gly281Ala, and His299Gln, may represent the key mutations that confer resistance to chloroquine. The presence of 14 tandemly repeated hexamer units in the kappa region has also been suggested to be indicative of chloroquine resistance. These 2 hypotheses were tested by determining the sequence of DNA fragments containing all 3 codons and kappa repetitive region (approximately 450-basepairs) for 53 randomly selected clinical isolates (obtained in Cameroon in 1994-97) with known response in vivo and/or in vitro to chloroquine. The cg2 genotypes based on the 3 codons and the response in vitro to chloroquine, as well as the number of kappa repeat units and responses in vivo and in vitro to chloroquine, were associated (P < 0.05). cg2 gene mutations were more common in parasites from patients with failure in vivo. However, this difference did not achieve statistical significance (P = 0.055). The sensitivity and specificity of the 3 codons and kappa repeat region to predict the response in vitro to chloroquine ranged between 75% and 85%. The sensitivity and specificity of these genetic markers to predict the response in vivo to chloroquine were of lower values. The kappa repeat region of the clinical isolates is polymorphic but characterized by several conserved features.

Analysis of the key pfcrt point mutation and in vitro and in vivo response to chloroquine in Yaoundé, Cameroon.

The putative key codon (Lys-76 in sensitive parasites and Thr-76 in resistant parasites) of the novel candidate gene for chloroquine resistance, Plasmodium falciparum chloroquine resistance transporter (pfcrt), was determined by polymerase chain reaction-restriction fragment length polymorphism from 111 Cameroonian isolates and was compared with in vivo and in vitro responses to chloroquine. The key codon was significantly associated (P< .001) with responses in vivo (92% sensitivity and 76% specificity) and in vitro (97% sensitivity and 81% specificity). Some discordant results were due to multiclonal infections. The high, but not perfect, correlation between the pfcrt polymorphism and the phenotype implies that a single point mutation in codon 76 of the pfcrt gene is the major, but possibly not the sole, determinant for chloroquine resistance.

In vitro activities of DU-1102, a new trioxaquine derivative, against Plasmodium falciparum isolates.

The antimalarial trioxaquine derivative DU-1102, synthesized by covalent linkage between aminoquinoline and trioxane moieties, was highly active against Cameroonian isolates (mean 50% inhibitory concentration of 43 nmol/liter) of Plasmodium falciparum. There was no correlation between the responses to DU-1102 and chloroquine and only a low correlation between the responses to DU-1102 and pyrimethamine, suggesting an independent mode of action of the trioxaquine against the parasites.

Kinetic properties of dihydrofolate reductase from wild-type and mutant Plasmodium vivax expressed in Escherichia coli.

Antifolate drugs inhibit malarial dihydrofolate reductase (DHFR). In Plasmodium falciparum, antifolate resistance has been associated with point mutations in the gene encoding DHFR. Recently, mutations at homologous positions have been observed in the P. vivax gene. Since P. vivax cannot be propagated in a continuous in vitro culture for drug sensitivity assays, the kinetic properties of DHFR were studied by expression of the DHFR domain in Escherichia coli. Induced expression yielded a protein product that precipitated as an inclusion body in E. coli. The soluble, active DHFR recovered after denaturation and renaturation was purified to homogeneity by affinity chromatography. Kinetic properties of the recombinant P. vivax DHFR showed that the wild-type DHFR (Ser-58 and Ser-117) and double mutant DHFR (Arg-58 and Asn-117) have similar K(m) values for dihydrofolate and NADPH. Antifolate drugs (pyrimethamine, cycloguanil, trimethoprim, and methotrexate), but not proguanil (parent compound of cycloguanil) inhibit DHFR activity, as expected. The kinetics of enzyme inhibition indicated that point mutations (Ser58Arg and Ser117Asn) are associated with lower affinity between the mutant enzyme and pyrimethamine and cycloguanil, which may be the origin of antifolate resistance.

Cardiac effects of amodiaquine and sulfadoxine-pyrimethamine in malaria-infected African patients.

The cardiac effect of amodiaquine and sulfadoxine-pyrimethamine was studied in adult Cameroonian patients with acute uncomplicated Plasmodium falciparum malaria by electrocardiographic monitoring over the course of 7 days. Clinical and parasitological responses were monitored until Day 14. Bradycardia was observed in 16 of 20 amodiaquine-treated patients on Day 2, which corresponds to the time when maximal cumulative plasma concentration is reached, and in 12 of 20 patients on Day 7. A bradycardic effect lasting several days was not noted in patients treated with sulfadoxine-pyrimethamine. Significantly prolonged P, PQ, QRS, and QTc intervals were recorded on Day 2 after both 30 and 35 mg of amodiaquine base per kilogram of body weight had been administered, but these intervals were not correlated with the plasma monodesethylamodiaquine (main human active metabolite of amodiaquine) level. Electrocardiographic changes after therapy with sulfadoxine-pyrimethamine were minor and transient. All patients had fever and parasite clearance on or before Day 3 and remained free of fever and parasites until Day 14. None of the patients complained of cardiovascular adverse effects during the follow-up. These results suggest the absence of significant cardiac effects of amodiaquine and sulfadoxine-pyrimethamine at usual therapeutic doses, but they should draw the attention of clinicians treating malaria-infected patients who have taken other antimalarial drugs with cardiovascular side effects or those who are under treatment with cardiovascular drugs.

Molecular epidemiology of malaria in Yaounde, Cameroon. VIII. Multiple Plasmodium falciparum infections in symptomatic patients.

The extent of genetically distinct parasite populations coinfecting individual human hosts (i.e., multiplicity) was studied by polymerase chain reaction amplification of 3 polymorphic genetic markers, circumsporozoite protein and merozoite surface antigens (MSA) 1 and 2, in symptomatic children and adults and analyzed in relation with age and initial parasitemia. Of the total of 177 DNA samples analyzed (of which 115 were paired pre- and posttreatment samples), 101 (57%) were composed of multiclonal infections, with up to 7 distinguishable parasite populations. Among the 3 polymorphic markers, msa-2 yielded the highest proportion of clinical isolates with multiclonal populations. Patients with multiclonal infections before treatment had, on average, 2.9 genetically distinct parasite populations. The extent of multiplicity decreased significantly (P < 0.05) in recrudescent parasites, but not with reinfections, as compared with the pretreatment samples. Neither age (5-60 years) nor initial parasitemia was correlated with multiplicity. Further studies in different epidemiological settings are required to understand the role of multiclonal Plasmodium falciparum infections in influencing malaria transmission.

Chemoresistance of P. falciparum in urban areas of Yaounde, Cameroon. Part 1: Surveillance of in vitro and in vivo resistance of Plasmodium falciparum to chloroquine from 1994 to 1999 in Yaounde, Cameroon. / Chimiorésistance de P. falciparum en milieu urbain à Yaoundé, Cameroun. Part 1: S urveillance in vitro et in vivo de la résistance de Plasmodium falciparum à la chloroquine entre 1994 et 1999 à Yaoundé, Cameroun.

Chloroquine is indicated for the first-line treatment of uncomplicated malaria in most African countries. However, the spread of chloroquine-resistant Plasmodium falciparum requires periodic monitoring. Between 1994 and 1999, we studied the evolution of chloroquine resistance in adults (aged > 15 years) and children aged 5-15 years by using tests of therapeutic efficacy and in vitro assays. Responses to the 14-day in vivo test were classified according to the new criteria established by the World Health Organization. The results of the semi-microtest and the microtest were expressed as the 50% inhibitory concentration (IC50), and the threshold level of resistance was set at IC50 > 100 nM. The overall percentages of clinical and parasitological failures were 39.7% (31. 3% - 48.1%) and 48.8% (40.2% - 57.4%), respectively. Similarly, the percentage of isolates that were resistant in vitro was 52.5%. During the study, IC50 geometric mean varied between 84,6 nM and 149, 8 nM. The results of the in vitro assays agreed with those of tests of therapeutic efficacy (kappa coefficient = 0.69). The patients' chloroquine plasma levels were measured on day 0, day 3, day 7, and day 14. Drug measurement showed wide inter-individual variations and higher plasma levels in adults than in children. Some cases of therapeutic failure were associated with inadequate plasma levels of chloroquine. Our results confirm the high level of chloroquine resistance in Yaoundé and suggest that the use of an alternative antimalarial drug for the first-line treatment of uncomplicated malaria is warranted.

Chemoresistance of Plasmodium falciparum in the urban region of Yaounde, Cameroon. Part 2: Evaluation of the efficacy of amodiaquine and sulfadoxine-pyrimethamine combination in the treatment of uncomplicated Plasmodium falciparum malaria in Yaounde, Cameroon. / Chimiorésistance de P. falciparum En milieu urbain à Yaoundé, Cameroun. Part 2: evaluation de l'efficacité de l'amodiaquine et de l'association sulfadoxine-pyriméthamine pour le traitement de l'accès palustre simple à Plasmodium falciparum à Yaoundé, Cameroun.

The spread of chloroquine resistance or its stabilization at a high level calls for a change in the therapeutic strategy, including a possible replacement of chloroquine. We assessed and compared the efficacy of amodiaquine and sulfadoxine-pyrimethamine in Yaoundé. Of 140 adults and children > 5 years enrolled in the study, 59 in the amodiaquine and 58 in the sulfadoxine-pyrimethamine treatment group were followed until day 14. The efficacy of amodiaquine was 100%, whereas 12.1% of the patients treated with sulfadoxine-pyrimethamine responded with an early treatment failure. Side effects in both treatment groups were mild and did not require any specific treatment. We did in vitro drug assays for monodesethylamodiaquine (active metabolite of amodiaquine) and pyrimethamine and measured plasma levels of monodesethylamodiaquine, sulfadoxine, and pyrimethamine. Unlike amodiaquine, the results of the in vitro drug sensitivity test for pyrimethamine were not concordant with the clinical response. A wide inter-individual variation in the plasma drug levels was observed. Unlike chloroquine, the mean plasma concentrations did not vary with age. There was no significant difference in the plasma concentrations of sulfadoxine and pyrimethamine between patients responding with an adequate clinical response and those responding with treatment failure. Amodiaquine has several advantages over sulfadoxine-pyrimethamine combination and may be considered to be an effective drug in an endemic zone with a moderate level of chloroquine resistance.

Sequence variations in the genes encoding dihydropteroate synthase and dihydrofolate reductase and clinical response to sulfadoxine-pyrimethamine in patients with acute uncomplicated falciparum malaria.

Mutations in dihydropteroate synthase (DHPS) and dihydrofolate reductase (DHFR) are associated with in vitro resistance to sulfadoxine and pyrimethamine, respectively. The response of 75 patients to sulfadoxine-pyrimethamine was determined, and the genes of the corresponding Plasmodium falciparum isolates were sequenced. Of 12 different unmixed allelic combinations, the triple dhfr mutation Asn-108/Arg-59/Ile-51 was observed in all patients responding with early treatment failure. Some, but not all, patients with an adequate clinical response also harbored isolates with the triple dhfr mutation. Higher initial parasitemia and fever distinguished these 2 patient groups. The dhps genotype apparently had no influence on the clinical outcome. The other dhfr alleles with 1 or 2 mutations and the wild-type allele were found in patients with an adequate clinical response. The triple dhfr mutation is one of the genetic determinants associated with in vivo resistance to sulfadoxine-pyrimethamine.

Molecular epidemiology of malaria in Yaounde, Cameroon. VI. Sequence variations in the Plasmodium falciparum dihydrofolate reductase-thymidylate synthase gene and in vitro resistance to pyrimethamine and cycloguanil.

Pyrimethamine and cycloguanil, the major human metabolite of proguanil, are inhibitors of dihydrofolate reductase that play a key role in the treatment and prevention of chloroquine-resistant Plasmodium falciparum infections in sub-Saharan Africa. Resistance to these antifolate drugs has emerged in some areas of Africa. Earlier molecular studies have demonstrated that point mutations at key positions of the dihydrofolate reductase-thymidylate synthase gene are strongly associated with antifolate resistance. However, whether the same or distinct mutations are involved in the development of resistance to both pyrimethamine and cycloguanil has not been well established in naturally occurring P. falciparum isolates. In this study, the in vitro responses to both antifolate drugs were measured in 42 Cameroonian isolates and compared with the complete sequence of the dihydrofolate reductase domain of the gene (from 34 of 42 isolates) to analyze the genotype that may distinguish between pyrimethamine and cycloguanil resistance. The wild-type profile (n = 11 isolates) was associated with low 50% inhibitory concentrations (IC50s) ranging from 0.32 to 21.4 nanamole for pyrimethamine and 0.60-6.40 nM for cycloguanil. Mutant isolates had at least one amino acid substitution, Asn-108. Only three mutant codons were observed among the antifolate-resistant isolates: Ile-51, Arg-59, and Asn-108. The increasing number of point mutations was associated with an increasing level of pyrimethamine IC50 and, to a much lesser extent, cycloguanil IC50. These results support a partial cross-resistance between pyrimethamine and cycloguanil that is based on similar amino acid substitutions in dihydrofolate reductase and suggest that two or three mutations, including at least Asn-108, may be necessary for cycloguanil resistance, whereas a single Asn-108 mutation is sufficient for pyrimethamine resistance.

In vitro antimalarial activity of limonoids from Khaya grandifoliola C.D.C. (Meliaceae).

The crude extract from the bark and seeds of Khaya grandifoliola was active in vitro against Plasmodium falciparum with an IC50 value of 13.23 microg/ml. The extract was purified to obtain seven limonoids--methylangolensate (1), 6-methylhydroxyangolensate (2), gedunin (3), 7-deacetylkhivorin (5), 1-deacetylkhivorin (6), swietenolide (7), 6-acetylswietenolide (8)--and one flavonoid, catechin (4). Five limonoids (1, 3, 5, 6, 8) were active with IC50 values between 1.25 and 9.63 microg/ml. Catechin was practically devoid of activity. The most active limonoid, gedunin, exhibited an additive effect when combined with chloroquine.

Molecular epidemiology of malaria in Yaounde, Cameroon. VII. Analysis of recrudescence and reinfection in patients with uncomplicated falciparum malaria.

In an endemic area where malaria transmission is intense and continuous, reappearance of asexual parasites may be ascribed to either recrudescence or reinfection. To distinguish between recrudescence and reinfection after oral treatment with chloroquine, amodiaquine, pyronaridine, sulfadoxine-pyrimethamine, halofantrine, or artesunate, three polymorphic markers (circumsporozoite protein, merozoite surface antigens 1 and 2) from pre-treatment and post-treatment samples were amplified by the polymerase chain reaction, and the in vitro response to chloroquine was determined for comparison. Of 52 paired samples, 22 (42%) were reinfections. Recrudescence occurred more frequently on or before Day 14 (22 of 30 cases, 73%). Except for one case, all reinfections were observed beyond Day 14. The phenotype determination was not sufficiently precise to distinguish between recrudescence and reinfection. Our results suggest that beyond Day 14 (and until Day 42), recrudescence and reinfection cannot be distinguished at our study site unless molecular techniques are used and that some results derived from the polymerase chain reaction need to be compared with the microscopic examination of thick blood smear to exclude gametocyte carriers without asexual parasites after treatment.