Chloroquine-resistant Plasmodium Falciparum Malaria Research Articles

Identifying inhibitors of β-haematin formation with activity against chloroquine-resistant Plasmodium falciparum malaria parasites via virtual screening approaches

The biomineral haemozoin, or its synthetic analogue β-haematin (βH), has been the focus of several target-based screens for activity against Plasmodium falciparum parasites. Together with the known βH crystal structure, the availability of this screening data makes the target amenable to both structure-based and ligand-based virtual screening. In this study, molecular docking and machine learning techniques, including Bayesian and support vector machine classifiers, were used in sequence to screen the in silico ChemDiv 300k Representative Compounds library for inhibitors of βH with retained activity against P. falciparum. We commercially obtained and tested a prioritised set of inhibitors and identified the coumarin and iminodipyridinopyrimidine chemotypes as potent in vitro inhibitors of βH and whole cell parasite growth.

A CASE OF TROPICAL ILLNESS MANAGED IN THE MEDICAL ICU WITH AN INVESTIGATIONAL NEW DRUG

SESSION TITLE: Case Report Semifinalists 3 SESSION TYPE: Fellow Case Report Posters PRESENTED ON: 10/21/2019 02:30 PM - 03:15 PM INTRODUCTION: Rates of international travel are increasing along with increasing exposure to tropical diseases. It is of importance to maintain knowledge of common tropical diseases and treatment options. CASE PRESENTATION: A 30-year-old male, who returned a week prior from admission, from a vocational trip to Nigeria. Patient presented with symptoms of headache, fever, nausea, vomiting, abdominal pain and diarrhea. Patient was septic but otherwise hemodynamically stable, with presenting labs demonstrating profound thrombocytopenia with low haptoglobin (table 1) and presence of malaria on Wright-Giemsa stain. Blood smear demonstrated 17% Plasmodium Falciparum paracitemia. The Center of Disease Control(CDC) was contacted. Patient was started on treatment with intravenous(IV) quinidine and doxycycline and admitted to the Medical Intensive Care Unit(MICU) for further monitoring. Due to lack of available IV quinidine to complete therapy the decision was made to transition to IV artesunate and continued on doxycycline. Hospital course remained uncomplicated with quick resolution of parasitic loads (<1%). DISCUSSION: Malaria with Plasmodium Falciparum occurring in certain geographical areas, including Nigeria, are categorized by the CDC as a chloroquine resistant. Four applicable pharmacological therapies are available in such cases: atovaquone-proguanil, artemether-lumefantrine, quinine in combination with doxycycline, tetracycline or clindamycin and mefloquine. Quinine is the only FDA approved IV medication for treatment of severe malaria. The CDC defines severe malaria by the presence of one of more specifically defined clinical signs and symptoms and/or parasitemia of >5%. Our patient was stratified into a category of severe malaria by presence of a paracitemia of 17%. Per CDC recommendations severe malaria should be treated with IV antimalarial medication. World Health Organization recommends artesunate over quinine therapy for severe malaria. The FDA has approved artesunate as an investigational option in certain individuals who qualify. CONCLUSIONS: Artesunate is an effective alternative treatment option for individuals with severe malaria. We demonstrate a case of successful treatment of severe chloroquine resistant plasmodium falciparum malaria with artesunate. Reference #1: Centers for Disease Control and Prevention. (2018). Treatment of Malaria: Guidelines For Clinicians (United States) Reference #2: Dilip R. Karnad, MD, Guy A. Richards, MD PhD, Gisele Sampaio Silva, MD, Pravin Amin, MD. Tropical diseases in the ICU: A syndromic approach to diagnosis and treatment. Journal of Critical Care 46(2018)119-126 DISCLOSURES: No relevant relationships by Shozab Ahmed, source=Web Response No relevant relationships by Monika Kakol, source=Web Response

Synthesis and stereochemical determination of an antiparasitic pseudo-aminal type monoterpene indole alkaloid.

5-Nor stemmadenine alkaloids, isolated from the genus Tabernaemontana, display a range of bioactivity. 16-Hydroxy-16,22-dihydroapparicine, the active component of an extract from the Tabernaemontana sp. (dichotoma, elegans, and divaricate), exhibited potent antimalarial activity, representing the first such report of the antimalarial property of 5-nor stemmadenine alkaloids. We, therefore, decided to attempt the total synthesis of the compound to explore its antimalarial activity and investigate structure and bioactivity relationships. As a result, we completed the first total synthesis of 16-hydroxy-16,22-dihydroapparicine, by combining a phosphine-mediated cascade reaction, diastereoselective nucleophilic addition of 2-acylindole or methylketone via a Felkin–Anh transition state, and chirality transferring intramolecular Michael addition. We also clarified the absolute stereochemistries of the compound. Furthermore, we evaluated the activity of the synthetic compound, as well as that of some intermediates, all of which showed weak activity against chloroquine-resistant Plasmodium falciparum (K1 strain) malaria parasites.

Prevalence of chloroquine resistant Plasmodium falciparum malaria in pregnant females attending North Indian hospital

Prevalence of chloroquine resistant Plasmodium falciparum malaria in pregnant females attending North Indian hospital

Double mutation in the pfmdr1 gene is associated with emergence of chloroquine-resistant Plasmodium falciparum malaria in Eastern India.

Malaria is a major public health problem in tropical and subtropical countries, including India. This study elucidates the cause of chloroquine treatment failure (for Plasmodium falciparum infection) before the introduction of artemisinin combination therapy. One hundred twenty-six patients were randomized to chloroquine treatment, and the therapeutic efficacy was monitored from days 1 to 28. An in vitro susceptibility test was performed with all isolates. Parasitic DNA was isolated, followed by PCR and restriction digestion of different codons of the pfcrt gene (codons 72 to 76) and the pfmdr1 gene (N86Y, Y184F, S1034C, N1042D, and D1246Y). Finally, sequencing was done to confirm the mutations. Forty-three (34.13%) early treatment failure cases and 16 (12.69%) late treatment failure cases were observed after chloroquine treatment. In vitro chloroquine resistance was found in 103 isolates (81.75%). Twenty-six (60.47%) early treatment failure cases and 6 (37.5%) late treatment failure cases were associated with the CVMNK-YYSNY allele (the underlined amino acids are those that were mutated). Moreover, the CVIEK-YYSNY allele was found in 8 early treatment failure (18.60%) and 2 late treatment failure (12.5%) cases. The presence of the wild-type pfcrt (CVMNK) and pfmdr1 (YYSNY) double mutant allele in chloroquine-nonresponsive cases was quite uncommon. In vivo chloroquine treatment failure and in vitro chloroquine resistance were strongly correlated with the CVMNK-YYSNY and CVIEK-YYSNY haplotypes (P < 0.01).

Idiosyncratic quinoline central nervous system toxicity: Historical insights into the chronic neurological sequelae of mefloquine

Mefloquine is a quinoline derivative antimalarial which demonstrates promise for the treatment of schistosomiasis. Traditionally employed in prophylaxis and treatment of chloroquine-resistant Plasmodium falciparum malaria, recent changes to the approved European and U.S. product labeling for mefloquine now warn of a risk of permanent and irreversible neurological sequelae including vertigo, loss of balance and symptoms of polyneuropathy. The newly described permanent nature of certain of these neurological effects challenges the conventional belief that they are due merely to the long half-life of mefloquine and its continued presence in the body, and raises new considerations for the rational use of the drug against parasitic disease. In this opinion, it is proposed that many of the reported lasting adverse neurological effects of mefloquine are consistent with the chronic sequelae of a well characterized but idiosyncratic central nervous system (CNS) toxicity syndrome (or toxidrome) common to certain historical antimalarial and antiparasitic quinolines and associated with a risk of permanent neuronal degeneration within specific CNS regions including the brainstem. Issues in the development and licensing of mefloquine are then considered in the context of historical awareness of the idiosyncratic CNS toxicity of related quinoline drugs. It is anticipated that the information presented in this opinion will aid in the future clinical recognition of the mefloquine toxidrome and its chronic sequelae, and in informing improved regulatory evaluation of mefloquine and related quinoline drugs as they are explored for expanded antiparasitic use and for other indications.

Signal detection to identify serious adverse events (neuropsychiatric events) in travelers taking mefloquine for chemoprophylaxis of malaria

BackgroundFor all medications, there is a trade-off between benefits and potential for harm. It is important for patient safety to detect drug-event combinations and analyze by appropriate statistical methods. Mefloquine is used as chemoprophylaxis for travelers going to regions with known chloroquine-resistant Plasmodium falciparum malaria. As such, there is a concern about serious adverse events associated with mefloquine chemoprophylaxis. The objective of the present study was to assess whether any signal would be detected for the serious adverse events of mefloquine, based on data in clinicoepidemiological studies.Materials and methodsWe extracted data on adverse events related to mefloquine chemoprophylaxis from the two published datasets. Disproportionality reporting of adverse events such as neuropsychiatric events and other adverse events was presented in the 2 × 2 contingency table. Reporting odds ratio and corresponding 95% confidence interval [CI] data-mining algorithm was applied for the signal detection. The safety signals are considered significant when the ROR estimates and the lower limits of the corresponding 95% CI are ≥2.ResultsTwo datasets addressing adverse events of mefloquine chemoprophylaxis (one from a published article and one from a Cochrane systematic review) were included for analyses. Reporting odds ratio 1.58, 95% CI: 1.49–1.68 based on published data in the selected article, and 1.195, 95% CI: 0.94–1.44 based on data in the selected Cochrane review. Overall, in both datasets, the reporting odds ratio values of lower 95% CI were less than 2.ConclusionBased on available data, findings suggested that signals for serious adverse events pertinent to neuropsychiatric event were not detected for mefloquine. Further studies are needed to substantiate this.

Limbic encephalopathy and central vestibulopathy caused by mefloquine: A case report

Mefloquine is a 4-methanolquinoline anti-malarial that in recent years has fallen out of favor for use as chemoprophylaxis against infection with chloroquine-resistant Plasmodium falciparum malaria owing in part to growing concerns of side effects and potential neurotoxicity. Despite over 20 years of licensed use, the pathophysiological mechanisms underlying mefloquine's neuropsychiatric and physical side effects and the clinical significance of the drug's neurotoxicity have remained poorly understood. In this report, an adverse reaction to mefloquine chemoprophylaxis is described characterized by prodromal symptoms of anxiety with subsequent development of psychosis, short-term memory impairment, confusion and personality change accompanied by complaints of disequilibrium and vertigo, with objective findings of central vestibulopathy. It is posited that these effects represent an idiosyncratic neurotoxic syndrome of progressive limbic encephalopathy and multifocal brainstem injury caused by the drug. This case provides insights into the clinical significance of mefloquine neuronal gap junction blockade and neurotoxicity demonstrated in animal models, points to recommendations for the management of affected patients including diagnostic considerations and appropriate referrals, and highlights critical implications for the continued safe use of the medication.

Ruthenium(II) arene complexes with chelating chloroquine analogue ligands: synthesis, characterization and in vitro antimalarial activity.

Three new ruthenium complexes with bidentate chloroquine analogue ligands, [Ru(η(6)-cym)(L(1))Cl]Cl (1, cym = p-cymene, L(1) = N-(2-((pyridin-2-yl)methylamino)ethyl)-7-chloroquinolin-4-amine), [Ru(η(6)-cym)(L(2))Cl]Cl (2, L(2) = N-(2-((1-methyl-1H-imidazol-2-yl)methylamino)ethyl)-7-chloroquinolin-4-amine) and [Ru(η(6)-cym)(L(3))Cl] (3, L(3) = N-(2-((2-hydroxyphenyl)methylimino)ethyl)-7-chloroquinolin-4-amine) have been synthesized and characterized. In addition, the X-ray crystal structure of 2 is reported. The antimalarial activity of complexes 1-3 and ligands L(1), L(2) and L(3), as well as the compound N-(2-(bis((pyridin-2-yl)methyl)amino)ethyl)-7-chloroquinolin-4-amine (L(4)), against chloroquine sensitive and chloroquine resistant Plasmodium falciparum malaria strains was evaluated. While 1 and 2 are less active than the corresponding ligands, 3 exhibits high antimalarial activity. The chloroquine analogue L(2) also shows good activity against both the chloroquine sensitive and the chloroquine resistant strains. Heme aggregation inhibition activity (HAIA) at an aqueous buffer/n-octanol interface (HAIR(50)) and lipophilicity (D, as measured by water/n-octanol distribution coefficients) have been measured for all ligands and metal complexes. A direct correlation between the D and HAIR(50) properties cannot be made because of the relative structural diversity of the complexes, but it may be noted that these properties are enhanced upon complexation of the inactive ligand L(3) to ruthenium, to give a metal complex (3) with promising antimalarial activity.

Prevalence of severe chloroquine resistance associates the point mutation in pfcrt and pfmdrI gene in eastern India

Objective To evaluate the molecular mechanism of chloroquine resistant Plasmodium falciparum malaria in West Bengal, eastern part, India. Methods Parasitic bloods were collected from patients in Kolkata and Purulia, in vitro drug susceptibility test were performed in those 179 isolates. Now parasitic DNA was isolated by phenol chloroform extraction method and then polymerase chain reaction and restriction fragment length polymorphism analysis of different codons of pfcrt gene (76) and the pfmdrI gene (86, 1246) were assessed. Results The response of 179 patients to chloroquine was determined. The prevalence of both pfcrt K76T (68.72%) and pfmdrI N86Y (43.1%) mutation was found here. But most importantly severe in vitro chloroquine resistance has been found (53.07%) here, with either double 76T + 86Y mutation or triple 76T + 86Y + 1246Y mutation. Conclusions Our present findings implicate that due to enormous drug (chloroquine) pressure, double mutation with pfcrt 76T + pfmdrI 86Y and triple mutation with pfcrt 76T + pfmdrI 86Y + pfmdrI 1246Y was highly correlated ( P = 0.001) with in vitro chloroquine resistance for the first time in eastern India.

FALCIPARUM MALARIA

Introduction: Quinine and quinidines remain the drugs of choice for chloroquine resistant Plasmodium falciparum malaria. In 1972, Chinese scientists discovered the antimalarial properties of a group of compounds from the qinghao plant (Artemisia annua) which have activity against all malaria causing parasites including multi-drug resistant strains of Plasmodium falciparum. Objective: To compare response to treatment between quinine and artemether in Plasmodium falciparum malaria. Design: Quasi-experimental study. Setting: Department of Medicine Pakistan Air Force Hospital Lahore. Period: 1st Jun 2008 to 1st Dec 2009. Patients: 80 consecutive adult patients with positive MP slide for Plasmodium falciparum malaria. Methods: Patients were randomly divided into two groups for treatment either with quinine or artemether. Results: Out of total 80 patients, 40 were given quinine and 40 were given artemether. Out of 40, 16 patients responded to quinine while 24 did not respond. The responders were 34.8% in case of quinine while 70.6% patients did not respond. Out of 40 patients treated with artemether, 30 responded while 10 did not. The responders were 65.2%while non responders were 29.4%.0n calculating the P-value from the chi-square it was found that difference in terms of response to the two treatment regimens was statistically significant.(P=.0022).Conclusion: The frequency of response in case of quinine was 34.8% while it was 65.2% in case of artemether. So based upon statistically significant difference (P=.0022) it is concluded that Artemether is a satisfactory alternative to Quinine for the treatment of falciparum malaria in adults.

Drugs to Prevent Malaria in Travellers: A Systematic Review of Randomized Controlled Trials

Background: Malaria infects 10,000 to 30,000 international travellers each year. It can be prevented through anti-mosquito measures and drug prophylaxis. We did a systematic review to assess the effects of currently used antimalaria drugs, given as prophylaxis to non- immune adult and child travellers to regions with chloroquine-resistant Plasmodium falciparum malaria. Methods: We included randomized and quasi-randomized controlled trials of any antimalaria drug regimen currently used by inter- national travellers, compared against any other currently used regimen. In August 2009 we searched MEDLINE, EMBASE, LILACS, BIOSIS, mRCT, and the Cochrane Register of Controlled Trials (CENTRAL), without time restrictions. We searched reference lists, conference proceedings and one specialist journal, and contacted researchers and drug companies. We summarized the characteristics of the eligible trials, assessed their quality using standard criteria, and extracted relevant outcomes data. Where appropriate, we combined the results of different trials. Results: Eight trials (4240 participants) were included. One-quarter of trial participants were soldiers. Duration of exposure to malaria ranged from 15 days to 13 weeks. All trials reported common adverse events from antimalaria drugs. Atovaquone-proguanil users and doxycycline users had similar frequencies of reported adverse effects. Atovaquone-proguanil users had fewer reports of any adverse effect than mefloquine users (RR 0.72, 95% CI 0.6 to 0.85), also fewer gastrointestinal adverse effects (RR 0.54, 95% CI 0.42 to 0.7), and fewer neuropsychiatric adverse effects (RR 0.49, 95% CI 0.38 to 0.63). Chloroquine-proguanil users had more reports of any adverse effect than users of other drugs (RR 0.84, 95% CI 0.73 to 0.96), also more gastrointestinal adverse effects (RR 0.71, 95% CI 0.6 to 0.85). We found no evidence on primaquine in travellers. Conclusions: There is limited evidence on which currently available drug is most effective in preventing malaria. Atovaquone-proguanil and doxycycline are the best tolerated regimens. Doxycycline monohydrate appears exceptionally useful due to its good safety profile, low cost and protective efficacy against many travel-related infections, besides malaria. Mefloquine is associated with adverse neuropsy- chiatric outcomes. Chloroquine-proguanil is associated with adverse gastrointestinal outcomes. There is no evidence to support the use of primaquine as prophylaxis in travellers.

Chloroquine-resistant isoforms of the Plasmodium falciparum chloroquine resistance transporter acidify lysosomal pH in HEK293 cells more than chloroquine-sensitive isoforms

The emergence of chloroquine-resistant Plasmodium falciparum malaria imperils the lives of millions of people in Africa, Southeast Asia and South America. Chloroquine resistance is associated with mutations in the P. falciparum chloroquine resistance transporter (PfCRT). We expressed chloroquine-sensitive (HB3) and resistant (Dd2) pfcrt alleles in HEK293 human embryonic kidney cells. PfCRT localized to the lysosomal limiting membrane and was not detected in the plasma membrane. We observed significant acidification of lysosomes containing PfCRT HB3 and Dd2, with Dd2 acidifying significantly more than HB3. A mutant HB3 allele expressing the K76T mutation (earlier found to be key for chloroquine resistance) acidified to the same extent as Dd2, whereas the acidification by a Dd2 allele expressing the T76K “back mutation” was significantly less than Dd2. Thus, the amino acid at position 76 is both an important determinant of chloroquine resistance in parasites and of lysosomal acidification following heterologous expression. PfCRT may be capable of modulating the pH of the parasite digestive vacuole, and thus chloroquine availability. Chloroquine accumulation and glycyl-phenylalanine-2-naphthylamide-induced release of lysosomal Ca2+ stores were unaffected by PfCRT expression. Cytoplasmic domain mutations did not alter PfCRT sorting to the lysosomal membrane. This heterologous expression system will be useful to characterize PfCRT protein structure and function, and elucidate its molecular role in chloroquine resistance.

MOLECULAR EPIDEMIOLOGY OF MALARIA IN CAMEROON. XXII. GEOGRAPHIC MAPPING AND DISTRIBUTION OF PLASMODIUM FALCIPARUM DIHYDROFOLATE REDUCTASE (DHFR) MUTANT ALLELES

Sulfadoxine-pyrimethamine (SP) is still a useful drug to combat chloroquine-resistant Plasmodium falciparum malaria in Cameroon. Because of several disadvantages of the in vivo test and in vitro drug sensitivity assays, molecular assays are an alternative laboratory tool to monitor the evolution of antifolate resistance, especially over the entire country that is characterized by several epidemiologic strata and malaria transmission patterns. In this study, 1,430 blood samples from either symptomatic children or asymptomatic carriers were collected from 14 sites throughout the country between 1999 and 2003 for the analysis of dihydrofolate reductase (dhfr) sequence. Of 1,368 samples (95.7%) that were successfully amplified, 1,180 were analyzed by direct sequencing of the polymerase chain reaction product, and 188 were analyzed by restriction enzymes. The prevalences of the wild-type, single Asn-108 mutation, double Arg-59/Asn-108 mutations, double Ile-51/Asn-108 mutations, triple Ile-51/Arg-59/Asn-108 mutations, and mixed alleles were 20.8%, 2.8%, 5.7%, 0.8%, 62.2%, and 7.6%, respectively. The proportions of triple dhfr mutations were > 60% at all study sites, with the exception of the eastern province (42% triple mutants in Bertoua in 1999) and the northern provinces (11-35% triple mutants in Ngaoundere, Garoua, and Maroua). In these two provinces, the proportion of mutant parasites increased significantly (P < 0.05) over the period of 2-4 years. Furthermore, there was a higher proportion (P < 0.05) of wild-type parasites in the northern provinces, compared with the rest of the country. The geographic mapping of molecular markers offers a novel tool for monitoring the epidemiology of drug-resistant malaria.

Malaria in Kenya's Western Highlands

Records from tea estates in the Kericho district in Kenya show that malaria reemerged in the 1980s. Renewed epidemic activity coincided with the emergence of chloroquine-resistant Plasmodium falciparum malaria and may have been triggered by the failure of antimalarial drugs. Meteorologic changes, population movements, degradation of health services, and changes in Anopheles vector populations are possible contributing factors. The highland malaria epidemics of the 1940s were stopped largely by sporontocidal drugs, and combination chemotherapy has recently limited transmission. Antimalarial drugs can limit the pool of gametocytes available to infect mosquitoes during the brief transmission season.

EMERGENCE OF ATOVAQUONE-PROGUANIL RESISTANCE DURING TREATMENT OF PLASMODIUM FALCIPARUM MALARIA ACQUIRED BY A NON-IMMUNE NORTH AMERICAN TRAVELLER TO WEST AFRICA

The importation of drug-resistant malaria is a growing public health problem in non-endemic countries. The combination of atovaquone and proguanil (Malarone) has become established as an agent of choice to prevent and treat chloroquine-resistant Plasmodium falciparum malaria in travelers. We describe the first reported case in North America of genetically confirmed atovaquone/proguanil-resistant P. falciparum malaria. Polymerase chain reaction and sequence analysis of the primary and recrudescent isolates confirmed the acquisition of a point mutation (Tyr268Ser) in the cytochrome b gene of the recrudescent isolate known to confer high-level resistance to atovaquone. Suboptimal therapy may have played a contributory role in the emergence of resistance.

Genotoxic evaluation of the antimalarial drug, fansidar, in cultured human lymphocytes

Fansidar (pyrimethamine-sulfadoxine) has been used extensively worldwide for the treatment of chloroquine resistant Plasmodium falciparum malaria, toxoplasmosis and Pneumocystis carinii pneumonia in patients with the acquired immunodeficiency syndrome. Because of the wide usage of pyrimethamine-sulfadoxine in developing countries and the lake of information from open literature and reports from manufacturers about the genotoxicity of such antimalarial drug, the present work was suggested. The possible genetic toxicity of fansidar has been evaluated in human peripheral blood lymphocyte cultures. The frequencies of sister-chromatid exchanges (SCE) and micronuclei (MN) were scored as genetic endpoints. Both tests covering a wide range of induced genetic damage as primary DNA damage, clastogenicity and aneugenicity. Cultures were set up by using blood samples from two healthy donors and the treatment was done using different fansidar concentrations ranging from 1:20 to 10:200 microg/ml. From our results, it appears that this drug is able to induce moderate genotoxic effects, as revealed by the increases found in SCE and MN frequencies in cultures from the two donors at the two highest concentrations tested (5:100 and 10:200 microg/ml). In addition, cyotoxic/cytostatic effects of fansidar were revealed by a decrease in the proliferative rate index (PRI) and in the cytokinesis block proliferation index (CBPI). Our findings suggest that the use of this drug should be restricted to situations where other antimalarial drugs cannot be used. The drug should never be given to pregnant women.

Plasmodium falciparum isolates in India exhibit a progressive increase in mutations associated with sulfadoxine-pyrimethamine resistance.

The combination of sulfadoxine-pyrimethamine (SP) is used as a second line of therapy for the treatment of uncomplicated chloroquine-resistant Plasmodium falciparum malaria. Resistance to SP arises due to certain point mutations in the genes for the dihydrofolate reductase (DHFR) and dihydropteroate synthetase (DHPS) enzymes of the parasite. We have analyzed these mutations in 312 field isolates of P. falciparum collected from different parts of India to assess the effects of drug pressure. The rate of mutation in the gene for DHFR was found to be higher than that in the gene for DHPS, although the latter had mutations in more alleles. There was a temporal rise in the number of isolates with double dhfr mutations and single dhps mutations, resulting in an increased total number of mutations in the loci for DHFR and DHPS combined over a 5-year period. During these 5 years, the number of isolates with drug-sensitive genotypes decreased and the number of isolates with drug-resistant genotypes (double DHFR mutations and a single DHPS mutation) increased significantly. The number of isolates with the triple mutations in each of the genes for the two enzymes (for a total of six mutations), however, remained very low, coinciding with the very low rate of SP treatment failure in the country. There was a regional bias in the mutation rate, as isolates from the northeastern region (the state of Assam) showed higher rates of mutation and more complex genotypes than isolates from the other regions. It was concluded that even though SP is prescribed as a second line of treatment in India, the mutations associated with SP resistance continue to be progressively increasing.

Age, temperature, and parasitaemia predict chloroquine treatment failure and anaemia in children with uncomplicated Plasmodium falciparum malaria

The prevalence of chloroquine-resistant Plasmodium falciparum malaria has been increasing in sub-Saharan Africa and parts of South America over the last 2 decades, and has been associated with increased anaemia-associated morbidity and higher mortality rates. Prospectively collected clinical and parasitological data from a multicentre study of 788 children aged 6–59 months with uncomplicated P. falciparum malaria were analysed in order to identify risk factors for chloroquine treatment failure and to assess its impact on anaemia after therapy. The proportion of chloroquine treatment failures (combined early and late treatment failures) was higher in the central-eastern African countries (Tanzania, 53%; Uganda, 80%; Zambia, 57%) and Ecuador (54%) than in Ghana (36%). Using logistic regression, predictors of early treatment failure included younger age, higher baseline temperature, and greater levels of parasitaemia. We conclude that younger age, higher initial temperature, and higher baseline parasitaemia predict early treatment failure and a higher probability of worsening anaemia between admission and days 7 or 14 post-treatment.

Reemergence of chloroquine-sensitive Plasmodium falciparum malaria after cessation of chloroquine use in Malawi.

In 1993, Malawi became the first African country to replace chloroquine with sulfadoxine-pyrimethamine nationwide in response to high rates of chloroquine-resistant falciparum malaria. To determine whether withdrawal of chloroquine can lead to the reemergence of chloroquine sensitivity, the prevalence of the pfcrt 76T molecular marker for chloroquine-resistant Plasmodium falciparum malaria was retrospectively measured in Blantyre, Malawi. The prevalence of the chloroquine-resistant pfcrt genotype decreased from 85% in 1992 to 13% in 2000. In 2001, chloroquine cleared 100% of 63 asymptomatic P. falciparum infections, no isolates were resistant to chloroquine in vitro, and no infections with the chloroquine-resistant pfcrt genotype were detected. A concerted national effort to withdraw chloroquine from use has been followed by a return of chloroquine-sensitive falciparum malaria in Malawi. The reintroduction of chloroquine, ideally in combination with another antimalarial drug, should be considered in areas where chloroquine resistance has declined and safe and affordable alternatives remain unavailable.