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EHP Malaria Bulletin—May 5-20, 2001

Social Sciences and Malaria

Trop Med Int Health 2001 Apr;6(4):280-95
Comparison of the cost and cost-effectiveness of insecticide-treated bednets and residual house-spraying in KwaZulu-Natal, South Africa.

Goodman CA, Mnzava AE, Dlamini SS, Sharp BL, Mthembu DJ, Gumede JK.

Health Policy Unit, Department of Public Health and Policy, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK. catherine.goodma[email protected]

Residual house-spraying (RHS) has been the mainstay of South African malaria prevention for more than 50 years, but it has been argued that insecticide-treated bednets (ITBN) could be a more effective and appropriate method of control. To provide a rational basis for choosing between the interventions, a trial was conducted during 1998 and 1999 in northern KwaZulu-Natal to collect comparable data on the effectiveness, acceptability and cost of the two interventions. The current practice of house-spraying once a year was compared with ITBN, distributed free to households and retreated annually at several specific centres. The base case results show ITBN to be significantly more effective in preventing malaria cases than RHS (overall adjusted rate ratio of 0.69), and also more costly, with an incremental economic cost per person of ITBN compared with RHS of R8.68 (US$1.42) per year, giving a gross incremental cost per case averted of R111 ($18) (1999 prices). Estimating the number of deaths averted, based on the average case fatality rate, gave a gross incremental cost per death averted of R11 718 ($1915). The additional cases averted were estimated to lead to drug cost savings of around R1 ($0.16) per capita per year, giving a net cost per case averted of R98 ($16), and net cost per death averted of R10 377 ($1696). Although the finding that the economic costs of ITBN were higher than those for RHS was relatively robust to parameter variations, the extent of the cost margin was sensitive to changes in the price and useful life of the net, and the price of the insecticide. Moreover, a switch to ITBN could lead to net financial savings if the price per net fell below $3.57 (R21.85), or if a change in policy allowed a significant reduction in the number of permanent full-time malaria control staff. In view of the greater effectiveness of ITBN, policy makers may view ITBN as a cost-effective use of resources, even if the economic costs are higher. If ITBN are implemented, close monitoring will be required of use, retreatment and useful life of nets, and resistance to insecticides, to assess any change over time in relative cost-effectiveness, and any threat to the role of the programme as a barrier to the spread of malaria transmission to other areas.

PMID: 11348519 [PubMed - in process]

Health Policy Plan 2001 May;16(2):171-9
 
Changing roles of grass-root level health workers in Kerala, India.

Nair V, Thankappan K, Sarma P, Vasan R.

Kerala Health Services and. Achutha Menon Centre for Health Science Studies, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Thiruvananthapuram, Kerala, India.

OBJECTIVE: Multipurpose health workers (MPWs) are envisioned as key personnel in the delivery of primary health care. We evaluated their role and participation in implementing different national health programmes in Kerala, INDIA: DESIGN: Cross-sectional, community-based survey. PARTICIPANTS: We selected three out of the 14 districts in KERALA: Three-hundred and twenty-six MPWs (95 male and 231 female) from 44 randomly selected primary health centres from the three districts were questioned using a structured pre-tested questionnaire that sought information regarding the provision of health services by the MPWs to eligible beneficiaries in the community. We randomly selected 90 subcentres (30 from each district) and 750 households using a cluster sampling technique, and conducted household surveys to compare the actual delivery of services at the doorstep with that reported by the MPWS: Work sampling of MPWs was also performed to examine the fieldwork time spent by them on implementing individual national health programmes. These data were supplemented with focus group discussions and personal interviews of MPWs and household members. RESULTS: MPWs consistently 'over-reported' their performance when self-reported information was compared with that obtained from household surveys. Male MPWs concentrated on the National Malaria Eradication Programme and health education while female workers focused on the family welfare and immunization programmes. Key national health programmes (such as for tuberculosis and acute respiratory infection) were neglected by all MPWS: MPWs were aware of health problems of the elderly, but were not adequately trained nor officially expected to deliver any services in these fields. CONCLUSIONS: Grass-root level workers apportion more time to select national health programmes to the detriment of other health programmes, thereby negating their multipurpose role. Our study emphasizes the need for interventions to derive 'multipurpose benefits' from the MPWS:

PMID: 11358918 [PubMed - in process]
 

Trans R Soc Trop Med Hyg 2001 Mar-Apr;95(2):125-6

Refugee health in the tropics. Malaria control in Afghan refugee camps: novel solutions.

Rowland M.

HealthNet International, P. O. Box 889, University Town, Peshawar, Pakistan. 
[email protected]

Malaria is one of the major communicable diseases to occur in refugee camps. Prevention of mortality by establishing good case management is always the priority. Various types of personal protection or vector control measures may be applied depending on local transmission conditions and stage of the emergency. The range of interventions applied in Afghan refugee camps, the factors influencing choice and the relevance to emergencies in other parts of the world are described.

PMID: 11355539 [PubMed - in process]

Trop Med Int Health 2001 Apr;6(4):273-9

Malaria diagnosis and treatment administered by teachers in primary schools in Tanzania.

Magnussen P, Ndawi B, Sheshe AK, Byskov J, Mbwana K.

Danish Bilharziasis Laboratory, Charlottenlund, Denmark; Primary Health Care Institute, Iringa, Tanzania; School of Environmental Health, Tanga, Tanzania; District Medical Office, Ministry of Health, Pangani, Tanzania.

A school health programme in Mwera Division, Pangani District included treatment of malaria attacks occurring in children during school time. A combination of symptoms (headache, muscle/joint pains, feeling feverish) and oral temperature >/= 37.5 degrees C was used for the diagnosis of malaria. Chloroquine (25 mg/kg given over 3 days) was used for treatment. Malariometric surveys on children aged 7-15 years (mean 10 years) were conducted once a year (1995-1997). Plasmodium falciparum accounted for 100% of infections and the parasite prevalence varied between 32.7 and 35.3% from 1995 to 1997. The number of malaria cases (cases/1000 registered school children) diagnosed and treated by school teachers was 159 (67) in 1995, 324 (124) in 1996, 348 (128) in 1997 and 339 (108) in 1998. Children in grades 1-4 (age 7-13) accounted for 64.6% of cases. Symptoms and oral temperature were recorded for 1258 children. Of those, 992 (78.9%) complained of fever and at least one other symptom when presenting to teachers, 98 (7.8%) had fever as their only complaint and 168 (13.5%) presented without a perception of fever, but with other symptoms. Of these children, 36 (21.4%) had a temperature >/=37.5 degrees C. The sensitivity of 'feeling feverish' was 96.5% with a specificity of 54.5%. The positive predictive value of feeling feverish was 89.9% and the negative predictive value 78.6%. Blood slides were prepared from 55.3 and 37.2% of children diagnosed by teachers during 1995 and 1996, respectively, and 71.4% were found positive. Among children who fulfilled the algorithm criteria 75.0% had a positive blood slide. With little training and regular supervision it was feasible for school teachers to make a presumptive diagnosis of malaria. We conclude that teachers can play a major role in school health programmes and are willing to be involved in health matters as long as they are supported by health and educational authorities.

PMID: 11348518 [PubMed - in process]

PubMed 
 
Am J Trop Med Hyg 2000 Jul-Aug;63(1-2):90-3

Enhanced development in nature of larval Anopheles arabiensis mosquitoes feeding on maize pollen.

Ye-Ebiyo Y, Pollack RJ, Spielman A.

Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts 02115, USA.

To determine whether pollen produced by maize (Zea m. mays) may contribute to the development of larval Anopheles gambiae complex mosquitoes, the main African vectors of malaria, we correlated duration of larval development, pupation success, and size of the resulting adults with degree of access to this potential nutriment. Maize pollen is abundant during the wet season on the surface of water near maize plantings in a malaria-endemic region of Ethiopia, and larval Anopheles arabiensis readily ingest these particles in nature. Larvae develop to the pupal stage more rapidly, more frequently, and produce larger adults where maize pollen is abundant than do those that have little access to this food. The force of transmission of malaria in sub-Saharan Africa might be reduced if maize plantings were excluded from the immediate vicinity of homes or, perhaps, if pollen of such maize were to express entomotoxins.

PMID: 11358003 [PubMed - in process]

Am J Trop Med Hyg 2000 Jul-Aug;63(1-2):80-4
A trial for a DNA diagnosis of Plasmodium vivax malaria recently reemerging in the Republic of Korea using microtiter plate hybridization assay.

Chai JY, Park YK, Guk SM, Oh KH, Oh MD, Lee SH, Kim HS, Wataya Y.

Department of Parasitology, Seoul National University College of Medicine, Institute of Endemic Diseases, Seoul National University Medical Research Center, Korea. [email protected]

The polymerase chain reaction-based microtiter plate hybridization (PCR-MPH) assay was utilized for a DNA diagnosis of Plasmodium vivax malaria, which has recently reemerged in the Republic of Korea. The subjects were 18 parasite-proven patients and 5 healthy controls. Follow-up blood samples were collected from 4 patients after a standard course of treatment. Polymerase chain reaction and electrophoresis of all the patients' blood showed a prominent band at the 138 base pair area, but not in the controls or after treating the patients. Hybridization of the PCR products with known species-specific probes of the 18S rRNA of various malaria species revealed strong positive reactions against the Plasmodium vivax-specific probe (absorbance 1.30-1.90 at 405 nm) in all of the patients. The absorbance was positively correlated with the degree of blood parasitemia, but with a borderline significance. Sequencing of the probe region of the Korean P. vivax revealed no significant variations from the typical P. vivax. The results show that the PCR-MPH is a highly useful technique for the DNA diagnosis of Korean vivax malaria.

PMID: 11358001 [PubMed - in process]


Am J Trop Med Hyg 2000 Jul-Aug;63(1-2):76-9
Use of the Parasight-F diagnostic test for imported malaria in a travel clinic.

Bouchaud O, Houze S, Longuet C, di Piazza JP, Ruggieri C, Secardin Y, Coulaud JP, Le Bras J.

Department of Infectious and Tropical Diseases, H pital Bichat-Claude Bernard, Paris, France. [email protected]

The Parasight-F test based on the detection of a soluble antigen specific for Plasmodium falciparum is designed for the immediate diagnosis of malaria infection. We evaluated its use by clinicians during consultations. This prospective study of its diagnostic utility in febrile patients consulting a travel clinic on their return from areas endemic for malaria was conducted between May 1996 and May 1997. The Parasight-F test was performed by the clinician with confirmation by means of standard microscopic examination of venous blood. One-hundred and forty patients were enrolled. Forty-three (31%) cases of malaria were identified by microscopic examination. Thirty-eight were due to P. falciparum. The Parasight-F tests yielded 6 false-positive and 3 false-negative results compared to the microscopic findings. The specificity and sensitivity for the diagnosis of P. falciparum malaria were 94% and 92%. These results show that the Parasight-F test alone cannot replace microscopic diagnosis of malaria in travel clinics.

PMID: 11358000 [PubMed - in process]


Mol Biochem Parasitol 2001 Apr 25;114(1):89-94
A phylogenetic comparison of gene trees constructed from plastid, mitochondrial and genomic DNA of Plasmodium species.

Rathore D, Wahl AM, Sullivan M, McCutchan TF.

Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 4 Center Drive MSC 0425, 20892-0425, Bethesda, MD, USA

Gene trees of Plasmodium species have been reported for the nuclear encoded genes (e.g. the Small Subunit rRNA) and a mitochondrial encoded gene, cytochrome b. Here, we have analyzed a plastid gene coding for caseinolytic protease ClpC, whose structure, function and evolutionary history have been studied in various organisms. This protein possesses a 220-250 amino acid long AAA domain (ATPases associated with a variety of cellular activities) that belongs to the Walker super family of ATPases and GTPases. We have sequenced the AAA motif of this gene, encoding the protein from nine different species of Plasmodium infecting rodents, birds, monkeys, and humans. The codon usage and GC content of each gene were nearly identical in contrast to the widely varying nucleotide composition of genomic DNAs. Phylogenetic trees derived from both DNA and inferred protein sequences have consistent topologies. We have used the ClpC sequence to analyze the phylogenetic relationship among Plasmodium species and compared it with those derived from mitochondrial and genomic sequences. The results corroborate well with the trees constructed using the mitochondrially encoded cytochrome b. However, an important element distinguishes the trees: the placement of Plasmodium elongatum near the base of the plastid tree, indicating an ancient lineage of parasites in birds that branches from the tree prior to other lineages of avian malaria and the human parasite, P. falciparum.

PMID: 11356517 [PubMed - in process]

Parasitol Res 2001 Apr;87(4):264-8

Cytoadherence of the malaria-infected erythrocyte membrane to C32 melanoma cells after merozoites are released from parasitized infected cells.

Winograd E, Robles WM, Caldas ML, Cortes GT.

Laboratorio de Biologia Celular, Instituto Nacional de Salud, Bogota, Colombia. 
[email protected]

Infections with the human malaria parasite Plasmodium falciparum are characterized by cytoadherence of infected erythrocytes to the venular endothelium of several organs. Video microscopy studies have shown that at the end of the asexual life of P. falciparum, the residual body containing haemozoin is released to the extracellular environment along with merozoites, leaving behind an infected erythrocyte "ghost". It is possible that these infected erythrocyte "ghosts" could remain sequestered within the blood vessels of patients infected with P. falciparum even after merozoites have been released from infected erythrocytes. In this study an in vitro cytoadherence assay was developed to show that infected erythrocyte "ghosts" can interact with C32 melanoma cells. Adherent infected erythrocyte "ghosts" contain some of the subcellular compartments of the malaria-infected red blood cell such as the tubo-vesicular membrane network and remnants of the parasitophorous vacuolar membrane, but lack haemozoin.

PMID: 11355673 [PubMed - in process]


Trans R Soc Trop Med Hyg 2001 Mar-Apr;95(2):225-32
Genotyping of Plasmodium falciparum infections by PCR: a comparative multicentre study.

Farnert A, Arez AP, Babiker HA, Beck HP, Benito A, Bjorkman A, Bruce MC, Conway DJ, Day KP, Henning L, Mercereau-Puijalon O, Ranford-Cartwright LC, Rubio JM, Snounou G, Walliker D, Zwetyenga J, do Rosario VE.

Division of Infectious Diseases, Department of Medicine, Karolinska Institutet, Huddinge University Hospital, 14186 Huddinge, Sweden. [email protected]

Genetic diversity of malaria parasites represents a major issue in understanding several aspects of malaria infection and disease. Genotyping of Plasmodium falciparum infections with polymerase chain reaction (PCR)-based methods has therefore been introduced in epidemiological studies. Polymorphic regions of the msp1, msp2 and glurp genes are the most frequently used markers for genotyping, but methods may differ. A multicentre study was therefore conducted to evaluate the comparability of results from different laboratories when the same samples were analysed. Analyses of laboratory-cloned lines revealed high specificity but varying sensitivity. Detection of low-density clones was hampered in multiclonal infections. Analyses of isolates from Tanzania and Papua New Guinea revealed similar positivity rates with the same allelic types identified. The number of alleles detected per isolate, however, varied systematically between the laboratories especially at high parasite densities. When the analyses were repeated within the laboratories, high agreement was found in getting positive or negative results but with a random variation in the number of alleles detected. The msp2 locus appeared to be the most informative single marker for analyses of multiplicity of infection. Genotyping by PCR is a powerful tool for studies on genetic diversity of P. falciparum but this study has revealed limitations in comparing results on multiplicity of infection derived from different laboratories and emphasizes the need for highly standardized laboratory protocols.

PMID: 11355566 [PubMed - in process]


Trans R Soc Trop Med Hyg 2001 Mar-Apr;95(2):179-82
Persistence of Plasmodium falciparum HRP-2 in successfully treated acute falciparum malaria.

Mayxay M, Pukrittayakamee S, Chotivanich K, Looareesuwan S, White NJ.

Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Bangkok 10400, Thailand.

The potential for Plasmodium falciparum histidine-rich protein-2 (PfHRP-2) dipstick tests to predict antimalarial treatment failure was investigated in a prospective study in Thailand of 38 patients admitted with severe malaria and 54 hospitalized with uncomplicated P. falciparum infections. Of these, 40 had subsequent recrudescence of their infections. Overall, 89% of patients with severe malaria and 61% of patients with uncomplicated malaria had positive PfHRP-2 dipstick tests for > 2 weeks following the start of treatment. Persistence was correlated positively with admission parasite counts, PfHRP-2 intensity scores and disease severity. PfHRP-2 tests which remained positive for > 2 weeks and PfHRP-2 reactive intensity scores on admission, at day 7 and day 14 did not predict treatment failure independent of admission parasitaemia. Freezing and thawing the blood samples did not significantly affect PfHRP-2 results tested by the dipstick technique. The PfHRP-2 dipstick test provides a useful indicator of recent severe malaria, but does not predict the therapeutic response.

PMID: 11355555 [PubMed - in process]

Trans R Soc Trop Med Hyg 2001 Mar-Apr;95(2):149-52

The lower susceptibility to Plasmodium falciparum malaria of Fulani of Burkina Faso (west Africa) is associated with low frequencies of classic malaria-resistance genes.

Modiano D, Luoni G, Sirima BS, Lanfrancotti A, Petrarca V, Cruciani F, Simpore J, Ciminelli BM, Foglietta E, Grisanti P, Bianco I, Modiano G, Coluzzi M.

Dipartimento di Biologia Molecolare, Cellulare e Animale, Universita di Camerino, Italy. 
[email protected]

The gene frequencies in 1993-94 for haemoglobin S, haemoglobin C, alpha-3.7 deletional thalassaemia, G6PDA-, HLAB*5301 were estimated in Fulani, Mossi and Rimaibe ethnic groups of Burkina Faso, West Africa. The aim of the study was to verify whether the previously reported Fulani lower susceptibility to Plasmodium falciparum malaria was associated with any of these malaria-resistance genes. Similar frequencies for haemoglobin S were recorded in the 3 ethnic groups (0.024 +/- 0.008, 0.030 +/- 0.011, 0.022 +/- 0.013; in Mossi, Rimaibe and Fulani, respectively). The Mossi and Rimaibe showed higher frequencies when compared to Fulani for haemoglobin C (0.117 +/- 0.018, 0.127 +/- 0.020, 0.059 +/- 0.020), alpha-3.7 deletional thalassaemia (0.227 +/- 0.040, 0.134 +/- 0.032, 0.103 +/- 0.028), G6PDA- (0.196 +/- 0.025, 0.187 +/- 0.044, 0.069 +/- 0.025) and HLA B*5301 (0.189 +/- 0.038, 0.202 +/- 0.041, 0.061 +/- 0.024). Among Fulani the proportion of individuals not having any of these protective alleles was more than 3-fold greater than in the Mossi-Rimaibe group (56.8% vs 16.7%; P < 0.001). These findings exclude the involvement of these genetic factors of resistance to P. falciparum in the lower susceptibility to malaria of Fulani. This evidence, in association with the previously reported higher immune reactivity to malaria of Fulani, further supports the existence in this ethnic group of unknown genetic factor(s) of resistance to malaria probably involved in the regulation of humoral immune responses.

PMID: 11355545 [PubMed - in process]


Trans R Soc Trop Med Hyg 2001 Mar-Apr;95(2):137-8
A double-blind randomized therapeutic trial of insect repellents for the prevention of malaria in pregnancy.

McGready R, Simpson JA, Htway M, White NJ, Nosten F, Lindsay SW.

Shoklo Malaria Research Unit, P.O. Box 46, Mae Sot, Tak 63110, Thailand.

PMID: 11355542 [PubMed - in process]


Antimicrob Agents Chemother 2001 Jun;45(6):1847-53
Human malaria in immunocompromised mice: new in vivo model for chemotherapy studies.

Moreno A, Badell E, Van Rooijen N, Druilhe P.

Biomedical Parasitology Unit, Pasteur Institute, 75724 Paris Cedex 15, France.

We have recently designed a new Plasmodium falciparum mouse model and documented its potential for the study of immune effector mechanisms. In order to determine its value for drug studies, we evaluated its response to existing antimalarial drugs compared to that observed in humans. Immunocompromised BXN (bg/bg xid/xid nu/nu) mice were infected with either the sensitive NF54 strain or the multiresistant T24 strain and then treated with chloroquine, quinine, mefloquine, or dihydroartemisinin. A parallelism was observed between previously reported human responses and P. falciparum-parasitized human red blood cell (huRBC)-BXN mouse responses to classical antimalarial drugs, measured in terms of speed of decrease in parasitemia and of morphological alterations of the parasites. Mice infected with the sensitive strain were successfully cured after treatment with either chloroquine or mefloquine. In contrast, mice infected with the multiresistant strain failed to be cured by chloroquine or quinine but thereafter responded to dihydroartemisinin treatment. The speed of parasite clearance and the morphological alterations induced differed for each drug and matched previously reported observations, hence stressing the relevance of the model. These data thus suggest that P. falciparum-huRBC-BXN mice can provide a valuable in vivo system and should be included in the short list of animals that can be used for the evaluation of P. falciparum responses to drugs.

PMID: 11353636 [PubMed - in process]

Antimicrob Agents Chemother 2001 Jun;45(6):1803-9
Population pharmacokinetics of intramuscular quinine in children with severe malaria.

Krishna S, Nagaraja NV, Planche T, Agbenyega T, Bedo-Addo G, Ansong D, Owusu-Ofori A, Shroads AL, Henderson G, Hutson A, Derendorf H, Stacpoole PW.

Department of Infectious Diseases, St. George's Hospital Medical School, Cranmer Terrace, London SW17 ORE, United Kingdom.

We present the first population pharmacokinetic analysis of quinine in patients with Plasmodium falciparum malaria. Ghanaian children (n = 120; aged 12 months to 10 years) with severe malaria received an intramuscular loading dose of quinine dihydrochloride (20 mg/kg of body weight). A two-compartment model with first-order absorption and elimination gave post hoc estimates for pharmacokinetic parameters that were consistent with those derived from non-population pharmacokinetic studies (clearance [CL] = 0.05 liter/h/kg of body weight; volume of distribution in the central compartment [V(1)] = 0.65 liter/kg; volume of distribution at steady state = 1.41 liter/kg; half-life at beta phase = 19.9 h). There were no covariates (including age, gender, acidemia, anemia, coma, parasitemia, or anticonvulsant use) that explained interpatient variability in weight-normalized CL and V(1). Intramuscular quinine was associated with minor, local toxicity in some patients (13 of 108; 12%), and 11 patients (10%) experienced one or more episodes of postadmission hypoglycemia. A loading dose of intramuscular quinine results in predictable population pharmacokinetic profiles in children with severe malaria and may be preferred to the intravenous route of administration in some circumstances.

PMID: 11353629 [PubMed - in process]

J Biol Chem 2001 May 14
The binding of the circumsporozoite protein to cell surface proteoglycans is required for plasmodium sporozoite attachment to target cells.

Pinzon-Ortiz C, Friedman J, Esko J, Sinnis P.

Medical and Molecular Parasitology, New York University School of Medicine, New York, NY 10010.

The major surface protein of malaria sporozoites, the circumsporozoite protein, binds to heparan sulfate proteoglycans on the surface of hepatocytes. It has been proposed that this binding event is responsible for the rapid and specific localization of sporozoites to the liver after their injection into the skin by an infected Anopheline mosquito. Previous in vitro studies performed under static conditions have failed to demonstrate a significant role for HSPGs during sporozoite invasion of cells. We performed sporozoite attachment and invasion assays under more dynamic conditions and found a dramatic decrease in sporozoite attachment to cells in the presence of heparin. In contrast to its effect on attachment, heparin does not appear to have an effect on sporozoite invasion of cells. When substituted heparins were used as competitive inhibitors of sporozoite attachment, we found that sulfation of the glycosaminoglycan chains at both the N- and O- positions was important for sporozoite adhesion to cells. We conclude that the binding of the circumsporozoite protein to hepatic heparan sulfate proteoglycans is likely to function during sporozoite attachment in the liver and that this adhesion event depends on the sulfated glycosaminoglycan chains of the proteoglycans.

PMID: 11352923 [PubMed - as supplied by publisher]


Pharmacol Res 2001 Apr;43(4):363-7
Aminonaphthoquinones-a novel class of compounds with potent antimalarial activity against plasmodium falciparum.

Kapadia GJ, Azuine MA, Balasubramanian V, Sridhar R.

Laboratory of Natural Drug Products, Department of Pharmaceutical Sciences, School of Pharmacy, Howard University, 2300 4th Street, NW, Washington DC 20059, USA

Malaria is a major tropical disease, which kills two million people annually. The population at risk from this disease has increased because of the difficulties in eradicating the mosquito vector in the endemic regions and the emergence and spread of parasite resistance to all the commonly used antimalarials. Since antimalarials are the major arsenal for treatment of the disease, there is an urgent need for newer drugs with novel mechanisms of action, which will be effective against all strains of the parasite. As a part of our anti-infective drug discovery program, we have investigated 18 compounds including several synthetic and natural naphthoquinones as potential antimalarial agents. We have identified aminonaphthoquinones, as a class of antimalarial compounds with antimalarial activity against Plasmodium falciparum. Among these compounds, 2-amino-3-chloro-1,4-naphthoquinone is the most potent. It had an IC(50)of 0.18 &mgr; M (37.3 ng ml(-1)) against the W2 clone, and is more potent than chloroquine, which had an IC(50)of 0.23 &mgr; M (72 ng ml(-1)). It was also active against the D6 clone. In general, 2-amino-1,4-naphthoquinone analogs and the 4-amino-1,2-napthoquinone analog showed promising antimalarial activity in the bioassay. In contrast, a number of 2-hydroxy-1,4-naphthoquinones and dimeric quinones were less active. Copyright 2001 Academic Press.

PMID: 11352541 [PubMed - in process]


Am J Physiol Cell Physiol 2001 Jun;280(6):C1576-87
Perturbation of the pump-leak balance for Na(+) and K(+) in malaria-infected erythrocytes.

Staines HM, Ellory JC, Kirk K.

University Laboratory of Physiology, Oxford OX1 3PT, United Kingdom.

In human erythrocytes infected with the mature form of the malaria parasite Plasmodium falciparum, the cytosolic concentration of Na(+) is increased and that of K(+) is decreased. In this study, the membrane transport changes underlying this perturbation were investigated using a combination of (86)Rb(+), (43)K(+), and (22)Na(+) flux measurements and a semiquantitative hemolysis technique. From >15 h postinvasion, there appeared in the infected erythrocyte membrane new permeation pathways (NPP) that caused a significant increase in the basal ion permeability of the erythrocyte membrane and that were inhibited by furosemide (0.1 mM). The NPP showed the selectivity sequence Cs(+) > Rb(+) > K(+) > Na(+), with the K(+)-to-Na(+) permeability ratio estimated as 2.3. From 18 to 36 h postinvasion, the activity of the erythrocyte Na(+)/K(+) pump increased in response to increased cytosolic Na(+) (a consequence of the increased leakage of Na(+) via the NPP) but underwent a progressive decrease in the latter 12 h of the parasite's occupancy of the erythrocyte (36-48 h postinvasion). Incorporation of the measured ion transport rates into a mathematical model of the human erythrocyte indicates that the induction of the NPP, together with the impairment of the Na(+)/K(+) pump, accounts for the altered Na(+) and K(+) levels in the host cell cytosol, as well as predicting an initial decrease, followed by a lytic increase in the volume of the host erythrocyte.

PMID: 11350753 [PubMed - in process]


Infect Immun 2001 Jun;69(6):4048-54
Disruption of Plasmodium falciparum Chitinase Markedly Impairs Parasite Invasion of Mosquito Midgut.

Tsai YL, Hayward RE, Langer RC, Fidock DA, Vinetz JM.

WHO Collaborating Center for Tropical Diseases, Department of Pathology, University of Texas Medical Branch, Galveston, Texas 77555-0609.

To initiate invasion of the mosquito midgut, Plasmodium ookinetes secrete chitinolytic activity to penetrate the peritrophic matrix surrounding the blood meal. While ookinetes of the avian malaria parasite Plasmodium gallinaceum appear to secrete products of two chitinase genes, to date only one chitinase gene, PfCHT1, has been identified in the nearly completed Plasmodium falciparum strain 3D7 genome database. To test the hypothesis that the single identified chitinase of P. falciparum is necessary for ookinete invasion, the PfCHT1 gene was disrupted 39 bp upstream of the stop codon. PfCHT1-disrupted parasites had normal gametocytogenesis, exflagellation, and ookinete formation but were markedly impaired in their ability to form oocysts in Anopheles freeborni midguts. Confocal microscopy demonstrated that the truncated PfCHT1 protein was present in mutant ookinetes but that the concentration of mutant PfCHT1 within the apical end of the ookinetes was substantially reduced. These data suggest that full-length PfCHT1 is essential for intracellular trafficking and secretion and that the PfCHT1 gene product is necessary for ookinetes to invade the mosquito midgut.

PMID: 11349075 [PubMed - in process]


Infect Immun 2001 Jun;69(6):4041-7
Knockout of the rodent malaria parasite chitinase pbcht1 reduces infectivity to mosquitoes.

Dessens JT, Mendoza J, Claudianos C, Vinetz JM, Khater E, Hassard S, Ranawaka GR, Sinden RE.

Department of Biology, Imperial College of Science, Technology, and Medicine, London SW7 2AZ, United Kingdom.

During mosquito transmission, malaria ookinetes must cross a chitin-containing structure known as the peritrophic matrix (PM), which surrounds the infected blood meal in the mosquito midgut. In turn, ookinetes produce multiple chitinase activities presumably aimed at disrupting this physical barrier to allow ookinete invasion of the midgut epithelium. Plasmodium chitinase activities are demonstrated targets for human and avian malaria transmission blockade with the chitinase inhibitor allosamidin. Here, we identify and characterize the first chitinase gene of a rodent malaria parasite, Plasmodium berghei. We show that the gene, named PbCHT1, is a structural ortholog of PgCHT1 of the avian malaria parasite Plasmodium gallinaceum and a paralog of PfCHT1 of the human malaria parasite Plasmodium falciparum. Targeted disruption of PbCHT1 reduced parasite infectivity in Anopheles stephensi mosquitoes by up to 90%. Reductions in infectivity were also observed in ookinete feeds-an artificial situation where midgut invasion occurs before PM formation-suggesting that PbCHT1 plays a role other than PM disruption. PbCHT1 null mutants had no residual ookinete-derived chitinase activity in vitro, suggesting that P. berghei ookinetes express only one chitinase gene. Moreover, PbCHT1 activity appeared insensitive to allosamidin inhibition, an observation that raises questions about the use of allosamidin and components like it as potential malaria transmission-blocking drugs. Taken together, these findings suggest a fundamental divergence among rodent, avian, and human malaria parasite chitinases, with implications for the evolution of Plasmodium-mosquito interactions.

PMID: 11349074 [PubMed - in process]


Infect Immun 2001 Jun;69(6):3845-52
Human Antibodies against Plasmodium falciparum Liver-Stage Antigen 3 Cross-React with Plasmodium yoelii Preerythrocytic-Stage Epitopes and Inhibit Sporozoite Invasion In Vitro and In Vivo.

Brahimi K, Badell E, Sauzet JP, BenMohamed L, Daubersies P, Guerin-Marchand C, Snounou G, Druilhe P.

Laboratoire de Parasitologie Biomedicale, Institut Pasteur, 75015 Paris Cedex 15, France.

The Plasmodium falciparum liver-stage antigen 3 (LSA3), a recently identified preerythrocytic antigen, induces protection against malaria in chimpanzees. Using antibodies from individuals with hyperimmunity to malaria affinity purified on recombinant or synthetic polypeptides of LSA3, we identified four non-cross-reactive B-cell epitopes in Plasmodium yoelii preerythrocytic stages. On sporozoites the P. yoelii protein detected has a molecular mass similar to that of LSA3. T-cell epitopes cross-reacting with P. yoelii were also demonstrated using peripheral blood lymphocytes from LSA3-immunized chimpanzees. In contrast, no cross-reactive epitopes were found in Plasmodium berghei. LSA3-specific human antibodies exerted up to 100% inhibition of in vitro invasion of P. yoelii sporozoites into mouse hepatocytes. This strong in vitro activity was reproduced in vivo by passive transfer of LSA3 antibodies. These results indicate that the homologous epitopes may be biologically functional and suggest that P. yoelii could be used as a model to assess the antisporozoite activity of anti-LSA3 antibodies.

PMID: 11349050 [PubMed - in process]

Infect Immun 2001 Jun;69(6):3713-8
Antibodies to variant antigens on the surfaces of infected erythrocytes are associated with protection from malaria in ghanaian children.

Dodoo D, Staalsoe T, Giha H, Kurtzhals JA, Akanmori BD, Koram K, Dunyo S, Nkrumah FK, Hviid L, Theander TG.

Immunology and Epidemiology Units, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana.

Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is a variant antigen expressed on the surface of infected erythrocytes. Each parasite genome contains about 40 PfEMP1 genes, but only 1 PfEMP1 gene is expressed at a given time. PfEMP1 serves as a parasite-sequestering ligand to endothelial cells and enables the parasites to avoid splenic passage. PfEMP1 antibodies may protect from disease by inhibiting sequestration, thus facilitating the destruction of infected erythrocytes in the spleen. In this study, we have measured antibodies in Ghanaian children to a conserved region of PfEMP1 by enzyme-linked immunosorbent assay and antibodies to variant molecules on erythrocytes infected with field isolates of P. falciparum by flow cytometry. Based on close clinical monitoring, the children were grouped into those who did (susceptible) and those who did not (protected) have malaria during the season. The prevalences of antibodies to both the conserved PfEMP1 peptide and the variant epitopes were greater than 50%, and the levels of immunoglobulin G (IgG) correlated with age. The levels of antibodies to both the conserved peptide and the variant epitopes were higher in protected than in susceptible children. After correcting for the effect of age, the levels of IgG to variant antigens on a Sudanese and a Ghanaian parasite isolate remained significantly higher in protected than in susceptible children. Thus, the levels of IgG to variant antigens expressed on the surface of infected erythrocytes correlated with protection from clinical malaria. In contrast, the levels of IgG to a peptide derived from a conserved part of PfEMP1 did not correlate with protection from malaria.

PMID: 11349035 [PubMed - in process]

J Am Mosq Control Assoc 2001 Mar;17(1):13-22

Insecticide-induced behavioral responses of anopheles minimus, a malaria vector in Thailand.

Chareonviriyaphap T, Sungvornyothin S, Ratanatham S, Prabaripai A.

Faculty of Liberal Arts and Science, Kasetsart University, Nakhon-Pathom, Thailand.

This study was designed to determine the behavioral responses of 2 test populations of Anopheles minimus females to DDT at 2 g/m2, deltamethrin at 0.0625 g/m2, and lambdacyhalothrin at 0.0369 g/m2 using an improved excito-repellency escape chamber. One test population was colonized in 1993 and referred to as a young colony. The 2nd field test population was collected from Ta-Soa County, Tri-Yok District, Kanchanaburi Province. in western Thailand and referred to as a wild population. Results showed that females of both young and wild test populations rapidly escaped from direct contact with DDT, deltamethrin, and lambdacyhalothrin. Lambdacyhalothrin exhibited the strongest irritant effect on female mosquitoes, followed by DDT and deltamethrin. Fewer females escaped from test chambers without direct contact with treated surfaces but the response was significantly different from that of the controls (P < 0.05). The noncontact response is indicative of a noncontact repellent action. Both contact irritancy and noncontact repellency are involved in An. minimus escape responses. Experimental hut studies that include monitoring of house-entering populations of An. minimus are needed for a meaningful assessment of noncontact repellent actions.

PMID: 11345412 [PubMed - in process]


J Infect Dis 2001 Jun 1;183(11):1653-61
Evidence for different mechanisms of chloroquine resistance in 2 plasmodium species that cause human malaria.

Nomura T, Carlton JM, Baird JK, del Portillo HA, Fryauff DJ, Rathore D, Fidock DA, Su Xz, Collins WE, McCutchan TF, Wootton JC, Wellems TE.

Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.

Chloroquine (CQ)-resistant Plasmodium vivax malaria was first reported 12 years ago, nearly 30 years after the recognition of CQ-resistant P. falciparum. Loss of CQ efficacy now poses a severe problem for the prevention and treatment of both diseases. Mutations in a digestive vacuole protein encoded by a 13-exon gene, pfcrt, were shown recently to have a central role in the CQ resistance (CQR) of P. falciparum. Whether mutations in pfcrt orthologues of other Plasmodium species are involved in CQR remains an open question. This report describes pfcrt homologues from P. vivax, P. knowlesi, P. berghei, and Dictyostelium discoideum. Synteny between the P. falciparum and P. vivax genes is demonstrated. However, a survey of patient isolates and monkey-adapted lines has shown no association between in vivo CQR and codon mutations in the P. vivax gene. This is evidence that the molecular events

PMID: 11343215 [PubMed - in process]


Blood 2001 May 15;97(10):3268-74
Modifications in the CD36 binding domain of the Plasmodium falciparum variant antigen are responsible for the inability of chondroitin sulfate A adherent parasites to bind CD36.

Gamain B, Smith JD, Miller LH, Baruch DI.

Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD; and the Department of Pathology, Colorado State University, Fort Collins, CO.

Adhesion of mature Plasmodium falciparum parasitized erythrocytes to microvascular endothelial cells or to placenta contributes directly to the virulence and severe pathology of P falciparum malaria. Whereas CD36 is the major endothelial receptor for microvasculature sequestration, infected erythrocytes adhering in the placenta bind chondroitin sulfate A (CSA) but not CD36. Binding to both receptors is mediated by different members of the large and diverse protein family P falciparum erythrocyte membrane protein-1 (PfEMP-1) and involves different regions of the molecule. The PfEMP-1-binding domain for CD36 resides in the cysteine-rich interdomain region 1 (CIDR-1). To explore why CSA-binding parasites do not bind CD36, CIDR-1 domains from CD36- or CSA-binding parasites were expressed in mammalian cells and tested for adhesion. Although CIDR-1 domains from CD36-adherent strains strongly bound CD36, those from CSA-adherent parasites did not. The CIDR-1 domain has also been reported to bind CSA. However, none of the CIDR-1 domains tested bound CSA. Chimeric proteins between CIDR-1 domains that bind or do not bind CD36 and mutagenesis experiments revealed that modifications in the minimal CD36-binding region (M2 region) are responsible for the inability of CSA-selected parasites to bind CD36. One of these modifications, mapped to a 3-amino acid substitution in the M2 region, ablated binding in one variant and largely reduced binding of another. These findings provide a molecular explanation for the inability of placental sequestered parasites to bind CD36 and provide additional insight into critical residues for the CIDR-1/CD36 interaction. (Blood. 2001;97:3268-3274)

PMID: 11342458 [PubMed - in process]

Rev Soc Bras Med Trop 2001 Jan;34(1):43-47
Malaria in the State of Parana, Brazil

Bertoli M, Moitinho Md M.

Departamento de Analises Clinicas, Universidade Estadual de Maringa, Maringa, PR, Brasil.

To collect data regarding registered cases of malaria in the state of Parana, attendance reports of suspected cases of malaria performed by Fundacao Nacional de Saude, Parana regional center, were analyzed from January, 1994 through December, 1999. Of 31,975 blood samples examined, 7.4% were positive: 86.4% for Plasmodium vivax, 12.7% for P. falciparum, 0.04% for P. malariae and 0.9% for P. vivax and P. falciparum. As to the epidemiological classification, 84.5% represented heterochthonous cases and 15.5% represented autochthonous cases. The municipalities showing higher rates of autochthonous cases were Foz do Iguacu, Santa Terezinha do Itaipu and Santa Helena, a region influenced by the Itaipu reservoir, where prevention and control actions must be concentrated.

PMID: 11340496 [PubMed - as supplied by publisher]


Ann Trop Med Parasitol 2001 Apr;95(3):237-43
Madagascan isolates of Plasmodium falciparum showing low sensitivity to artemether in vitro.

Randrianarivelojosia M, Raharimalala LA, Randrianasolo L, Ratsimbasoa A, Rason MA, Ariey F, Jambou R.

Laboratoire de Paludisme, Institut Pasteur de Madagascar, B.P. 1274, (101) Antananarivo, Madagascar.

In Madagascar, although chloroquine (CQ) remains the first-line treatment of choice for malaria, the gradual spread of resistance to this antimalarial drug is of increasing concern. As part of a larger investigation of the effectiveness of the second- and third-line drugs used to treat malaria, the in-vitro susceptibilities of Plasmodium falciparum collected in Madagascar to CQ, mefloquine (MQ) and artemether (ART) were therefore investigated. Median inhibitory concentrations (IC(50)) were determined for isolates collected from residents of two villages in the foothills of the central highlands. The IC(50) for ART ranged from 0.23-17.50 nM [N = 51; geometric mean = 4.02 nM; 95% confidence interval (CI) = 2.99-5.05 nM], four isolates exhibiting IC(50) (> 12 nM) indicative of resistance to this drug. The artemether IC(50) were found to be correlated with those of CQ (N = 46; Spearman's r = 0.51; P = 0.0002), which varied widely (0.4-254.3 nM; mean = 23.4 nM; CI = 7.1-39.7 nM; N = 46). Five (11%) of the 46 isolates exposed to CQ in vitro were considered resistant to this drug (i.e. to have IC(50) > 100 nM), with IC(50) ranging from 109-245.3 nM (mean = 171.6 nM; CI = 110.4-232.8 nM). However, all the CQ-resistant isolates were considered sensitive to ART and vice versa. All the isolates tested also appeared sensitive to MQ (IC(50) = 2.21-43.1 nM; mean = 10.5 nM; CI = 7.95-13.07 nM; N = 46), the IC(50) for MQ being correlated with those for CQ (N = 46; Spearman's r =0.46; P = 0.001). There was no significant correlation between ART and MQ activities. Although the sample was fairly small, the present results indicate that P. falciparum in Madagascar is generally becoming less sensitive to CQ and ART. The observation of a correlation between the IC(50) for these two drugs perhaps indicates that artemisinin derivatives would be better used in combination with antimalarial drugs other than 4-aminoquinolines.

PMID: 11339883 [PubMed - in process]

East Mediterr Health J 1999 Jul;5(4):698-705

Bionomics of anopheline vectors in Zabid District, Al-Hodeidah Governorate, Republic of Yemen.

al-Maktari MT, Bassiouny HK.

Medical Parasitology and Entomology Department, Faculty of Medicine and Health Sciences, Sana'a University, Sana'a, Republic of Yemen.

The bionomics of anopheline vectors were analysed in randomly selected centres, representing fixed and spot-check stations. Three anopheline species were found. Anopheles arabiensis was the most prevalent species (84.2%) with a sporozoite rate of 0.7%, followed by A. culicifacies adenensis (14.9%) and A. rhodesiensis rupicolus (0.9%). Maximum indoor resting density was recorded during March, July and August. Positive sprayed sites for females were higher in bedrooms (40.4%) than animal sheds (26.9%). A total of 2560 anopheline larvae were collected of which 79.5% were A. arabiensis, 19.4% were A. culicifacies adenensis and 1.1% A. rhodesiensis rupicolus. A. arabiensis was assumed to be the most efficient malaria vector based on epidemiological evidence and the finding of natural sporozoite infected females.

PMID: 11338692 [PubMed - in process]
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Last modified September 21, 2001