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EHP Library Malaria Bulletin: April 6-19, 2001

Social Sciences and Malaria

Impact of asymptomatic malaria parasitaemia on cognitive function and school achievement of schoolchildren in the Yemen Republic.

Al Serouri AW.  Grantham-McGregor SM.  Greenwood B.  Costello A.
Institution Parasitology.  121 ( Pt 4):337-45, 2000 Oct.

Asymptomatic malaria parasitaemia is prevalent among schoolchildren in many countries. The relationship between asymptomatic parasitaemia and children's cognitive functions was examined in a case control study and then in a natural experiment. A group (n = 445) of asymptomatic parasitaemic boys were compared with a group of non-parasitaemic boys (n = 142) matched for grade and school on their performance on a battery of cognitive tests. Two weeks later the parasitaemic children were re-screened and 150 children of those who remained parasitaemic were matched for grade and school with 150 children who were no longer parasitaemic. These children were then re-tested and their cognitive function compared. Initially, after controlling for age, socio-economic background and nutritional status the parasitaemic children performed worse than the non-parasitaemic children in fine motor function tests. There was no difference in change in cognitive test scores between those who became non-parasitaemic and those who remained parasitaemic. However, children who initially had the highest parasite density improved the most in 2 fine motor tests and a picture memory test. We were unable to show a benefit from losing parasitaemia over a 2 week period, but it remains possible that parasitaemia may affect cognition and longer term trials should be conducted.

 

Cost analysis of malaria patients in Taikkyi Township Myanmar.

Lwin AM. Umenai T.
Asia-Pacific Journal of Public Health. 11(2):94-100, 1999.

A hospital and clinic-based study was conducted in one malaria endemic area, Taikkyi Township, Yangon Division, Myanmar, for analysis of cost incurred by different types of malaria cases and the factors influencing the cost of illness from July to October 1995. A total of 100 patients admitted to hospital and 100 patients receiving ambulatory care from malaria clinics were interviewed using a structured questionnaire. Total cost of one episode of malaria was estimated to be kyats 559 for ambulatory care, kyats 2582 for an uncomplicated admitted case, kyats 4056 for one episode of cerebral malaria, kyats 4568 for one episode of other severe and complicated malaria and kyats 4758 for one episode of malaria with other disease. This study showed that the cost of illness for patients attending outpatient malaria clinics who received early diagnosis and prompt treatment was four to seven times cheaper than the cost of illness for hospitalized malaria cases. Multivariate analysis revealed the factors that contributed to high cost of care. Duration of illness before getting any type of treatment was the key factor that contributed to high or low cost of care. Long duration of illness before getting any type of treatment can lead to high malaria parasite density, long duration of actual illness and high total attendance cost. Therefore, it is recommended that people from malaria endemic areas should be informed to seek early treatment from health staff, and primary health care services should be made accessible to people who live in malaria endemic areas. The information obtained from this study will be useful in planning future malaria control programs and influencing policy makers to focus on timely and effective treatment of non-severe cases, which can save a large amount of economic loss due to treatment of severe malaria.

 

Community knowledge and perceptions about malaria and practices influencing malaria control in Mpumalanga Province, South Africa.

Govere J. Durrheim D. la Grange K. Mabuza A. Booman M.
South African Medical Journal. 90(6):611-6, 2000 Jun.

OBJECTIVE: To assess community knowledge and perceptions about malaria and its control in a rural setting. DESIGN: Descriptive cross-sectional survey. SETTING: Tonga district with a population of 116,418, seasonal malaria with an annual incidence of 3,200 cases. SUBJECTS: Female heads of 299 randomly selected households. METHODOLOGY: A total of 299 households were selected from a random sample of 30 clusters. Community knowledge and perceptions about malaria and its control were assessed by interviews with the female head of each of the 299 selected households. RESULTS: Respondents ranked malaria as the third most serious health problem facing the community after TB and AIDS. Seventy-two per cent (214/299) of respondents reported that they knew what malaria disease was and of these, 92.1% (197/214) mentioned mosquito bites as the cause of malaria. The respondents' understanding of the causal role of mosquitoes in malaria was significantly related to their knowledge about disease symptoms (P < 0.001). Reported community compliance with the malaria control programme (MCP) was satisfactory; 86.6% (259/299) of respondents reported that their homes had been sprayed during the past 2 years but 10.0% (30/299) did not know why homes were sprayed. Hospitals or clinics were the facilities where respondents most commonly sought treatment for fever; 66.9% (200/299) reported that they would seek treatment immediately after the onset of high fever. Specific practices such as replastering or washing of inside walls compromised the effectiveness of the MCP. Personal preventive measures were sometimes used against malaria (50.8%, 152/299) and use was positively associated with education level (P = 0.001). Respondents expressed their desire for more information about malaria and their willingness to contribute to the control of malaria in their community. CONCLUSION: The survey collected information which was directly relevant to the development of health education messages to increase community awareness of the problem of malaria, to emphasise the importance of early diagnosis and prompt treatment of malaria, to improve community understanding of the function of indoor residual spraying, and to enlighten the population of the role of mosquitoes in malaria transmission and the availability and benefits of personal protection measures against mosquito bites.

 

Economic burden of malaria illness on households versus that of all other illness episodes: a study in five malaria holo-endemic Nigerian communities.

Onwujekwe O.  Chima R.  Okonkwo P.
Health Policy.  54(2):143-59, 2000 Nov 17.

We compared the financial and economic costs of malaria attack to that of a combination of other illness episodes on households in five malaria holo-endemic rural communities. The data was collected from household heads or their representatives using pre-tested interviewer-administered questionnaire. Information was collected on the amount of money household spent to treat both malaria and other illnesses respectively, together with the time lost due to both the groups of illnesses within 1 month prior to the interview. The findings showed that the cost of treating malaria illness accounted for 49.87% of curative health care costs incurred by the households. Average malaria expenditure was $1.84 per household per month, while it was $2.60 per month for the combination of other illness episodes. The average person-days lost due to malaria and the combination of other illnesses were almost equal. If the financial costs of treating malaria and other illnesses are combined, this cost will deplete 7.03% of the monthly average household income, with treatment of malaria illness alone depleting 2.91%. Thus, malaria is a big contributor to the economic burden of disease, in malaria holo-endemic communities. Community-effective malaria control programs are needed to reduce this burden on the households.

 

PubMed

Mol Pharmacol 2001 May;59(5):1298-1306
Diamidine Compounds: Selective Uptake and Targeting in Plasmodium falciparum.

Stead AM, Bray PG, Edwards IG, DeKoning HP, Elford BC, Stocks PA, Ward SA.
Department of Pharmacology and Therapeutics, The University of Liverpool, Liverpool, United Kingdom.

Extensive drug resistance in Plasmodium falciparum emphasizes the urgent requirement for novel antimalarial agents. Here we report potent antimalarial activity of a number of diamidine compounds. The lead compound pentamidine is concentrated 500-fold by erythrocytes infected with P. falciparum. Pentamidine accumulation can be blocked by inhibitors of hemoglobin digestion, suggesting that the drug binds to ferriprotoporphyrin IX (FPIX). All of the compounds bound to FPIX in vitro and inhibited the formation of hemozoin. Furthermore, inhibitors of hemoglobin digestion markedly antagonized the antimalarial activity of the diamidines, indicating that binding to FPIX is crucial for the activity of diamidine drugs. Pentamidine was not accumulated into uninfected erythrocytes. Pentamidine transport into infected cells exhibits an initial rapid phase, nonsaturable in the micromolar range and sensitive to inhibition by furosemide and glibenclamide. Changing the counter-ion in the order Cl(-) < Br(-) < NO(2)(-) < I(-) <SCN(-) markedly stimulated pentamidine transport. These data suggest that pentamidine is transported although a pore or ion channel with properties similar to those of the recently characterized 'induced permeability pathway' on the infected red cell membrane. In summary, the diamidines exhibit two levels of selectivity against P. falciparum. The route of entry and molecular target are both specific to malaria-infected cells and are distinct from targets in other protozoa. Drugs that target the hemoglobin degradation pathway of malaria parasites have a proven record of accomplishment. The employment of induced permeability pathways to access this target represents a novel approach to antiparasite chemotherapy and offers an additional level of selectivity.

PMID: 11306715 [PubMed - as supplied by publisher]

 

Bull Mem Acad R Med Belg 2000;155(5-6):218-26
Natural history of Plasmodium falciparum malaria and determining factors of the acquisition of antimalaria immunity in two endemic areas, Dielmo and Ndiop (Senegal).

Rogier C.
Laboratoire d'epidemiologie du paludisme, Institut Pasteur de Dakar, Senegal.
 
Development of new anti malaria strategies and particularly vaccines, needs an in-depth understanding of the relationships between transmission, infection, immunity, morbidity and mortality. The intensive and longitudinal collection of entomological, parasitological and clinical data from the Senegalese populations of Dielmo (250-300 inhab.), exposed to a perennial and intense transmission (about 200 infective bites/person/year) and of Ndiop (300-350 inhab.), exposed to a seasonal transmission (about 20 infective bites/person/year), allows to respond to many questions about this subject. The existence of a pyrogenic threshold effect of parasitaemia allows the individual diagnosis of malaria attacks. The initial intensity of clinical manifestations does not differ perceptibly among children and adults, is not related to the duration of the attacks, is not predictive of their severity, and the clearance of parasites and manifestations is longer among youngest persons. The risk of malaria attacks is lower as one gets older and among carriers of AS haemoglobin, is higher when transmission increases and during pregnancy up to three month after delivery, and vary between children. The risk of malaria attack per infective bite is negatively related to the intensity of transmission. Because of their high sensitivity in malaria case detection, this type of small community-based studies are powerful and useful for the identification of protective immunological mechanisms as well as for testing rapidly and cheaply the clinical efficacy of any intervention such as antimalarial vaccines and drug therapy or prophylaxis.
 
PMID: 11304957 [PubMed - in process]

 

Indian J Malariol 1999 Mar-Jun;36(1-2):42-8
A controlled study on haemograms of malaria patients in Calcutta.
Biswas R, Sengupta G, Mundle M.
All India Institute of Hygiene and Public Health, 110 Chittaranjan Avenue, Calcutta-700 073, India.
 
A study was carried out at the Urban Health Centre, Chetla, Calcutta to evaluate the efficacy of quantitative buffy coat (QBC) analysis of haemograms in malaria patients suffering from fever with bodyache and chill and/or rigour attending the Fever Treatment Depot during a three months period (March-June 1996) who had undergone both malaria parasite study and haematological investigation by the QBC method from blood samples collected by finger prick. To avoid bias, malaria parasite studies and haemograms were done separately, and investigators were kept 'blind' about the results of other investigations. The haematological findings obtained of 180 slide-positive malaria cases were compared with a sample of 177 age- and sex-matched slide-negative controls selected by random sampling. The results revealed that haemoglobin levels (g%), haematocrit values (%), WBC and platelet counts of malaria cases were significantly lower than in the matched controls. Thus, QBC estimation correlates well with existing knowledge about malarial haematology. This relatively easier, quicker and reliable method of taking haemograms may be recommended for field testing for assessing haematological parameters of malaria cases under field conditions, before its introduction for large-scale use.
 
PMID: 11304918 [PubMed - in process]
 

Indian J Malariol 1999 Mar-Jun;36(1-2):33-41
Patterns of parasitaemia, antibodies, complement and circulating immune complexes in drug-suppressed simian Plasmodium knowlesi malaria.

Biswas S.
Malaria Research Centre (ICMR), 22 Sham Nath Marg, Delhi-110 054, India.
 
Rhesus monkeys were inoculated intravenously with 1 x 10(4) P. knowlesi infected erythrocytes. After about three days prepatency, peripheral smears were found positive and the animals were cured with chloroquine phosphate when parasitaemia reached about 15-25 per cent. The monkeys were repeatedly exposed with three bouts of infection. The first and second bouts were cured but after the third challenge, all 10 monkeys showed a longer prepatent period, lower parasitaemia and then self-recovery. Sera were collected in different phases of infection to assess immune responses. Antimalarial IgG and IgM responses were measured by ELISA. The presence of IgM antibody was associated with every bout of infection. With repeated infections until self-recovery, a substantial amount of IgG was found in circulation. A significant level of schizont-infected cell agglutination antibody was also detected in the animals after survival from challenge infection. Antigen-specific circulating immune complexes, both of IgG and IgM types, appeared in various phases of infection, but their appearance did not coincide with the acquired immune responses of the animals. During the self-recovery phase, almost all monkeys had an elevated level of serum C3 and C4.
 
PMID: 11304917 [PubMed - in process]
 

Indian J Malariol 1999 Mar-Jun;36(1-2):12-8
Naturally occurring plasmodia-specific circulating immune complexes in individuals of malaria endemic areas in India.

Tyagi P, Biswas S.
Malaria Research Centre, 22 Sham Nath Marg, Delhi-110 054, India.

Blood samples collected from individuals belonging to malaria endemic areas were assayed for antigen-specific circulating immune complexes in polyethylene glycol precipitates of serum by enzyme immunoassay. Sera were tested from patients with acute P. vivax and P. falciparum infections, from clinically immune individuals and also from healthy normals. Circulating immune complexes (CICs) containing immunoglobulin G and M isotypes were found to be abundant in individuals with ongoing and past infections and also in clinically immune donors. In patients with acute infection but without any past history of malaria, CICs of IgM type were found to be significantly higher. Demonstration of antigen/antibody specific CICs could be a useful indicator of active, ongoing and recent/past infection, also of the status of immune responses of individuals belonging to various endemic areas.

PMID: 11304915 [PubMed - in process]

 

Am J Trop Med Hyg 2000 Jun;62(6):726-32
Dry season refugia of malaria-transmitting mosquitoes in a dry savannah zone of east Africa.

Charlwood JD, Vij R, Billingsley PF.
Department of Entomology, University of Wageningen, The Netherlands. [email protected]
 
Dry season survival of Anopheles funestus, Anopheles gambiae and Anopheles arabiensis in the Kilombero valley a dry savannah zone of east Africa, was investigated with over 400 collections from 23 areas, covering 300 sq km of the valley. Anopheles gambiae was found only in association with humans, in forested areas of high annual rainfall, while An. funestus occurred at high densities at the valley edge where large non-moving bodies of water remained. A large population of An. arabiensis was present along the river system throughout the middle of the valley, and mosquitoes probably derived from this population were occasionally caught in villages bordering the valley. No evidence was obtained of aestivation in any mosquito species. Anopheles gambiae was the most long lived, 6.3% compared to 2.0% of the An. arabiensis and 4% of the An. funestus surviving for four or more gonotrophic cycles, the approximate duration of the extrinsic cycle of most malaria parasites. Oocysts of malaria parasites were found in 5.4% of An. funestus and 2.3% of An. arabiensis from villages. Oocyst rates in An. funestus differed significantly between areas but not between houses within areas. Anopheles funestus is the most important dry season malaria vector in the valley, and remains in foci closely associated with groups of houses. All three species survive at high densities but as otherwise hidden refugia populations.
 
PMID: 11304064 [PubMed - in process]
 

Am J Trop Med Hyg 2000 Jun;62(6):693-7
Assessing drug sensitivity of Plasmodium vivax to halofantrine or choroquine in southern, central Vietnam using an extended 28-day in vivo test and polymerase chain reaction genotyping.

Taylor WR, Doan HN, Nguyen DT, Tran TU, Fryauff DJ, Gomez-Saladin E, Kain KC, Le DC, Baird JK.
US NAMRU-2, Jakarta, Indonesia.
 
Chloroquine-resistant Plasmodium vivax malaria is emerging in Oceania, Asia, and Latin America. We assessed the drug sensitivity of P. vivax to chloroquine or halofantrine in two villages in southern, central Vietnam. This area has chloroquine-resistant Plasmodium falciparum but no documented chloroquine-resistant P. vivax. Standard dose chloroquine (25 mg/kg, over 48 hours) or halofantrine (8 mg/kg, 3 doses) was administered to 29 and 25 patients, respectively. End points were parasite sensitivity or resistance determined at 28 days. Of the evaluable patients, 23/23 100% (95% confidence interval [CI] 85.1-100) chloroquine and 21/24 (87.5%) (95% CI 67.6-97.3) halofantrine-treated patients were sensitive. Three halofantrine recipients had initial clearance but subsequent recurrence of their parasitemias. Genotyping of the recurrent and Day 0 parasitemias differed, suggesting either new infections or relapses of liver hypnozoites from antecedent infections. Among these Vietnamese patients, P. vivax was sensitive to chloroquine and halofantrine. Genotyping was useful for differentiating the recurrent vivax parasitemias.
 
PMID: 11304056 [PubMed - in process]
 

Am J Trop Med Hyg 2000 Jun;62(6):686-92
Predictors of chloroquine treatment failure in children and adults with falciparum malaria in Kampala, Uganda.

Dorsey G, Kamya MR, Ndeezi G, Babirye JN, Phares CR, Olson JE, Katabira ET, Rosenthal PJ.
Department of Medicine, San Francisco General Hospital and The University of California 94143-0811, USA.
 
Chloroquine-resistant falciparum malaria is a serious problem in much of sub-Saharan Africa. However, it is desirable to continue to use chloroquine as first-line therapy for uncomplicated malaria where it remains clinically effective. To identify predictors of chloroquine treatment failure, a 14-day clinical study of chloroquine resistance in patients with uncomplicated falciparum malaria was performed in Kampala, Uganda. Among the 258 patients (88% follow-up), 47% were clinical failures (early or late treatment failure) and 70% had parasitological resistance (RI-RIII). Using multivariate analysis, an age less than five (odds ratio [OR] = 3.4, 95% CI = 1.8-6.3) and a presenting temperature over 38.0 degreesC (OR = 2.0, 95% CI = 1.1-3.7) were independent predictors of treatment failure. In addition, patients who last took chloroquine 3 to 14 days prior to study entry were significantly more likely to be treatment failures compared to patients with very recent (less than 3 days) or no recent chloroquine use. In areas with significant chloroquine resistance, easily identifiable predictors of chloroquine treatment failure might be used to stratify patients into those for whom chloroquine use is acceptable and those for whom alternative treatment should be used.
 
PMID: 11304055 [PubMed - in process]
 

Am J Trop Med Hyg 2000 Jun;62(6):670-4
Severe anemia in young children after high and low malaria transmission seasons in the Kassena-Nankana district of northern Ghana.

Koram KA, Owusu-Agyei S, Utz G, Binka FN, Baird JK, Hoffman SL, Nkrumah FK.
Noguchi Memorial Institute for Medical Research, University of Ghana, Legon. [email protected]
 
Malaria and anemia accounted for 41% and 18% respectively of hospital deaths in the Kassena-Nankana district of northern Ghana during 1996. We measured hemoglobin (Hb), malaria prevalence, and anthropometric indices of 6--24-month-old infants and young children randomly selected from this community at the end of the high (May-October, n = 347) and low (November-April, n = 286) malaria transmission seasons. High transmission season is characterized by rainfall (the equivalent of 800-900 mm/yr.), while the remaining months receive less than 50 mm/yr. Severe anemia, defined as Hb < 6.0 g/dL, was 22.1% at the end of the high transmission season compared to 1.4% at the end of the low transmission season (Odds Ratio [OR] = 20.1; 95% CI: 7.1-55.3). Parasitemia was 71% and 54.3% at these time points (OR = 2.1; 95% CI: 1.5-2.9). Nutritional anemia appeared to have little impact upon this seasonal difference since anthropometric indices were comparable. Although the relative contributions of other causes of severe anemia were not assessed, repeated malaria infections may be a primary determinant of severe anemia among infants and young children during the high transmission season.
 
PMID: 11304052 [PubMed - in process]
 

Am J Trop Med Hyg 2000 Jun;62(6):663-9
The influence of zinc supplementation on morbidity due to Plasmodium falciparum: a randomized trial in preschool children in Papua New Guinea.

Shankar AH, Genton B, Baisor M, Paino J, Tamja S, Adiguma T, Wu L, Rare L, Bannon D, Tielsch JM, West KP Jr, Alpers MP.
Department of International Health, Johns Hopkins School of Hygiene and Public Health, Baltimore, Maryland 21205, USA.
 
Zinc is crucial for normal immune function and can reduce morbidity from multiple infectious diseases. To determine the influence of zinc on malaria morbidity we conducted a randomized placebo-controlled trial of daily zinc supplementation in children residing in a malaria endemic region of Papua New Guinea. A total of 274 preschool children aged 6 to 60 months were given 10 mg elemental zinc (n = 136) or placebo (n = 138) for 6 days a week for 46 weeks. Slide-confirmed malaria episodes were detected by surveillance of cases self-reporting to a local health center. Cross-sectional surveys were conducted at the beginning, middle, and end of the study to assess infection rates, parasite density, spleen enlargement, and hemoglobin levels. Zinc supplementation resulted in a 38% (95% CI 3-60, P = 0.037) reduction in Plasmodium falciparum health center-based episodes, defined as parasitemia > or = 9200 parasites/microl with axial temperature > or = 37.5 degreesC or reported fever. Episodes accompanied by any parasitemia were also reduced by 38% (95% CI 5-60, P = 0.028), and episodes with parasitemia > or = 100,000/microl were reduced by 69% (95% CI 25-87, P = 0.009). There was no evidence of the effects of zinc on Plasmodium vivax morbidity or on health center attendance for causes other than P. falciparum. Zinc had no consistent effect on cross-sectional malariometric indices. Although P. falciparum prevalence tended to be lower at the end of the study in children given the placebo, such changes were absent at the mid-study survey. These results suggest that improved dietary zinc intake may reduce morbidity due to P. falciparum.
 
PMID: 11304051 [PubMed - in process]
 

J Med Chem 2001 Mar 15;44(6):873-85
Inhibition of heme detoxification processes underlies the antimalarial activity of terpene isonitrile compounds from marine sponges.

Wright AD, Wang H, Gurrath M, Konig GM, Kocak G, Neumann G, Loria P, Foley M, Tilley L.
Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, Bonn 53115, Germany. 
[email protected]
 
A series of terpene isonitriles, isolated from marine sponges, have previously been shown to exhibit antimalarial activities. Molecular modeling studies employing 3D-QSAR with receptor modeling methodologies performed with these isonitriles showed that the modeled molecules could be used to generate a pharmacophore hypothesis consistent with the experimentally derived biological activities. It was also shown that one of the modeled compounds, diisocyanoadociane (4), as well as axisonitrile-3 (2), both of which have potent antimalarial activity, interacts with heme (FP) by forming a coordination complex with the FP iron. Furthermore, these compounds were shown to inhibit sequestration of FP into beta-hematin and to prevent both the peroxidative and glutathione-mediated destruction of FP under conditions designed to mimic the environment within the malaria parasite. By contrast, two of the modeled diterpene isonitriles, 7-isocyanoamphilecta-11(20),15-diene (12) and 7-isocyano-15-isothiocyanatoamphilecta-11(20)-ene (13), that displayed little antimalarial activity also showed little inhibitory activity in these FP detoxification assays. These studies suggest that the active isonitrile compounds, like the quinoline antimalarials, exert their antiplasmodial activity by preventing FP detoxification. Molecular dynamics simulations performed with diisocyanoadociane (4) and axisonitrile-3 (2) allowed their different binding to FP to be distinguished.
 
PMID: 11300869 [PubMed - as supplied by publisher]
 

Ann Trop Med Parasitol 2001 Mar;95(2):133-40
Low incidence of the severe complications of malaria and absence of malaria-specific mortality, in Tensa, Sundergarh district, Orissa state, India, an area hyper-endemic for malaria.

Prusty SK, Das BS.
BIM Hospital, Tensa, Sundergargh, Orissa, India.
 
The incidence of severe malaria and malaria-specific mortality were investigated in a hospital, for miners and their families, at Tensa in the Sundergarh district of Orissa state in India. Tensa lies in area where malaria (predominantly caused by Plasmodium falciparum) is hyper-endemic. The hospital records for 1995-1999 showed that, although annual admissions for malaria increased over the study period, there were very few admissions for severe, complicated malaria and no reports of malaria-specific deaths. Most of the patients who had been admitted with cerebral malaria either came from areas around but not within the town of Tensa or were recent arrivals in the town. It appears that the outcome of malaria is influenced not only by the intensity of local transmission (which affects the immunological status of the human hosts) but also by social factors such as the education and health-seeking behaviour of the local population and the health-care facilities available. The low incidence of severe malaria observed in Tensa was probably the result of patients presenting early in the course of their illness and taking antimalarial treatment, iron supplementation and supportive therapy at the appropriate times.
 
PMID: 11299120 [PubMed - in process]

 

Ann Trop Med Parasitol 2001 Mar;95(2):117-32
Geographical patterns of allelic diversity in the Plasmodium falciparum malaria-vaccine candidate, merozoite surface protein-2.

Hoffmann EH, da Silveira LA, Tonhosolo R, Pereira FJ, Ribeiro WL, Tonon AP, Kawamoto F, Ferreira MU.
Department of Parasitology, Institute for Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil.
 
The polymorphic merozoite surface protein-2 (MSP-2) of Plasmodium falciparum is a major malaria-vaccine candidate. In the present study, PCR and hybridization with allelic-specific probes were used to type the Msp-2 gene from isolates from hypo-endemic Brazil (N = 113), meso-endemic Vietnam (N = 208) and holo-endemic Tanzania (N = 67). The typing methods were designed to group isolates into the dimorphic allelic families FC27 and IC1 and to detect possible between-family recombination events. The analysis was complemented by a comparison of 156 Msp-2 sequences from the GenBank database with 12 additional sequences obtained during the present study. Statistically significant differences were detected in pair-wise comparisons of the distribution of Msp-2 allelic types in Brazil and Vietnam, and in Brazil and Tanzania, but not in Vietnam and Tanzania. The extent of allelic diversity in the Msp-2 gene, as estimated by the total number of different alleles found in a given parasite population and the mean multiplicity of infections, clearly paralleled the levels of malaria endemicity in the study areas. However, no correlation between age and multiplicity of infections was found in the subjects. The patterns of Msp-2 diversity in Brazil appeared to be temporally stable, since no significant difference was observed in the distribution of Msp-2 allelic types among isolates collected, 10-13 years apart, in the same area of Rondonia. Despite the extensive sequence diversity found in Msp-2 alleles, especially in the central repetitive region of the molecule, several instances of identical or nearly identical alleles were found among isolates from different countries and regions, possibly as a result of extensive homoplasy. No recombinant allele was detected by molecular typing in any of the study sites, and the GenBank database included only 12 recombinant sequences (representing 7% of all reported Msp-2 sequences), all of them with an IC1-type 5' end and an FC27-type 3' end. A single, putative, crossover site was characterised for all recombinant alleles. Most of the allelic diversity observed was therefore attributable to variation in the repetitive region of the gene, instead of recombination between alleles of dimorphic families (as commonly found, for example, in the Msp-1 gene). The implications of these findings for studies on the genetic and antigenic diversity of malarial parasites are discussed.
 
PMID: 11299119 [PubMed - in process]
 

Trop Med Int Health 2001 Mar;6(3):196-201
Rapid therapeutic response onset of a new pharmaceutical form of chloroquine phosphate 300 mg: effervescent tablets.

Yanze MF, Duru C, Jacob M, Bastide JM, Lankeuh M.
Laboratoire de Galenique, Pharmacotechnie et Biopharmacie, UFR de sciences pharmaceutiques, Universite de Montpellier I, France. [email protected]
 
OBJECTIVE: To compare the efficiency, safety and taste of two pharmaceutical forms of chloroquine phosphate 300 mg: effervescent tablets against uncoated tablets. METHOD: An open randomized study with 60 adults who suffered from acute uncomplicated Plasmodium falciparum malaria in three health centres in Nkongsamba health district, Cameroon. RESULTS: Mean times to fever clearance, symptoms clearance and asexual parasites clearance were longer in the uncoated tablets group: 36 h (range 24-48 h, SD = 16.8) vs. 60 h (range 24-96 h, SD = 31.2, P = 0.001) for fever clearance, 36 h (24-48 h, SD = 16.8) vs. 48 h (24-72, SD = 24, P = 0.001) for symptoms clearance and 48 h (24-72, SD = 1) vs. 72 h (48-96, SD = 24, P = 0.001) for parasitaemia clearance. Uncoated tablets took significantly longer to achieve 50% reduction of the initial asexual parasite density: (mean/SD) 19.2 h/7 vs. 52.8 h/16.8, P < 0.00001. The adverse effects in the two groups were similar, P > 0.05. The cure rate at day 7 in the two groups was similar, P > 0.05. There was no chloroquine resistance in the effervescent tablets group but one RI and one RII resistance in the uncoated tablets group. The taste of the two pharmaceutical forms was significantly different, P < 0.00001. Effervescent tablets tasted sweet (score = 7.93), whereas uncoated tablets were bitter (score = 2.07). CONCLUSION: Effervescent tablets of chloroquine phosphate 300 mg work faster than uncoated tablets and because of their safe use and sweet taste achieve good therapeutic compliance.
 
PMID: 11299036 [PubMed - in process]
 

Cytokine 2001 Apr 7;14(1):11-8
The role of tumour necrosis factor-alpha in the pathogenesis of complicated falciparum malaria.

Odeh M.
Department of Internal Medicine, Bnai Zion Medical Center, Haifa, Israel
 
Plasmodium falciparum malaria is the most important parasitic infection of humans and is one of the most serious health problems facing the inhabitants of developing countries. It is responsible for about 2 million deaths every year. To date there is no specific treatment for the disease apart from anti-malarials. The declining sensitivity to these drugs is a serious therapeutic problem, while no safe and effective vaccine is likely to be available for general use in the near future. There is now abundant laboratory and clinical evidence to suggest that tumour necrosis factor-alpha (TNF-alpha) plays a major role in the pathogenesis of complicated falciparum malaria. Modulation of TNF-alpha response in combination with the current anti-malarial drugs, may represent a novel approach to the treatment of the serious complications associated with the disease. Copyright 2001 Academic Press.
 
PMID: 11298488 [PubMed - in process]

 

Med Vet Entomol 2001 Mar;15(1):97-104
Olyset Net efficacy against pyrethroid-resistant Anopheles gambiae and Culex quinquefasciatus after 3 years' field use in C te d'Ivoire.

N'Guessan R, Darriet F, Doannio JM, Chandre F, Carnevale P.
Institute Pierre Richet, Bouake, C te d'Ivoire.
 
Pyrethroid-impregnated bednets are advocated for personal protection against malaria vectors. To avoid the need for periodic re-treatment, it would be advantageous to have nets that retain insecticidal efficacy for years and withstand repeated washing. Such a type of commercially produced bednet with permethrin 2% incorporated in polyethylene fibres (trademark Olyset Net supplied by Sumika Life-Tech Co., Osaka, Japan) was evaluated against mosquitoes in veranda-trap huts at Yaokoffikro, near Bouake, C te d'Ivoire, by standard WHOPES phase II procedures. Four Olyset Nets were compared with a standard untreated polyester net as control. They comprised three examples previously used in a village for over 3 years (one washed, one dirty, one very dirty) and a previously unused Olyset Net, newly unwrapped, from the same original batch. Bioassays with 3 min exposure of susceptible Anopheles gambiae Giles (Diptera: Culicidae) gave >99% mortality of female mosquitoes tested on the 'new' Olyset Net. The used Olyset Nets gave mortality rates averaging 83% for the washed net, 85% for the dirty net and 55% for the very dirty net (within 24-h following 3 min exposure). Thus, Olyset Nets were found to remain remarkably effective against susceptible An. gambiae for at least 3 years under field conditions. Wild pyrethroid-resistant populations of Culex quinquefasciatus Say and An. gambiae (savanna cytotype with 96% kdr) were assessed during June-August 1999 for their responses to sleepers protected by nets in the experimental huts. With regard to hut entry by foraging female mosquitoes, Olyset Nets showed some deterrency against An. gambiae (44% reduction by the new net, approximately 20% by the dirty nets, none by the washed net), but not against Cx. quinquefasciatus. Among mosquitoes entering the hut with untreated control net, 30-34% tried to leave (exophily) but were caught in the verandah trap. The permethrin repellency of Olyset Nets increased exophily by 19% for An. gambiae and 14% for Cx. quinquefasciatus. Blood-feeding rates were 16% An. gambiae and 35% Cx. quinquefasciatus in the hut with sleeper under the untreated net (showing considerable prevention of biting), 22-26% of both species in huts with washed or dirty used Olyset Nets (not significantly different from control), while the biting success rate of Cx. quinquefasciatus (but not kdr An. gambiae) was more than halved by the 'new' Olyset Net. Mortality rates of pyrethroid-resistant An. gambiae and Cx. quinquefasciatus from the huts were, respectively, 3% and 8% with the untreated polyester net, 27.5% and 17% with the 'new' Olyset, 15% and 17.5% with the washed Olyset, 16-25% and 17-20% with dirty old Olyset Nets. Kill differences between nets are significantly different for both An. gambiae and Cx. quinquefasciatus. Unfortunately the washed used Olyset Net showed least activity against resistant mosquitoes, despite its greatest activity against susceptible An. gambiae. In each case there was evidence that a high proportion of mosquitoes failed to feed through the net (many of them dying from starvation when they could not leave the closed hut), with indications that dirty Olyset nets enhanced this protective value.
 
PMID: 11297108 [PubMed - in process]
 

Med Vet Entomol 2001 Mar;15(1):58-63
Quantification of pyrethroid insecticides from treated bednets using a mosquito recombinant glutathione S-transferase.

Enayati AA, Vontas JG, Small GJ, McCarroll L, Hemingway J.
Cardiff School of Biosciences, Cardiff University, Wales, UK.
 
Recombinant glutathione S-transferase (agGST1-6) from the malaria vector mosquito Anopheles gambiae Giles (Diptera: Culicidae) was expressed in Escherichia coli using a pET3a vector system. The expressed enzyme was biochemically active with reduced glutathione (GSH) and 1-chloro-2,4-dinitrobenzene (CDNB). Activity of agGST1-6 with GSH and CDNB was inhibited to different degrees by both alpha-cyano and non-alpha-cyano pyrethroid insecticides. This inhibition was used to develop an assay for quantification of pyrethroids. Standard curves of insecticide concentration against percentage of enzyme inhibition or volume of iodine solution were established by spectrophotometry and iodine volumetric titration, respectively, for permethrin and deltamethrin. These assays allowed estimation of pyrethroid concentrations both spectrophotometrically and visually. For the residue assay of each insecticide, a cut-off point of 50% of the initial pyrethroid impregnation concentration was used, which should differentiate between biologically active and inactive treated bednets. The cross-reactivity of the primary permethrin photodegradants (3-phenoxyalcohol and 3-phenoxybenzoic acid) with the recombinant agGST1-6 was assayed in the same system. No agGST1-6 inhibition by the insecticide metabolites was observed, suggesting that the system is unaffected by primary permethrin metabolites and will accurately measure insecticide parent compound concentrations. The estimated pyrethroid insecticide concentrations, given spectrophotometrically and by iodine titration assay, were comparable to those obtained by direct HPLC quantification of residues extracted from bednets. Hence, it should be relatively easy to adapt this method to produce a test kit for residue quantification in the field.
 
PMID: 11297102 [PubMed - in process]
 

Med Vet Entomol 2001 Mar;15(1):105-12
Combined pyrethroid and carbamate 'two-in-one' treated mosquito nets: field efficacy against pyrethroid-resistant Anopheles gambiae and Culex quinquefasciatus.

Guillet P, N'Guessan R, Darriet F, Traore-Lamizana M, Chandre F, Carnevale P.
Institut Pierre Richet, Bouake, C te d'Ivoire. 
[email protected]
 
A new approach is proposed in the treatment of mosquito nets, using a 'two-in-one' combination of pyrethroid and non-pyrethroid insecticides applied to different parts of bednets. The objectives are mainly to overcome certain limitations of pyrethroid-impregnated bednets currently recommended for malaria control purposes. Apart from developing alternatives to pyrethroid dependency, we sought to counteract pyrethroid irritant effects on mosquitoes (excito-repellency) and resistance to pyrethroids. The idea takes advantage of the presumed host-seeking behaviour of mosquitoes confronted by a net draped over a bed, whereby the mosquito may explore the net from the top downwards. Thus, nets could be more effective if treated on the upper part with residual non-irritant insecticide (carbamate or organophosphate) and with a pyrethroid on the lower part. Sequential exposure to different insecticides with distinct modes of action is equivalent to the use of a mixture as a potential method of managing insecticide resistance. We also intended to improve the control of nuisance mosquitoes, especially Culex quinquefasciatus Say (Diptera: Culicidae) that often survive pyrethroids, in order to encourage public compliance with use of insecticide-treated nets (ITNs). Polyester bednets were pretreated with residual pyrethroid (bifenthrin 50 mg/m2 or deltamethrin 25 mg/m2) on the lower half and with carbamate (carbosulfan 300 mg/m2) on the upper half to minimize contact with net users. Unreplicated examples of these 'two-in-one' treated nets were field-tested against wild mosquitoes, in comparison with an untreated net and bednets treated with each insecticide alone, including PermaNet wash-resistant formulation of deltamethrin 50 mg/m2. Overnight tests involved volunteers sleeping under the experimental bednets in verandah-trap huts at Yaokofikro, near Bouake in C te d'Ivoire, where the main malaria vector Anopheles gambiae Giles, as well as Culex quinquefasciatus Say, are highly resistant to pyrethroids. Efficacy of these ITNs was assessed in the huts by four entomological criteria: deterrency and induced exophily (effects on hut entry and exit), blood-feeding and mortality rates (immediate and delayed). Overall, the best impact was achieved by the bednet treated with carbosulfan alone, followed by 'two-in-one' treatments with carbosulfan plus pyrethroid. Blood-feeding rates were 13% An. gambiae and 17% Cx. quinquefasciatus in huts with untreated nets, but only 3% with carbosulfan ITNs, 7-11% with combined ITN treatment, 6-8% An. gambiae and 12-14% Cx. quinquefasciatus with pyrethroid alone. Mosquitoes that entered the huts were killed sooner by nets with combined treatment than by pyrethroid alone. Mortality-rates in response to ITNs with carbosulfan (alone or combined with pyrethroid) were significantly greater for Cx. quinquefasciatus, but not for An. gambiae, compared to ITNs with only pyrethroid. About 20% of sleepers reported potential side-effects (headache and/or sneezing) from use of ITN treated with carbosulfan alone. Further development of this new 'two-in-one' ITN concept requires a range of investigations (choice of effective products, cost-benefit analysis, safety, etc.) leading to factory production of wash-resistant insecticidal nets treated with complementary insecticides.
 
PMID: 11297094 [PubMed - in process]
 

Med Vet Entomol 2001 Mar;15(1):1-11
Impact of irrigation on malaria in Africa: paddies paradox.

Ijumba JN, Lindsay SW.
Tropical Pesticides Research Institute, Arusha, Tanzania. [email protected]
 
The high population growth rate of the African continent has led to an increased demand for food and is in danger of outstripping agricultural production. In order to meet this need, many governments have sought ways of improving food production by initiating large-scale irrigation projects, involving reclamation of arid and semi-arid areas for the cultivation of crops. Although crop irrigation promises one solution to alleviating hunger and encourages economic growth, irrigation has often been blamed for aggravating disease in local communities. Malaria is one of the major tropical diseases associated with irrigation schemes, and changes in the transmission pattern of this disease following irrigation development have been a perennial subject of debate. It has often been assumed that high numbers of malaria vector Anopheles mosquitoes (Diptera: Culicidae) resulting from irrigation schemes lead inevitably to increased malaria in local communities. However, recent studies in Africa have revealed a more complex picture. Increased numbers of vectors following irrigation can lead to increased malaria in areas of unstable transmission, where people have little or no immunity to malaria parasites, such as the African highlands and desert fringes. But for most of sub-Saharan Africa, where malaria is stable, the introduction of crop irrigation has little impact on malaria transmission. Indeed, there is growing evidence that for many sites there is less malaria in irrigated communities than surrounding areas. The explanation for this finding is still unresolved but, in some cases at least, can be attributed to displacement of the most endophilic and anthropophilic malaria vector Anopheles funestus Giles by An. arabiensis Patton with lower vectorial capacity, as the latter thrives more than the former in ricefields. Similarly, among members of the An. gambiae complex, some cytotypes of An. gambiae sensu stricto are more vectorial than others. For example, the Mopti form has high vectorial capacity and breeds perennially in irrigated sites, whereas the savanna form is often sympatric but more seasonal. Also we suggest that many communities near irrigation schemes benefit from the greater wealth created by these schemes. Consequently irrigation communities often have greater use of bednets, better access to improved healthcare and receive fewer infective bites compared with those outside such development schemes. Thus, in most cases, irrigation schemes in Africa do not appear to increase malaria risk, except in areas of unstable transmission. However, developers should take the opportunity to improve health-care facilities for local communities when planning irrigation schemes wherever they occur.
 
PMID: 11297093 [PubMed - in process]
 

J Med Entomol 2001 Mar;38(2):341-3
Occurrence of Anopheles hermsi (Diptera: Culicidae) in Arizona and Colorado.

Hayden CW, Fink TM, Ramberg FB, Mare JC, Mead DG.
Department of Veterinary Science and Microbiology, University of Arizona, Tucson 85721, USA.
 
Historically, malaria was a significant cause of morbidity and mortality throughout the western United States, and Anopheles freeborni Aitken was thought to be the vector west of the Continental Divide. In 1989, Anopheles hermsi Barr & Guptavanij was described and subsequently found to be an effective laboratory vector of Plasmodium. The adults of these two species are morphologically indistinguishable, and therefore polymerase chain reaction was used to analyze the DNA from 48 mosquitoes collected in Arizona and Colorado (identified morphologically as An. freeborni). All specimens were identified as An. hermsi. This was the first report of An. hermsi in Arizona and Colorado and indicated that this Anopheles species historically may have been a malaria vector in these two western states.
 
PMID: 11296846 [PubMed - in process]
 

J Med Entomol 2001 Mar;38(2):242-4
Attraction of Anopheles (Diptera: culicidae) to volatile chemicals in Western Kenya.

Murphy MW, Dunton RF, Perich MJ, Rowley WA.
Department of Entomology, Iowa State University, Ames 50011, USA.
 
Anopheles gambiae s.l. and Anopheles funestus Giles are the primary vectors of malaria in East Africa. Identification of host-location olfactory cues may increase trap sensitivity for vector control and surveillance programs. Solid-state army miniature light traps were operated near sleeping humans in huts at night without lights and augmented with the potential attractants: L-lactic acid, Limburger cheese volatiles, hexanoic acid, and carbon dioxide. Mosquito response varied between species and gender. Female An. funestus exhibited a greater response to traps baited with L-lactic acid in combination with carbon dioxide than carbon dioxide alone in two different experiments.
 
PMID: 11296830 [PubMed - in process]
 

Mol Biochem Parasitol 2001 Apr;113(2):271-8
Gene targeting in the rodent malaria parasite Plasmodium yoelii.

Mota MM, Thathy V, Nussenzweig RS, Nussenzweig V.
Michael Heidelberger Division, Department of Pathology (MSB131), New York University Medical Center, 550 First Avenue, 10016, New York, NY, USA
 
It is anticipated that the sequencing of Plasmodium falciparum genome will soon be completed. Rodent models of malaria infection and stable transformation systems provide powerful means of using this information to study gene function in vivo. To date, gene targeting has only been developed for one rodent malaria species, Plasmodium berghei. Another rodent species, Plasmodium yoelii, however, is favored to study the mechanisms of protective immunity to the pre-erythrocytic stages of infection and vaccine development. In addition, it offers the opportunity to investigate unique aspects of pathogenesis of blood stage infection. Here, we report on the stable transfection and gene targeting of P. yoelii. Purified late blood stage schizonts were used as targets for electroporation with a plasmid that contains a pyrimethamine-resistant form of the P. berghei dihydrofolate reductase-thymidylate synthase (Pbdhfr-ts) fused to green fluorescent protein (gfp) gene. After drug selection, fluorescent parasites contained intact, non-rearranged plasmids that remain stable under drug-pressure. In addition, we used another dhfr-ts/gfp based plasmid to disrupt the P. yoelii trap (thrombospondin-related anonymous protein) locus by site-specific integration. The phenotype of P. yoelii TRAP knockout was identical to that previously reported for the P. berghei TRAP knockout. In the absence of TRAP, the erythrocytic cycle, gametocyte and oocyst development of the mutant parasites were indistinguishable from wild type (WT). Although the sporozoites appeared morphologically normal, they failed to glide and to invade the salivary glands of mosquitoes.
 
PMID: 11295181 [PubMed - in process]
 

Mol Biochem Parasitol 2001 Apr;113(2):251-60
Gene discovery in Plasmodium chabaudi by genome survey sequencing.

Janssen CS, Barrett MP, Lawson D, Quail MA, Harris D, Bowman S, Phillips RS, Turner CM.
Division of Infection & Immunity, IBLS, University of Glasgow, G12 8QQ, Glasgow, UK
 
The first genome survey sequencing of the rodent malaria parasite Plasmodium chabaudi is presented here. In 766 sequences, 131 putative gene sequences have been identified by sequence similarity database searches. Further, 7 potential gene families, four of which have not previously been described, were discovered. These genes may be important in understanding the biology of malaria, as well as offering potential new drug targets. We have also identified a number of candidate minisatellite sequences that could be helpful in genetic studies. Genome survey sequencing in P. chabaudi is a productive strategy in further developing this in vivo model of malaria, in the context of the malaria genome projects.
 
PMID: 11295179 [PubMed - in process]
 

J Infect Dis 2001 May 1;183(9):1417-20
Polymorphisms in the Plasmodium falciparum pfcrt and pfmdr-1 Genes and Clinical Response to Chloroquine in Kampala, Uganda.

Dorsey G, Kamya MR, Singh A, Rosenthal PJ.
Department of Medicine, San Francisco General Hospital, University of California, San Francisco, CA 94143-0811, USA. 
[email protected]
 
The molecular mechanism of chloroquine resistance in Plasmodium falciparum remains uncertain. Polymorphisms in the pfcrt and pfmdr-1 genes have been associated with chloroquine resistance in vitro, although field studies are limited. In evaluations of known polymorphisms in parasites from patients with uncomplicated malaria in Kampala, Uganda, the presence of 8 pfcrt mutations and 2 pfmdr-1 mutations did not correlate with clinical response to therapy with chloroquine. Most notably, the pfcrt lysine-->threonine mutation at position 76, which recently correlated fully with chloroquine resistance in vitro, was present in 100% of 114 isolates, of which about half were from patients who recovered clinically after chloroquine therapy. These results suggest that, although key pfcrt polymorphisms may be necessary for the elaboration of resistance to chloroquine in areas with high levels of chloroquine resistance, other factors, such as host immunity, may contribute to clinical outcomes.
 
PMID: 11294677 [PubMed - in process]
 

J Infect Dis 2001 May 1;183(9):1388-94
Regulatory Interactions between Iron and Nitric Oxide Metabolism for Immune Defense against Plasmodium falciparum Infection.

Fritsche G, Larcher C, Schennach H, Weiss G.
Department of Internal Medicine, University Hospital, Innsbruck, Austria.
 
Iron chelation therapy of Plasmodium falciparum infection alleviates the clinical course of cerebral malaria in children. This study assessed the underlying mechanisms of this therapy. Cytokine stimulation of human (intestinal cell line DLD-1) or murine cells (murine macrophage cell line RAW 264.7) resulted in increased nitric oxide (NO) formation and decreased survival of plasmodia within cocultured human erythrocytes. The addition of desferrioxamine (DFO) before cytokine treatment increased both NO formation and parasite killing but had no effect in the presence of the inhibitor of NO formation, L-N6-(1-iminoethyl)-lysine. Moreover, peroxynitrite, which is formed after chemical reaction of NO with superoxide, appears to be the principal effector molecule for macrophage-mediated cytotoxicity toward P. falciparum, and interferon-gamma is a major regulatory cytokine for this process. The effect of DFO on the clearance of plasmodia appears to be due to enhanced generation of NO, rather than to limitation of iron availability to the parasite.
 
PMID: 11294671 [PubMed - in process]
 

Lancet 2001 Mar 31;357(9261):1014-6
Chronic nervous-system effects of long-term occupational exposure to DDT.

van Wendel de Joode B, Wesseling C, Kromhout H, Monge P, Garcia M, Mergler D.
 
Dichlorodiphenyltrichloroethane (DDT) is a compound with moderate toxicity that is judged to be safe for occupational use, although little is known about its long-term effects on the human nervous system. We investigated chronic nervous-system effects of long-term occupational exposure to DDT by comparing the neurobehavioural performance of retired malaria-control workers with a reference group of retired guards and drivers. DDT-exposed workers did worse on tests assessing various neurobehavioural functions than controls; performance significantly deteriorated with increasing years of DDT application. Our results could not be explained by exposure to cholinesterase-inhibiting pesticides or other potential confounding factors.
 
PMID: 11293598 [PubMed - in process]
 

Parasitol Res 2001 Mar;87(3):239-44
In vitro and in vivo antimalarial activity of ferrochloroquine, a ferrocenyl analogue of chloroquine against chloroquine-resistant malaria parasites.

Delhaes L, Abessolo H, Biot C, Berry L, Delcourt P, Maciejewski L, Brocard J, Camus D, Dive D.
INSERM Unite 167, Institut Pasteur, Lille, France.
 
Previous studies have shown that ferrochloroquine (FQ) exhibited an antimalarial activity against Plasmodium spp. The present work confirmed this activity, described the curative effect on P. vinckei and investigated the FQ toxicity in vitro and in vivo. The in vitro and in vivo growth inhibition of P. falciparum and P. berghei N, respectively, showed that FQ antimalarial activity was 1.5-10 times more potent than chloroquine. FQ completely inhibited the in vivo development of both chloroquine-susceptible and resistant P. vinckei strains and protected mice from lethal infection at a dose of 8.4 mg kg(-1) day(-1) given for 4 days subcutaneously or orally. This curative effect was 5-20 times more potent than chloroquine, according to the strains' resistance to chloroquine. At this curative dose, no clinical changes were observed in mice up to 14 days after the last administration. Nevertheless, the acute toxicity and lethality of ferrochloroquine seemed to be dependent on gastric surfeit. The FQ security index determined in vitro confirmed that it might be a promising compound.
 
PMID: 11293573 [PubMed - in process]
 

J Biol Chem 2001 Apr 5; [epub ahead of print]
Functional equivalence of structurally distinct ribosomes in the malaria parasite, plasmodium berghei.

Free article full-text at http://www.jbc.org
 
van Spaendonk RM, Ramesar J, van Wigcheren A, Eling W, Beetsma AL, van Gemert GJ, Hooghof J, Janse CJ, Waters AP.
Department of Parasitology, Leiden University Medical Centre, Leiden, Zuid Holland 2333 AL.
 
Unlike most eukaryotes many apicomplexan parasites contain only a few unlinked copies of ribosomal RNA (rRNA) genes. Based on stage specific expression of these genes and structural differences between the rRNA molecules it has been suggested that Plasmodium spp. produce functionally different ribosomes in different developmental stages. This hypothesis was investigated through comparison of the structure of the large subunit (LSU) rRNA molecules of the rodent malaria parasite, Plasmodium berghei and by disruption of both of the rRNA gene units that are exclusively transcribed during development of this parasite in the mosquito (S-type rRNA gene units). In contrast to the human parasite, Plasmodium falciparum, we did not find evidence for structural differences in core regions of the distinct LSU rRNAs that are known to be associated with catalytic activity including the GTP-ase site that varies in P. falciparum. Knockout (ko) P. berghei parasites lacking either of the S-type gene units were able to complete development in both the vertebrate and mosquito hosts. These results formally exclude the hypothesis that two functionally different ribosome types distinct from the predominantly blood stage expressed A-type ribosomes, are required for development of all Plasmodium species in the mosquito. The maintenance of two functionally equivalent rRNA genes might now be explained as a gene dosage phenomenon.
 
 

Infect Immun 2001 May;69(5):3286-94
Specificity of the protective antibody response to apical membrane antigen 1.

Hodder AN, Crewther PE, Anders RF.
The Cooperative Research Center for Vaccine Technology and The Walter and Eliza Hall Institute of Medical Research, Melbourne, Victoria, 3052, Australia.
 
Apical membrane antigen 1 (AMA1) is considered one of the leading candidates for inclusion in a vaccine against blood stages of Plasmodium falciparum. Although the ama1 gene is relatively conserved compared to those for some other potential vaccine components, numerous point mutations have resulted in amino acid substitutions at many sites in the polypeptide. The polymorphisms in AMA1 have been attributed to the diversifying selection pressure of the protective immune responses. It was therefore of interest to investigate the impact of sequence diversity in P. falciparum AMA1 on the ability of anti-AMA1 antibodies to inhibit the invasion of erythrocytes in vitro by P. falciparum merozoites. For these studies, we used antibodies to recombinant P. falciparum 3D7 AMA1 ectodomain, which was prepared for testing in early clinical trials. Antibodies were raised in rabbits to the antigen formulated in Montanide ISA720, and human antibodies to AMA1 were isolated by affinity purification from the plasma of adults living in regions of Papua New Guinea where malaria is endemic. Both rabbit and human anti-AMA1 antibodies were found to be strongly inhibitory to the invasion of erythrocytes by merozoites from both the homologous and two heterologous lines of P. falciparum. The inhibitory antibodies targeted both conserved and strain-specific epitopes within the ectodomain of AMA1; however, it appears that the majority of these antibodies reacted with strain-specific epitopes in domain I, the N-terminal disulfide-bonded domain, which is the most polymorphic region of AMA1.
 
PMID: 11292751 [PubMed - in process]
 

Infect Immun 2001 May;69(5):3190-6
Perturbation and Proinflammatory Type Activation of Vdelta1(+) gammadelta T Cells in African Children with Plasmodium falciparum Malaria.

Hviid L, Kurtzhals JA, Adabayeri V, Loizon S, Kemp K, Goka BQ, Lim A, Mercereau-Puijalon O, Akanmori BD, Behr C.
Centre for Medical Parasitology at Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet) and Institute for Medical Microbiology and Immunology, University of Copenhagen, Copenhagen, Denmark.
 
gammadelta T cells have variously been implicated in the protection against, and the pathogenesis of, malaria, but few studies have examined the gammadelta T-cell response to malaria in African children, who suffer the large majority of malaria-associated morbidity and mortality. This is unfortunate, since available data suggest that simple extrapolation of conclusions drawn from studies of nonimmune adults ex vivo and in vitro is not always possible. Here we show that both the frequencies and the absolute numbers of gammadelta T cells are transiently increased following treatment of Plasmodium falciparum malaria in Ghanaian children and they can constitute 30 to 50% of all T cells shortly after initiation of antimalarial chemotherapy. The bulk of the gammadelta T cells involved in this perturbation expressed Vdelta1 and had a highly activated phenotype. Analysis of the T-cell receptors (TCR) of the Vdelta1(+) cell population at the peak of their increase showed that all expressed Vgamma chains were used, and CDR3 length polymorphism indicated that the expanded Vdelta1 population was highly polyclonal. A very high proportion of the Vdelta1(+) T cells produced gamma interferon, while fewer Vdelta1(+) cells than the average proportion of all CD3(+) cells produced tumor necrosis factor alpha. No interleukin 10 production was detected among TCR-gammadelta(+) cells in general or Vdelta1(+) cells in particular. Taken together, our data point to an immunoregulatory role of the expanded Vdelta1(+) T-cell population in this group of semi-immune P. falciparum malaria patients.
 
PMID: 11292740 [PubMed - in process]
 

J Mol Biol 2001 Apr 13;307(5):1381-94
Inhibitory and Blocking Monoclonal Antibody Epitopes on Merozoite Surface Protein 1 of the Malaria Parasite Plasmodium falciparum.

Uthaipibull C, Aufiero B, Syed SE, Hansen B, Patino JA, Angov E, Ling IT, Fegeding K, Morgan WD, Ockenhouse C, Birdsall B, Feeney J, Lyon JA, Holder AA.
 
Merozoite surface protein 1 (MSP-1) is a precursor to major antigens on the surface of Plasmodium spp. merozoites, which are involved in erythrocyte binding and invasion. MSP-1 is initially processed into smaller fragments; and at the time of erythrocyte invasion one of these of 42 kDa (MSP-1(42)) is subjected to a second processing, producing 33 kDa and 19 kDa fragments (MSP-1(33) and MSP-1(19)). Certain MSP-1-specific monoclonal antibodies (mAbs) react with conformational epitopes contained within the two epidermal growth factor domains that comprise MSP-1(19), and are classified as either inhibitory (inhibit processing of MSP-1(42) and erythrocyte invasion), blocking (block the binding and function of the inhibitory mAb), or neutral (neither inhibitory nor blocking). We have mapped the epitopes for inhibitory mAbs 12.8 and 12.10, and blocking mAbs such as 1E1 and 7.5 by using site-directed mutagenesis to change specific amino acid residues in MSP-1(19) and abolish antibody binding, and by using PEPSCAN to measure the reaction of the antibodies with every octapeptide within MSP-1(42). Twenty-six individual amino acid residue changes were made and the effect of each on the binding of mAbs was assessed by Western blotting and BIAcore analysis. Individual changes had either no effect, or reduced, or completely abolished the binding of individual mAbs. No two antibodies had an identical pattern of reactivity with the modified proteins. Using PEPSCAN each mAb reacted with a number of octapeptides, most of which were derived from within the first epidermal growth factor domain, although 1E1 also reacted with peptides spanning the processing site. When the single amino acid changes and the reactive peptides were mapped onto the three-dimensional structure of MSP-1(19), it was apparent that the epitopes for the mAbs could be defined more fully by using a combination of both mutagenesis and PEPSCAN than by either method alone, and differences in the fine specificity of binding for all the different antibodies could be distinguished. The incorporation of several specific amino acid changes enabled the design of proteins that bound inhibitory but not blocking antibodies. These may be suitable for the development of MSP-1-based vaccines against malaria. Copyright 2001 Academic Press.
 
PMID: 11292349 [PubMed - in process]
 

Am J Trop Med Hyg 2000 May;62(5):590-7
Vitamin A supplementation and other predictors of anemia among children from Dar Es Salaam, Tanzania.

Villamor E, Mbise R, Spiegelman D, Ndossi G, Fawzi WW.
Department of Nutrition, Harvard School of Public Health, Boston, Massachusetts 02115, USA.
 
The associations of hemoglobin, hematocrit, and packed cell volume with socioeconomic factors, malaria, human immunodeficiency virus (HIV) infection, and nutritional status were examined among 687 children admitted to hospital with pneumonia participating in a double blind, placebo-controlled trial of vitamin A supplementation. Children were randomized to receive 2 doses of vitamin A (200,000 IU) or placebo at baseline, and additional doses at 4 and 8 months after discharge from hospital. Hemoglobin levels were measured at enrollment and, on a subset of 161 children, during follow-up. At baseline, hemoglobin concentration was positively associated with the number of possessions in the household, maternal level of education and quality of water supply, and inversely related to malaria infection after controlling for potential confounding variables. Children infected with HIV experienced a significant fall in mean hemoglobin levels over time. The risk of developing severe anemia (< 7 g/dL) during follow-up was lower for children who were breastfed for longer than 18 months as compared to those with less than 6 months of breastfeeding (adjusted prevalence ratio = 0.14, 95% confidence interval [CI] = 0.02, 0.93; P = 0.04), and higher for children over two years of age as compared to 6 to 11 months-old infants (adjusted prevalence ratio = 8.11, 95% CI = 1.2, 55.8; P = 0.03). Children with repeated diagnoses of malaria had 4.1 times the risk of developing severe anemia than did children without the diagnosis (95% CI = 1.3, 13.5; P = 0.02). Vitamin A supplements were associated with an overall nonsignificant reduction of 14% in the risk of developing severe anemia (adjusted prevalence ratio = 0.86, 95% CI = 0.37, 1.99; P = 0.73). We conclude that malaria, HIV infection, low socioeconomic status, and short duration of breastfeeding are strong and independent determinants of adverse hematologic profiles in this population.
 
PMID: 11289670 [PubMed - in process]
 

Am J Trop Med Hyg 2000 May;62(5):566-72
Antibody responses to Plasmodium falciparum: evolution according to the severity of a prior clinical episode and association with subsequent reinfection.

Luty AJ, Ulbert S, Lell B, Lehman L, Schmidt-Ott R, Luckner D, Greve B, Matousek P, Schmid D, Herbich K, Dubois B, Deloron P, Kremsner PG.
Department of Parasitology, Institute for Tropical Medicine, University of Tubingen, Germany.
 
We measured sporozoite- and total parasite antigen-specific IgG and IgM antibodies before and after treatment in matched groups of Gabonese children who presented with either mild or severe Plasmodium falciparum malaria. We investigated the influence of various parameters on these antibody responses, including clinical presentation, age, and post-treatment reinfection profiles. IgG but not IgM responses were strongly influenced by both clinical and parasitological status. IgG responses to the repeat region of the circumsporozoite protein, which were low at admission, particularly so in those with severe anemia, increased after treatment but showed no association with either age or reinfection profiles. Total parasite antigen-specific IgG responses were strongly influenced by parasitological status, and also differed significantly when segregated according to clinical status at admission, age, and reinfection histories. Most notably, anti-parasite IgG responses measured when children were parasite-free were higher and a good indicator of recent reinfections in those who presented with mild rather than with severe malaria. The profile of responses in the latter group suggests some immune system dysfunction, which may reflect the induction of tolerance to parasite antigens.
 
PMID: 11289665 [PubMed - in process]
 

Am J Trop Med Hyg 2000 May;62(5):545-51
The potential impact of integrated malaria transmission control on entomologic inoculation rate in highly endemic areas.

Killeen GF, McKenzie FE, Foy BD, Schieffelin C, Billingsley PF, Beier JC.
Department of Tropical Medicine, School of Public Health and Tropical Medicine, Center for Infectious Diseases, Tulane University Health Sciences Center, New Orleans, Louisiana 70112-2824, USA.
 
We have used a relatively simple but accurate model for predicting the impact of integrated transmission control on the malaria entomologic inoculation rate (EIR) at four endemic sites from across sub-Saharan Africa and the southwest Pacific. The simulated campaign incorporated modestly effective vaccine coverage, bed net use, and larval control. The results indicate that such campaigns would reduce EIRs at all four sites by 30- to 50-fold. Even without the vaccine, 15- to 25-fold reductions of EIR were predicted, implying that integrated control with a few modestly effective tools can meaningfully reduce malaria transmission in a range of endemic settings. The model accurately predicts the effects of bed nets and indoor spraying and demonstrates that they are the most effective tools available for reducing EIR. However, the impact of domestic adult vector control is amplified by measures for reducing the rate of emergence of vectors or the level of infectiousness of the human reservoir. We conclude that available tools, including currently neglected methods for larval control, can reduce malaria transmission intensity enough to alleviate mortality. Integrated control programs should be implemented to the fullest extent possible, even in areas of intense transmission, using simple models as decision-making tools. However, we also conclude that to eliminate malaria in many areas of intense transmission is beyond the scope of methods which developing nations can currently afford. New, cost-effective, practical tools are needed if malaria is ever to be eliminated from highly endemic areas.
 
PMID: 11289662 [PubMed - in process]
 

Am J Trop Med Hyg 2000 May;62(5):535-44
A simplified model for predicting malaria entomologic inoculation rates based on entomologic and parasitologic parameters relevant to control.

Killeen GF, McKenzie FE, Foy BD, Schieffelin C, Billingsley PF, Beier JC.
Department of Tropical Medicine, School of Public Health and Tropical Medicine, Center for Infectious Diseases, Tulane University Health Sciences Center, New Orleans, Louisiana 70112-2824, USA.
 
Malaria transmission intensity is modeled from the starting perspective of individual vector mosquitoes and is expressed directly as the entomologic inoculation rate (EIR). The potential of individual mosquitoes to transmit malaria during their lifetime is presented graphically as a function of their feeding cycle length and survival, human biting preferences, and the parasite sporogonic incubation period. The EIR is then calculated as the product of 1) the potential of individual vectors to transmit malaria during their lifetime, 2) vector emergence rate relative to human population size, and 3) the infectiousness of the human population to vectors. Thus, impacts on more than one of these parameters will amplify each other's effects. The EIRs transmitted by the dominant vector species at four malaria-endemic sites from Papua New Guinea, Tanzania, and Nigeria were predicted using field measurements of these characteristics together with human biting rate and human reservoir infectiousness. This model predicted EIRs (+/- SD) that are 1.13 +/- 0.37 (range = 0.84-1.59) times those measured in the field. For these four sites, mosquito emergence rate and lifetime transmission potential were more important determinants of the EIR than human reservoir infectiousness. This model and the input parameters from the four sites allow the potential impacts of various control measures on malaria transmission intensity to be tested under a range of endemic conditions. The model has potential applications for the development and implementation of transmission control measures and for public health education.
 
PMID: 11289661 [PubMed - in process]
 

Southeast Asian J Trop Med Public Health 2000 Sep;31(3):515-20
Introduction of a rapid dipstick assay for the detection of Leptospira-specific immunoglobulin m antibodies in the laboratory diagnosis of leptospirosis in a hospital in Makassar, Indonesia.

Hatta M, Smits HL, Gussenhoven GC, Gooskens J.
Department of Medical Microbiology, Faculty of Medicine, Hasanuddin University, Makassar, Indonesia. 
[email protected]
 
An easy, rapid and robust dipstick assay for detection of leptospira-specific immunoglobulin M (IgM) antibodies was evaluated on 403 patients admitted for hospitalization because of fever. The clinical symptoms and signs of 35 patients were consistent with leptospirosis. The final diagnosis for the remaining patients was as follows: 136 with typhoid fever, 82 with hepatitis, 74 with malaria, 48 with infections of the respiratory tract, and 20 with fever of unknown origin. The clinical diagnosis of leptospirosis was confirmed for 24 (68.6%) patients by the combined results of the microscopic agglutination test (MAT), the reference test for leptospirosis, and of IgM ELISA, a standard laboratory test for the serodiagnosis of leptospirosis. In addition, serum specimens from 8 (2.2%) patients with a final clinical diagnosis other than leptospirosis were found to be positive in MAT and/or IgM ELISA. Compared with the results of MAT and IgM ELISA a sensitivity of 91.6% and specificity of 93.6% was calculated for the dipstick assay. Most of the serum samples from the laboratory confirmed patients gave a moderate to strong staining intensity of the antigen band of the dipstick and were easy to read. The results demonstrate that the dipstick assay is convenient to use and allows the rapid and accurate confirmation of patients with clinical suspicion of leptospirosis in areas where the disease is endemic.
 
PMID: 11289012 [PubMed - in process]
 

Southeast Asian J Trop Med Public Health 2000 Sep;31(3):444-7
Promotion of insecticide-treated mosquito nets in Myanmar.

Lin K, Aung S, Lwin S, Min H, Aye NN, Webber R.
Vector Borne Diseases Control Project, Department of Health, Yangon, Myanmar.
 
A simple health promotion message administered by village midwives raised bednet usage to over 60% in trial hamlets in north Shan State, Myanmar. Treatment of the nets in the study villages produced a reduction in malaria cases. Most villagers were prepared to buy their nets at market prices and were willing to pay for the cost of re-treatment of nets, but very poor, members of the Wa ethnic group required a half-price subsidy for them to afford them. The use of insecticide treated bednets was felt to be appropriate for undeveloped and remote areas of the country where malaria control was difficult.
 
PMID: 11288998 [PubMed - in process]
 

Southeast Asian J Trop Med Public Health 2000 Sep;31(3):439-43
Characterization of specific monoclonal antibodies for detection of mefloquine in body fluids.

Trisirivanich S, Laothavorn J, Na-Bangchang K, Khusmith S.
Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
 
Specific monoclonal antibodies (MAbs) to mefloquine conjugated to bovine serum albumin (mefloquine-BSA) were produced by hybridoma technology. The mefloquine-BSA was synthesized by converting mefloquine into hemisuccinate followed by convalently linked to bovine serum albumin (BSA) and coupling with N,N' disuccinimidyl carbonate (DSC). The conjugate was purified by Sephadex G-75 gel filtration using 0.01 M PBS pH 7.2. An average of 19.34 molecules of mefloquine were conjugated to each molecule of protein determined by differential UV absorption spectra of hapten and protein carrier. Sixteen monoclones producing antibody specific to mefloquine were screened by indirect ELISA using homologous antigens. The specificity of MAbs was determined by reacting with BSA and the structurally related antimalarial drug, quinine. Three, three, five and two MAbs belonged to IgG1, IgG2a, IgG2b and IgG3, respectively. Most of the MAbs slightly reacted with quinine-BSA due to the closely related structure of mefloquine to quinine. The selected MAb designated 11F9(G5)G9 which showed no cross reaction with quinine-BSA gave high reactivity with blood samples from malaria patients previously treated with mefloquine when compared to normal blood by indirect ELISA. The preliminary results indicated that such specific MAb could be used as antibody probe for detection of mefloquine in biological fluids.
 
PMID: 11288997 [PubMed - in process]
 

Southeast Asian J Trop Med Public Health 2000 Sep;31(3):434-8
Modeling factors influencing malaria incidence in Myanmar.

Cho-Min-Naing, Lertmaharit S, Kamol-Ratanakul P, Saul A.
Malaria and Arbovirus Unit, Queensland Institute of Medical Research Brisbane, Australia.
[email protected]

This is a documentary study to determine factors influencing malaria incidence in Myanmar. The period of study covered was from 1989 to 1998 using time series data. Multiple regression analysis was performed on the dependent variable, yearly incidence of malaria in Myanmar, with hypothesized independent variables including variables related to epidemiology, demography, service and socioeconomic status. Malaria incidence was inversely associated with the government budget for malaria control at the 5% level and with the case fatality rate of malaria at the 10% level. Other variables: yearly gross domestic product, yearly proportion of Plasmodium falciparum cases and yearly DDT use of spraying displayed expected signs but were not statistically significant.

PMID: 11288996 [PubMed - in process]

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Last modified January 28, 2002