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EHP Library Malaria Bulletin: March 21 - April 5, 2001

Social Sciences and Malaria

Soc Sci Med 2001 Apr;52(7):1043-55
Disease and dislocation: the impact of refugee movements on the geography of malaria in NWFP, Pakistan.

Kazmi JH, Pandit K
Department of Geography, University of Karachi, Pakistan. 
Email: [email protected]
 
Studies of the health implications of refugee movements have generally focused on the effects of dislocation on the health of refugees and the impacts on health care provision at the destination. A somewhat more neglected aspect of the refugee-health research has been the impact of refugee flows on the geography of disease, i.e., how the spatial patterns of disease prevalence are modified through the influx and settlement of refugee populations. We examine this issue by examining the changing geography of malaria in Pakistan's North West Frontier Province (NWFP) between 1972 and 1997. Until the late 1970s, the highest incidence of malaria in the region was seen in the southern and eastern parts. During the 1980s, however, two and a half million Afghan refugees entered the NWFP and were housed in tented villages along the border and in some interior areas. As the decade progressed, there was a significant shift in the spatial pattern of malaria, with the regions of highest incidence shifting to the west and north, coinciding strongly with refugee concentrations. Our study draws attention to the manner in which refugee influx and settlement can alter the ecology of the disease system, leading to long-term changes in the geography of malaria.
 
PubMed

Trends Parasitol 2001 Mar 1;17(3):145-14
Child mortality and malaria transmission intensity in Africa.

Smith TA, Leuenberger R, Lengeler C
Swiss Tropical Institute, Socinstrasse 57, PO Box CH-4002, Basel, Switzerland
 
The desirability of controlling malaria transmission in the areas of highest endemicity of Plasmodium falciparum has long been debated. Most recently, it has been claimed that rates of malaria morbidity are no higher in areas of very high transmission in Africa than they are in places with lower inoculation rates. We now review the literature on the relationship of morbidity and mortality to malaria transmission intensity, and have linked published child mortality and malaria transmission rates to examine how age-specific mortality actually varies with the inoculation rate of P. falciparum.
 

Trends Parasitol 2001 Mar 1;17(3):122-126
Possible modes of action of the artemisinin-type compounds.

Olliaro PL, Haynes RK, Meunier B, Yuthavong Y
UNDP/World Bank/WHO Special Programme on Research and Training in Tropical Diseases, CDS Cluster, 20, avenue Appia, CH-1211, Geneva, Switzerland
 
Artemisinin-type compounds are used for the treatment of uncomplicated and severe forms of malaria. They reduce parasitaemia more rapidly than any other antimalarial compound known, and are effective against multidrug-resistant parasites. However, uncertainties remain as to how they act on the parasite and cause toxicity. In this review, we summarize current ideas.
 

Mem Inst Oswaldo Cruz 2001 Feb;96(2):221
Protective CD8+ T cell responses against the pre-erythrocytic stages of malaria parasites: an overview.

Oliveira-Ferreira J, Daniel-Ribeiro C
Laboratorio de Pesquisas em Malaria, Instituto Oswaldo Cruz, Rio de Janeiro, RJ, 21045-900, Brasil.
 
CD8+ T cells have been implicated as critical effector cells in protection against the pre-erythrocytic stage of malaria in mice and humans following irradiated sporozoite immunization. Immunization experiments in animal models by several investigators have suggested different strategies for vaccination against malaria and many of the targets from liver stage malaria antigens have been shown to be immunogenic and to protect mice from the sporozoite challenge. Several prime/boost protocols with replicating vectors, such as vaccinia/influenza, with non-replicating vectors, such as recombinant particles derived from yeast transposon (Ty-particles) and modified vaccinia virus Ankara, and DNA, significantly enhanced CD8+ T cell immunogenicity and also the protective efficacy against the circumsporosoite protein of Plasmodium berghei and P. yeti. Based on these experimental results the development of a CD8+ T cell inducing vaccine has moved forward from epitope identification to planning stages of safety and immunogenicity trials of candidate vaccines.
 

Mem Inst Oswaldo Cruz 2001 Feb;96(2):179-184
Malaria vectors in the municipality of Serra do Navio, State of Amapa, Amazon Region, Brazil.

 
Povoa M, Wirtz R, Lacerda R, Miles M, Warhurst D
Secao de Parasitologia, Instituto Evandro Chagas, Funasa, Belem, PA, 66090-000, Brasil.
 
We conducted a survey to determine the vectors of malaria in six localities of Serra do Navio municipality, State of Amapa, from 1990 to 1991. Malaria infection rates of 29.3%, 6.2% and 20.4% were detected by human blood smears in Colonia Agua Branca, Porto Terezinha and Arrependido, respectively. There was no malaria infection detected in Serra do Navio. Fifteen species were identified among 3,053 anopheline mosquitoes collected by human bait and 64.4% were identified as Anopheles albitarsis s.l., 16.7% An. braziliensis, 9.5% An. nuneztovari and 5.8% An. triannulatus. An. darlingi, the main vector of malaria in the Amazon region of Brazil, was scare. Using enzyme-linked immunosorbent assay (ELISA), a total positive rate of 0.8% (23/2876) was found for six species: fifteen An. albitarsis s.l., four An. nuneztovari, and one of each: An. braziliensis, An. triannulatus, An. oswaldoi and An. rangeli. Nine of 23 positive mosquitoes were infected with Plasmodium malariae, eight with P. vivax VK210, three with P. vivax VK247 and three with P. falciparum. Since An. albitarsis s.l. was collected feeding on humans, was present in the highest density and was positive by ELISA for malaria sporozoites, it probably plays an important role in malaria transmission in this area.
 

Mem Inst Oswaldo Cruz 2001 Jan;96(1):105-11
Characterization of constitutive and putative differentially expressed mRNAs by means of expressed sequence tags, differential display reverse transcriptase-PCR and randomly amplified polymorphic DNA-PCR from the sand fly vector Lutzomyia longipalpis.

Ramalho-Ortigao J, Temporal P, Oliveira Sd, Barbosa A, Vilela M, Rangel E, Brazil R, Traub-Cseko Y
Departamento de Bioquimica e Biologia Molecular, Instituto Oswaldo Cruz, Rio de Janeiro, RJ, 21045-900, Brasil.
 
Molecular studies of insect disease vectors are of paramount importance for understanding parasite-vector relationship. Advances in this area have led to important findings regarding changes in vectors' physiology upon blood feeding and parasite infection. Mechanisms for interfering with the vectorial capacity of insects responsible for the transmission of diseases such as malaria, Chagas disease and dengue fever are being devised with the ultimate goal of developing transgenic insects. A primary necessity for this goal is information on gene expression and control in the target insect. Our group is investigating molecular aspects of the interaction between Leishmania parasites and Lutzomyia sand flies. As an initial step in our studies we have used random sequencing of cDNA clones from two expression libraries made from head/thorax and abdomen of sugar fed L. longipalpis for the identification of expressed sequence tags (EST). We applied differential display reverse transcriptase-PCR and randomly amplified polymorphic DNA-PCR to characterize differentially expressed mRNA from sugar and blood fed insects, and, in one case, from a L. (V.) braziliensis-infected L. longipalpis. We identified 37 cDNAs that have shown homology to known sequences from GeneBank. Of these, 32 cDNAs code for constitutive proteins such as zinc finger protein, glutamine synthetase, G binding protein, ubiquitin conjugating enzyme. Three are putative differentially expressed cDNAs from blood fed and Leishmania-infected midgut, a chitinase, a V-ATPase and a MAP kinase. Finally, two sequences are homologous to Drosophila melanogaster gene products recently discovered through the Drosophila genome initiative.
 

Biochem J 2001 Apr 15;355(Pt 2):333-338
Mechanism of malarial haem detoxification inhibition by chloroquine.

Pandey AV, Bisht H, Babbarwal VK, Srivastava J, Pandey KC, Chauhan VS
Malaria Research Group, International Center for Genetic Engineering and Biotechnology (ICGEB), Aruna Asaf Ali Marg, New Delhi 110067, India.
 
The haem detoxification pathway of the malaria parasite Plasmodium falciparum is a potential biochemical target for drug development. Free haem, released after haemoglobin degradation, is polymerized by the parasite to form haemozoin pigment. Plasmodium falciparum histidine-rich protein-2 (Pfhrp-2) has been implicated as the catalytic scaffold for detoxification of haem in the malaria parasite. Previously we have shown that a hexapeptide repeat sequence (Ala-His-His-Ala-Ala-Asp), which appears 33 times in Pfhrp-2, may be the major haem binding site in this protein. The haem binding studies carried out by ourselves indicate that up to 18 equivalents of haem could be bound by this protein with an observed K(d) of 0.94 ?M. Absorbance spectroscopy provides evidence that chloroquine is capable of extracting haem bound to Pfhrp-2. This was supported by the K(d) value, of 37 nM, observed for the haem-chloroquine complex. The native PAGE studies reveal that the formation of the haem-Pfhrp-2 complex is disrupted by chloroquine. These results indicate that chloroquine may be acting by inhibiting haem detoxification/binding to Pfhrp-2. Moreover, the higher affinity of chloroquine for haem than Pfhrp-2 suggests a possible mechanism of action for chloroquine; it may remove the haem bound to Pfhrp-2 and form a complex that is toxic to the parasite.
 

Br J Biomed Sci 2001;58(1):20-3
False-positive serological tests in acute malaria.

Ghosh K, Javeri KN, Mohanty D, Parmar BD, Surati RR, Joshi SH
Institute of Immunohaematology (ICMR), 13th Floor, KEM Hospital MS Building, Parel, Mumbai-400012, India.
Email: [email protected]
 
A range of serological tests, including rapid plasma reagin (RPR), Widal test, enzyme-linked immunosorbent assay (ELISA) for human immunodeficiency virus (HIV)-1 and -2, direct Coombs' test (DCT), and rheumatoid factor (RF) were performed in a well-characterised cohort of 100 patients with acute malaria (Plasmodium vivax infection: 31 patients; P. falciparum infection: 69 patients). Twenty-five healthy volunteers from a similar area were used as controls. Three patients from the severe P. falciparum group died, the remainder of the patients recovered completely. A large proportion of these patients showed false-positive serological reactions during the acute stage of infection, which became negative on re-testing, four weeks after recovery. In tropical countries such as India, where malaria is endemic, results of serological tests should be interpreted with caution in a patient with pyrexia of unknown origin (PUO)
 

Trends Parasitol 2001 Apr;17(4):194-7
Antibodies and Plasmodium falciparum merozoites.

Ramasamy R, Ramasamy M, Yasawardena S
Dept of Genetics, University of Groningen, Kerklaan 30, 9751 NN, Haren, The Netherlands
 
There is considerable interest in using merozoite proteins in a vaccine against falciparum malaria. Observations that antibodies to merozoite surface proteins block invasion are a basis for optimism. This article draws attention to important and varied aspects of how antibodies to Plasmodium falciparum merozoites affect red blood cell invasion.
 

Trends Parasitol 2001 Apr;17(4):189-94
Trade-offs, conflicts of interest and manipulation in Plasmodium-mosquito interactions.

Schwartz A, Koella JC
Department of Zoology, Aarhus University, Universitetsparken B135, DK-8000, Aarhus, Denmark
 
A long-held view among parasitologists is that infection by malaria parasites does not harm the mosquito vector. One of the reasons for this belief is that the two partners of the association share interests in the most important life-history traits of the mosquito. Both partners benefit from increased survival and an increased rate of bloodfeeding - the mosquito to increase its reproductive success and the parasite to ensure its transmission. Problems with this line of reasoning appear when one considers possible trade-offs among the mosquito's life-history parameters, which constrain the attempts by the mosquito and the parasite to maximize their success. Could these constraints differ between the two partners and thus lead to conflicts of interest and what would be the evolutionary and epidemiological consequences of conflicting interests? These questions will be investigated below.
 

Exp Parasitol 2001 Feb;97(2):61-9
Plasmodium falciparum: Immunogenicity of Alum-Adsorbed Clinical-Grade TBV25-28, a Yeast-Secreted Malaria Transmission-Blocking Vaccine Candidate.

Gozar MM, Muratova O, Keister DB, Kensil CR, Price VL, Kaslow DC
Malaria Vaccines Section, National Institutes of Health, Bethesda, Maryland, 20892, U.S.A.
 
Gozar, M. M. G., Muratova, O., Keister, D. B., Kensil, C. R., Price, V. L., and Kaslow, D. C. 2001. Plasmodium falciparum: Immunogenicity of alum-adsorbed clinical-grade TBV25-28, a yeast-secreted malaria transmission-blocking vaccine candidate. Experimental Parasitology 97, 61-69. The fusion of Pfs25 and Pfs28, two major surface antigens on zygotes and ookinetes of Plasmodium falciparum, as a single recombinant protein (TBV25-28) was previously shown to elicit potent transmission-blocking antibodies in mice. Clinical-grade TBV25-28 was subsequently manufactured and its potency was evaluated in rabbits. Rabbits received three doses of either clinical-grade TBV25H or clinical-grade TBV25-28 adsorbed to alum with or without QS-21. As measured in a standard membrane-feeding assay, addition of QS-21 to the formulations appeared to enhance transmission-blocking potency of rabbit sera after two vaccinations but not after three vaccinations. Surprisingly, TBV25H elicited more potent transmission-blocking antibodies than did TBV25-28, a result strikingly different from those of previous mouse experiments using research-grade TBV25-28. The apparent decrease in potency of clinical-grade TBV25-28 in rabbits appears to reflect an enhancement in potency of clinical-grade TBV25H in a new formulation rather than simply a species difference in immunogenicity of TBV25-28. Copyright 2001 Academic Press.

 

Trans R Soc Trop Med Hyg 2001 Jan-Feb;95(1):7-13
Area effects of bednet use in a malaria-endemic area in Papua New Guinea.

Hii JL, Smith T, Vounatsou P, Alexander N, Mai A, Ibam E, Alpers MP
Guinea Institute of Medical Research, P.O. Box 378, Madang, Papua New Guinea. Email: [email protected]
 
Relationships between area coverage with insecticide-free bednets and prevalence of Plasmodium falciparum were investigated in 7 community-based surveys over a 33-month period in 1990-93 in 6 villages in the Wosera area of Papua New Guinea. Spatial patterns in circumsporozoite rates for P. falciparum, P. vivax isomorphs K210 and K247, and P. malariae, and the proportions of mosquito blood meals positive for specific human, goat, cat, dog and pig antigens were determined using ELISAs. P. falciparum prevalence in humans was better explained by bednet coverage in the immediate vicinity than by personal protection alone. Circumsporozoite rates for both P. falciparum and P. vivax were also inversely related to coverage with bednets. There was some increase in zoophagy in areas with high coverage, but relatively little effect on the human blood index or on overall mosquito densities. In this setting, protracted use of untreated bednets apparently reduces sporozoite rates, and the associated effects on prevalence are greater than can be accounted for by personal protection. Even at high bednet coverage most anophelines feed on human hosts, so the decreased sporozoite rates are likely to be largely due to reduction of mosquito survival. This finding highlights the importance of local vector ecology for outcomes of bednet programmes and suggests that area effects of untreated bednets should be reassessed in other settings.
 

Trans R Soc Trop Med Hyg 2001 Jan-Feb;95(1):50-5
The comparative efficacy of chloroquine and sulfadoxine-pyrimethamine for the treatment of uncomplicated falciparum malaria in Kampala, Uganda.

Kamya MR, Dorsey G, Gasasira A, Ndeezi G, Babirye JN, Staedke SG, Rosenthal PJ
Department of Medicine, Makerere University, P.O. Box 7072, Kampala, Uganda. Email: [email protected]
 
Chloroquine (CQ) remains the first-line treatment for uncomplicated malaria in much of Africa despite the growing problem of resistance to this drug. Sulfadoxine-pyrimethamine (SP) is often used after CQ treatment failure and has replaced CQ as the first-line treatment in parts of Africa. To compare the efficacy of these 2 regimens, we evaluated, in March-August 1999, clinical and parasitological responses over 28 days in 214 children and adults from Kampala, Uganda, with uncomplicated falciparum malaria. Compared to SP, significantly more patients treated with CQ developed early or late clinical failure (54% vs 11%, P < 0.001) and parasitological failure (72% vs 30%, P < 0.001) during 14 days of follow-up. The risk of treatment failure occurring after day 14 was similar between the 2 treatment groups. Among those treated with CQ, children aged < 5 years were at higher risk of clinical failure than older individuals (76% vs 28%, P < 0.001), an association not seen with SP (11% vs 10%, P = 0.91). Although early parasite clearance was significantly better in the SP group (P = 0.001), fever clearance at day 3 was the same (CQ 85%, SP 86%). These and other recent findings suggest that consideration be given to replacing CQ as the first-line therapy for uncomplicated malaria in Uganda, particularly in young children.
 

Trans R Soc Trop Med Hyg 2001 Jan-Feb;95(1):
Malaria in the highlands of Madagascar after five years of indoor house spraying of DDT.

Jambou R, Ranaivo L, Raharimalala L, Randrianaivo J, Rakotomanana F, Modiano D, Pietra V, Boisier P, Rabarijaona L, Rabe T, Raveloson N, De Giorgi F
Pasteur Institute of Madagascar, Madagascar. 
Email: [email protected]
 
The central region of Madagascar is a vast area of highlands (altitude 700-2000 m). Malaria transmission has re-established itself here since the last epidemic of 1985-90 and has caused the deaths of 40,000 persons according to the Minister of Health. To combat the main malaria vector in the region, Anopheles funestus, annual programmes of indoor house spraying of DDT were carried out between December 1993 and January 1998 in most rural areas at altitude 1000-1500 m. A parasitological and serological study was then conducted in the highland schools to evaluate the impact of the programme and set up a database on the region. Using a cluster-sampling method 2 independent selections were conducted (one of 130 sites, the other of 40 sites). During the study, 13,462 schoolchildren were examined, 71% living in sprayed villages. Parasite prevalence among schoolchildren declined as altitude increases, from 11% at 700-900 m to 0.4% at > 1500 m. Below 1500 m, the impact of the spraying on the prevalence of the parasite was very clear (an average decrease of from 20% to 2.7% below 1000 m and of from 4.5% without spraying to 0.8% at 1000-1500 m). Geographical analysis of the data showed that the marginal regions remained the most affected by malaria (especially outside spraying zones), and persistence of 'pockets of transmission' at 1000-1500 m, essentially in areas where spraying has never been used. In 9 schools, anti-Plasmodium antibodies were sought by indirect immunofluorescence on thick smears of parasitized red blood cells. The seroprevalence ranged from 22% to 63%, which suggests that the parasite is still circulating in the region. Even though our data show that vector control continues to be very successful in the Madagascan highlands, rapid reinfection could occur and must be monitored following spraying. To this end, the Minister for Health, with the support of the Italian Co-operation, has placed the region under epidemiological surveillance since 1997. An alert system for the timely detection of the sources of epidemics and the targeting of the antivectoral campaign is also in operation. Our study suggests that this strategy should be reinforced by the spraying of DDT in the marginal zones in order to consolidate the results obtained at higher altitudes.
 

Trans R Soc Trop Med Hyg 2001 Jan-Feb;95(1):1-6
Associations of peak shifts in age--prevalence for human malarias with bednet coverage.

Smith T, Hii JL, Genton B, Muller I, Booth M, Gibson N, Narara A, Alpers MP
Papua New Guinea Institute of Medical Research, P.O. Box 378, Madang, Papua New Guinea. 
Email: [email protected]
 
Effects of bednet coverage (C) on prevalence of malaria were analysed using data from 1990-92 from 9 Papua New Guinean villages. Effects of coverage varied by age, resulting in a shift in age of peak prevalence from 4.7 (C = 0%) to 11.6 (C = 100%) years for Plasmodium falciparum, from 3.4 to 4.9 years for P. vivax and from 11.0 to 16.8 years for P. malariae. In small areas with no bednets the age distribution of P. falciparum parasitaemia was like that of a holoendemic area. Where coverage was complete the pattern corresponded to mesoendemicity. Thus, protracted use of bednets can result in profound changes in the endemicity of malaria even when coverage is incomplete and without insecticide treatment. Average entomological inoculation rates (EIRs) estimated from indoor landing rates on individuals without bednets were 35, 12 and 10 infectious bites per person per annum for P. falciparum, P. vivax and P. malariae, respectively. Logistic regression analyses indicated that the EIR estimate for P. falciparum was related to prevalence of this species independently of effects of bednet coverage. However, the recent EIR still accounted for much less variation than did the bednets. A similar pattern was seen for P. malariae, while there were no significant relationships between the recent EIR and the parasite positivity for P. vivax. It is concluded that short-term variations in inoculation rate are not important determinants of parasite prevalence in this population.
 

Bioorg Med Chem Lett 2001 Mar 26;11(6):761-4
Peptidomimetic inhibitors of protein farnesyltransferase show potent antimalarial activity.

Ohkanda J, Lockman JW, Yokoyama K, Gelb MH, Croft SL, Kendrick H, Harrell MI, Feagin JE, Blaskovich MA, Sebti SM, Hamilton AD
Department of Chemistry, Yale University, New Haven, CT 06520, USA.
 
Malaria continues to represent a very serious health problem in the tropics. The current methods of clinical treatment are showing deficiencies due to the increased incidence of resistance in the parasite. In the present paper we report the design, synthesis, and evaluation of potential antimalarial agents against a novel target, protein farnesyltransferase. We show that the most potent compounds are active against Plasmodium falciparum in vitro at submicromolar concentrations.
 

Trends Immunol 2001 Apr;22(4):171-2
Immunology, climate change and vector-borne diseases.

Patz JA, Reisen WK
Program on Health Effects of Global Environmental Change, Dept of Environmental Health Sciences, Johns Hopkins School of Hygiene and Public Health, 615 N. Wolfe St, 21205, Baltimore, MD, USA
 
Global climate change might expand the distribution of vector-borne pathogens in both time and space, thereby exposing host populations to longer transmission seasons, and immunologically naive populations to newly introduced pathogens. In the African highlands, where cool temperatures limit malaria parasite development, increases in temperature might enhance malaria transmission. St Louis encephalitis viral replication and the length of the transmission season depend upon ambient temperature. Warming temperatures in the American southwest might place at risk migratory, non-immune elderly persons that arrive in early fall to spend the winter. Warm temperatures might intensify or extend the transmission season for dengue fever. Immunologists should examine this interplay between human immunocompetence and vector-borne disease risks in a warmer world.
 
PMID: 11274908

 

Physiol Rev 2001 Apr;81(2):495-537
Membrane transport in the malaria-infected erythrocyte.

Kirk K
Division of Biochemistry and Molecular Biology, Faculty of Science, Australian National University, Canberra, Australian Capital Territory, Australia.
 
The malaria parasite is a unicellular eukaryotic organism which, during the course of its complex life cycle, invades the red blood cells of its vertebrate host. As it grows and multiplies within its host blood cell, the parasite modifies the membrane permeability and cytosolic composition of the host cell. The intracellular parasite is enclosed within a so-called parasitophorous vacuolar membrane, tubular extensions of which radiate out into the host cell compartment. Like all eukaryote cells, the parasite has at its surface a plasma membrane, as well as having a variety of internal membrane-bound organelles that perform a range of functions. This review focuses on the transport properties of the different membranes of the malaria-infected erythrocyte, as well as on the role played by the various membrane transport systems in the uptake of solutes from the extracellular medium, the disposal of metabolic wastes, and the origin and maintenance of electrochemical ion gradients. Such systems are of considerable interest from the point of view of antimalarial chemotherapy, both as drug targets in their own right and as routes for targeting cytotoxic agents into the intracellular parasite.
 

J Assoc Physicians India 1998 Apr;46(4):360-2
The changed clinical spectrum of malaria due to drug resistance.

Mehta SR, Kohle VS, Chauhan SS
Medical Division, Army Hospital (Referral and Research), Delhi Cantt-110 010.

The clinical spectrum of 14 cases of Plasmodium falciparum malaria (PF) who received empirical treatment and suffered from initial prolonged mild illness culminating into severe complicated malaria are presented. The empirical treatment (ET) consisted of adequate doses of chloroquine in 9, chloroquine with pyrimethamine-sulphadoxine combination in 3 and pyrimethamine-sulphadoxine alone in 2 cases. Moderate fever and weakness persisted for 7 to 28 days leading to anaemia and progressive hepatosplenomegaly in all patients. Other clinical features noticed included jaundice in 5, sudden shock with pulmonary oedema in 4, cerebral malaria and renal failure in 3 each and multiorgan in 4 cases. Subsequent investigations revealed PF rings in 9 cases, mixed PF and vivax infection in 3 and PF gametocytaemia only in 2 patients. Seven patients received quinine, 4 quinine with doxycycline and 3 were given quinine followed by injection artemether. Exchange transfusion was carried out in two cases. Four patients died. The empirical treatment with first line antimalarials alters the clinical profile of resistant PF, makes it milder temporarily, delays in confirming the diagnosis and leads to high mortality. There is urgent need for more diligent early workup for these patients who linger on with moderate pyrexia, progressive hepatosplenomegaly, anaemia and jaundice after ET till better diagnostic methods are available to avoid the prolonged illness and high mortality.

 

J Assoc Physicians India 2000 May;48(5):473-7
Prognostic significance of eye changes in cerebral malaria.

Kochar DK, Shubhakaran, Kumawat BL, Vyas SP
Department of Medicine, Divisionof Neurology, SP Medical College, Bikaner-334003.
 
AIMS: Eye in Plasmodium falciparum malaria are described by various workers all over the world but its prognostic significance is not clear because of conflicting observation by different authors from different regions. No such study is available on Indian adult patients of cerebral malaria. So we want to describe our observations on various eye abnormalities in these patients and study its prognostic significance. METHODOLOGY: Two hundred and fourteen adult (> 14 years) patients of strictly defined cerebral malaria admitted in classified malaria ward in this tertiary level health care station were studies. Detailed ophthalmoscopic examination was done through dilated pupils at the time of admission, daily thereafter, at the time of discharge and at weekly intervals in those with persistent changes at the time of discharge. RESULT: Retinal haemorrhage was found in 25 (11.68%) patients, papilloedema in 17 (7.94%), blurring of disc margins in 25 (11.68%), retinal oedema in six (2.8%), disc pallor in five (2.33%), vitreous haemorrhage and hard exudate in one (0.46%) each and subconjunctival haemorrhage in six (2.8%) patients. The mortality associated with individual finding was not statistically significant except disc pallor. CONCLUSION: None of the above finding except disc pallor (p < 0.05) was associated with statistically significant mortality (p > 0.05); whereas any of the fundus findings as a whole was related to statistically significant mortality (p < 0.05).
 

Parasitology 2001 Feb;122(Pt 2):233-51
Methods for estimation of associations between multiple species parasite infections.

Howard SC, Donnell CA, Chan MS
Wellcome Trust Centre for the Epidemiology of Infectious Disease, Department of Zoology, University of Oxford, UK. 
Email: [email protected]
 
Human populations are often infected with more than one species of parasite, especially in developing countries where overall rates of parasitism are high. Infections with multiple parasite species may not necessarily be independent within an individual as physiological, immunological or ecological factors may result in positive or negative associations between infections with different parasite species. A general framework for estimation of these associations is presented. Data from over 215000 individuals are analysed and the associations between geohelminth (Ascaris lumbricoides, Trichuris trichiura and hookworm) and malaria species are investigated. A method is presented for analysing data from multiple communities and testing whether the associations in different communities are equal. Overall estimates of the associations between species are obtained for each country and continent where data were available. Associations between geohelminth species were, in general, found to be positive whilst both positive and negative associations were found between the different Plasmodium species. There was evidence for significant geographical heterogeneity between the associations. A method for using these parameter estimates to predict the distribution of multiple infections when only marginal prevalence data are available is described and demonstrated.
 

Paediatr Drugs 2001;3(2):113-21
Antimalarial chemoprophylaxis in infants and children.

Kramer MH, Lobel HO
Division of Parasitic Diseases, National Center for Infectious Diseases, Centers for Diseases Control and Prevention, Atlanta, Georgia 30341, USA.
 
The evolving patterns of drug resistance in malaria parasites and changes in recommendations for malaria prevention present a challenge to physicians who advise travellers on chemoprophylaxis. Because compliance with personal protection measures is usually low, children should receive appropriate chemoprophylaxis, including breast-fed infants who are not protected through maternal chemoprophylaxis. For travel to areas where chloroquine resistance has not yet been reported (i.e. parts of Central America, the Caribbean and parts of the Middle East), chloroquine alone is sufficient for antimalarial prophylaxis. Mefloquine is the drug of choice for chemoprophylaxis in areas with chloroquine-resistant Plasmodium falciparum, and can be given to infants and young children. The combination of chloroquine and proguanil is well tolerated in children but is much less effective against drug-resistant malaria. Further research is needed to determine the best dosage regimen for antimalarial drugs used for chemoprophylaxis in children.
 

Parasitol Int 1999 Aug;48(2):157-67
Suppressed expression of hypoxanthine-guanine phosphoribosyltransferase (HGPRT) in an irradiation-attenuated Plasmodium berghei XAT strain.

Onda T, Miyamoto K, Sugioka Y, Kangawa K, Kano S, Suzuki M
Department of Parasitology, Gunma University School of Medicine, Maebashi, Japan.
 
Plasmodium berghei XAT (XAT) is a non-reversible, non-lethal type malaria parasite strain derived from the highly virulent lethal P. berghei NK65 (NK65) by X-irradiation. The difference in polypeptide expression between NK65 and XAT was examined in this study. Western blot patterns of the parasite polypeptides showed that a 30-kDa polypeptide was not detected in XAT. In the present paper, we focused the study on the difference in the expression of the 30-kDa polypeptide between XAT and NK65. Although several other significant differences were noted in the spots shown by two-dimensional gel electrophoresis, the 30-kDa polypeptide was isolated by means of preparative 2D-gel electrophoresis followed by HPLC, and N-terminal amino acid sequence of the polypeptide was eventually determined. Complementary DNA clones encoding the 30-kDa polypeptide were isolated and characterized. Full-length cDNA clones from XAT encoded a protein of 231 amino acid residues with a 693-bp open reading frame. The deduced amino acid sequence exhibited 67% identity with that for P. falciparum hypoxanthine-guanine phosphoribosyltransferase (HGPRT; EC 2.4.2.8), suggesting that this protein is P. berghei HGPRT. Northern blot analysis revealed that expression of HGPRT in XAT was only one-eighth of that in NK65. This finding indicates that HGPRT gene expression is markedly suppressed in XAT. The amino acid sequence of HGPRT from NK65 was identical to that from XAT. This finding showed that the amino acid sequence of XAT-HGPRT was not mutated and had not undergone deletion.
 

J Med Entomol 2001 Jan;38(1):22-8
Effects of available sugar on the reproductive fitness and vectorial capacity of the malaria vector Anopheles gambiae (Diptera: Culicidae).

Gary RE Jr, Foster WA
Department of Entomology, the Ohio State University, 1735 Neil Avenue, Columbus, OH 43210, USA.
 
Although females of most mosquito species are known to use sugar as a necessary source of energy, female Anopheles gambiae Giles sensu stricto are thought to use it facultatively or not at all. However, field evidence of sugar-free living is inconclusive, and the implications for reproductive fitness and vectorial capacity are unknown. To evaluate the role that sugar may play in the ecology of these mosquitoes, mated female An. gambiae in the laboratory were given access to either no food (water only), 10% sucrose, human blood, or human blood + 10% sucrose, and comparisons of daily mortality, fecundity, and biting frequency were made. The effect of sugar availability on vectorial capacity and the intrinsic rate of increase, a measure of fitness, then were determined. Females (pooled and individual) given blood + sugar lived significantly longer than did those on the other diets. Daily fecundity was higher for females given blood alone than for those fed blood + sugar (13 versus 9 eggs per female daily). However, total fecundity and intrinsic rate of increase were not affected by sugar availability. Biting frequency was significantly higher (0.41 versus 0.26 bites per female per day) for females given blood alone. Despite the reduced survivorship, exclusive blood-feeding led to a theoretically higher vectorial capacity for Plasmodium falciparum at 27 degrees C. These data indicate that female An. gambiae could replace sugar with increased blood feeding without suppressing reproductive fitness. Increased blood feeding could, in turn, increase the rate of malaria transmission and may explain the unusual efficiency of this vector.
 

J Med Entomol 2001 Jan;38(1):122-5
Dogs as a favored host choice of Anopheles gambiae sensu stricto (Diptera: Culicidae) of Sao Tome West Africa.

Sousa CA, Pinto J, Almeida AP, Ferreira C, do Rosario VE, Charlwood JD
Unidade de Entomologia Medica, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa. Rua da Junqueira 96, 1349-008 Lisbon, Portugal.
 
The host source and human blood index (HBI) of an exophilic population of the "forest" cytoform of Anopheles gambiae Giles sensu stricto, from a peri-urban area of the island of Sao Tome were assessed. Blood meals of 434 An. gambiae females from all-night indoor light-trap collections, 193 from indoor and 422 from outdoor resting collections, were determined by ELISA. Significant differences were found in the HBI estimates from insects collected indoors (0.93) and outdoors (0.27). Blood-fed insects collected resting outdoors provided the most representative sample for host determination. Dogs were the predominant hosts, followed by humans and pigs. Of all human feeds, it was estimated that 81.5% were taken inside houses. The low HBI of 0.27 for the An. gambiae population explains the low sporozoite rate and the meso-endemicity of malaria in the island.
 

Parasitol Int 2001 Mar;50(1):33-9
A potent antimalarial activity of Hydrangea macrophylla var. Otaksa leaf extract against Plasmodium yoelii 17XL in mice.

Ishih A, Ikeya C, Yanoh M, Takezoe H, Miyase T, Terada M
Department of Parasitology, Hamamatsu University School of Medicine, 3600 Handa-cho, 431-3192, Hamamatsu, Japan
 
The antimalarial activity of the hot-water extract of Hydrangea macrophylla var. Otaksa leaves was evaluated against Plasmodium yoelii 17XL in mice. Non-treated control mice died from 6 to 7 days after infection, but mice treated with the leaf extract survived during the experiment. Mice given the extract orally showed low parasitemia levels during administration. Following a transient recrudescence of malaria parasites in the bloodstream of treated mice, no parasites could be detected by a microscopic examination. Furthermore, the 30% MeOH aq. eluate and 50% MeOH aq. eluate from dried leaves of H. macrophylla var. Otaksa showed an antimalarial activity in vivo. Sulfamonomethoxine was orally given to infected mice to compare with the antimalarial activity of the hot-water extract of leaves. Sulfamonomethoxine given orally reduced parasitemia, but no complete cure of mice was observed.
 

Parasitol Int 2001 Mar;50(1):9-13
Variation of incubation time in an in vitro drug susceptibility test of Plasmodium falciparum isolates studied in the Solomon Islands.

Inaba H, Ohmae H, Kano S, Faarado L, Boaz L, Leafasia J, Suzuki M
Department of Parasitology, Gunma University School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma, Japan
 
A study on chloroquine resistance of falciparum malaria was conducted in the Solomon Islands. Both in vitro and clinical tests were performed. In our regular studies of in vitro chloroquine susceptibility tests on Plasmodium falciparum from non-immuners in Japan, the threshold point to differentiate resistant and susceptible isolates was set at a 0. 114 ?M chloroquine in the semi-micro culture system, and this point was also applicable in the study of the malaria parasite taken in the highly endemic malarious area with good coincidence with clinical observation. Variation in the incubation time (24-63) to reach the schizont stage of the isolated parasites were noted. It appeared that chloroquine resistant P. falciparum showed traits to reach the schizont stage within a shorter incubation period.
 

Emerg Infect Dis 2001 Jan-Feb;7(1):35-42
Geographic subdivision of the range of the malaria parasite Plasmodium vivax.

Li J, Collins WE, Wirtz RA, Rathore D, Lal A, McCutchan TF
National Institutes of Health, Bethesda, Maryland, USA.
 
We examined geographically distinct isolates of Plasmodium vivax and categorized them according to developmental success in Anopheles albimanus. We found that parasites from Central America and Colombia form a group distinct from those of Asia. New World isolates have a distinct chromosomal translocation and an episomal variation in the open reading frame (ORF) 470 DNA sequence that distinguishes them from the other isolates tested. Old World types of P. vivax were introduced into the Americas, and a remnant of this lineage remains in P. simium. It is indistinguishable from Old World P. vivax to the extent determinable by using our encoded markers and the examination of its developmental pattern in mosquitoes. The cohesive characteristics that separate types of P. vivax are predictors of range and potential for transmission and hence require taxonomic distinction.
 

Immunol Cell Biol 2001 Apr;79(2):101-20
Central nervous system in cerebral malaria: 'Innocent bystander' or active participant in the induction of immunopathology?

Medana IM, Chaudhri G, Chan-Ling T, Hunt NH
Departments of Pathology and Anatomy/Histology, University of Sydney, New South Wales, Australia.
 
Cerebral malaria (CM) is a major life-threatening complication of Plasmodium falciparum infection in humans, responsible for up to 2 million deaths annually. The mechanisms underlying the fatal cerebral complications are still not fully understood. Many theories exist on the aetiology of human CM. The sequestration hypo-thesis suggests that adherence of parasitized erythrocytes to the cerebral vasculature leads to obstruction of the microcirculation, anoxia or metabolic disturbances affecting brain function, resulting in coma. This mechanism alone seems insufficient to explain all the known features of CM. In this review we focus on another major school of thought, that CM is the result of an over-vigorous immune response originally evolved for the protection of the host. Evidence in support of this second hypothesis comes from studies in murine malaria models in which T cells, monocytes, adhesion molecules and cytokines, have been implicated in the development of the cerebral complications. Recent studies of human CM also indicate a role for the immune system in the neurological complications. However, it is likely that multiple mechanisms are involved in the induction of cerebral complications and both the presence of parasitized erythrocytes in the central nervous system (CNS) and immunopathological processes contribute to the pathogenesis of CM. Most studies examining immunopathological responses in CM have focused on reactions occurring primarily in the systemic circulation. However, these also do not fully account for the develop-ment of cerebral complications in CM. In this review we summarize results from human and mouse studies that demonstrate morphological and functional changes in the resident glial cells of the CNS. The degree of immune activation and degeneration of glial cells was shown to reflect the extent of neurological complications in murine cerebral malaria. From these results we highlight the need to consider the potentially important contribution within the CNS of glia and their secreted products, such as cytokines, in the development of human CM.
 

J Infect Dis 2001 Apr 15;183(8):1260-8
Malaria infection induces virus expression in human immunodeficiency virus transgenic mice by cd4 t cell-dependent immune activation.

Freitag C, Chougnet C, Schito M, Near KA, Shearer GM, Li C, Langhorne J, Sher A
Immunobiology Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, and 4Howard Hughes Medical Institute, Research Scholars Program, National Institutes of Health, Bethesda, Maryland, USA.
 
To test the capacity of malaria parasites to trigger virus expression in vivo, human immunodeficiency virus (HIV) transgenic mice were infected with Plasmodium chabaudi chabaudi clone AS. Splenocytes recovered during peak parasitemia showed a dramatic elevation in viral p24 production that returned to baseline by day 15 and failed to rebound at recrudescence or after reinfection. The major sources of virus expression were antigen-presenting cells (APCs) rather than T lymphocytes. Nevertheless, T cells from infected mice stimulated with plasmodial antigen triggered 5-10-fold increases in p24 production from dendritic cells in vitro, which suggests that viral induction stems from interaction of malaria-specific T lymphocytes with HIV-expressing APCs. Indeed, depletion of CD4 T cells resulted in a 70% reduction in the p24 response stimulated by malaria in vivo. These findings demonstrate the ability of Plasmodium species to immunologically activate latently integrated HIV in vivo but suggest that this process may be restricted to acute infection.
 

J Infect Dis 2001 Apr 15;183(8):1254-9
Artesunate Reduces but Does Not Prevent Posttreatment Transmission of Plasmodium falciparum to Anopheles gambiae.

Targett G, Drakeley C, Jawara M, von Seidlein L, Coleman R, Deen J, Pinder M, Doherty T, Sutherland C, Walraven G, Milligan P
Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London WC1E 7HT, United Kingdom. 
Email: [email protected]
 
Combination therapy that includes artemisinin derivatives cures most falciparum malaria infections. Lowering transmission by reducing gametocyte infectivity would be an additional benefit. To examine the effect of such therapy on transmission, Gambian children with Plasmodium falciparum malaria were treated with standard regimens of chloroquine or pyrimethamine-sulfadoxine alone or in combination with 1 or 3 doses of artesunate. The infectivity to mosquitoes of gametocytes in peripheral blood was determined 4 or 7 days after treatment. Infection of mosquitoes was observed in all treatment groups and was positively associated with gametocyte density. The probability of transmission was lowest in those who received pyrimethamine-sulfadoxine and 3 doses of artesunate, and it was 8-fold higher in the group that received pyrimethamine-sulfadoxine alone. Artesunate reduced posttreatment infectivity dramatically but did not abolish it completely. The study raises questions about any policy to use pyrimethamine-sulfadoxine alone as the first-line treatment for malaria.
 

Cell Microbiol 2001 Mar;3(3):125-131
Molecular mechanisms of Plasmodium falciparum placental adhesion.

Scherf A, Pouvelle B, Buffet PA, Gysin J
Unite de Biologie des Interactions Hote-Parasite, CNRS URA 1960, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris, France; Laboratoire de Parasitologie Experimentale, Faculte de Medecine, Universite de la Mediterranee (Aix-Marseille II), 13385 Marseille Cedex 5, France.
 
In natural Plasmodium falciparum infections, parasitized erythrocytes (PEs) circulate in the peripheral blood for a period corresponding roughly to the first part of the erythrocytic life cycle (ring stage). Later, in blood-stage development, parasite-encoded adhesion molecules are inserted into the erythrocyte membrane, preventing the circulation of the PEs. The principal molecule mediating PE adhesion is P. falciparum erythrocyte membrane protein 1 (PfEMP1), encoded by the polymorphic var gene family. The population of parasites is subject to clonal antigenic variation through changes in var expression, and a single PfEMP1 variant is expressed at the PE surface in a mutually exclusive manner. In addition to its role in immune evasion, switches in PfEMP1 expression may be associated with fundamental changes in parasite tissue tropism in malaria patients. A switch from CD36 binding to chondroitin sulphate A (CSA) binding may lead to extensive sequestration of PEs in placenta syncytiotrophoblasts. This is probably a key event in malaria pathogenesis during pregnancy. The CSA-binding phenotype of mature PEs is linked to another distinct adhesive phenotype: the recently described CSA-independent cytoadhesion of ring-stage PEs. Thus, a subpopulation of PEs that sequentially displays these two different phenotypes may bind to an individual endothelial cell or syncytiotrophoblast throughout the asexual blood-stage cycle. This suggests that non-circulating (cryptic) parasite subpopulations are present in malaria patients.
 

J Indian Med Assoc 2000 Oct;98(10):615-6, 618
Review of trends of malaria in an urban community of Calcutta during 1984-1997.

Chattopadhyay O, Sengupta G
All India Institute of Hygiene and Public Health, Calcutta.
 
The trends in the malaria situation over the last 14 years in an urban community of Calcutta with a population of 1,04,000 have been analysed with particular reference to the malaria epidemic which took place in Calcutta in November-December, 1995. Annual and monthwise data on malariometric indices pertaining to 1984-1997 were collected from health centre records. The total number of blood slides examined every year has steadily increased from around 8,000 in 1984 to more than 23,000 in 1996 with some decline in 1997. About 95% of the confirmed malaria cases were of the benign tertian type, while remaining 5% were of the malignant tertian type. The slide vivax rate has steadily declined over the years 1984-1997 from around 50 per cent in 1984 to between 20 to 30 per cent during 1993-1997. The slide falciparum rate over the same period varied between 0.5 to 2 per cent and did not show any clear secular trend. The annual parasite incidence (API) which varied cyclically between 40 to 60 per thousand during 1984-87 increased (with a cyclical trend superimposed on a secular increasing trend) to vary between 50 to 70 per thousand during 1994-97. The 1995 winter epidemic of malaria was characterised by an increased occurrence of both P vivax and P falcipanrum malaria.
 

Med Trop (Mars) 2000;60(3):251-5
[No title available].

[Article in French]
Nahum A, Akogbeto M
Centre de Recherche Entomologique de Cotonou, 06 BP 2604 Cotonou, Republique du Benin.
 
The purpose of this study was to evaluate the state of knowledge and use of drug in pregnant women diagnosed with malaria at the first prenatal examination. Survey data were conducted of physicians and paramedical staff working the public and private sector in Cotonou, Benin from November 1996 to January 1997. A questionnaire including items on the type of antimalarials used, therapeutic regimens and compliance with the treatment posology and duration guidelines as defined by the WHO and recommended by the National Program against Malaria. A study of informational supports allowed validation of responses obtained during the interview on the day of survey. A random two-degree, stratified sample of 208 prescribers including 109 physicians, 51 midwives, and 48 nurses was interviewed. Data analysis showed that chemoprophylaxis was prescribed by all midwives, 87.5 p. 100 of nurses, and 8.2 p. 100 of physicians. Midwives prescribed this strategy in all pregnant women. For 5.5 p. 100 of physicians and 6.3 p. 100 of nurses, primigravid women were considered as a target group. Chloroquine was the most widely used antimalarial. It was sometimes used in association with proguanil. Of the other drugs used for prevention, quinine was prescribed by 2.4 p. 100 of nurses and 1.1 p. 100 of physicians. The therapeutic regimes and posologies used by the health care workers were not in compliance with the policies of the National Program for Control of Malaria. The findings warrant the creation of an organization to promote consultation and communication between health care authorities and workers.
 

Med Trop (Mars) 2000;60(3):243-9
[No title available].

[Article in French]
Randrianarivelojosia M, Raharimalala L, Randriamanantena A, Jambou R
Laboratoire du Paludisme, l'Institut Pasteur de Madagascar, Antananarivo, Madagascar.
 
Chloroquine is still the drug of choice for first-line treatment of uncomplicated malaria in Madagascar. However development and spread of chloroquine-resistance could compromise this therapeutic strategy in the future. The purpose of this 1997 study was to compare the efficacy of combined treatment using sulfadoxine and pyrimethamine and single-agent treatment using chloroquine for management of uncomplicated malaria. Study data were collected at four sites in coastal areas of Madagascar where transmission of malaria is perennial. Prevalence of malaria ranged from 15 p. 100 to 22 p. 100 in school children and from 24 p. 100 to 72 p. 100 in outpatient consulting spontaneously at community health centers. All four Plasmodium species affecting man were identified. Plasmodium falciparum was involved in 83 p. 100 of cases. In vivo testing of the susceptibility of Plasmodium falciparum to chloroquine was performed in 149 patients according to the standard simplified 7-day protocol of the WHO. The 35 tests in school children demonstrated no evidence of resistance. However type R1 + R2 resistance was noted in 17 of the 114 tests performed on outpatients, i.e. 14.9 p. 100. In vitro testing demonstrated chloroquine resistance in four of the 90 specimens tested, i.e. 4.4 p. 100. With regard to combined sulfadoxine/pyrimethamine treatment, 45 of 46 in vivo tests in outpatients showed no evidence of resistance. Combination treatment was more effective than single-agent treatment (p = 0.02) and could offer an effective alternative for future use.
 

Vaccine 2001 Mar 21;19(17-19):2315-8
Genomic tools for gene and protein discovery in malaria: toward new vaccines.

Carucci DJ
Malaria Program, Naval Medical Research Center, 20910, Silver Spring, MD, USA
 
Advances in malaria vaccine and drug development have been hindered in part by the complex multistage life cycle of the parasite, much of which is inaccessible to study, and by a large genome encoding over 5000 genes. Two human models of immunity to malaria, however, suggest that the development of an effective vaccine is within reach. We have outlined a strategy to identify the expression of hundreds to thousands of potential vaccine targets employing recently developed technologies for gene and protein expression. Combined with the exciting developments of malaria DNA vaccine technologies, these approaches form the basis for malaria subunit vaccines that may mimic the protective efficacy of our human model systems and provide the foundation for novel approaches to vaccine development for a range of pathogens.
 

Vaccine 2001 Mar 21;19(17-19):2309-14
Transmission blocking malaria vaccines.

Carter R
University of Edinburgh, Division of Biological Sciences, West Mains Road, EH9 3JT, Edinburgh, UK
 
Transmission blocking vaccines (TBVs) against malaria are intended to induce immunity against the stages of the parasites which infect mosquitoes so that TBV-immunised individuals cannot transmit malaria. As malarial infections are transmitted mainly within a few hundreds of meters from an infectious human source, TBVs used within in a community would protect the immediate neighbourhood of the vaccinated individuals. TBVs against the two major species of human malaria, Plasmodium falciparum and P. vivax, are under development. Candidate TBV constructs for both Plasmodium species have been successfully tested in animal systems and testing is in progress with clinical grade material in humans.
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Last modified May 02, 2001