Species Of Malarial Parasites Research Articles

Recent Trends in Malaria Vaccine Research Globally: A Bibliometric Analysis From 2005 to 2022.

Aim: Malaria vaccine is one of the critical areas in tropical health research, considering the success recorded in other vaccine-preventable diseases. This study is aimed at reviewing recent trends in global malaria vaccine research from 2005 to 2022. Method: A validated search strategy was undertaken to identify scientific literature on the malaria vaccine in the Scopus database. Bibliometric indicators identified include a pattern of publication growth and citations over the study period; top authors, countries, funding organizations, and journals; keywords, including different malarial parasite species, and the overall research themes. Result: A total of 6457 documents were found from 2005 to 2022, published in 160 journals/sources in 189 countries/territories. Malaria Journal published the highest number of research outputs (478, 7.4%) within the study period, and the highest number of documents (468, 7.3%) were published in 2021. There were 214,323 total citations, with 33.2 average citations per document and 167 documents' h-index. The United States, United Kingdom, and Australia combined produced more than 60% of the publication output, with most collaboration with African countries such as Kenya. Plasmodium falciparum is the most occurring parasite species keyword (754, 11.7%), with a growing interest in Plasmodium knowlesi (30, 0.5%). Merozoite surface protein, characterization, trials, infant/children, traveler, and research/review were the six themes that emerged from the studies. Conclusion: The last one and half decades have seen a significant increase in malaria vaccine research and citations, mainly targeting vaccine development, safety, and efficacy in Africa. This necessitates more international efforts to improve the vaccines' effectiveness considering different Plasmodium species.

Breaking the silos, stopping the spread: an interview with Jyoti Joshi.

Breaking the silos, stopping the spread: an interview with Jyoti Joshi.

Development of a Multiplex Loop-Mediated Isothermal Amplification Assay for Diagnosis of Plasmodium spp., Plasmodium falciparum and Plasmodium vivax.

Malaria, caused by the parasite Plasmodium and transmitted by mosquitoes, is an epidemic that mainly occurs in tropical and subtropical regions. As treatments differ across species of malarial parasites, there is a need to develop rapid diagnostic methods to differentiate malarial species. Herein, we developed a multiplex malaria Pan/Pf/Pv/actin beta loop-mediated isothermal amplification (LAMP) to diagnose Plasmodium spp., P. falciparum, and P. vivax, as well as the internal control (IC), within 40 min. The detection limits of the multiplex malaria Pan/Pf/Pv/IC LAMP were 1 × 102, 1 × 102, 1 × 102, and 1 × 103 copies/µL for four vectors, including the 18S rRNA gene (Plasmodium spp.), lactate dehydrogenase gene (P. falciparum), 16S rRNA gene (P. vivax), and human actin beta gene (IC), respectively. The performance of the LAMP assay was compared and evaluated by evaluating 208 clinical samples (118 positive and 90 negative samples) with the commercial RealStar® Malaria S&T PCR Kit 1.0. The developed multiplex malaria Pan/Pf/Pv/IC LAMP assay showed comparable sensitivity (100%) and specificity (100%) with the commercial RealStar® Malaria S&T PCR Kit 1.0 (100%). These results suggest that the multiplex malaria Pan/Pf/Pv/IC LAMP could be used as a point-of-care molecular diagnostic test for malaria.

Prevalence of asymptomatic submicroscopic malaria in eastern Indonesia: a cross sectional survey and spatial analysis

Abstract Background In 2013 in Indonesia, 4·8 million people were infected with malaria, and 23 483 malaria-related deaths were reported. Most infections were reported in eastern Indonesia, with two dominant species of malarial parasite: Plasmodium falciparum (62%) and P vivax (33%). Annual parasite incidence was 15·6 per 1000 population. In 2016, the Indonesian Ministry of Health announced that Indonesia would reach the WHO-defined pre-elimination stage for malaria by 2020, and be free of malaria transmission by 2030. Unfortunately, real data on incidence, surveillance, and mapping of malaria cases is scarce. This study will assess whether East Nusa Tenggara Province in eastern Indonesia should proceed with the malaria pre-elimination stage activities. Methods We did a survey of 555 people who were systematically selected from five districts in eastern Indonesia. We included healthy participants aged 14 years and older who had a blood haemoglobin concentration ≥100 g/L. We recorded baseline characteristics and risk factors for malaria infection via a standardised questionnaire, and blood samples were taken for analysis. All participants were examined by a local medical doctor. A malaria case was defined as the presence of Plasmodium spp in blood detected with nested PCR (nPCR) or microscopy. Data were collected by standard questionnaire, physical examination and laboratory tests (haemoglobin concentration measurements, microscopic analysis, and nPCR). We mapped nPCR-confirmed cases of malaria using ArcGIS 9.1 spatial and SaTScan analysis. We used univariate and bivariate statistical analysis for statistical analysis. Findings Between August, 2013, and September, 2014, we included 555 samples in our survey. 181 (32·6%) samples tested positive for malaria with n-PCR: only nine (1·6%) of these cases were detected by microscopy. P vivax was the most common Plasmodium spp detected (94 cases [51·9%]). Not using bednets was the most important risk factors for malaria in our population (OR 2·34, 95% CI 1·98–4·83); fever, which is the most commonly presented symptom, was noted in only five cases (0·9%). Results of spatial analysis showed three distinct and significant clusters: 13 cases (7·2%, p=0·0041), 54 cases (29·9%, p=0·0025), and 87 cases (48·1%, p=0·001). However, all malaria clusters were in areas of low malaria incidence. Interpretation A malaria pre-elimination programme in eastern Indonesia should be delayed. Routine treatment to stop silent transmission of malaria, and improved laboratory surveillance, are needed. Funding Asia Pacific Malaria Elimination Network (APMEN) Project number 103-02 as part of the APMEN Country Partner Technical Development Program Round-X. Major funding for APMEN is provided by Australian Government Department of Foreign Affair and Trade, alongside funds received from Bill and Melinda Gates Foundation.

From the Fifth to the Seventh Human Malarial Species: A New Concern in Infectious Medicine

Dear Editor, Malaria, a parasitic infection caused by Plasmodium spp., is a global public health threat. In humans, four species of malarial parasites are well known: Plasmodium vivax, P. falciparum, P. ovale, and P.malariae. Within the past decade, there are new emerging human malarial species, and this becomes a very interesting issue in malariology. The fifth malarial species, P. knowlesi, which was first reported in Southeast Asia, has become a worldwide public health concern (1). Many cases of P. knowlesi malaria have been reported in travelers returning from Southeast Asia (2). In 2014, the sixth malarial species, P. cynomolgi, was identified in Southeast Asia, with a single case reported in Malaysia (3). Malaria caused by P. cynomolgi is very difficult to differentiate from that caused by P. vivax (3). In 2015, Lalremruata et al. (4) reported the seventh human malarial species, P. brasilianum, this time in South America. Similar to malaria caused by P. cynomolgi, malaria caused by P. brasilianum cannot be easily differentiated from classical human malaria by a blood smear. There are also no differences in the clinical presentations. Thus, identification depends on the use of molecular diagnostic methods. Based on 18S rRNA gene sequencing, Lalremruata et al. (4) identified 12 patients harboring malaria parasites, which were 100% identical to those of P. brasilianum isolated from the monkey Alouatta seniculus. Indeed, P. brasilianum malaria is important monkey malaria, and the chance for human cross-species infection had already been highlighted (3). Of interest, other carriers of malaria, such as the monkeys P. eylesi, P. inui, P. schwetzi, and P. simium, provide an opportunity for cross-species infection. Surveillance and studies of these species for possible new human infections are recommended.

Modeling malaria in humanized mice: opportunities and challenges.

About half of the world is at risk for developing malaria, which killed over 600,000 people in 2012 alone. The limited host range of the Plasmodium species that cause malaria in humans poses challenges for studying these parasites in experimentally tractable in vivo systems. To address this challenge, humanized mice have been constructed in which the tissue compartments relevant to the mammalian stages of plasmodial parasites are humanized. The development of human liver chimeric mice, human erythroid chimeric mice, and dually engrafted mice now allows for faithful replication of the entire Plasmodium falciparum life cycle. Although refinements to these models are still needed, humanized mice provide a promising small-animal model to study development of P. falciparum and, conceivably, other human malarial parasite species, and may also aid in drug and vaccine development.

Malaria Diagnosis Using Automated Analysers: A Boon for Hematopathologists in Endemic Areas.

Haematological abnormalities are common in acute febrile tropical illnesses. Malaria is a major health problem in tropics. In endemic areas especially in the post monsoon season, it is not practical to manually screen all peripheral blood films (PBF) for malarial parasite. Automated analysers offer rapid, sensitive and cost effective screening of all samples. The study was done to evaluate the usefulness of automated cell counters analysing their histograms, scatter-grams and the flaggings generated in malaria positive and negative cases. The comparison of other haematological parameters were also studied which could help to identify malaria parasite in peripheral blood smear. The blood samples were analysed using Beckman coulter LH-750. The abnormal scatter grams and additional peaks in WBC histograms were observed diligently & compared with normal controls. Haematological abnormalities were also evaluated. Statistical analysis was done by using software Epi-Info version 7.1.4 freely available from CDC website. Fisher exact test was applied to calculate the p-value and value < 0.05 was considered as significant. Final identification of malarial parasite species was done independently by peripheral blood smear examination by two pathologists. Of all the 200 cases evaluated abnormal scatter grams were observed in all the cases of malaria while abnormal WBC histogram peaks were noted in 96% cases demonstrating a peak at the threshold of the histogram. The difference between number of slides positive for abnormal WBC scatter gram and abnormal WBC histogram peaks were statistically highly significant (p=0.007). So abnormal WBC scatter gram can better give idea of malarial parasite presence. Of the haematological parameters thrombocytopenia (92% cases) emerged as the strongest predictor of malaria. It is recommended for haematopathologists to review the haematological data and the scatter plots on the analyser along with peripheral blood smear examination.

Calculation skills for nurses: malaria chemoprophylaxis

T tropical disease malaria is transmitted by mosquito bites and caused by the infection of red blood cells by a Plasmodium protozoan parasite, with travellers from malariafree countries being very vulnerable to the disease once infected (World Health Organization, 2013). The most common malarial parasite, Plasmodium falciparum, can cause a range of serious illnesses including renal failure, pulmonary oedema, disseminated intravascular coagulation and severe anaemia (National Institute for Health and Care Excellence (NICE), 2010). It is also the species of malarial parasite most likely to be fatal. In the UK in 2012, there were 1378 identified cases of imported malaria, two of which resulted in death (Public Health England, 2013a). Combining chemoprophylaxis with steps to avoid mosquito bites when travelling to countries with a high risk of infection can provide significant protection (National Travel Health Network and Centre, 2013).

Efficacy of Immunodiagnosis of Falciparum Malaria at Different Levels of Parasitemia

Background: Among the several human species of malarial parasites, Plasmodium falciparum can cause severe infection and if left untreated, there may be fatal complications. Early diagnosis and prompt treatment have been proposed to reduce the morbidity and mortality from malaria. Objective: To assess the diagnostic efficacy of antigen detection by immunochromatographic test (ICT) at different levels of parasitemia for diagnosis of malaria. Materials and Methods: This study was carried out in the department of Microbiology, Mymensingh Medical College for a period of one year from July 2005 to June 2006. A total of 98 clinically suspected malaria patients were included in this study. Peripheral blood films (PBF) were examined under microscope and parasite count/?L of blood was performed. Subsequently ICT for malaria antigen was done for each case. Results: Out of 59 cases positive by microscopic examination of blood films, 54 cases had parasitemia &gt;600 parasites/?L of blood and all these cases were positive by ICT for malaria antigen. Rest 5 cases showed parasitemia &lt;600 parasites/?L of blood and one case was found positive by ICT for malaria antigen. Conclusion: Immunochromatographic test can be used for early diagnosis of malaria with hyperparasitemia, especially for cerebral malaria. Journal of Enam Medical College; Vol 3 No 2 July 2013; Page 88-90 DOI: http://dx.doi.org/10.3329/jemc.v3i2.16130

Characterizing Pv ARP, a novel Plasmodium vivax antigen

BackgroundPlasmodium vivax continues to be the most widely distributed malarial parasite species in tropical and sub-tropical areas, causing high morbidity indices around the world. Better understanding of the proteins used by the parasite during the invasion of red blood cells is required to obtain an effective vaccine against this disease. This study describes characterizing the P. vivax asparagine-rich protein (PvARP) and examines its antigenicity in natural infection.MethodsThe target gene in the study was selected according to a previous in silico analysis using profile hidden Markov models which identified P. vivax proteins that play a possible role in invasion. Transcription of the arp gene in the P. vivax VCG-1 strain was here evaluated by RT-PCR. Specific human antibodies against PvARP were used to confirm protein expression by Western blot as well as its subcellular localization by immunofluorescence. Recognition of recombinant PvARP by sera from P. vivax-infected individuals was evaluated by ELISA.ResultsVCG-1 strain PvARP is a 281-residue-long molecule, which is encoded by a single exon and has an N-terminal secretion signal, as well as a tandem repeat region. This protein is expressed in mature schizonts and is located on the surface of merozoites, having an apparent accumulation towards their apical pole. Sera from P. vivax-infected patients recognized the recombinant, thereby suggesting that this protein is targeted by the immune response during infection.ConclusionsThis study showed the characterization of PvARP and its antigenicity. Further assays orientated towards evaluating this antigen’s functional importance during parasite invasion are being carried out.

Disease Dynamics and Surveillance of Malaria in Malwa Region of Punjab and Evaluation of RDT Test

Aim: Malaria remains an enormous public health problem. Regular and ongoing surveillance to detect changes in its trends to initiate the control measures is the need of the hour. The present study was undertaken to provide the malaria transmission dynamics using surveillance indicators through active and passive surveillance in district Faridkot. Usefulness of rapid malaria diagnostic test was also evaluated. Methodology: This retrospective study extended over a period of two years (2010-2011). Thick and thin blood smears were prepared from suspected cases of malaria complaining of fever and headache for the last three days (i) of 2 CHC’s, 8 PHC’s and 68 sub centers as a part of active surveillance and (ii) those who visited GGS Medical College & Hospital and civil hospital Faridkot as a part of passive surveillance. Out of all the samples collected during the passive surveillance 995 samples collected at GGS Medical College and Hospital, Faridkot were also subjected to rapid diagnostic test (OptiMAL). Results: The annual blood examination rate (ABER) was 9.0 and 9.7 in 2010 and 2011 respectively. Annual parasite incidence (API) recorded was < 2 (0.5) in both the years and slide positive rate (SPR) was 0.5 and 0.05 in the two respective years of study. Significant gap in the rate of case detection of active and passive surveillance systems was observed with predominance of passive surveillance. More than 96% of cases were of P. vivax. Research Article British Microbiology Research Journal, 3(3): 339-345, 2013 340 RDT’s showed an excellent correlation with conventional microscopy. Conclusion: Malaria (P. vivax) is a persistent problem in the Malwa region with variation in its transmission dynamics with in the year. P. vivax is the main species of malarial parasite in the Faridkot district with occasional cases of falciparum malaria. Prevention strategy should be targeted towards on the spot diagnosis by using RDT and hence prompt treatment. It could help to prevent spread of drug resistance and complicated malaria.

Investigating the activity of quinine analogues versus chloroquine resistant Plasmodium falciparum

Plasmodium falciparum, the deadliest malarial parasite species, has developed resistance against nearly all man-made antimalarial drugs within the past century. However, quinine (QN), the first antimalarial drug, remains efficacious worldwide. Some chloroquine resistant (CQR) P. falciparum strains or isolates show mild cross resistance to QN, but many do not. Further optimization of QN may provide a well-tolerated therapy with improved activity versus CQR malaria. Thus, using the Heck reaction, we have pursued a structure–activity relationship study, including vinyl group modifications of QN. Certain derivatives show good antiplasmodial activity in QN-resistant and QN-sensitive strains, with lower IC50 values relative to QN.

Cysteine-3 and cysteine-4 are essential for the thioredoxin-like oxidoreductase and antioxidant activities of Plasmodium falciparum macrophage migration inhibitory factor

Plasmodium falciparum macrophage migration inhibitory factor (PfMIF) exhibits thioredoxin (Trx)-like oxidoreductase activity but the active site for this activity and its function have not been evaluated. A bioinformatics search revealed that the conserved CXXC motif, which is responsible for Trx-like oxidoreductase activity, is absent from PfMIF. In contrast, the adjacent N-terminal Cys-3 and Cys-4 are conserved in MIF across species of malarial parasites. Mutation of either vicinal Cys-3 or Cys-4 of PfMIF abolished the Trx-like activity, whereas the mutation of the remaining Cys-59 or Cys-103 did not affect it. PfMIF has an antioxidant function. It prevents reactive oxygen species-mediated lipid peroxidation and oxidative damage of DNA as evident from DNA nicking assay. Interestingly, chemical modification of the vicinal cysteines by phenylarsine oxide (PAO), a specific vicinal thiol modifier, significantly prevented this antioxidant activity. Modification of Cys-3 and Cys-4 was confirmed by MALDI-TOF mass spectroscopy of peptide fragments obtained after cyanogen bromide digestion of PAO-modified PfMIF. Furthermore, mutation of either Cys-3 or Cys-4 of PfMIF resulted in the loss of both Trx-like oxidoreductase and antioxidant activities of PfMIF. Altogether, our results suggest that the vicinal Cys-3 and Cys-4 play a critical role in the Trx-like oxidoreductase activity and antioxidant property of PfMIF.

MALARIAL PARASITE

Objectives: To determine the slide positivity rate and to document the different species of malarial parasite at district Shikarpur,Sindh, Pakistan. D e s i g n : A retrospective study. Setting: This study was conducted at district Malaria control centre Shikarur with collaborationof Pathology Department CMC Larkana and Leishmaniaisis/Mosquito Zoology Lab: University of Balochistan Quetta overthe period of one yeari.e. 2006. Patients a n d M e t h o d s : During the study period blood smears were prepared from the suspected cases of malaria. The patients withdifferentiated fever referred from various areas of Shikarpur District by general practitioners, basic health units, rural health centres and talukahospitals were included in the study for confirmation of malaria. The parasites were identified by using Giemsa stained thick and thin smearsfollowing Mansen-Bahar and Bell, 1987. Results: During the study period total of 67550 Blood smears were examined irrespective of age andse and 740 were confirmed for malarial parasites, giving an overall slide positivity rate of 1.09%. Plasmodium falciparum was identified in 267(36.08%) cases and Plasmodium vivax in 473 (63.92%) cases. C o n c l u s i o n : The slide positivity rate of malarial parasite in this study was 1.09%and Plasmodium vivax found as most predominant species in this part of the world

Malaria and water resource development: the case of Gilgel-Gibe hydroelectric dam in Ethiopia

BackgroundEthiopia plans to increase its electricity power supply by five-fold over the next five years to fulfill the needs of its people and support the economic growth based on large hydropower dams. Building large dams for hydropower generation may increase the transmission of malaria since they transform ecosystems and create new vector breeding habitats. The aim of this study was to assess the effects of Gilgel-Gibe hydroelectric dam in Ethiopia on malaria transmission and changing levels of prevalence in children.MethodsA cross-sectional, community-based study was carried out between October and December 2005 in Jimma Zone, south-western Ethiopia, among children under 10 years of age living in three 'at-risk' villages (within 3 km from dam) and three 'control' villages (5 to 8 km from dam). The man-made Gilgel-Gibe dam is operating since 2004. Households with children less than 10 years of age were selected and children from the selected households were sampled from all the six villages. This included 1,081 children from 'at-risk' villages and 774 children from 'control' villages. Blood samples collected from children using finger prick were examined microscopically to determine malaria prevalence, density of parasitaemia and identify malarial parasite species.ResultsOverall 1,855 children (905 girls and 950 boys) were surveyed. A total of 194 (10.5%) children were positive for malaria, of which, 117 (60.3%) for Plasmodium vivax, 76 (39.2%) for Plasmodium falciparum and one (0.5%) for both P. vivax and P. falciparum. A multivariate design-based analysis indicated that, while controlling for age, sex and time of data collection, children who resided in 'at-risk' villages close to the dam were more likely to have P. vivax infection than children who resided farther away (odds ratio (OR) = 1.63, 95% CI = 1.15, 2.32) and showed a higher OR to have P. falciparum infection than children who resided in 'control' villages, but this was not significant (OR = 2.40, 95% CI = 0.84, 6.88). A classification tree revealed insights in the importance of the dam as a risk factor for malaria. Assuming that the relationship between the dam and malaria is causal, 43% of the malaria occurring in children was due to living in close proximity to the dam.ConclusionThis study indicates that children living in close proximity to a man-made reservoir in Ethiopia are at higher risk of malaria compared to those living farther away. It is recommended that sound prevention and control programme be designed and implemented around the reservoir to reduce the prevalence of malaria. In this respect, in localities near large dams, health impact assessment through periodic survey of potential vectors and periodic medical screening is warranted. Moreover, strategies to mitigate predicted negative health outcomes should be integral parts in the preparation, construction and operational phases of future water resource development and management projects.

Duffy Antigen/Receptor for Chemokines (DARC): Is There a Role in Prostate Cancer?.

Introduction: The Duffy blood group antigens function as chemokine receptors and as receptors for several species of malarial parasites. Approximately 70% of African Americans are Duffy negative as a result of a single nucleotide polymorphism in the promoter region of the Duffy antigen/receptor for chemokines (DARC) gene in a consensus-binding site for GATA 1. This mutation abolishes the promoter activity in erythrocytes, impairing the expression of DARC on red blood cells. Other than resistance to certain species of malaria, the functional consequence of Duffy negativity is unclear; however, it has recently been proposed that the Duffy antigen acts as a biological ‘sink' to clear pro-inflammatory chemokines from tissue microcirculation. Further it has been suggested that since the incidence of prostate cancer in African Americans is 60% higher than in Caucasians, absence of the Duffy antigen might predispose African Americans to prostate cancer by impairing downregulation of proinflammatory cytokines. We tested the hypothesis that lack of expression of DARC on erythrocytes predisposes African American men to develop prostate cancer.Methods: We conducted a case control study of 89 African American men with confirmed prostate cancer and 51 age matched healthy African American men. The samples were genotyped for the promoter polymorphism using an allele specific real time PCR assay (Taqman assay) developed for this study.Results: The frequency of the Duffy negative allele was 75.8% among the patients and 81.4% among the controls (odds ratio = 0.72, p value = 0.28). The distribution of heterozygous and homozygous Duffy negative patients did not differ between the cases and controls.Conclusion: It has been suggested that individuals lacking erythrocyte expression of DARC have higher prostate levels of angiogenic chemokines that might promote more rapid development of prostate cancer. The data presented here found no difference in the frequency of the Duffy negative allele between African American men with prostate cancer and healthy age matched African American controls. Since several studies suggest that polymorphisms associated with differential production of IL-8, IL-10 and VEGF are risk factors for prostate cancer, it remains possible that a polymorphism associated with differential cytokine production in combination with Duffy negativity increases the risk for prostate cancer.

In vitro culture of Plasmodium parasites.

Because it has been 25 yr since the successful cultivation of Plasmodium falciparum (1), most researchers do not remember how difficult it was to work with malaria parasites, especially in vitro. Before the development of current methods, malaria parasite cultures were always short-term, lasting only a few days with decreasing numbers until the parasites died out. Not only was it extremely inconvenient to constantly begin new cultures, but investigators worked with parasites that were abnormal in the sense that the overall population was dying. Sixty-four years passed between the initial studies of Bass and Johns (2) and the successful development of continuous cultures of P. falciparum. During that time, many reported advances were able to extend the time of cultivation by only a few days but always with the inevitable terminal results. Most of the early investigators on in vitro cultivation used the bird malaria parasite P. lophurae or the simian parasite P. knowlesi, but the first successful cultivation of any malarial parasite was P. falciparum, the most important of the human malaria species. Using essentially the same procedures, other species of malarial parasites now have been cultured, including P. fragile, P. inui, and P. cynomolgi, but these species offer no real advantages over the use of P. falciparum. Methods for the cultivation of P. vivax have been reported but these cultures apparently require a continuous source of human reticulocytes which limits the suitability and presents a nearly insurmountable barrier to all but a few laboratories (3). A recent review of the impact of continuous cultures of P. falciparum underscores the tremendous contributions of this technique on malaria research (4).

Temporal variation in fish community structure in a newly created wetland lake (Lake Agmon) in Israel

Lake Agmon was constructed in summer 1994 in the northern part of the drained Lake Hula swamp, as part of the Hula Reclamation Project. One of the main goals of the project was to attract aquatic and semi- aquatic birds to the area as a basis for planned “eco-tourism” and one of the main concerns of the project was the potential for increased proliferation of mosquitoes (including vector species of malarial parasites). There was a perceived need, therefore, to establish and maintain a suitable fish community. This present study documents the developments in the fish community in Lake Agmon between May 1995 and December 1996. The lake was initially stocked with two fish species, Tilapia zillii and Gambusia affinis, to control mosquitoes and to provide suitable small- bodied forage species for piscivorous birds. Subsequent stocking also included Oreochromis aureus, and Cyprinus carpio. Additional species were established by immigration from the Jordan River. Relatively large species ( e.g., Clarias gariepinus and C. carpio) flowed into the lake as eggs or juveniles, whereas the smaller species ( e.g., Hemigrammocapoeta nana, Pseudophoxinus kervillei and Aphanius mento) entered the lake as adults. In the first year, eight fish species were found in Lake Agmon: T. zillii, G. affinis, C. gariepinus, C. carpio, Capoeta damascina, P. kervillei, Acanthobrama lissneri and H. nana. Of these, T. zillii, G. affinis and H. nana were dominant, though the relative abundance of H. nana was very low in spring, and increased during summer. In the second year, O. aureus, A. mento and Anguilla anguilla also occurred in the lake. The density of P. kervillei increased, in comparison with the previous year. The relative proportions of juvenile and adult fish also changed in the second year. A high percentage of young T. zillii was found during the first spring, decreasing in the summer and autumn. The proportion of juveniles of both G. affinnis and H. nana was very low during the first year, but increased during the second. These results indicate that the fish community of Lake Agmon had not stabilized by the end of 1996 and that further changes in relative abundances, and species, age and sex compositions should be expected.

PfEMP1, polymorphism and pathogenesis

The virulence of Plasmodium falciparum relative to the other species of malarial parasite which infect humans is thought to be due both to this parasite's ability to adhere to endothelial cells lining small blood vessels and, in some cases, to its ability to form rosettes with uninfected erythrocytes. The latter phenotype has been found more frequently in cases of severe disease. The former property means that only the younger, asexual, intra-erythrocytic forms circulate whereas the more mature developmental stages are sequestered in the vasculature of a variety of organs. When large numbers of parasites accumulate in a vulnerable target organ such as the brain, then the life-threatening condition of cerebral malaria may result. While the factors that control whether or not cerebral malaria develops are not clearly defined, one crucial determinant may be the endothelial receptors utilised by the infecting isolate. Many such receptors have been identified, including CD36, thrombospondin, ICAM-1, VCAM, E-selectin and chondroitin-4-sulphate. The results of laboratory, field, post-mortem and direct receptor-binding studies indicate that, of the receptors currently identified, ICAM-1 binding is most likely to be associated with the development of cerebral malaria.The molecule expressed on the surface of the infected erythrocyte which mediates adherence to endothelium belongs to a large family of clonally variable antigens encoded by the var genes. The evidence for this conclusion and progress in defining the regions of var-gene products responsible for receptor-specific binding are discussed. Finally, the organization of the var genes within and between parasites is discussed in relation to the evolution of the var-gene family and its functions of antigenic variation and endothelial adhesion.

PfEMP1, polymorphism and pathogenesis.

The virulence of Plasmodium falciparum relative to the other species of malarial parasite which infect humans is thought to be due to this parasite's ability to adhere to endothelial cells lining small blood vessels and, in some cases, to its ability to form rosettes with uninfected erythrocytes. The latter phenotype has been found more frequently in cases of severe disease. The former property means that only the younger, asexual, intra-erythrocytic forms circulate whereas the more mature developmental stages are sequestered in the vasculature of a variety of organs. When large numbers of parasites accumulate in a vulnerable target organ such as the brain, the the life-threatening condition of cerebral malaria may result. While the factors that control whether or not cerebral malaria develops are not clearly defined, one crucial determinant my be the endothelial receptors utilised by the infecting isolate. Many such receptors have been identified, including CD36, thrombospondin, ICAM-1, VCAM, E-selectin and chondroitin-4-sulphate. The results of laboratory, field, post-mortem and direct receptor-binding studies indicate that, of the receptors currently identified, ICAM-1 binding is more likely to be associated with the development of cerebral malaria. The molecule expressed on the surface of the infected erythrocyte which mediates adherence to endothelium belongs to a large family of clonally variable antigens encoded by the var genes. The evidence for this conclusion and progress in defining the regions of var-gene products responsible to receptor-specific binding are discussed. Finally, the organization of the var genes within and between parasites is discussed in relation to the evolution of the var-gene family and its functions of antigenic variation and endothelial adhesion.