Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

There is accumulating evidence for the involvement of genetic factors in the human response to malaria infection, mostly based on results obtained in studies of severe clinical malaria. The role of major gene(s) controlling blood parasitemia levels in human malaria has also been detected by means of segregation analysis. To confirm and to localize such gene(s), we performed a sib-pair linkage analysis investigating the role of five candidate chromosomal regions: 6p21 (HLA-tumor necrosis factor region), 2q13-q21 (genes coding for interleukin-1 alpha and beta), 14q11 (locus coding for the alpha chain of T cell antigen receptor), 7q35 (gene cluster for the beta subunit of T cell receptor), and 5q31-q33, which includes several candidate genes and was recently linked to a locus controlling infection levels by Schistosoma mansoni, denoted as SM1. The analysis was carried out on nine families from a southern Cameroon village, and the phenotype under study was blood infection levels with Plasmodium falciparum. No linkage was found with any of the four markers outside the 5q31-q33 region. A trend in favor of linkage was observed in the distal part of the 5q31-q33 region, especially with the marker D5S636 (P < 0.05 using the Monte Carlo P value), which was the marker that provided the highest evidence for linkage with SM1. These results suggest that a locus influencing P. falciparum levels in malaria could be located in the same genetic region as that containing SM1, indicating that the 5q31-q33 region may be critical in the control of different parasite infections.
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PMID:Linkage analysis of blood Plasmodium falciparum levels: interest of the 5q31-q33 chromosome region. 966 Apr 49

Mixed parasitic infections are common in many parts of the world. However, little is known about how concurrent infections affect the immunity to and/or pathogenesis of each other. Protection and elimination of blood-stage Plasmodium chabaudi chabaudi AS in resistant mice are characterized by a sequential activation of CD4(+) Th1 and Th2 cells. The patent egg-laying stage of the murine model of Schistosoma mansoni is associated with a strong Th2 response to both Schistosoma and unrelated antigens. In this study, we investigated how infection of mice with S. mansoni would affect the immune response to and pathogenesis of a P. chabaudi infection. C57BL/6 mice infected with S. mansoni for 8 weeks were infected with blood-stage P. chabaudi. Malaria parasitemias were significantly higher in these mice than in mice infected with P. chabaudi only. In doubly infected mice, both spleen cell proliferative and Th2 responses to S. mansoni soluble egg antigen (SEA) or anti-CD3 were suppressed up to 1 month after the malaria infection. Findings for SEA-specific immunoglobulin M (IgM) and IgG serum antibody levels were similar. No significant effects were seen on P. chabaudi-induced gamma interferon responses. However, tumor necrosis factor alpha (TNF-alpha) production was significantly lower in double-infected mice. Thus, a defect in TNF-alpha production might contribute to the increased malaria parasitemias seen in S. mansoni-P. chabaudi-infected mice. Taken together, our data show that schistosoma and malaria infections profoundly affect each other, findings which might have implications for the development of vaccines.
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PMID:Altered immune responses in mice with concomitant Schistosoma mansoni and Plasmodium chabaudi infections. 978 18

A cross-sectional study of 729 children and adults in western Kenya investigated the impact of infection with hookworm, Ascaris lumbricoides, Trichuris trichiura, Schistosoma mansoni and malaria on iron status. In bivariate analyses, hookworm intensities as low as 300 eggs/g of faeces were negatively related to levels of haemoglobin (Hb) and serum ferritin (SF). Malaria parasitaemia was negatively related to Hb and positively related to SF, while S. mansoni intensities were negatively related to SF. Multivariate regression analysis was done to identify predictors of Hb and SF levels. In children, age (in years) was the only predictor for Hb (B = 1.7 g/L) and only malaria parasitaemia (negative, light, moderate, heavy) was retained in the model for log10 SF (B = 0.097 microgram/L). In adults, hookworm infection and malaria parasitaemia together with age, sex, pregnancy, SF levels < 12 micrograms/L and elevated body temperature were significant predictors of low Hb. The regression coefficient for hookworm egg count (for increments of 100 eggs/g) was -1.3 g/L. Significant interactions between sex and age and between sex and malaria parasitaemia were revealed. Age and malaria parasitaemia were significant predictors only among females, with a regression coefficient for malaria parasitaemia of -6.9 g/L. The regression coefficient for hookworm did not change when SF < 12 micrograms/L was taken out of the model, indicating that the effect of hookworm cannot be explained by low iron stores alone. Using SF as the dependent variable, hookworm and S. mansoni intensities together with age and sex were retained in the model. The regression coefficients for hookworm egg count (increments of 100 eggs/g) and S. mansoni egg count (increments of 10 eggs/g) were -0.011 microgram/L and -0.012 microgram/L, respectively. Iron deficiency was a problem in this population and hookworm infections contributed significantly to this situation.
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PMID:The contribution of hookworm and other parasitic infections to haemoglobin and iron status among children and adults in western Kenya. 1032 10

A survey was undertaken in Tigray, Northern Ethiopia, to assess the prevalence of malaria, schistosomiasis, and intestinal helminths in relation to microdams. The survey took place from March to June 1995, during the dry season, at 41 microdams. At each site the village nearest the dam (within thirty minutes walk) was selected, ten households were randomly chosen, and all family members were examined for malaria and intestinal parasites. The overall study sample was 2271 people, of all age groups. Plasmodium falciparum infection was documented in four villages (at 10% of microdams); prevalence was 1.2% (range 0-20% by village). Larvae of Anopheles gambiae s.l. were found at one microdam. Infection with intestinal schistosomiasis was documented in 20 villages (at 49% of microdams), and one third of those infected had moderate to heavy infections. Biomphalaria species, the intermediate host snails of Schistosoma mansoni, were found at 16 microdams (39%), and snails infected by mammalian cercariae were found in one locality. Infections with soil-transmitted nematodes were prevalent: hookworm was detected in more than two thirds of the villages, and Ascaris lumbricoides and Trichuris trichiura were present in almost half of the villages. Out of 2078 stool examinations, the prevalence of S. mansoni infection was 7.2% (range 0-48% by village), of A. lumbricoides 2.3% (range 0-31%), of T. trichiura 2.4% (range 0-21%), and of hookworm 8.9% (range 0-78%). The prevalence of malaria, S. mansoni and hookworm was higher at altitudes below 2000 metres above sea level. S. mansoni was more prevalent in microdams built more than 5 years before the survey, while T. trichiura was more prevalent at recently constructed microdams. The widespread distribution of schistosomiasis and intestinal helminths, and the presence of malaria infection during the dry season confirm that microdams create favourable conditions for the transmission of these parasitic diseases. Health safeguards must be incorporated into the planning, construction, and operation of microdams and irrigation systems in order to prevent or reduce these diseases. In areas with high prevalence, control activities should be intensified.
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PMID:Malaria, schistosomiasis, and intestinal helminths in relation to microdams in Tigray, northern Ethiopia. 1037 81

Susceptibility to Plasmodium chabaudi depends on the relative dominance of T(h)1/T(h)2 responses in host mice. A T(h)2-dominant response during the early phase of infection in susceptible A/J mice causes a fatal disease course due to severe malaria. Schistosoma mansoni is a potent inducer of a T(h)2-dominant response not only to the parasite antigens, but also to other antigens concurrently existing in the host animals. In spite of S. mansoni infection, these A/J mice escape death from malaria and showed accompanied enhanced production of IFN-gamma to malaria antigens. Treatment with anti-IFN-gamma mAb in S. mansoni-infected A/J mice abolished the resistance to malaria, indicating that IFN-gamma was responsible for the resistance to P. chabaudi in S. mansoni-infected A/J mice. Results in this study show that under certain circumstances, S. mansoni infection can promote type 1 immune responses in A/J mice that normally develop T(h)2 responses.
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PMID:Schistosoma mansoni infection cancels the susceptibility to Plasmodium chabaudi through induction of type 1 immune responses in A/J mice. 1091 86

Schistosomiasis and malaria constitute major health problems in Madagascar. The main objectives of the national schistosomiasis control programme--launched in 1998--are to improve knowledge about the modes of transmission of the disease and conduct mass treatment in hyperendemic areas, so as to lower incidence rates. A Geographic Information System (GIS) was established aiming to conduct a series of remote sensing studies based on digital image processing and analysis from Landsat TM and panchromatic Spot. The importance of local environmental and geographic characteristics in the Ihosy region such as proximity to roads and water were assessed by spatial analysis in order to construct a predictive model of Schistosoma mansoni endemicity. Unstable transmission in the Central Highlands of Madagascar caused severe outbreaks of malaria in the 1980s. Attempts to prevent such events reoccurring have been highlighted in the national malaria control programme. Thanks to intense vector control measures introduced in the area over a five-year period, a marked decrease in incidence of malaria was observed. This region borders on the Highlands as well as southern areas, allowing for vector control evaluation. The GIS and remote sensing system were applied to analyse ricefield areas, where the main vector are Anopheles funestus. Rice-field surfaces were statistically linked with abundance of vectors evaluated by entomological parametres.
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PMID:[Malaria and schistosomiasis: 2 examples using systems of geographical information and teledetection in Madagascar]. 1103 60

Although a disease of great antiquity, scientific studies of schistosomiasis began only 150 years ago. The complete life-cycle was not described until just before the First World War, making it possible at last to plan proper community control programmes. Inadequate tools prevented their effective implementation until well after the Second World War when new tools became available, thanks to the newly formed World Health Organization. Molluscicides spearheaded control programmes until the late 1970s but were then replaced by the newly developed, safe drugs still used today. Whatever the method used, the initial goal of eradication was, in the light of experience and cost, gradually replaced by less ambitious targets; first to stop transmission and then to reduce morbidity. The most successful programmes combined several methods to minimise reinfection after chemotherapy. Comparisons between different programmes are difficult without using appropriate, standardised diagnostic techniques and the correct epidemiological measurements. Some examples will be presented, mainly from our studies on Schistosoma mansoni in Kenya. Drug resistance on a scale comparable with malaria has not occurred in schistosomiasis but the likely withdrawal of all drugs except praziquantel leaves its control extremely vulnerable to this potential problem. An effective, affordable vaccine for use in endemic countries is unlikely to be ready for at least 5 years, and developing strategies for its use could take a further decade or more, judging from experience with drugs and molluscicides. In the interim, by analogy with malaria, the most cost-effective approach would the use of drugs combined with other methods to stop transmission, including molluscicides. The cost of molluscicides needs to be reduced and fears allayed about their supposedly adverse ecological effects.
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PMID:Schistosomiasis epidemiology and control: how did we get here and where should we go? 1158 22

Schistosomiasis continues to rank--following malaria--at the second position of the world's parasitic diseases in terms of the extent of endemic areas and the number of infected people. There is yet no vaccine available and the current mainstay of control is chemotherapy with praziquantel used as the drug of choice. In view of concern about the development of tolerance and/or resistance to praziquantel, there is a need for research and development of novel drugs for the prevention and cure of schistosomiasis. Interestingly, derivatives of artemisinin, which are already effectively used in the treatment of malaria, also exhibit antischistosomal properties. Significant advances have been made with artemether, the methyl ether derivative of artemisinin. We review the discovery of the antischistosomal activity of artemether by Chinese scientists two decades ago; the detailed laboratory studies of the susceptibility of, and effect on, the different developmental stages of Schistosoma japonicum, Schistosoma mansoni and Schistosoma haematobium to artemether; the possible mechanism of action and the potential long-term toxicity. Finally, we look at the effect of combined treatment with artemether and praziquantel; and clinical findings thus far obtained from randomised controlled trials with oral artemether for the prevention of patent infections and morbidity. The review intends to create a forum for strategic discussion of how these laboratory and clinical findings could be translated into public health actions. We conclude that artemether--as part of integrated current control measures and adapted to specific socio-ecological and epidemiological settings--has considerable potential to significantly reduce the current burden of schistosomiasis in many parts of the world.
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PMID:The potential of artemether for the control of schistosomiasis. 1173 Jul 81

Hospital based studies were conducted to investigate the occurrence of Plasmodium/intestinal helminth co-infections among pregnant Nigerian women, and their effects on birthweights, anaemia and spleen size. From 2,104 near-term pregnant women examined, 816 (38.8%) were found to be infected with malaria parasites. Among the 816 parasitaemic subjects, 394 (48.3%) were also infected with intestinal helminths, 102 (12.5%) having mixed helminth infections. The prevalence of the helminth species found in stool samples of parasitaemic subjects examined was, Ascaris lumbricoides (19.1%), hookworm (14.2%), Trichuris trichiura (7%) Schistosoma mansoni (3.4%), Enterobius vermicularis (2%), Hymenolepis sp. (1.6%) and Taenia sp. (1%). Mothers with Plasmodium infection but without intestinal helminth infection had neonates of higher mean birthweights than those presenting both Plasmodium and intestinal helminth infections and this effect was more pronounced in primigravids. The mean haemoglobin values of malarial mothers with intestinal helminth infections were lower than those with Plasmodium infection but without intestinal helminth infections but these were not statistically significant. Severe splenomegaly was predominant among parasitaemic gravidae who also harboured S. mansoni infection in two of the hospitals studied.
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PMID:Plasmodium/intestinal helminth co-infections among pregnant Nigerian women. 1178 22

Artemether and artesunate, derivatives of the antimalarial artemisinin, also exhibit antischistosomal properties. There is a need to assess comparatively the activity of both compounds against different developmental stages of schistosome parasites. Since artemisinin derivatives will be increasingly used to treat malaria, it is important to study the effects of 7-day monotherapy regimens on schistosome infections. We carried out experiments with mice, infected with juvenile or adult Schistosoma mansoni, and treated with artemether or artesunate at various doses and regimens including those currently used for monotherapy of malaria. Three doses of artemether, at concentrations of 150 or 300 mg/kg, administered to mice with juvenile S. mansoni resulted in worm reductions of 88-97%, which were significantly higher than the 67-77% obtained with artesunate (P < 0.05). Total concentrations of 600 or 800 mg/kg artemether, administered over 2 or 4 consecutive days to mice with adult S. mansoni, reduced the worm burden significantly by 46-51% (P < 0.05). The reduction of the worm burden observed with artesunate was considerably lower, 24-33%, and not significant when compared with untreated control mice. Seven-day monotherapy regimens of artemether or artesunate given at different concentrations to mice with adult S. mansoni showed total worm reductions of 53-61% or 34-49%, respectively. We conclude that artemether and artesunate are efficacious antischistosomal agents, with artemether displaying consistently higher activities. Our findings may contribute to the current strategic discussions on the effect and use of artemisinin derivatives against schistosomes when they are used in malaria chemotherapy in areas of co-endemicity of both parasites.
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PMID:Comparative study of the effects of artemether and artesunate on juvenile and adult Schistosoma mansoni in experimentally infected mice. 1217 87


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