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Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The negative consequences of parasitic infection (virulence) were examined for two lizard malaria parasite-host associations: Plasmodium agamae and P. giganteum, parasites of the rainbow lizard, Agama agama, in Sierra Leone, West Africa; and P. mexicanum in the western fence lizard, Sceloporus occidentalis, in northern California. These malaria species vary greatly in their reproductive characteristics: P. agamae produces only 8 merozoites per schizont, P. giganteum yields over 100, and P. mexicanum an intermediate number. All three parasites appear to have had an ancient association with their host. In fence lizards, infection with malaria is associated with increased numbers of immature erythrocytes, decreased haemoglobin levels, decreased maximal oxygen consumption, and decreased running stamina. Not affected were numbers of erythrocytes, resting metabolic rate, and sprint running speed which is supported by anaerobic means in lizards. Infected male fence lizards had smaller testes, stored less fat in preparation for winter dormancy, were more often socially submissive and, unexpectedly, were more extravagantly coloured on the ventral surface (a sexually dimorphic trait) than non-infected males. Females also stored less fat and produced smaller clutches of eggs, a directly observed reduction in fitness. Infected fence lizards do not develop behavioural fevers. P. mexicanum appears to have broad thermal buffering abilities and thermal tolerance; the parasite's population growth was unaffected by experimental alterations in the lizard's body temperature. The data are less complete for A. agama, but infected lizards suffered similar haematological and physiological effects. Infected animals may be socially submissive because they appear to gather less insect prey, possibly a result of being forced into inferior territories. Infection does not reduce clutch size in rainbow lizards, but may lengthen the time between clutches. These results are compared with predictions emerging from several models of the evolution of parasite virulence. The lack of behavioural fevers in fence lizards may represent a physiological constraint by the lizards in evolving a thermal tolerance large enough to allow elimination of the parasite via fever. Such constraints may be important in determining the outcome of parasite-host coevolution. Some theory predicts low virulence in old parasite-host systems and higher virulence in parasites with greater reproductive output. However, in conflict with this argument, all three malarial species exhibited similar high costs to their hosts.
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PMID:Virulence of lizard malaria: the evolutionary ecology of an ancient parasite-host association. 223 62

The case is presented of a 20-year-old tourist with mild falciparum malaria and bilateral preretinal and intraretinal hemorrhage, including a macular hemorrhage with reversible visual loss, which developed during his return flight from West Africa. The diagnosis was initiated by the university eye hospital originally consulted. Possible pathogenic mechanisms, ocular findings in malaria, and the increasing problems of imported malaria are summarized and reviewed.
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PMID:[Fundus hemorrhage in malaria tropica]. 224 79

High technologies of molecular biology and genetics, supported by computer use brought considerable advances in taxonomy, physiology, host/parasite relationships, ecology and epidemiology. New insecticides, IGR and bacteria are now available. Both simple methods (e.g. tsetse trapping, impregnated bednets) and large programs using heavy material (e.g. O. C. P. in West Africa, mosquito control in Northern hemisphere) have been successful. Guineaworm control lies in an intermediate position. Malaria control has difficulties and needs new tools and a better use of those already existing. A few progresses are noticed in biological and genetical control. Appropriate structures, well trained and motivated personnel, adequate funding and political willingness are the keys for the implementation of any control programme.
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PMID:[Recent achievements and perspectives in medical entomology and vector control]. 226 70

Environmental impact of pesticides used in vector control programmes against Onchocerciasis, Trypanosomiasis, Malaria and Bilharziasis, depends on chemicals used and control strategies. Dealing with the experience of the Onchocerciasis control Programme in West Africa, we introduce in what perspective, it is possible to establish an environmental monitoring programme in order to minimize the impact of treatments. In tropical Africa, vector control chemicals pressure, decreased in the years 1980.
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PMID:[Impact of vector control on the aquatic environment]. 226 73

Thirty-two episodes of malaria (10 confirmed by laboratory tests) were reported by 162 people living in 18 developing countries under the auspices of one British missionary society. Malaria was endemic in all countries involved, and a total of 367 person-years were observed. The overall incidence rate for malaria was 87.3 per 1000 person-years at risk. Important factors identified were residence in West Africa compared with elsewhere (relative risk (RR) = 13.0, P less than 0.001), being in the 20-39 year age group (RR = 3.2, P less than 0.002), history of gastroenteritis (RR = 3.1, P less than 0.002) and living in a rural area (RR = 1.7, n.s.). Chemoprophylaxis was taken by 119 people (73.5%).
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PMID:Risk factors for malaria among British missionaries living in tropical countries. 227 4

In a clinical trial of stabilized yellow fever vaccine from Institute Pasteur in 77 children aged seven to eight months, fever was the most significant immediate and delayed side effect. Fever occurred in 12 (15.6%) children with in 48 hours of vaccination while it occurred in 10 (12.9%) children within ten days of vaccination. Other recorded side effects were pain at innoculation site in four (5.2%) children and vomiting in one (1.3%) child. Temperature recorded in 20 of the 22 febrile episodes ranged from 37.8 degrees C to 38.6 degrees C. One of the two patients who had temperatures of 39 degrees C and above had malaria parasites in her blood film. All episodes of fever except one responded to antipyretic. There was no episode of febrile convulsion and no feature suggestive of encephalitis. Of the 20 children who had neutralization test carried out against yellow fever virus six weeks after vaccination, the test was positive in post vaccination sera of 12 (60%) children whose pre-vaccination sera were negative. Two others showed evidence of partial protection. Although the seroconversion rate of 60% is less than reported in adults and older children, the result of this study shows that yellow fever vaccine is safe and fairly effective in infants. It is our suggestion that if a larger trial confirms our findings, the vaccine may be incorporated into the expanded programme on immunization (EPI) to be given at the age of seven months after completion of diptheria, tetanus, pertussis and poliomyelitis vaccinations and before measles vaccination is due.
West Afr J Med
PMID:Safety and efficacy of yellow fever vaccine in children less thanone-year-old. 227 33

In order to determine knowledge, attitudes and practices towards malaria prophylaxis, as well as its side-effects and efficacy, a self-administered questionnaire was distributed to European travellers on return flights from tropical Africa to Europe. Between 1985 and 1988 the questionnaire was completed by 44,472 passengers (80.1% of those on board) on 242 flights. A follow-up questionnaire was completed by 42,202 (94.9%) of the same travellers 3 months later. Almost all knew about the risk of malaria, but 10% relied solely on advice from nonmedical sources. While 55.6% had taken at least one measure against mosquito bites, only 4.5% adopted three such measures (used repellents and insecticides and wore long clothing after dusk). Compliance with chemoprophylaxis use was reported by 57.0% of travellers who spent less than 3 months in Africa, compared with 29.2% who stayed 3-12 months. Depending on the antimalaria regimen taken, 11-44% of the travellers experienced adverse effects, while four deaths were attributed to the chemoprophylaxis. The incidence of malaria per month of exposure for travellers who took no chemoprophylaxis was 15.2 per 1000 in East Africa and 24.2 per 1000 in West Africa. In East Africa, the prophylactic efficacy of the currently recommended antimalaria regimens (relative to that of no chemoprophylaxis) was zero for a chloroquine dosage of 300 mg base per week (4 malaria fatalities), 64.1% for a chloroquine dosage of 600 mg base per week (P = 0.03), and 94.0% for mefloquine (P = 0.003).
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PMID:Malaria chemoprophylaxis among European tourists in tropical Africa: use, adverse reactions, and efficacy. 239 77

We studied the relationship between exposure to malaria, the use of long-term chemoprophylaxis with chloroquine, and the prevalence of sporozoite antibodies in 446 expatriates who had lived in 7 West African countries for 6 months-41 years. Filter paper blood samples from 12% of the subjects had antibodies to the repeat region of the Plasmodium falciparum circumsporozoite protein, with a positive correlation between enzyme-linked immunosorbent assay (ELISA) absorbance and years of exposure (r = 0.32, P = less than 0.01). Development of sporozoite antibodies did not correlate with reported use of chloroquine. Ten samples from expatriates with the highest ELISA titers and 10 samples from West African nationals, which were matched for ELISA titer and duration of exposure, were characterized more fully. All 20 samples reacted strongly with sporozoites by immunofluorescence. The 10 samples from nationals reacted strongly with liver-stage antigens by immunofluorescence and with blood-stage antigens by immunofluorescence and immunoblotting. In contrast, the 10 samples from expatriates were negative or only weakly positive in the liver- and blood-stage assays. These results imply that sporozoite antibodies are generally not cross-reactive with blood-stage antigens, and suggest that protective immunity to malaria does not develop during long-term malaria chemoprophylaxis against the erythrocytic stage.
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PMID:Effect of malaria chemoprophylaxis on the development of antibodies to Plasmodium falciparum in expatriates living in west Africa. 240 26

The pathophysiological mechanism of sickle cell anemia has been thoroughly studied and is now well understood, in contrast to the extreme clinical heterogeneity of the disease. A possible genetic explanation for this diversity arose from the discovery of an HpaI restriction polymorphism 3' to the beta globin gene, in linkage disequilibrium with the Hb S mutation. This linkage is unequally distributed among ethnic groups in Africa and predominantly found in Central West Africa. A multipolymorphic analysis spanning 60 Kb of the beta globin gene cluster demonstrated that the sickle mutation arose at least 3 times in 3 different geographical areas (Atlantic West Africa, Central West Africa and Equatorial Central Africa) and expanded by malaria selection. Two genetic factors seem to have epistatic effects which differ when comparing the two first groups. The alpha thalassemia gene (-alpha) is distributed equally among African Black control populations (0.10). The frequency is significantly higher in the SS patients of the Benin area (Central West Africa), whereas it is unmodified in the patients of Senegal (Atlantic West Africa). Alpha thalassemia does not seem therefore to have exercised the same selective effect in this latter group. Secondly, fetal hemoglobin is quantitatively and qualitatively different in both groups. A high G gamma phenotype (greater than 60%) is found in Senegal, whereas a low G gamma phenotype is constant in Benin, without overlap between the two series. The total production of fetal hemoglobin is statistically higher, although only moderately, so in the first group.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Genetic polymorphism of drepanocytosis]. 240 89

The definition of human T-cell antigenic sites is important for subunit vaccine development of a peptide immunogen if the goal is to allow antibody boosting during infection or to stimulate antibody-independent T-cell immunity. To identify such sites on the circumsporozoite (CS) protein of Plasmodium falciparum, 29 overlapping synthetic peptides spanning the entire CS protein were made and tested for their ability to stimulate peripheral blood lymphocytes from 35 adults living in a P. falciparum malaria-endemic region of West Africa. Three immunodominant domains were located outside the repetitive region. These domains, however, occurred in the polymorphic regions of the molecule, suggesting that parasite mutation and selection has occurred in response to immune pressure from T cells. Such polymorphism may impose an obstacle for vaccine development.
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PMID:Human T-cell recognition of the circumsporozoite protein of Plasmodium falciparum: immunodominant T-cell domains map to the polymorphic regions of the molecule. 244 93


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