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Biomedical subjects

A Spiegel

Publications and source records attributed to A Spiegel.

At least 19 recordsLinked to original sources
PubMed2003

[Cohorts and bio-libraries for studying malaria in tropical areas].

The relationship between Plasmodii transmission, infection, morbidity, genetic susceptibility and acquisition of natural immunity is studied among two cohorts in the Senegalese villages of Dielmo (300 inhabitants) and Ndiop (350 inhabitants) where malaria is holoendemic (about 200 P. falciparum infective bites/person/year) and mesoendemic (about 20 P. falciparum infective bites/person/year), respectively. The populations are under a daily active clinical survey. Blood samples are collected at least once per month. Plasma and red blood cells are stored in bio-libraries that allow longitudinal studies of the immune responses against plasmodial antigens and the investigation of the natural history of P. falciparum infections by molecular genotyping methods.

Animals↗
PubMed2003

[Use of satellites for public health purposes in tropical areas].

The epidemiological hallmark of the new millennium has been the emergence or recrudescence of transmissible diseases with high epidemic potential. Disease tracking is becoming an increasingly global task requiring implementation of more and more sophisticated control strategies and facilities for sustainable development. A promising initiative involves the use of satellite technology to monitor and forecast the spread of disease. The Health Early Warning System (HEWS) was designed based on successful application of satellite data in food programs as well as in other areas (e.g. weather, farming and fishing). The HEWS integrates data from communications, remote-sensing and positioning satellites. The purpose of this review is to present the main studies containing satellite data on public health in tropical areas. Satellite data has allowed development of more reactive epidemiological tracking networks better suited to increasing population mobility, correlation of environmental factors (vegetation index, rainfall and ocean surface color) with human, animal and insect factors in epidemiological studies and assessment of the role of such factors in the development or reappearance of disease. Satellite technology holds great promise for more efficient management of public health problems in tropical areas.

Cholera↗
PubMed2003

[Correlation measures in epidemiology].

When a significant correlation has been noted between the occurrence of a disease and exposure to a risk factor, it becomes necessary to measure the strength of the correlation. This can be done using either relative risk or odds ratio techniques depending on the type of study. The purpose of article this article is to present guidelines for calculation and interpretation of these indicators using examples taken from the Médecine Tropicale journal.

Confidence Intervals↗
PubMed2002

In vitro activities of ferrochloroquine against 55 Senegalese isolates of Plasmodium falciparum in comparison with those of standard antimalarial drugs.

The in vitro activities of ferrochloroquine, chloroquine, quinine, mefloquine, halofantrine, amodiaquine, artesunate, atovaquone, cycloguanil and pyrimethamine were evaluated against Plasmodium falciparum isolates from Senegal (Dielmo, Ndiop), using an isotopic micro-drug susceptibility test. The IC50 values for ferrochloroquine ranged from 0.55 to 28.2 nM and the geometric mean IC50 for the 55 isolates was 7.9 nM (95% CI, 6.5-9.7 nM). Ferrochloroquine was 35 times more active than chloroquine (35-fold greater against chloroquine-resistant isolates), quinine, mefloquine, amodiaquine, cycloguanil and pyrimethamine. Weak positive correlations were observed between the responses to ferrochloroquine and that to chloroquine, quinine, and amodiaquine, but not compulsorily predictive of cross-resistance. There was no significant correlation between the response to ferrochloroquine and that to mefloquine, halofantrine, artesunate, atovaquone, cycloguanil and pyrimethamine. Ferrochloroquine may be an important alternative drug for the treatment of chloroquine-resistant malaria.

Animals↗
PubMed2002

Use of reverse transcriptase PCR in early diagnosis of Rift Valley fever.

Reverse transcriptase PCR (RT-PCR) for diagnosis of Rift Valley fever (RVF) was evaluated by using 293 human and animal sera sampled during an RVF outbreak in Mauritania in 1998. Results of the RT-PCR diagnostic method were compared with those of virus isolation (VI) and detection of immunoglobulin M (IgM) antibodies. Our results showed that RT-PCR is a specific, sensitive tool for RVF diagnosis in the early phase of the disease and that its results do not differ significantly from those obtained by VI. Moreover, the combined results of RT-PCR and IgM antibody detection were in 100% concordance with the results of VI.

Animals↗
PubMed2002

Multicenter study of street foods in 13 towns on four continents by the food and environmental hygiene study group of the international network of pasteur and associated institutes.

An international multicenter study of ready-to-eat foods, sandwiches, and ice creams or sorbets sold in the streets and their vendors was carried out to assess the microbiological quality of these foods and to identify characteristics of the vendors possibly associated with pathogens. Thirteen towns in Africa, America, Asia, and Oceania were involved in the study. A single protocol was used in all 13 centers: representative sampling was by random selection of vendors and a sample of foods bought from each of these vendors at a time and date selected at random. Microbiological analyses were carried out using standardized Association Française de Normalisation methods, and the use of a standardized questionnaire to collect data concerning the characteristics of the vendors. Fifteen surveys were carried out, with 3,003 food samples from 1,268 vendors. The proportion of unsatisfactory food samples was between 12.7 and 82.9% for ice creams and sorbets and between 11.3 and 92% for sandwiches. For ice creams and sorbets, the sale of a large number of units (>80 per day) increased the risk of unsatisfactory food by a factor of 2.8 (95% confidence interval [CI]: 1.5 to 5.1), lack of training in food hygiene by 6.6 (95% CI: 1.1 to 50). and by a factor of 2.8 (95% CI: 1.4 to 5.4) for mobile vendors. These risk factors were not identified for sandwiches, this difference may be due to the presence of a cooking step in their preparation. These results show that the poor microbiological quality of these street foods constitutes a potential hazard to public health, that the extent of this hazard varies between the cities studied, and that vendors' health education in food safety is a crucial factor in the prevention of foodborne infections.

Colony Count, Microbial↗
PubMed2002

[Statistical tests: value, principle and interpretation].

Comparison of data groups requires the use of statistical tests. This article utilizes an example taken from the Revue Médicine Tropicale to illustrate the value of statistical testing as well as an interpretation of the probability value "p" associated with test results.

Data Interpretation, Statistical↗
PubMed2001

Rapid and efficient homing of human CD34(+)CD38(-/low)CXCR4(+) stem and progenitor cells to the bone marrow and spleen of NOD/SCID and NOD/SCID/B2m(null) mice.

Stem cell homing into the bone microenvironment is the first step in the initiation of marrow-derived blood cells. It is reported that human severe combined immunodeficient (SCID) repopulating cells home and accumulate rapidly, within a few hours, in the bone marrow and spleen of immunodeficient mice previously conditioned with total body irradiation. Primitive CD34(+)CD38(-/low)CXCR4(+) cells capable of engrafting primary and secondary recipient mice selectively homed to the bone marrow and spleen, whereas CD34(-)CD38(-/low)Lin(-) cells were not detected. Moreover, whereas freshly isolated CD34(+)CD38(+/high) cells did not home, in vivo stimulation with granulocyte colony-stimulating factor as part of the mobilization process, or in vitro stem cell factor stimulation for 2 to 4 days, potentiated the homing capabilities of cytokine-stimulated CD34(+)CD38(+) cells. Homing of enriched human CD34(+) cells was inhibited by pretreatment with anti-CXCR4 antibodies. Moreover, primitive CD34(+)CD38(-/low)CXCR4(+) cells also homed in response to a gradient of human stromal cell-derived factor 1 (SDF-1), directly injected into the bone marrow or spleen of nonirradiated NOD/SCID mice. Homing was also inhibited by pretreatment of CD34(+) cells with antibodies for the major integrins VLA-4, VLA-5, and LFA-1. Pertussis toxin, an inhibitor of signals mediated by Galpha(i) proteins, inhibited SDF-1-mediated in vitro transwell migration but not adhesion or in vivo homing of CD34(+) cells. Homing of human CD34(+) cells was also blocked by chelerythrine chloride, a broad-range protein kinase C inhibitor. This study reveals rapid and efficient homing to the murine bone marrow by primitive human CD34(+)CD38(-/low)CXCR4(+) cells that is integrin mediated and depends on activation of the protein kinase C signal transduction pathway by SDF-1.

ADP-ribosyl Cyclase↗
PubMed2001

Rapid reappearance of Plasmodium falciparum after drug treatment among Senegalese adults exposed to moderate seasonal transmission.

To investigate the relationship between the entomologic inoculation rate (EIR) and time to reappearance of malaria parasites after radical treatment under moderate seasonal transmission conditions, a study was undertaken in a mesoendemic area of Senegal where malaria transmission is concentrated over an annual three-month period and averages 12 infective bites per person per year. A three-day course of quinine was administered to 48 asymptomatic adults between 19 and 66 years of age. Malaria transmission and parasitemia were monitored every week for two months and cases of fever or symptoms were investigated as part of a daily clinical surveillance. The proportion of persons reinfected at Days 28, 35, and 56 was 25%, 38%, and 54%, respectively. Adults less than 40 years of age had a shorter time to reinfection. In this age group, the median Plasmodium falciparum reappearance time was 28 days, and it was estimated that only one infected mosquito bite was able to induce a patent infection among half of the subjects. Only 8% (2 of 26) of the reinfections caused a clinical attack. These data are discussed in the light of previous studies conducted among adults naturally exposed to intense perennial transmission or among naive volunteers receiving artificial challenges. Rapid reinfection occurs at very low EIRs and dramatic differences in actual and cumulated exposure to infected mosquito bites poorly affect the median time to reappearance of malaria parasites in endemic populations.

Adult↗
PubMed2001

[Diagnosis of malaria attacks in endemic areas: theoretical aspects and practical implications].

What criteria can be used to diagnose malaria in health centers located in endemic areas? Can an algorithm be developed for management of fever episodes? What parameters should be used to assess the morbidity of malaria for public health surveys or for studies to determine the efficacy insecticide-impregnated bednets, drug prophylaxis protocols, or anti-malarial vaccinations? Finding a useful definition for malaria attack is a perennial problem that becomes more difficult to resolve as the transmission rate and immunity level of the population increases. This review presents the fundamental aspects of diagnosing malaria. The choice of diagnostic technique requires knowledge of physiopathological, epidemiological, and clinical features. There is no single method. It depends on the circumstances, epidemiological context, available facilities, and goals. Diagnosis for treatment is one thing. Diagnosis for evaluation is another. In addition to discussing these concepts, this article provides references from the recent literature and up-to-date information needed to deal with the problem of diagnosing malaria attacks in endemic areas.

Diagnosis, Differential↗
PubMed2001

[Disease vector control strategy in the French army].

Disease vector control is a major priority for the Medical Health Corps of the French Armed Forces which maintains around 23,000 troops in tropical areas and is involved in numerous military and humanitarian missions throughout the world. Control strategy includes both general and personal control measures. Personal control measures include wearing permetherin-impregnated combat uniforms, application of repellents to the skin, and use of deltamethrin-impregnated bednets. General measures are implemented in facilities and in the environment. Measures in facilities include not only physical deterrents such as screens on openings and air-conditioning but also application of chemical insecticides to walls, curtains, and screening. Environmental measures include control of larval deposits and elimination of potential breeding areas. Low-volume wide-area spraying of imagocides is a supplemental option used in case of disease outbreak. For units stationed in tropical areas, command and surveillance of vector control operations is under the responsibility of the mosquito control committee which includes personnel from the affected field unit. Strategies are chosen in function of local climate and operational conditions. The efficacy of vector control programs is assessed annually by reviewing the incidence in armed forces personnel of the main vector-transmitted diseases: malaria, dengue fever, and leishmaniasis. Documentation and training are dispensed to all units stationed in tropical areas. To ensure that knowledge of military physicians remains current, three courses on malaria control are offered each year at the Tropical Medicine Institute of the Armed Forces Health Corps (Le Pharo) in Marseille. Field research conducted in collaboration with military or civilian organizations independent of the Armed Services Health Corps makes it possible to keep chiefs of staff informed of state-of-the art vector control measures adapted to use by personnel on assignment or mission in tropical areas.

Animals↗
PubMed2000

Bayesian analysis of an epidemiologic model of Plasmodium falciparum malaria infection in Ndiop, Senegal.

Plasmodium falciparum has a complex transmission cycle. Public health planning and research would benefit from the ability of a calibrated model to predict the epidemiologic characteristics of populations living in areas of malaria endemicity. This paper describes the application of Bayesian calibration to a malaria transmission model using longitudinal data gathered from 176 subjects in Ndiop, Senegal, from July 1, 1993, to July 31, 1994. The model was able to adequately predict P. falciparum parasitemia prevalence in the study population. Further insight into the dynamics of malaria in Ndiop was provided. During the dry season, the estimated fraction of nonimmune subjects goes down to 20% and then increases up to 80%. The model-predicted time-weighted average incidences contributed by nonimmune and immune individuals are 0.52 cases per day and 0.47 cases per day, respectively. The median times needed to acquire infection (conversion delay) for nonimmune and immune individuals are estimated at 39 days and 285 days, respectively.

Adolescent↗
PubMed2000

Increased susceptibility to malaria during the early postpartum period.

BACKGROUND: Pregnancy is associated with increased susceptibility to malaria. It is generally agreed that this increased risk ends with delivery, but the possible persistence of increased susceptibility during the puerperium had not been investigated. METHODS: From June 1, 1990, to December 31, 1998, we monitored exposure to malaria, parasitemia, and morbidity among the residents of a village in Senegal in which the rate of transmission of malaria was high. In this population we analyzed 71 pregnancies in 38 women from the year before conception and through one year after delivery. RESULTS: Among the 38 women, there were 58 episodes of clinical Plasmodium falciparum malaria during 61,081 person-days of observation. The incidence of malaria was 20.2 episodes per 1000 person-months during the year preceding conception and 12.0 episodes per 1000 person-months during the period from 91 to 365 days after delivery. The incidence of episodes of malaria increased significantly during the second and third trimesters of pregnancy and reached a maximum of 75.1 episodes per 1000 person-months during the first 60 days after delivery. The adjusted relative risk of an episode of malaria was 4.1 (95 percent confidence interval, 1.8 to 9.5) during the first 60 days post partum, as compared with the year preceding pregnancy. The duration of fever during the episodes of malaria was longer and the prevalence and density of asymptomatic malarial parasitemia were significantly higher during pregnancy and the early postpartum period than during the other periods. CONCLUSIONS: Among women who live in areas with high rates of transmission of malaria, the susceptibility to malaria is highest during the second and third trimesters of pregnancy and the early postpartum period.

Adolescent↗
PubMed2000

Effects of MPEG compression on the quality and diagnostic accuracy of digital echocardiography studies.

The advantages of digital echocardiography studies include ease of retrieval, review, comparison, duplication, and quantitation as well as the potential for moving studies over networks. However, the large amounts of data associated with digital echocardiography studies have posed new problems. Reduction of the amount of data can be accomplished with image compression, in particular MPEG-1 (Moving Pictures Expert Group), which is designed for dynamic image sequences. However the effects of different levels of compression on the quality and diagnostic content of echocardiographic images need to be established. Digital sequences of single cardiac cycles were acquired in 40 consecutive patients, MPEG-1-compressed at different effective ratios (60:1, 80:1, 120:1, 200:1, 300:1, 370:1, 500:1), reviewed, and scored for endocardial visualization. The overall visualization scores and percentages of nonvisualized segments in the compressed images were not different from the uncompressed images up to a compression ratio of 200:1. Differential effects of compression were noted on a segmental basis and also varied with baseline image quality. The ability to correctly identify regional wall motion abnormalities did not decrease until compression ratios of 1:200 or higher were used. Digital echocardiography loops, MPEG-1-compressed at an effective ratio of 200:1, demonstrate no degradation in endocardial visualization quality or diagnostic content. Compression at this ratio has the potential to reduce the storage size of digital echocardiography studies to less than 1% of their current size.

Echocardiography↗
PubMed2000

Apoptosis modulation in mononuclear cells recovered from individuals exposed to Plasmodium falciparum infection.

In endemic areas, asymptomatic infection by the malaria parasite Plasmodium falciparum was found associated with elevated percentages of human host's mononuclear cell spontaneous in-vitro apoptosis. In Dielmo, a village where malaria is holoendemic, apoptosis was age-and parasite-dependent. In-vitro exposure of peripheral blood mononuclear cells (PBMC) to the parasite extract induced a marked increase in the mononuclear cell membrane expression of functional CD95 antigen: a 3-h exposure of the mononuclear cells to anti-CD95 antibodies led to a detectable increase in the mean percentage of apoptotic nuclei found in the cultures carried out in the presence of P. falciparum extracts compared to control cultures. IL-2, IL-4, IL-6 and IL-10 promoted the viability of PBMC in cultures while IL-1alpha or IFN-gamma had no obvious impact and TNFalpha gave conflicting results. IL-2 was the most efficient cytokine at rescuing PBMC from cell death and this effect was associated with a strong increase in T cell activation. In contrast, IL-4 and IL-10 had no such effect on T cell activation, hence they acted as survival factors and not through their mitogenic activity. Taken together, these different observations suggested that the levels of in-vitro apoptosis observed were not only associated with parasite infection, but also potentially modulated by the human host through different pathways.

Animals↗
PubMed2000

Epidemiological and virological influenza survey in Dakar, Senegal: 1996-1998.

An influenza survey was conducted in seven sentinel sites in Dakar, Senegal from June 1996 to December 1998. Throat or nasal swab cultures were randomly collected from 804 patients suffering from influenza-like symptoms. Influenza viruses were isolated at a similar proportion in adults and in children (P = 0.29). Strains of influenza B viruses were isolated from sporadic cases in 1997, whereas type A virus was associated with an isolated peak. Proportions of influenza virus isolation varied from 17.5% to 40.0% between 1996 and 1998 during the peak period (July/September) of acute respiratory infection in Dakar. Rainfall, humidity, and temperatures rose during the same period. Influenza in Dakar seems to be an-all-age groups respiratory infection characterized by high transmission during the hot and rainy season. The antigenic similarity of the A(H3N2) and B viruses to those circulating elsewhere in the world at the same time was confirmed. However, the A(H1N1) strains were found to be more closely related to an Asiatic strain which had not been isolated outside Asia previously. Consequently, the strain close to the A(H1N1)/Wuhan/371/95 strain isolated in Dakar was included in the composition of the 1998/1999 influenza vaccine. This reinforces the importance of setting up a national influenza control strategy in tropical regions.

Adolescent↗