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Biomedical subjects

C Lengeler

Publications and source records attributed to C Lengeler.

At least 55 records · Page 3Linked to original sources
PubMed1996

Impact of permethrin impregnated bednets on child mortality in Kassena-Nankana district, Ghana: a randomized controlled trial.

A community-based randomized, controlled trial of permethrin impregnated bednets was carried out in a rural area of northern Ghana, between July 1993 and June 1995, to assess the impact on the mortality of young children in an area of intense transmission of malaria and no tradition of bednet use. The district around Navrongo was divided into 96 geographical areas and in 48 randomly selected areas households were provided with permethrin impregnated bednets which were re-impregnated every 6 months. A longitudinal demographic surveillance system was used to record births, deaths and migrations, to evaluate compliance and to measure child mortality. The use of permethrin impregnated bednets was associated with 17% reduction in all-cause mortality in children aged 6 months to 4 years (RR = 0.83; 95% CI 0.69-1.00; P = 0.05). The reduction in mortality was confined to children aged 2 years of younger, and was greater in July-December, during the wet season and immediately after (RR = 0.79; 95% CI 0.63-1.00), a period when malaria mortality is likely to be increased, than in the dry season (RR = 0.92, 95% CI 0.73-1.14). The ready acceptance of bednets, the high level of compliance in their use and the subsequent impact on all-cause mortality in this study has important implications for programmes to control malaria in sub-Saharan Africa.

Bedding and Linens↗
PubMed1996

Promoting operational research on insecticide-treated netting: a joint TDR/IDRC initiative and call for research proposals.

The evidence in favour of insecticide-treated nets for reducing mortality from malaria among Africa children is becoming compelling. In order to support the next step in the development of this promising intervention the UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases (TDR) and the International Development Research Centre (IDRC) decided to launch a joint initiative on operational research. In the first step, 3 reviews on the essential aspects of net technology, programme implementation and programme promotion were commissioned and will be published soon as a book. Secondly, expert opinion was sought regarding priority topics for research. Finally, a first round of research projects was funded and a call for more proposals is being widely advertised.

Africa↗
PubMed1996

From efficacy to effectiveness: insecticide-treated bednets in Africa.

Insecticide-treated bednets and curtains (ITBC) have proven in recent large-scale trials to have a high efficacy in reducing morbidity and mortality from malaria in African children. However, it is unlikely that the efficacy measured in trials can be entirely sustained under programme conditions. This has important implications for the cost-effectiveness of the intervention. Furthermore, there is a need to assess the long-term impact of ITBC. This article traces the history of ITBC and the different phases of their assessment, especially the determination of efficacy in randomized controlled trials (phase III assessment). It then outlines the reasons for continued assessment of their effectiveness under programme conditions (phase IV assessment). The methodologies for measuring effectiveness are discussed, and a critical review of the issues reveals that it is impractical to measure effectiveness directly. A simple effectiveness model, allowing for differentiation between individual and community effectiveness, provides a useful conceptual framework. First, individual effectiveness is measured through a case-control study. This estimate is then combined with a coverage indicator to estimate community effectiveness. This approach could provide programme managers with a powerful tool to monitor the impact of health interventions at the community level.

Africa↗
PubMed1995

The 1990 meningococcal meningitis epidemic of Sarh (Chad): how useful was an earlier mass vaccination?

A large outbreak of meningococcal meningitis (Serogroup A) occurred in southern Chad in 1990. We describe the epidemic in the town of Sarh, where a mass vaccination against meningococcal meningitis had taken place two years before, in 1988 (estimated coverage: 66%). Early warning that an epidemic was imminent was given at the end of February, following more than 15 recorded cases per 100,000 population on 3 consecutive weeks. This threshold proved to be adequate to predict the outbreak. A total of 721 cases were recorded at Sarh hospital and at a nearby health centre. Direct agglutination tests confirmed that Neisseria meningitis serogroup A was the only causative agent. The overall incidence rate in this population of 80,000 was 0.9%. The highest weekly incidence rate was 186 cases per 100,000 population. The mean age of the patients was 12.6 years and age-specific incidence rates ranged from 0.23% to 1.42%. The male/female sex ratio was 1.36. Overall, the mortality among hospitalized patients was 7.9%. Mortality increased during the epidemic. The major risk factor for dying was the delay until reaching hospital. Only 4 out of 29 interviewed parents said that their child had been vaccinated two years before. Among adult patients this proportion was 12/38 (32%). Because of the small numbers and because of the impossibility to check the vaccination records it was not possible to assess precisely the impact of earlier mass vaccination. However, the previous mass vaccination did not prevent this major epidemic and its impact is likely to have been unimportant.

Adolescent↗
PubMed1994

Aggregation in schistosomiasis: comparison of the relationships between prevalence and intensity in different endemic areas.

Distributions of the intensities of helminth infections within their host populations are invariably aggregated. In the case of the intestinal nematodes, the degrees of aggregation have been shown to be species specific, and constant for any given species despite geographical variation in study sites. This species-specific aggregation can be quantified and used as a tool in planning control interventions. One practical application is that the prevalence of infection can be used to predict the prevalence of heavy infection and thus the risks of morbidity. This paper investigates the patterns of aggregation in schistosome egg counts in different endemic areas in Africa (data sets were obtained from Burundi, Cameroon, Tanzania, Zambia and Zaire). The analysis demonstrates that the degree of parasite aggregation, for both Schistosoma mansoni and S. haematobium, differs amongst the different study localities. This is probably due to area-specific differences in host exposure and immunity. This implies that for these schistosome species, it is not possible to predict egg count distributions or morbidity levels from prevalence data alone.

Adolescent↗
PubMed1994

Controlling schistosomiasis: the cost-effectiveness of alternative delivery strategies.

Sustainable schistosomiasis control cannot be based on large-scale vertical treatment strategies in most endemic countries, yet little is known about the costs and effectiveness of more affordable options. This paper presents calculations of the cost-effectiveness of two forms of chemotherapy targeted at school-children and compares them with chemotherapy integrated into the routine activities of the primary health care system. The focus is on Schistosoma haematobium. Economic and epidemiological data are taken from the Kilombero District of Tanzania. The paper also develops a framework for possible use by programme managers to evaluate similar options in different epidemiological settings. The results suggest that all three options are more affordable and sustainable than the vertical strategies for which cost data are available in the literature. Passive testing and treatment through primary health facilities proved the most effective and cost-effective option given the screening and compliance rates observed in the Kilombero District.

Child↗
PubMed1993

Urinary schistosomiasis: testing with urine filtration and reagent sticks for haematuria provides a comparable prevalence estimate.

The relationship between school prevalence rates of urinary schistosomiasis, measured by urine filtration and by reagent sticks detecting haematuria, was investigated in nine primary schools in Tanzania. The aim of the study was to provide a methodological tool to compare results from studies that used these two different diagnostic techniques. A strong correlation was found between both measures (r = 0.96, P < 0.0001), and the equation of this linear relationship could be used to extrapolate the parasitological prevalence rate on the basis of the reagent stick testing, or the reverse. A review of the available literature indicated that the relationship holds true for certain settings, mainly in East Africa, but not for others, and it is therefore likely to be setting-specific. The same data demonstrated also a good relationship, at school level, between the mean school parasitological intensity and the sensitivity of the reagent sticks. A comparative testing of two different reagent stick brands (Hemastix and Combur 9) on 320 samples showed that the latter detected about 1.2-times more haematuria positives, and that this had also to be taken into account when aiming for a comparison of different techniques.

Child↗
PubMed1993

The distribution of Schistosoma haematobium in the Isoka district, Zambia; and a possible strategy for its control.

The distribution of schools prevalent for Schistosoma haematobium in the Isoka district, Zambia was estimated by examining haematuria in the urine of the pupils found in Grades Three, Four or Five using reagent sticks. Thirty three (57 pc) schools had prevalence rates of 25 pc or more. The distribution of S. haematobium was patchy with significant differences in prevalence rates between some areas only short distances apart. A sociological study in the same schools showed that 68 (97 pc) head/senior teachers associated the disease with blood in urine and agreed to perform a reagent stick test on their pupils' urine. Thirty five (50 pc) of these respondents considered S. haematobium infection as a major problem and 66 (94 pc) of them were ready to administer a diagnostic questionnaire to their pupils in a study to identify high risk schools for S. haematobium. We conclude that the identification of high risk schools in the Isoka district, Zambia, using a diagnostic questionnaire and reagent stick testing by teachers, should proceed as a step to controlling S. haematobium infection in the district.

Adolescent↗
PubMed1991

Community-based questionnaires and health statistics as tools for the cost-efficient identification of communities at risk of urinary schistosomiasis.

Self-administered questionnaires, distributed by existing administrative channels to village party chairmen, head-teachers and schoolchildren, showed good diagnostic performance for the qualitative assessment of urinary schistosomiasis endemicity. At a cost 34 times below that of the WHO-recommended parasitological screening strategy, the schoolchildren's questionnaire allowed the screening of 75 out of 77 schools of a rural Tanzanian district in six weeks, and the exclusion of schools not at high risk for urinary schistosomiasis with over 90% confidence. The headteacher and party questionnaires made it possible to assess the perceived importance of a spectrum of diseases and symptoms, among which was schistosomiasis. The priority rank of schistosomiasis control was strongly correlated with the prevalence rate of the disease in the community. The questionnaires also looked for the prioritization of health among other community issues and thus contributed important information for planning at district level. Standardized monthly disease reports, sent by all primary health services, were also analysed. They allowed a zonal schistosomiasis endemicity classification.

Adolescent↗
PubMed1991

Rapid, low-cost, two-step method to screen for urinary schistosomiasis at the district level: the Kilosa experience.

The operational and diagnostic performance of a two-step method for the cost-effective screening of urinary schistosomiasis was investigated in the Kilosa District of east-central Tanzania. In the first step a simple questionnaire was administered to 15,073 primary schoolchildren by their class teachers over a 4-week period. The answers to the questionnaires had a high negative predictive value for schistosomiasis, and this permitted the safe exclusion of schools where the risk of the disease was low. In the second step, the head-teachers of the 49 high-risk schools and of 26 low-risk schools were instructed on the use of reagent sticks to detect haematuria. Each head-teacher then performed this test on 80 children selected at random in their schools (5750 children were screened within 6 weeks). Crosschecks of the results in 18 schools confirmed the reliability of the head-teachers' testing and their findings were therefore used to prepare an epidemiological map of the district and to arrange for treatment of positive children. This two-step approach relied entirely on the existing school system and permitted screening of a rural district of area 15,000 km2 (population, 350,000) over a 4-month period at a cost of only US$3000.

Child↗
PubMed1991

The value of questionnaires aimed at key informants, and distributed through an existing administrative system, for rapid and cost-effective health assessment.

The requirement for a careful interview set-up in the classical key-informant approach considerably limits its extension to a larger scale. However, the administration of simplified questionnaires entirely through an existing administrative system can provide an alternative approach and become a valuable tool for fast and cost-efficient community health assessment. This methodology relies on a well-structured and working administrative system, and is restricted to health problems that are well and distinctly perceived by community members. It gives mainly qualitative results, and can therefore be used to single out rapidly and inexpensively high-risk and low-risk units. The biomedical screening of a large number of negative units can thus be avoided, and available resources can be concentrated on the positive ones. An extensive validation of this "indirect" approach by standardized biomedical measurements is a crucial requirement for its usefulness. In addition to biomedical information, questionnaires also provide information on the perception and prioritization of community health problems, which is of interest for health planning.

Child↗
PubMed1989

Presence of the schistosome circulating anodic antigen (CAA) in urine of patients with Schistosoma mansoni or S. haematobium infections.

We investigated the presence of the circulating anodic antigen (CAA) in the urine of schistosomiasis patients. This genus specific antigen was hitherto demonstrated only in the serum of schistosomiasis patients. The urine of 80 patients with Schistosoma mansoni infections, 33 patients with S. haematobium infections, and 2 patients with mixed S. haematobium and S. mansoni infections were screened by a quantitative enzyme-linked immunosorbent assay (ELISA). CAA was demonstrated in 81% of those with intestinal schistosomiasis and in 97% of those with urinary schistosomiasis. CAA titers were less than 1:0.2-1:51.2. Results were compared with circulating cathodic antigen (CCA) titers in urine obtained in an indirect hemagglutination assay (IHA). CCA was generally not detectable in the urine of patients with S. haematobium infection, but was demonstrated in the urine of 85% of the patients with S. mansoni infection. Both CAA titers and CCA titers correlated positively with the number of S. mansoni eggs excreted in the feces, but CAA titers did not show a significant correlation with the number of S. haematobium eggs in urine. Both antigen titers showed a moderate correlation with the serum CAA level in schistosomiasis mansoni. The discovery of CAA in the urine of the majority of schistosomiasis patients tested suggests the use of urine samples for non-invasive immunodiagnosis of the disease.

Adolescent↗
PubMed1989

Field diagnosis of urinary schistosomiasis by multiple use of nuclepore urine filters.

It has been recognized recently that the standard field technique for the diagnosis of urinary schistosomiasis, urine filtration using reusable polyamide mesh filters, may give false-positive findings because filters cannot be washed adequately in all circumstances. In this study the alternative filtration method using polycarbonate membrane filters was tested, and the same problem existed. A variety of more vigorous washing procedures was field tested with the conclusion that polycarbonate filters can be washed adequately for reuse by a simple procedure that includes boiling for 5 min in tap water prior to washing with detergent.

Animals↗
PubMed1987

Sero-epidemiological survey for alveolar echinococcosis (by Em2-ELISA) of blood donors in an endemic area of Switzerland.

Sera from 17,166 blood donors living in 10 cantons of northern Switzerland in an area endemic for Echinococcus multilocularis were investigated by serological survey for alveolar echinococcosis (AE). A highly species-specific antigen (Em2) and a commonly used E. granulosus hydatid fluid antigen (EgHF) were compared for their suitability in seroepidemiology. EgHF showed a degree of nonspecificity which did not allow direct detection of AE cases. Antibody reaction with Em2 resulted in the detection of 2 asymptomatic clinical cases of AE (seroprevalence 0.01%) within this population of blood donors. A further 4 persons were positive in Em2-ELISA. These 4 persons had negative imaging studies and will be followed serologically and clinically.

Adult↗
PubMedDate not supplied

Case studies from the biomedical and health systems research activities of the Swiss Tropical Institute in Africa.

Neither high theoretical efficacy of disease control tools, nor diagnostic accuracy, nor good compliance, nor adequate coverage can lead on its own to the final goal of community effectiveness. There is a complex relationship between these factors. The different steps in the process leading to effective health care in the community are discussed on the basis of biomedical and health systems research activities of the Swiss Tropical Institute. Schistosomiasis and malaria control provide the background to problems related to the efficacy of tools. In particular, information on the trial of a malaria vaccine candidate (SPf66) is given. Approaches to the rapid, accurate and economical diagnosis of communities at risk are discussed with reference to Schistosoma haematobium and S. mansoni. Health service support projects in Tanzania and Chad are presented to exemplify problems linked to the compliance of users/providers and coverage. Finally, it is shown that community effectiveness depends on the highest possible success rate for each step. This requires the co-operative efforts of all those involved: the scientist, the manager, the community health worker and, last but not least, the community itself.

Adult↗