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D le Sueur

Publications and source records attributed to D le Sueur.

12 recordsLinked to original sources
PubMed2001

Malaria control--two years' use of insecticide-treated bednets compared with insecticide house spraying in KwaZulu-Natal.

OBJECTIVES: The objective of this study was to produce data indicating whether insecticide-treated bednets should replace insecticide house spraying as a malaria control method in South Africa. We report 2 years of preliminary data on malaria incidence comparing areas receiving insecticide-treated bednets and those subjected to house spraying in northern KwaZulu-Natal. DESIGN, SETTING AND SUBJECTS: In order to measure significant reductions in malaria incidence between the two interventions, a geographical information system (GIS) was used to identify and create seven pairs of geographical blocks (areas) in the malaria high-risk areas of Ndumu and Makanis in Ingwavuma magisterial district, KwaZulu-Natal. Individual blocks were then randomly allocated to either insecticide-treated bednets or house spraying with deltamethrin. Malaria cases were either routinely recorded by surveillance agents at home or were reported to the nearest health facility. RESULTS AND CONCLUSIONS: The results show that 2 years' use of insecticide-treated bednets by communities in Ndumu and Makanis, KwaZulu-Natal, significantly reduced the malaria incidence both in 1997 (rate ratio (RR) = 0.879, 95% confidence interval (CI) 0.80-0.95, P = 0.04) and in 1998 (RR = 0.667, CI 0.61-0.72, P = 0.0001). Using a t-test, these significant reductions were further confirmed by an assessment of the rate of change between 1996 and 1998, showing a 16% reduction in malaria incidence in blocks using treated bednets and an increase of 45% in sprayed areas (t = 2.534, P = 0.026 (12 df)). In order to decide whether bednets should replace house spraying in South Africa, we need more data on the efficacy of treated bednets, their long-term acceptability and the cost of the two interventions.

Aerosols↗
PubMed2000

Distribution of African malaria mosquitoes belonging to the Anopheles gambiae complex.

The distribution of malaria vector mosquitoes, especially those belonging to species complexes that contain non-vector species, is important for strategic planning of malaria control programmes. Geographical information systems have allowed researchers to visualize distribution data on maps together with environmental parameters, such as rainfall and temperature. Here, Maureen Coetzee, Marlies Craig and David le Sueur review our current knowledge on the distribution of the members of the Anopheles gambiae complex.

Africa South of the Sahara↗
PubMed1999

A preliminary continental risk map for malaria mortality among African children.

Approaches to global public health are increasingly driven by an understanding of regional patterns of disease-specific mortality and disability. Current estimates of disease risks associated with Plasmodium falciparum in sub-Saharan Africa remain poorly defined. Through the integration of high-resolution population and climate probability models of P. falciparum transmission, geographical information systems have been used to define the spatial limits of populations exposed to the risk of infection in Africa. These estimates were combined with a range of annual malaria-specific mortality rates, derived from a variety of epidemiological approaches, among children aged 0-4 years. The best estimates of malaria-attributable mortality using this approach ranged between 0. 43 million and 0.68 million deaths per annum among an exposed population of approximately 66 million children in 1990. Despite the limitations of modelled transmission and population distributions, these empirical approaches to probabilities of infection risk and epidemiological data on mortality provide a novel approach to present and projected burdens of malaria mortality, as discussed here by Bob Snow, Marlies Craig, Uwe Deichmann and Dave le Sueur.

Africa South of the Sahara↗
PubMed1999

A climate-based distribution model of malaria transmission in sub-Saharan Africa.

Malaria remains the single largest threat to child survival in sub-Saharan Africa and warrants long-term investment for control. Previous malaria distribution maps have been vague and arbitrary. Marlies Craig, Bob Snow and David le Sueur here describe a simple numerical approach to defining distribution of malaria transmission, based upon biological constraints of climate on parasite and vector development. The model compared well with contemporary field data and historical 'expert opinion' maps, excepting small-scale ecological anomalies. The model provides a numerical basis for further refinement and prediction of the impact of climate change on transmission. Together with population, morbidity and mortality data, the model provides a fundamental tool for strategic control of malaria.

Africa South of the Sahara↗
PubMed1998

Mapping malaria transmission intensity using geographical information systems (GIS): an example from Kenya.

That there are so few examples of the use of epidemiological maps in malaria control may be explained by the lack of suitable, spatially defined data and of an understanding of how epidemiological variables relate to disease outcome. However, recent evidence suggests that the clinical outcomes of infection are determined by the intensity of parasite exposure, and developments in geographical information systems (GIS) provide new ways to represent epidemiological data spatially. In the present study, parasitological data from 682 cross-sectional surveys conducted in Kenya were abstracted and spatially defined. Risks of infection with Plasmodium falciparum among Kenyan children, estimated from combinations of parasitological, geographical, demographic and climatic data in a GIS platform, appear to be low for 2.9 million, stable but low for another 1.3 million, moderate for 3.0 million and high for 0.8 million. (Estimates were not available for 1.4 million children.) Whilst the parasitological data were obtained from a variety of sources across different age-groups and times, these markers of endemicity remained relatively stable within the broad definitions of high, moderate and low transmission intensity. Models relating ecological and climatic features to malaria intensity and improvements in our understanding of the relationships between parasite exposure and disease outcome will hopefully provide a more rational basis for malaria control in the near future.

Climate↗
PubMed1996

Schistosoma mansoni in migrants entering South Africa from Moçambique--a threat to public health in north-eastern KwaZulu-Natal?

OBJECTIVES: To identify possible public health consequences of Schistosoma mansoni infections in migrants entering north-eastern KwaZulu-Natal and Mpumalanga and Northern Province from southern Moçambique. DESIGN: (i) Intestinal parasite surveys, one sample per person, within a 4-month period; (ii) temperature recordings and snail collections in an irrigation system. SETTING: North-eastern KwaZulu-Natal and Kruger National Park, Mpumalanga and Northern Province. PARTICIPANTS: Ninety-seven migrants (1-68 years) from north-eastern KwaZulu-Natal and 47 from the Kruger Park (1 - 70 years). MAIN OUTCOME MEASURES: The relatively high S. mansoni prevalence may cause problems on the rice paddy scheme in north-eastern KwaZulu-Natal. Ranges and prevalence rates of other parasites were recorded. RESULTS: S. mansoni prevalence in Moçambicans entering north-eastern KwaZulu-Natal was 14.4%, seven times more than in local residents. S. mansoni is not endemic to this region because most bodies of water become too warm for either the parasite or its snail host, Biomphalaria pfeifferi, to develop. Recordings in paddies suggest, however, that the rice modifies the temperature pattern as it grows and provides a suitable habitat for transmission. Migrants entering the Transvaal lowveld where S. mansoni is endemic may become more severely infected. Thirteen other parasite species were recorded from migrants entering KwaZulu-Natal and 8 from those entering Mpumalanga and Northern Province. CONCLUSIONS: The relatively high S. mansoni prevalence among migrants entering north-eastern KwaZulu-Natal may have public health implications as it could encourage transmission in a non-endemic area. The range of parasites carried by migrants entering KwaZulu-Natal, Mpumalanga and Northern Province was similar to that harboured by local people but prevalence rates were generally lower.

Adolescent↗
PubMed1991

Temperature-dependent variation in Anopheles merus larval head capsule width and adult wing length: implications for anopheline taxonomy.

Seasonal variations in mosquito larval head capsule width and adult female wing length were investigated in a field population of Anopheles merus Dönitz at Nceswana Lake, Ophansi, within the endemic malaria area of Natal, South Africa. An inverse relationship was detected between each of these morphological characters and seasonal fluctuations in air/water temperatures. Mean head capsule width in all larval instars decreased by 4.8-7.9% in summer, while mean wing length decreased by 19.6%. These changes are discussed in relation to the annual range in mean air temperature in southern Africa and the distribution of An.merus. Implications for the use of such morphological characteristics in existing taxonomic keys are discussed.

Animals↗
PubMedDate not supplied

Models to predict the intensity of Plasmodium falciparum transmission: applications to the burden of disease in Kenya.

There is an increasing need to provide spatial distribution maps of the clinical burden of Plasmodium falciparum malaria in Africa. Recent evidence suggests that risk groups and the clinical spectrum of severe malaria are related to the intensity of P. falciparum transmission. Climate operates to affect the vectorial capacity of P. falciparum transmission and this is particularly important in the Horn of Africa and parts of East Africa. We have used a fuzzy logic climate suitability model to define areas of Kenya unsuitable for stable transmission. Kenya's unstable transmission areas can be divided into areas where transmission potential is limited by low rainfall or low temperature and, combined, encompass over 8 million people. Among areas of stable transmission we have used empirical data on P. falciparum infection rates among 124 childhood populations in Kenya to develop a climate-based statistical model of transmission intensity. This model correctly identified 75% (95% confidence interval CI 70-85) of 3 endemicity classes (low, < 20%; high, > or = 70%; and intermediate parasite prevalences). The model was applied to meteorological and remote sensed data using a geographical information system to provide estimates of endemicity for all of the 1080 populated fourth level administrative regions in Kenya. National census data for 1989 on the childhood populations within each administrative region were projected to provide 1997 estimates. Endemicity-specific estimates of morbidity and mortality were derived from published and unpublished sources and applied to their corresponding exposed-to-risk childhood populations. This combined transmission, population and disease-risk model suggested that every day in Kenya approximately 72 and 400 children below the age of 5 years either die or develop clinical malaria warranting in-patient care, respectively. Despite several limitations, such an approach goes beyond 'best guesses' to provide informed estimates of the geographical burden of malaria and its fatal consequences in Kenya.

Child, Preschool↗