The application of geographical information systems to important public health problems in Africa

Spatial analysis of malaria incidence at the village level in areas with unstable transmission in Ethiopia

BACKGROUND

Malaria is the leading cause of morbidity and mortality in Ethiopia, accounting for over five million cases and thousands of deaths annually. The risks of morbidity and mortality associated with malaria are characterized by spatial and temporal variation across the country. This study examines the spatial and temporal patterns of malaria transmission at the local level and implements a risk mapping tool to aid in monitoring and disease control activities.

METHODS

In this study, we examine the global and local patterns of malaria distribution in 543 villages in East Shoa, central Ethiopia using individual-level morbidity data collected from six laboratory and treatment centers between September 2002 and August 2006.

RESULTS

Statistical analysis of malaria incidence by sex, age, and village through time reveal the presence of significant spatio-temporal variations. Poisson regression analysis shows a decrease in malaria incidence with increasing age. A significant difference in the malaria incidence density ratio (IDRs) is detected in males but not in females. A significant decrease in the malaria IDRs with increasing age is captured by a quadratic model. Local spatial statistics reveals clustering or hot spots within a 5 and 10 km distance of most villages in the study area. In addition, there are temporal variations in malaria incidence.

CONCLUSION

Malaria incidence varies according to gender and age, with males age 5 and above showing a statistically higher incidence. Significant local clustering of malaria incidence occurs between pairs of villages within 1-10 km distance lags. Malaria incidence was higher in 2002-2003 than in other periods of observation. Malaria hot spots are displayed as risk maps that are useful for monitoring and spatial targeting of prevention and control measures against the disease.

Synthesis of bicyclic amines and their activities against Trypanosoma brucei rhodesiense and Plasmodium falciparum K1

New alkenes, aziridines, and diamines were prepared from antiprotozoal 4-dialkylaminobicyclo[2.2.2]octan-2-imines to investigate the influence of several functional groups in position 2 of the ring skeleton on the antitrypanosomal and antiplasmodial activities. They were synthesized from 4-dialkylaminobicyclo[2.2.2]octan-2-imines and tested for their activities against Trypanosoma b. rhodesiense and Plasmodium falciparum K1 (resistant to chloroquine and pyrimethamine) using in vitro microplate assays. 4-Aminobicyclo[2.2.2]oct-2-enes and 3-azatricyclo[3.2.2.0(2,4)]nonylamines exhibit similar antiprotozoal activities as 4-aminobicyclo[2.2.2] octanes. 4-Aminobicyclo[2.2.2]oct-2-ylamines and their N-benzyl derivatives showed decreased antiplasmodial but enhanced antitrypanosomal (IC50 = 0.22-0.41 microM) activities compared to their parent oximes and to formerly synthesized 4-amino-2-azabicyclo[3.2.2]nonanes. Some of the 4-aminobicyclo[2.2.2]oct-2-ylamines exhibit moderate in vivo activity in mice against Trypanosoma brucei brucei.

Participatory mapping of target areas to enable operational larval source management to suppress malaria vector mosquitoes in Dar es Salaam, Tanzania

Background

Half of the population of Africa will soon live in towns and cities where it can be protected from malaria by controlling aquatic stages of mosquitoes. Rigorous but affordable and scaleable methods for mapping and managing mosquito habitats are required to enable effective larval control in urban Africa.

Methods

A simple community-based mapping procedure that requires no electronic devices in the field was developed to facilitate routine larval surveillance in Dar es Salaam, Tanzania. The mapping procedure included (1) community-based development of sketch maps and (2) verification of sketch maps through technical teams using laminated aerial photographs in the field which were later digitized and analysed using Geographical Information Systems (GIS).

Results

Three urban wards of Dar es Salaam were comprehensively mapped, covering an area of 16.8 km². Over thirty percent of this area were not included in preliminary community-based sketch mapping, mostly because they were areas that do not appear on local government residential lists. The use of aerial photographs and basic GIS allowed rapid identification and inclusion of these key areas, as well as more equal distribution of the workload of malaria control field staff.

Conclusion

The procedure developed enables complete coverage of targeted areas with larval control through comprehensive spatial coverage with community-derived sketch maps. The procedure is practical, affordable, and requires minimal technical skills. This approach can be readily integrated into malaria vector control programmes, scaled up to towns and cities all over Tanzania and adapted to urban settings elsewhere in Africa.

Antiprotozoal activities of new bis-chlorophenyl derivatives of bicyclic octanes and aza-nonanes

The in vitro activity of newly synthesized bis-(chlorophenyl)-azabicyclo[3.2.2]nonanes and bis-(chlorophenyl)-bicyclo[2.2.2]octanes against Plasmodium falciparum K(1) (resistant to chloroquine and pyrimethamine) and Trypanosoma brucei rhodesiense was investigated. Especially the bis-(chlorophenyl)-azabicyclo[3.2.2]nonanes exhibit promising antitrypanosomal activity and were tested in vivo against Trypanosoma brucei brucei featuring moderate activities.

Mapping transactional sex on the Northern Corridor highway in Kenya

Even in generalized HIV/AIDS epidemics, vulnerable populations such as sex workers and truckers require special attention in programming. Combining a number of elicitation methods, centred on Geographical Information Systems (GIS) mapping, the Kenyan section of the Northern Corridor highway was studied to characterize the 'hot spots' where transactional sex is concentrated and to provide estimates of numbers of truckers and sex workers and the volumes of transactional sex taking place on the highway. An average of 2400 trucks park overnight at the 39 hot spots identified. These spots have an estimated sex worker population of 5600 women. Analysis of 403 sex worker diaries shows an average of 13.6 different clients and 54.2 sex acts in a month. Condom use is 69% in liaisons with regular clients and 90% with casual clients. The use of GIS is demonstrated at regional and local scales. The 'bridge population' of clients of sex workers, containing a wide rage of occupations, supports the concept of programming for 'vulnerable places' as well as vulnerable groups.

Synthesis of new esters and oximes with 4-aminobicyclo[2.2.2]octane structure and evaluation of their antitrypanosomal and antiplasmodial activities

New 4-amino-6,7-diphenylbicyclo[2.2.2]octane derivatives, esters of bicyclo[2.2.2]octan-2-ols and O-methyl oximes of bicyclo[2.2.2]octan-2-ones were synthesised. Their activities against Trypanosoma brucei rhodesiense (STIB 900) and their activity against the K1 strain of Plasmodium falciparum (resistant to chloroquine and pyrimethamine) were determined by use of microplate assays. The cytotoxicity was assessed using L6 cells. The antiprotozoal activities of the new compounds are compared with those of former prepared derivatives and drugs in use. Structure-activity relationships are discussed.

Antiplasmodial and antitrypanosomal activity of new esters and ethers of 4-dialkylaminobicyclo[2.2.2]octan-2-ols

Only three drugs are available for the treatment of East African trypanosomiasis. Patients suffer from painful application, severe side effects and increasing resistance against these drugs. Malaria tropica kills more than 2 million people every year mainly due to growing drug resistance. 4-Dialkylaminobicyclo[2.2.2]octan-2-ols and some of their esters have shown activity against both the causative organisms, Trypanosoma brucei rhodesiense and Plasmodium falciparum. Ethers and new esters with markedly higher lipophilicity were prepared in three-step procedures from acyclic synthons. The new compounds were screened for their antiprotozoal activities against T. b. rhodesiense (STIB 900) and P. falciparum K1 (resistant to chloroquine and pyrimethamine), and for their cytotoxicity with L-6 cells by means of in vitro microplate assays. The results were compared to those of the parent compounds indicating that higher lipophilicity increases the antiprotozoal activities. The pivalate 10a showed the highest antitrypanosomal activity. The 4-chlorobenzoate 9b exhibited good antiplasmodial activity and low cytotoxicity. The most active antiplasmodial agent was the benzhydryl ether 13c which was nearly as active as chloroquine against sensitive strains.

Towards understanding the presence/absence of Human African Trypanosomosis in a focus of Côte d'Ivoire: a spatial analysis of the pathogenic system

Background

This study aimed at identifying factors influencing the development of Human African Trypanosomosis (HAT, or sleeping sickness) in the focus of Bonon, located in the mesophile forest of Côte d'Ivoire. A previous study mapping the main daytime activity sites of 96 patients revealed an important disparity between the area south of the town- where all the patients lived- and the area north of the town, apparently free of disease. In order to explain this disparity, we carried out a spatial analysis of the key components of the pathogenic system, i.e. the human host, the tsetse vector and the trypanosomes in their environment using a geographic information system (GIS).

Results

This approach at the scale of a HAT focus enabled us to identify spatial patterns which linked to the transmission and the dissemination of this disease. The history of human settlement (with the rural northern area exploited much earlier than the southern one) appears to be a major factor which determines the land use pattern, which itself may account for differences found in vector densities (tsetse were found six times more abundant in the southern rural area than in the northern). Vector density, according to the human and environmental context in which it is found (here an intense mobility between the town of Bonon and the rural areas), may explain the observed spatial differences in HAT prevalence.

Conclusion

This work demonstrates the role of GIS analyses of key components of the pathogenic system in providing a better understanding of transmission and dissemination of HAT. Moreover, following the identification of the most active transmission areas, and of an area unfavourable to HAT transmission, this study more precisely delineates the boundaries of the Bonon focus. As a follow-up, targeted tsetse control activities starting north of Bonon (with few chances of reinvasion due to very low densities) going south, and additional medical surveys in the south will be proposed to the Ivoirian HAT control program to enhance the control of the disease in this focus. This work also shows the evolution of HAT regarding time and environment, and the methodology used may be able to predict possible sleeping sickness development/extinction in areas with similar history and space organization.

Oblique decision trees for spatial pattern detection: optimal algorithm and application to malaria risk

BACKGROUND

In order to detect potential disease clusters where a putative source cannot be specified, classical procedures scan the geographical area with circular windows through a specified grid imposed to the map. However, the choice of the windows' shapes, sizes and centers is critical and different choices may not provide exactly the same results. The aim of our work was to use an Oblique Decision Tree model (ODT) which provides potential clusters without pre-specifying shapes, sizes or centers. For this purpose, we have developed an ODT-algorithm to find an oblique partition of the space defined by the geographic coordinates.

METHODS

ODT is based on the classification and regression tree (CART). As CART finds out rectangular partitions of the covariate space, ODT provides oblique partitions maximizing the interclass variance of the independent variable. Since it is a NP-Hard problem in RN, classical ODT-algorithms use evolutionary procedures or heuristics. We have developed an optimal ODT-algorithm in R2, based on the directions defined by each couple of point locations. This partition provided potential clusters which can be tested with Monte-Carlo inference. We applied the ODT-model to a dataset in order to identify potential high risk clusters of malaria in a village in Western Africa during the dry season. The ODT results were compared with those of the Kulldorff' s SaTScan.

RESULTS

The ODT procedure provided four classes of risk of infection. In the first high risk class 60%, 95% confidence interval (CI95%) [52.22-67.55], of the children was infected. Monte-Carlo inference showed that the spatial pattern issued from the ODT-model was significant (p < 0.0001). Satscan results yielded one significant cluster where the risk of disease was high with an infectious rate of 54.21%, CI95% [47.51-60.75]. Obviously, his center was located within the first high risk ODT class. Both procedures provided similar results identifying a high risk cluster in the western part of the village where a mosquito breeding point was located.

CONCLUSION

ODT-models improve the classical scanning procedures by detecting potential disease clusters independently of any specification of the shapes, sizes or centers of the clusters.

The utility of geographic information systems (GIS) in rapid epidemiological assessments following weather-related disasters: methodological issues based on the Tropical Storm Allison Experience

Flooding is the most common natural disaster worldwide, and is the leading cause of weather-related deaths in the United States. Tropical storm Allison hit landfall near Galveston, Texas on June 5, 2001, causing the most severe flood-related damage ever recorded in the Houston metropolitan area. This devastating storm dumped 37 in of rain in 24h on parts of the city, killing 22 people and causing more than $5 billion in damage. The main goal of the public health response to tropical storm Allison was to rapidly evaluate the immediate health needs of the community. Geographical information system (GIS) technology was instrumental to the timeliness of this effort. We conducted a rapid needs assessment in the areas most affected by flooding using modified cluster sampling facilitated by GIS methodology. Of the 420 households participating in the survey, we found a significant increase in illness (OR, 5.1; 95% CI, 2.7-9.4), injuries (OR, 4.8; 95% CI, 1.9-12.8), and immediate health needs (OR, 3.3; 95% CI, 1.7-6.1) among persons living in flooded homes compared to non-flooded homes. There were 60 households reporting serious damage, 24 of which were outside the 500-year flood plain. We also obtained reliable estimates of the extent of damage and household needs to help guide relief efforts. These findings underscore the usefulness of rapid needs assessment as a tool to identify actual health threats and to facilitate delivery of resources to those with the greatest and most immediate need. Our ability to swiftly plan and implement a rapid needs assessment over a large geographical region within 1 week following the damage would not have been possible without the utilization of GIS methodology and the availability of skilled personnel and timely data resources.

Antiprotozoal activities of new bicyclo[2.2.2]octan-2-imines and esters of bicyclo[2.2.2]octan-2-ols

Several bicyclo[2.2.2]octan-2-imines and esters of bicyclo[2.2.2]octan-2-ols were prepared. Their antitrypanosomal and antiplasmodial activities against Trypanosoma brucei rhodesiense (STIB 900) and the K1 strain of Plasmodium falciparum (resistant to chloroquine and pyrimethamine) were determined using microplate assays. Two of the synthesized bicyclo[2.2.2]octan-2-one 4'-phenylthiosemicarbazones showed the highest antitrypanosomal activity (IC(50)<0.3 microM) of the so far prepared 4-amino-6,7-diarylbicyclo[2.2.2]octane derivatives, but they are distinctly less active than suramine (IC(50)=0.0075 microM). Most of the 4'-phenylthiosemicarbazones and a single bicyclo[2.2.2]octan-2-yl benzoate exhibit attractive antimalarial activity (IC(50)=0.23-0.72 microM). Two bicyclooctanone oximes are even as active as chloroquine (IC(50)=0.08-0.15 microM, chloroquine: IC(50)=0.12 microM against sensitive strains).

Using GIS technology to identify areas of tuberculosis transmission and incidence

Background

Currently in the U.S. it is recommended that tuberculosis screening and treatment programs be targeted at high-risk populations. While a strategy of targeted testing and treatment of persons most likely to develop tuberculosis is attractive, it is uncertain how best to accomplish this goal. In this study we seek to identify geographical areas where on-going tuberculosis transmission is occurring by linking Geographic Information Systems (GIS) technology with molecular surveillance.

Methods

This cross-sectional analysis was performed on data collected on persons newly diagnosed with culture positive tuberculosis at the Tarrant County Health Department (TCHD) between January 1, 1993 and December 31, 2000. Clinical isolates were molecularly characterized using IS6110-based RFLP analysis and spoligotyping methods to identify patients infected with the same strain. Residential addresses at the time of diagnosis of tuberculosis were geocoded and mapped according to strain characterization. Generalized estimating equations (GEE) analysis models were used to identify risk factors involved in clustering.

Results

Evaluation of the spatial distribution of cases within zip-code boundaries identified distinct areas of geographical distribution of same strain disease. We identified these geographical areas as having increased likelihood of on-going transmission. Based on this evidence we plan to perform geographically based screening and treatment programs.

Conclusion

Using GIS analysis combined with molecular epidemiological surveillance may be an effective method for identifying instances of local transmission. These methods can be used to enhance targeted screening and control efforts, with the goal of interruption of disease transmission and ultimately incidence reduction.

Challenges in using geographic information systems (GIS) to understand and control malaria in Indonesia

Malaria is a mosquito-borne disease of global concern with 1.5 to 2.7 million people dying each year and many more suffering from it. In Indonesia, malaria is a major public health issue with around six million clinical cases and 700 deaths each year. Malaria is most prevalent in the developing countries of the world. Aid agencies have provided financial and technical assistance to malaria-prone countries in an effort to battle the disease. Over the past decade, the focus of some of this assistance has been in the provision of geographic information systems (GIS) hardware, software and training. In theory, GIS can be a very effective tool in combating malaria, however, in practice there have been a host of challenges to its successful use.This review is based, in part, on the literature but also on our experience working with the Indonesian Ministry of Health. The review identifies three broad problem areas. The first of these relates to data concerns. Without adequate data, GIS is not very useful. Specific problem areas include: accurate data on the disease and how it is reported; basic environmental data on vegetation, land uses, topography, rainfall, etc.; and demographic data on the movement of people. The second problem area involves technology - specifically computer hardware, GIS software and training. The third problem area concerns methods - assuming the previous data and technological problems have been resolved - how can GIS be used to improve our understanding of malaria? One of the main methodological tools is spatial statistical analysis, however, this is a newly developing field, is not easy to understand and suffers from the fact that there is no agreement on standard methods of analysis.The paper concludes with a discussion of strategies that can be used to overcome some of these problems. One of these strategies involves using ArcView GIS software in combination with ArcExplorer (a public domain program that can read ArcView files) to deal with the problem of needing multiple copies of GIS software. Another strategy involves the development of a self-paced training package that can be used to train individuals

Challenges in using geographic information systems (GIS) to understand and control malaria in Indonesia

Malaria is a mosquito-borne disease of global concern with 1.5 to 2.7 million people dying each year and many more suffering from it. In Indonesia, malaria is a major public health issue with around six million clinical cases and 700 deaths each year. Malaria is most prevalent in the developing countries of the world. Aid agencies have provided financial and technical assistance to malaria-prone countries in an effort to battle the disease. Over the past decade, the focus of some of this assistance has been in the provision of geographic information systems (GIS) hardware, software and training. In theory, GIS can be a very effective tool in combating malaria, however, in practice there have been a host of challenges to its successful use.

This review is based, in part, on the literature but also on our experience working with the Indonesian Ministry of Health. The review identifies three broad problem areas. The first of these relates to data concerns. Without adequate data, GIS is not very useful. Specific problem areas include: accurate data on the disease and how it is reported; basic environmental data on vegetation, land uses, topography, rainfall, etc.; and demographic data on the movement of people. The second problem area involves technology – specifically computer hardware, GIS software and training. The third problem area concerns methods – assuming the previous data and technological problems have been resolved – how can GIS be used to improve our understanding of malaria? One of the main methodological tools is spatial statistical analysis, however, this is a newly developing field, is not easy to understand and suffers from the fact that there is no agreement on standard methods of analysis.

The paper concludes with a discussion of strategies that can be used to overcome some of these problems. One of these strategies involves using ArcView GIS software in combination with ArcExplorer (a public domain program that can read ArcView files) to deal with the problem of needing multiple copies of GIS software. Another strategy involves the development of a self-paced training package that can be used to train individuals