Schistosomiasis and neglected tropical diseases: towards integrated and sustainable control and a word of caution.

In May 2001, the World Health Assembly (WHA) passed a resolution which urged member states to attain, by 2010, a minimum target of regularly administering anthelminthic drugs to at least 75% and up to 100% of all school-aged children at risk of morbidity. The refined global strategy for the prevention and control of schistosomiasis and soil-transmitted helminthiasis was issued in the following year and large-scale administration of anthelminthic drugs endorsed as the central feature. This strategy has subsequently been termed 'preventive chemotherapy'. Clearly, the 2001 WHA resolution led the way for concurrently controlling multiple neglected tropical diseases. In this paper, we recall the schistosomiasis situation in Africa in mid-2003. Adhering to strategic guidelines issued by the World Health Organization, we estimate the projected annual treatment needs with praziquantel among the school-aged population and critically discuss these estimates. The important role of geospatial tools for disease risk mapping, surveillance and predictions for resource allocation is emphasised. We clarify that schistosomiasis is only one of many neglected tropical diseases and that considerable uncertainties remain regarding global burden estimates. We examine new control initiatives targeting schistosomiasis and other tropical diseases that are often neglected. The prospect and challenges of integrated control are discussed and the need for combining biomedical, educational and engineering strategies and geospatial tools for sustainable disease control are highlighted. We conclude that, for achieving integrated and sustainable control of neglected tropical diseases, a set of interventions must be tailored to a given endemic setting and fine-tuned over time in response to the changing nature and impact of control. Consequently, besides the environment, the prevailing demographic, health and social systems contexts need to be considered.

Case studies in public-private-partnership in health with the focus of enhancing the accessibility of health interventions.

Various definitions have been framed for public-private partnerships (PPPs) in health depending on the desired relationship and the characteristics of the respective sectors. These relationships span from a continuum of loose relationships with narrow objectives, lack of a legal status and an absence of a formalized membership or governing body to high level institutionalization. The latter includes concrete objectives, the presence of a legal status and permanent multi-sectoral membership. The study used qualitative research methods including case studies, literature review and interview with key informants. The research undertakes an extensive literature review of various PPP models in health in scale and in scope which are aimed at advancing public health goals in developing countries. The major emphasis is on a qualitative description of some of the PPPs in the planning and implementation phases, including the challenges encountered. This background is used to analyse in-depth two case studies which are both health oriented; the first one is a national level NGO consortium with a focus on malaria and the second one is an international advocacy group with an overarching goal of protecting children against malaria through an innovative mechanism. The case study approach is used to analyze why the PPP approach was used to address malaria control and how it was implemented. Both PPPs demonstrated that relationships between the public and private sector may begin from very humble and loose beginnings. However, with perseverance from committed individuals, a vision and trustworthiness may become powerful advocates for meeting prescribed health agendas. In conclusion, three key themes (trust, sacrifice and championship) run vividly through the case studies and are significant for developing countries to emulate.

Towards a comprehensive simulation model of malaria epidemiology and control.

Planning of the control of Plasmodium falciparum malaria leads to a need for models of malaria epidemiology that provide realistic quantitative prediction of likely epidemiological outcomes of a wide range of control strategies. Predictions of the effects of control often ignore medium- and long-term dynamics. The complexities of the Plasmodium life-cycle, and of within-host dynamics, limit the applicability of conventional deterministic malaria models. We use individual-based stochastic simulations of malaria epidemiology to predict the impacts of interventions on infection, morbidity, mortality, health services use and costs. Individual infections are simulated by stochastic series of parasite densities, and naturally acquired immunity acts by reducing densities. Morbidity and mortality risks, and infectiousness to vectors, depend on parasite densities. The simulated infections are nested within simulations of individuals in human populations, and linked to models of interventions and health systems. We use numerous field datasets to optimise parameter estimates. By using a volunteer computing system we obtain the enormous computational power required for model fitting, sensitivity analysis, and exploration of many different intervention strategies. The project thus provides a general platform for comparing, fitting, and evaluating different model structures, and for quantitative prediction of effects of different interventions and integrated control programmes.

An atlas of malaria in Africa.

PIP: The Mapping Malaria Risk in Africa (MARA) project will use computerized geographic information systems (GIS) to create an atlas of malaria risk in Africa. This is the first time GIS will be used to predict such risk and the first attempt to map malaria risk on a continental scale. Many heterogenous data sets relevant to the transmission dynamics of the disease will be combined, including the manipulation of the climatic factors which affect vector distribution and malaria transmission into a new index of malaria risk, and its validation against actual data. Specifically, the MARA project will collate measures of malaria risk, mainly the parasite ratio and annual incidence, to obtain an index for Africa and to create a continental, spatial, and temporal database. Five planned regional centers will work with a coordinating center in Durban, South Africa. The effort recently received its first funding. Canada's International Development Research Center, the World Health Organization/TDR bednet task force, the Wellcome Trust, and the South African Medical Research Council are supporting the effort.^ieng

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.

A new Canadian health care initiative in Tanzania.

One of the main conclusions of the World Bank's World Development Report 1993--Investing in Health was that equitable access to a package of essential clinical and public health services could significantly reduce the overall burden of disease in low-income countries. The report argued that more rational and effective decisions with regard to the allocation of limited resources could be made on the basis of burden-of-disease and cost-effectiveness analyses. In collaboration with the Canadian International Development Agency and several other organizations, the International Development Research Centre has developed the Essential Health Interventions Project to test the feasibility of this approach in a few districts in Tanzania. Outcome assessment wil focus on improved planning at the district level and on changes to the health status of the study population.

As Canadians butt out, the developing world lights up.

Although rates of tobacco smoking in Canada have dropped dramatically over the last 30 years this is not a global trend. For every tonne of tobacco that Canadian adults gave up between 1970 and 1990, aggressive marketing by multinational tobacco companies has ensured that an additional 20 tonnes is now consumed in developing countries. The authors describe the dilemma faced by policymakers in their efforts to control the epidemic of tobacco smoking in the developing world: although tobacco consumption leads to increased rates of mortality and morbidity and lost productivity, its production creates employment, generates tax revenue and earns foreign exchange. Canadian experience has proved that trends in tobacco consumption can be reversed through policies that address not only health issues but also economic social and agricultural concerns. The authors propose a framework for harnessing expertise in the service of worldwide tobacco control.

Endod: safety evaluation of a plant molluscicide.

Toxicity tests, in accordance with the Minimal Data Requirements (Tier 1) of the OECD Guidelines for Pre-Market Chemicals, were conducted on a standard extract (Endod-S) from the unripe berries of Phytolacca dodecandra, a potent botanical molluscicide of potential importance in the control of schistosomiasis. In acute mammalian toxicity tests, except for the eye irritation toxicity test which indicated severe irritancy, all test results were classified as either nontoxic or slightly toxic. Eye protection is therefore recommended during berry crushing and handling of dry powders. Ecotoxicity tests indicated that Endod is no more toxic than currently recommended synthetic molluscicides; however, environmental fate and additional local ecotoxicity tests are recommended for nontarget aquatic organisms present in the endemic situations of field trials. Given these toxicological data and recognizing the need for an affordable, locally cultivated, botanical molluscicide, it is concluded that field trials of Endod in schistosomiasis control are now justifiable.

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.

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.

In vitro resistance patterns of Plasmodium falciparum to chloroquine--a reflection of strain-specific immunity?

Studies in vitro among children on the response of Plasmodium falciparum to chloroquine were conducted as part of the national long-term monitoring of drug resistance in a holo- to hyperendemic malarious area of Tanzania between 1983 and 1989. Overall, no significant increase in chloroquine resistance was observed. However, in children under 5 years old resistance increased during this period, whereas in schoolchildren resistance decreased from 1986 to 1989. A hypothesis based on antigenic differences between resistant and sensitive strains is proposed to explain this age-specific pattern. If immunity develops principally against the most frequent parasite strains, then as it develops the numbers of the most frequent strains will be reduced, whilst, the rare strains may become predominant and thus be detected in the blood of immune patients. Thus, in an endemic area, the observed resistance pattern in non-immune infants will differ from that in immune schoolchildren, as was observed in the present study. These findings may have important implications for the control of malaria and the development of vaccines.

Training of village health workers in Tanzania; a comparison of two approaches.

The paper compares the costs of training for two groups of Village Health Workers (VHWs) in Tanzania, where the policy of developing a system based on Primary Health Care principles will require the training of more than 16,000 VHWs during the next decade. In the Kilombero District, one group of VHWs was trained according to the guidelines of the National Programme of the Ministry of Health, and another group followed the training programme of the Kilombero Project, based on the Swiss Tropical Institute Field Laboratory. The training scheme of the Kilombero project cost almost 80% less for one VHW, largely because it depended on on-the-spot training by local staff. The results of a first investigation of the efficacy of the training were encouraging; a long-term evaluation is in progress. The curricula for the two programmes also differed; the Kilombero programme had shorter blocks of theory, interspersed with supervised practical work, and introduced curative medicine earlier in the course. The advantage and disadvantages of the two programmes are discussed, not only in terms of cost but also in terms of their efficacy in training VHWs who will be motivated, efficient and accepted by the community.

Ultrasound scanning for detecting morbidity due to Schistosoma haematobium and its resolution following treatment with different doses of praziquantel.

A study to assess the resolution of urinary tract morbidity due to Schistosoma haematobium was conducted on 2 cohorts of schoolchildren attending neighbouring schools in Kilombero District, southern Tanzania. Schoolchildren were screened for S. haematobium infection using the standard World Health Organization filtration technique and subsequently examined for urinary tract pathology using a portable 3.0 MHz sector scanner (Siemens Sonoline 1300). Treatment with praziquantel was given to all infected children. Children with observed urinary tract pathology received either 20 (n = 52) or 40 (n = 79) mg/kg body weight and were sonographically re-examined one, 2, 3 and 6 months following treatment. Geometric mean outputs of 21 and 19 eggs/ml of urine were detected in the 2 cohorts before treatment. Urinary tract pathology correlated positively with egg output (chi 2, P = 0.02) and microhaematuria (P = 0.0001). Bladder (wall irregularities and polyps) and kidney (congestive changes) pathologies were found in 81% and 36%, respectively, of the group that received 20 mg/kg of praziquantel, and in 78% and 46% of the group that received 40 mg/kg. Six months after treatment, 90.4% and 88.0% parasitological cure rates were obtained using 20 or 40 mg praziquantel/kg body weight. The respective pathology clearances were 88% and 91%. 20 mg/kg of praziquantel was as effective with regard to cure rates and reversibility of morbidity as 40 mg/kg.

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.

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.

Prevalence of dental caries among children in a rural Tanzanian community.

The age specific prevalences of mixed caries were determined in 346 children aged 1 to 15 years in a rural community in Morogoro Region, south-eastern Tanzania. In primary dentition 58.9% of children were caries free while dmf index averages 1.08. In permanent dentition 74.3% were caries free while DMF index averaged 0.43. Permanent dentition showed a constant increase in caries prevalence with age such that over half of 15 year old children had caries experience with a DMF index of 1.2. This relatively low prevalence of caries is associated with low consumption of refined sugars. Recommendations are made to support preventive dental health services and programmes in primary schools and maternal and child health clinics.

Longitudinal study on the health status of children in Kikwawila village, Tanzania: study area and design.

The paper describes the study area and the project design of a longitudinal study on the health status of children undertaken in Kikwawila village in southeastern Tanzania from 1982 to 1984. This rural village is situated in the Kilombero river plain (270 m above sea level) and extends over 50 km2. A census in 1982 (repeated in 1984) revealed that 1152 (1406) people lived in 260 (299) households of the nucleated roadside settlements of the sectors Kikwawila and Kapolo. The vital statistics showed an infant mortality rate estimate of 198/1000 which was far above the regional (140%) and the national (137%) averages. Over 30 tribes were recorded but 6 tribes formed 84% of the population. The population was predominantly muslim (75%). Most adult inhabitants (90%) were subsistence farmers cultivating an average of 3.7 acres per household. Rice, maize and cassava were the main crops of the area. At the beginning of the study, the village had no village health post, dispensary or health centre and it lacked an adequate and safe water supply. A great proportion of the population (67%) had to rely on water from unprotected hand dug wells and from rivers for domestic purposes. Only half of the households had a simple pit latrine. Even when latrines were present, they collapsed after heavy rains due to loose, unconsolidated soils, termites and the high water table. These difficulties affected the sustained success of sanitation campaigns. The study area represented a typical settlement of the Kilombero valley and was, with regard to most demographic, ethnic, agricultural and health characteristics, considered a suitable pilot area. A primary health care programme based on village health workers was implemented in parallel with complementary community based studies on the causes, interrelations and control measures of the major health problems faced by the community, and possible control measures.

Longitudinal study on the health status of children in a rural Tanzanian community: parasitoses and nutrition following control measures against intestinal parasites.

Three repeated cross-sectional surveys were undertaken among children (1 month to 15 years) of a rural community in southeastern Tanzania. The study was part of a longitudinal project on the interactions among nutrition, parasitic infections and immunity within a primary health care programme emphasizing village health workers. All children underwent interviews and parasitological, anthropometric, anamnestic and clinical examinations. Out of 550-590 children examined each year, a cohort of 170 children could be followed for three consecutive years. Malaria was holo- to hyperendemic in the community, P. falciparum accounting for greater than 90% of the infections. The parasite and spleen rates were 88% and 67%, respectively, and the average enlarged spleen index was 2.0 among children from 2-9 years in 1982. Transmission of malaria was high and stable as indicated by a parasite rate of 80% among infants between 1 month and 1 year during the whole period of study. G. lamblia, hookworm (N. americanus), Strongyloides spp. and Schistosoma haematobium were highly prevalent and annual incidence rates were high, while Entamoeba histolytica, Ascaris and Trichuris were of minor importance. Prevalence and incidence of parasitic infections did not differ by sex. Multiparasitism was very frequent and less than 11% of all children were parasite-free in each year. Not a single child remained parasite-free for three consecutive years. An anthropometric assessment showed a high degree of stunting (35-71%) and a substantial proportion of wasting (3-20%). The growth potential was normal in girls and boys during the whole period of study. There were indications that malaria was the main contributory factor to growth retardation among young children. Hookworm infection did not significantly affect the packed-cell volume of the children, probably owing to the low intensity of infection. Due to the multiparasitism and the lack of parasite-free individuals, single-parasite and single-nutrient effects were difficult to unravel. A latrine campaign followed by a single mass treatment against hookworm (single oral dose of albendazole, 400 mg) and/or G. lamblia (single oral dose of ornidazole, 40 mg/kg) only temporarily affected the prevalence and incidence of G. lamblia, and only resulted in a decrease in the intensity of hookworm infections up to six months after the interventions. As the effects of the latrine campaign and a single mass treatment on the parasite load were only transient, no sustained impact on nutritional variables was observed.(ABSTRACT TRUNCATED AT 400 WORDS)