[Technology of preventing Oncomelania snail diffusion in east route of South-to-North Water Diversion Project. I. Field test of blocking diffusion of Oncomelania snails with blocking network via collecting water from middle layer]

OBJECTIVE

To evaluate the effectiveness of blocking diffusion of Oncomelania snails with the blocking network via collecting water from middle layer.

METHODS

According to the principle of the installation preventing snails via collecting water from middle layer without snails, the blocking network was manufactured. The field test of the blocking diffusion of snails with the blocking network was carried out in the electric pumping station and the irrigation located in the area with snails. The snails stained were put into the water inlet of the pump when the pump was actuating, and the snails pumped were observed during the test period. The cost of the test was also calculated.

RESULTS

The rate of blocking diffusion of snails with the blocking network was 100%, and the direct costs were only 11 030 CNY.

CONCLUSIONS

The blocking network via collecting water from middle layer has good effect for prevention of snail dispersal. It is simple for manutacturing and installation, and suitable for emergency blocking diffusion of snails in the east route of South-to-North Water Diversion Project and the electric pumping station with snails.

[Effect of jian-gan-le on advanced schistosomiasis]

A total of 80 cases of advanced schistosomiasis were selected and divided into an experiment group and a control group, 40 cases each group, by the random sampling method. The patients in the experiment group were administered with Jian-gan-le, and the patients in the control group received compound purple granules. In the experiment group, the curative rate was 25.0%, the improving rate was 70.0%, the inefficacy rate was 5%, and the efficiency rate was 95.0%. In the control group, the curative rate was 12.5%, the improving rate was 75%, the inefficacy rate was 12.5%. There was no statistic difference between the 2 groups (P all > 0.05). The expense was cheaper in the experiment group than in the control group.

[Effect of project of afforestation for schistosomiasis prevention on snail control in marshland and lake regions]

OBJECTIVE

To evaluate the effect of the project of afforestation for schistosomiasis prevention on Oncomelania hupensis control.

METHODS

The situation of afforestation for schistosomiasis prevention in the field and the snail distribution in marshland regions were surveyed with the systematic sampling method in the spring, 2009. The database of snail distribution was established and the status of afforestation was investigated, and the effect of the project on snail control was evaluated.

RESULTS

The rates of frames with living snails in the environment with plantations and the environment without a plantation were 14.9% and 19.7%, respectively, and there was a significant difference (Chi2 = 2 267, P < 0.01). The rate of frames with living snails in agroforestry model was lower than that in other models except for fishery-husbandry-forestry model. The average densities of living snails in the environment with plantations and the environment without a plantation were 0.552 snails/0.1 m2 and 0. 989 snails/0.1 m2, respectively. The average densities of living snails in the cultivating group and un-cultivating group were 0.354 snails/0.1 m2 and 0.653 snails/0.1 m2, respectively. The rate of frames with living snails and the average density of living snails were the lowest in the environment of long-term afforestation.

CONCLUSIONS

The project of afforestation for schistosomiasis prevention has a good effect on snail control in Anhui Province. Long-term afforestation could stably maintain the effect on snail control.

[Cost-effectiveness and cost-benefit analysis on the integrated schistosomiasis control strategies with emphasis on infection source in Poyang Lake region]

OBJECTIVE

To evaluate the cost-effectiveness and cost-benefit on the integrated schistosomiasis control strategies with emphasis on infection source, and provide scientific basis for the improvement of schistosomiasis control strategy.

METHODS

Aiguo and Xinhe villages in Jinxian County were selected as intervention group where the new comprehensive strategy was implemented, while Ximiao and Zuxi villages in Xinzi County served as control where routine control program was implemented. New strategy of interventions included removing cattle from snail-infested grasslands and providing farmers with farm machinery, improving sanitation by supplying tap water and building lavatories and methane gas tanks, and implementing an intensive health education program. Routine interventions were carried out in the control villages including diagnosis and treatment for human and cattle, health education, and focal mollusciciding. Data were collected from retrospective investigation and field survey for the analysis and comparison of cost-effectiveness and cost-benefit between intervention and control groups.

RESULTS

The control effect of the intervention group was better than that of the control. The cost for 1% decrease of infection rate per 100 people, 100 cattle, and 100 snails in intervention group was 480.01, 6 851.24, and 683.63 Yuan, respectively, which were about 2.70, 4.37 and 20.25 times as those in the control respectively. The total cost/benefit ratio (BCR) was lower than 1 (0.94 in intervention group and 0.08 in the control). But the total benefit of intervention group was higher than that of the control from 2005 to 2008. The forecasting analysis indicated that the total BCR in intervention group would be 1.13 at the 4th year and all cost could be recalled. Sensitivity analysis revealed that the BCR in intervention group changed in the range around 1.0 and that of the control ranged blow 0.5. The cost-benefit of intervention group was evidently higher than that of the control.

CONCLUSIONS

The integrated control strategy focusing on infection source control brings about triplex benefits in schistosomiasis control, social development (and ecological protection) and economic efficacy, and shows better effects and benefits than the conventional control strategy.

Improving control of African schistosomiasis: towards effective use of rapid diagnostic tests within an appropriate disease surveillance model

Contemporary control of schistosomiasis is typically reliant upon large-scale administration of praziquantel (PZQ) to school age children. Whilst PZQ treatment of each child is inexpensive, the direct and indirect costs of preventive chemotherapy for the whole school population are more substantive and, at the national level where many schools are targeted, maximising cost effectiveness and the health impact are essential requirements for ensuring longer-term sustainability (i.e. >5 years). To this end, the WHO has issued a set of treatment guidelines, inclusive of re-treatment schedules, such that, where possible, treatment decisions by school are based upon local disease prevalence as determined by parasitological and/or questionnaire methods. As each diagnostic method has known shortcomings, presumptive treatment of at-risk schools may initially be preferred, especially if the existing infrastructure for disease surveillance is poor. It is against this background of school-based preventive chemotherapy that a rapid diagnostic test (RDT) for schistosomiasis is most urgently needed, not only to improve initial disease surveillance but also to focus drug delivery better through time. In this paper, the development, evaluation and application of selected diagnostic tests are reviewed to identify barriers that impede progress, foremost of which is that a new disease surveillance and evaluation model is required where the in-country price of each RDT ideally needs to be less than US$1 to be cost effective both in the short- and long-term perspective.

[Evaluation indices of social burden caused by advanced schistosomiasis]

OBJECTIVE

To study the evaluation indices and their weights of social burden caused by advanced schistosomiasis so as to provide scientific basis for control of the disease.

METHODS

Primary indices of social burden evaluation for advanced schistosomiasis were summarized based on literature review. Secondary indices were put forward by a brainstorming process of experts. After the first round Delphi method, the secondary indices that needed were chosen, and the importance of primary indices was prioritized. Through the second and third round Delphi method, the weight of each secondary index was obtained.

RESULTS

Four primary indices and 16 secondary indices consisted the index system of social burden induced by the disease. According to the significance, the 4 primary indices were arranged as social economy, government image, public psychology and social security. The weight of "funding for schistosomiasis control from central and local governments" in "social economic" stood the largest (14.063), while that of "equity to patients" in "government image", the smallest (3.125).

CONCLUSION

The study covers all major aspects and their significance in social burden of advanced schistosomiasis, and an evaluation index system has been established for field validation.

Willingness to pay for praziquantel treatment in a hyperendemic community of Ogun State, Nigeria

BACKGROUND

Schistosomiasis is highly endemic in Nigeria. However, very little is known about the usage and social marketing of praziquantel in the control of schistosomiasis in endemic communities and on the persons willingness to pay for the drug to support its extensive use and thus aid control efforts in Nigeria.

OBJECTIVE

The study examined the willingness of people in a hyperendemic community, to pay for treatment with praziquantel before and after provision of the drug, with a view to assess the feasibility of achieving widespread coverage.

METHODS

Data were collected through focus group discussions among household heads and other adult family members and through the use of a questionnaire to survey household heads in Imala-Odo, a community hyperendemic for schistosomiasis, in southwest Nigeria. The main outcome measure was the respondents' willingness to pay for schistosomiasis treatment.

RESULTS

The results showed that in contrast to the 92.3% of respondents who expressed willingness to buy the drug in the preintervention study, only 46.5% actually purchased the drug during intervention for the treatment of their infected household members. The respondents' level of education, occupation, and income influenced their willingness to pay (P<.05). Statistical tests showed that those willing to pay for treatment had a higher income score than those unwilling to do so. Most respondents preferred their community head and reliable persons chosen by the community as convenient outlets for drug distribution. The number of household members respondents were willing to treat increased from 4 to 6 at N320.00 (US $2.52) in the preintervention and postintervention phases, respectively. Gender factor was found to influence the respondents' perceived average treatment cost; the females wanted N300.00 (US $2.36) against N100.00 (US $0.79) among the males.

CONCLUSION

Efforts need to be made and sustained to ensure that all families can afford to praziquantel drug to achieve the ultimate goal of controlling the infection in endemic communities of Nigeria.

Reassessment of the cost of chronic helmintic infection: a meta-analysis of disability-related outcomes in endemic schistosomiasis

BACKGROUND

Schistosomiasis is one of the world's most prevalent infections, yet its effect on the global burden of disease is controversial. Published disability-adjusted life-year (DALY) estimates suggest that the average effect of schistosome infection is quite small, although this is disputed. To develop an evidenced-based reassessment of schistosomiasis-related disability, we did a systematic review of data on disability-associated outcomes for all forms of schistosomiasis.

METHODS

We did structured searches using EMBASE, PUBMED, and Cochrane electronic databases. Published bibliographies were manually searched, and unpublished studies were obtained by contacting research groups. Reports were reviewed and abstracted independently by two trained readers. All randomised and observational studies of schistosomiasis morbidity were eligible for inclusion. We calculated pooled estimates of reported disability-related effects using weighted odds ratios for categorical outcomes and standardised mean differences for continuous data.

FINDINGS

482 published or unpublished reports (March, 1921, to July, 2002) were screened. Of 135 selected for inclusion, 51 provided data for performance-related symptoms, whereas 109 reported observed measures of disability-linked morbidities. Schistosomiasis was significantly associated with anaemia, chronic pain, diarrhoea, exercise intolerance, and undernutrition.

INTERPRETATION

By contrast with WHO estimates of 0.5% disability weight assigned to schistosomiasis, 2-15% disability seems evident in different functional domains of a person with schistosomiasis. This raised estimate, if confirmed in formal patient-preference studies, indicates a need to reassess our priorities for treating this silent pandemic of schistosomiasis.

Schistosomiasis control in Ghana: case management and means for diagnosis and treatment within the health system

An essential component of integrated schistosomiasis control as promoted by WHO is adequate clinical care for patients presenting at health care facilities. We evaluated the functioning of the Ghanaian health system for diagnosis and treatment of schistosomiasis by interviewing health workers from 70 health care facilities in 4 geographical areas in April and May 2000. Results from presentation of 4 hypothetical cases and a subsequent interview demonstrated that patients presenting with symptoms related to schistosomiasis have a small chance of receiving adequate treatment: often health workers do not recognize the symptoms, especially those of Schistosoma mansoni; patients are frequently referred for a diagnostic test or treatment with a large risk of non-compliance; and praziquantel was not available in 78% of the health care facilities with reported schistosomiasis in their coverage area. The overall cost of treatment is considerable: [symbol: see text] 2.13 for S. haematobium and [symbol: see text] 1.81 for S. mansoni patients, with drug costs contributing approximately 40% of the total cost. To better meet WHO recommendations for passive case detection as part of integrated schistosomiasis control, the Ghanaian health system needs to emphasize training of health workers in schistosomiasis case recognition and case management and increase the availability of praziquantel. Experience from other West African countries indicate that this is feasible.

Achievement of the World Bank loan project on schistosomiasis control (1992-2000) in Hubei province and the challenge in the future

Since the World Bank provided a loan for control of schistosomiasis in China, started from 1992, with the objective of a reduction of prevalence and intensity of the infection both in humans and animals by 40%, through mass chemotherapy in areas of high prevalence, and selective chemotherapy in areas with medium and low endemicity together with focal mollusciciding, the objective of morbidity control of the project has been reached in Hubei Province.

Is equity being sacrificed? Willingness and ability to pay for schistosomiasis control in China

Decentralization of the health care system in China has led to an increasing need for income generation at all operational levels, both for curative services and for public health programmes. In general, people have accepted the costs of curative services, although the impact of charges on health-seeking behaviour has yet to be assessed. Public health programmes present particular problems in terms of revenue generation, however, because of the less direct impact of these activities on individual health and well-being. In this paper, we report the results of a cross-sectional study of willingness and ability to pay for schistosomiasis control. Questionnaires were administered to household heads of six representative villages in the Dongting Lake Region of Hunan Province, China. A total of 628 valid questionnaires were analyzed. The yearly mean household expenditure on schistosomiasis diagnosis and treatment was RMB 59.50 +/- 146.04 Yuan (US$1 = 8 RMB Yuan), accounting for 0.94% of the total yearly household income. Most household heads (514, 82%) thought schistosomiasis was the greatest health threat in their communities, but only 30.9% of them were willing to pay for screening, diagnosis and treatment of the infection. On the other hand, 72.3% of the respondents were willing to undertake volunteer work for control.

Pattern and cost of medical care for workers with schistosomiasis

This study describes the pattern of medical care provided to workers with schistosomiasis, estimate the total medical cost and to identify the proportional rates of sickness retirement attributed to schistosomiasis. The observational approach was adopted for this study 170 schistosomiasis workers and a similar number of controls were included in this study. An interviewing schedule and a special format were designed for collecting personal, medical and early retirement data. The results revealed that the mean total cost in the outpatient clinics was significantly higher for schistosomiasis workers than their controls (320.2 " 330.11 versus 210.8 " 260.01 L.E). The hospital cost was also higher for schistosomiasis workers compared with their controls (265.9 " 674.47 vs 195.8 " 629.72 L.E) but this differencewas not statistically significant. More than 80% of the total hospital cost was spent on bed cost. The average operative cost/worker was significantly higher among the schistosomiasis workers than the control workers (7.08 " 22.07 vs 2.35 " 5.2 L.E). The total medical cost (outpatient and hospital) was significantly higher for workers with schistosomiasis compared with their controls (586.02" 845.77 vs 406.57 " 694.34). The total number of workers who retired because of sickness disability other than schistosomiasis increased from 1994 to 1998 with a ratio of 2.54 while those who retired because of schistosomiasis and its complications increased with a ratio of 3.64.

The cost of large-scale school health programmes which deliver anthelmintics to children in Ghana and Tanzania. The Partnership for Child Development

It has been argued that the delivery of anthelmintics to school-children through existing education infrastructure can be one of the most cost-effective approaches to controlling parasitic worm infection. This paper examines the actual costs of a combination of mass and selective treatment for schistosomiasis using praziquantel and mass treatment for intestinal nematodes using albendazole, as an integral part of school health programmes reaching 80442 pupils in 577 schools in Volta Region, Ghana, and reaching 109099 pupils in 350 schools in Tanga Region, Tanzania. The analysis shows that financial delivery costs per child treated using praziquantel, which involved a dose related to body mass and a prior screening at the school level, were US$ 0.67 in Ghana and US$ 0.21 in Tanzania, while the delivery costs for albendazole, which was given as a fixed dose to all children, were US$ 0.04 in Ghana and US$ 0.03 in Tanzania. The higher unit costs in Ghana reflect the epidemiology of infection; overall, fixed costs were similar in both countries, but fewer children required treatment in Ghana. Analysis of economic costs-which includes the cost of unpaid days of labour--indicates that the financial costs are increased in Ghana by 78% and in Tanzania by 44%. It is these additional costs which are avoided by integration into an existing infrastructure. It is concluded that: the base cost of delivering a universal, standard, school-based health intervention can be as low as US$ 0.03 per child treated; that even a slight increase in the complexity of delivery can have a significant impact on the cost of intervention; and that the use of the education infrastructure does indeed offer significant savings in delivery costs.

Different approaches to modelling the cost-effectiveness of schistosomiasis control

This paper reviews three different approaches to modelling the cost-effectiveness of schistosomiasis control. Although these approaches vary in their assessment of costs, the major focus of the paper is on the evaluation of effectiveness. The first model presented is a static economic model which assesses effectiveness in terms of the proportion of cases cured. This model is important in highlighting that the optimal choice of chemotherapy regime depends critically on the level of budget constraint, the unit costs of screening and treatment, the rates of compliance with screening and chemotherapy and the prevalence of infection. The limitations of this approach is that it models the cost-effectiveness of only one cycle of treatment, and effectiveness reflects only the immediate impact of treatment. The second model presented is a prevalence-based dynamic model which links prevalence rates from one year to the next, and assesses effectiveness as the proportion of cases prevented. This model was important as it introduced the concept of measuring the long-term impact of control by using a transmission model which can assess reduction in infection through time, but is limited to assessing the impact only on the prevalence of infection. The third approach presented is a theoretical framework which describes the dynamic relationships between infection and morbidity, and which assesses effectiveness in terms of case-years prevented of infection and morbidity. The use of this model in assessing the cost-effectiveness of age-targeted treatment in controlling Schistosoma mansoni is explored in detail, with respect to varying frequencies of treatment and the interaction between drug price and drug efficacy.

Field activity cost estimates for the first 3 years of the World Bank Loan Project for schistosomiasis control in China

The World Bank Loan Project for schistosomiasis in China commenced field activities in 1992. In this paper, we describe disease control strategies for levels of different endemicity, and estimate unit costs and total expenditure of screening, treatment (cattle and humans) and snail control for 8 provinces where Schistosoma japonicum infection is endemic. Overall, we estimate that more than 21 million US dollars were spent on field activities during the first three years of the project. Mollusciciding (43% of the total expenditure) and screening (28% of the total) are estimated to have the most expensive field activities. However, despite the expense of screening, a simple model predicts that selective chemotherapy could have been cheaper than mass chemotherapy in areas where infection prevalence was higher than 15%, which was the threshold for mass chemotherapy intervention. It is concluded that considerable cost savings could be made in the future by narrowing the scope of snail control activities, redefining the threshold infection prevalence for mass chemotherapy, defining smaller administrative units, and developing rapid assessment tools.

Economic evaluation in schistosomiasis: valuation of health states preferences. A research note

Poor countries can ill-afford ineffective health care. An effective disease intervention is one which produces a net improvement in beneficiaries' quality of life and/or increases life expectancy. Unlike developed countries, very little research has been done in developing countries on the measures of the ultimate output of health care. The objectives of this study were to: (i) apply the existing health-related quality of life (HRQoL) methods in eliciting health state valuations from farmers, teachers and health professionals living and working in the schistosomiasis endemic Mwea Irrigation Scheme in Kenya; (ii) determine whether there is significant difference between average health states valuations from the three main groups of people at risk of schistosomiasis infection; and (iii) assess the relative effect of different respondent characteristics and health states prognosis on valuations. The instrument consists of seven health state descriptions-each defined along six functional dimensions: self-care, mobility, livelihood activities, energy, social participation and pain. Cardinal health state values were measured using a visual-analogue-scale (VAS). Values were elicited from three random samples of farming general public, medical professionals and teachers. The Kruskal-Wallis one-way ANOVA test showed that there is significant difference in the average health state values (for mild, moderate, severe, very severe and comatose states) obtained from the three samples. Generally, except for the valuation of the immediately following state, the other explanatory variables are not statistically significant determinants of valuations for the mild, moderate, severe and very severe states. The results suggest that VAS valuations are primarily affected by prognosis. There is urgent need for more representative and systematic HRQoL studies to test the relevance of the Western-based generic instruments in African countries contexts, with a view to developing more appropriate tool(s) if necessary.

Financing changes of schistosomiasis control programmes in China 1980-1995: a case study in Songzi county

To assess the financing changes of schistosomiasis control programmes in China and estimate the impact of these changes on patients' treatment-seeking behaviour and control of schistosomiasis, a survey was conducted in five schistosomiasis-endemic areas of the lake regions, Hubei province, in 1996. This paper reports financing changes and their impact on the incidence and prevalence of schistosomiasis from one of the five areas as a case study. By examining the surveillance and financial data from 1980 to 1995, and through focus group discussions we found that the schistosomiasis control programmes in People's Republic of China have gone through dramatic financing changes from 1980 to 1995, when the transitions of China's social, economic, and political systems happened. The proportions of funding to schistosomiasis control programmes from high level governmental agencies, county budgets, and services revenue changed from 60%, 23%, and 17%, respectively, in 1980-1987 to 0.7%, 22.3%, and 72% in 1995. The percentages of expenditure of schistosomiasis control activities, salaries and bonuses, and other activities unrelated to schistosomiasis control, were 53.5%, 14.4, and 17.2% in 1980. These percentages changed to 7.7%, 33.3%, and 53.3%, respectively, in 1995. The preponderant role of the state in organizing, financing, and delivery of the services was replaced with the new system which is more influenced by the market economy. The incidence and the prevalence of schistosomiasis in the study area have increased year by year from 1980 to 1990, although there has been a tendency to decrease after 1991 but not to the low pre1980 levels. The collapse of the community-based medical system in rural areas and the dramatic financing changes of schistosomiasis control programmes have created major difficulties for schistosomiasis control in China.

Eradication of schistosomiasis in Guangxi, China. Part 2: Political economy, management strategy and costs, 1953-92

Reported are the results of a study of the political economy, management, and costs of the successful Guangxi schistosomiasis eradication programme, spanning 40 years from 1953 to 1992. For this purpose we analysed all government data and memoranda on the policy, management, technical support, finance, and the control strategy of the programme. We also interviewed many local staff involved in the programme over the 40-year period and obtained cost data from annual county-level records on seven major categories of variable costs. Schistosomiasis control in Guangxi began with one of the first examples of community participation and rapid assessment in public health history--the use of pre-franked envelopes to return disease questionnaires and suspect snails from rural areas. This approach quickly and accurately delineated the endemic area. This was Mao Zedong's "mass line", incorporating ideas and knowledge from peasants directly into services run for and by them, here the schistosomiasis control programme. Recognition by China's leaders that schistosomiasis was a great economic burden, steadfast prioritizing of the programme over 40 years, local innovative scientific study, agricultural and environmental focus on eradicating the snail hosts and boosting rural production, and mass community education and support were all key factors in the final success. Local leaders motivated programme staff and everyone involved knew the objectives. The programme was always multisectoral, with policy developed centrally, and strategy and collaboration encouraged and rewarded at the grass-roots. These features explain how a very poor autonomous region such as Guangxi finally eradicated schistosomiasis, spending less than US$ 0.50 per protected citizen per year; it is remarkable that the disease and snails were initially found across a large area of complex environments and modern drugs such as praziquantel were not available for most of the 40-year period. The lessons from Guangxi can be adapted elsewhere and should encourage other areas to control endemic schistosomiasis using methods devised to suit the local culture and geography.

Human behaviour, cost-effectiveness analysis and research and development priorities: the case of a schistosomiasis vaccine

Cost-effectiveness analysis has been widely used in the health sector to guide decisions about where scarce resources aimed at disease prevention or control should be invested. It has rarely been used to guide decisions about what type of health research should be funded. In addition, the validity of the behavioural assumptions underlying the economic analysis is rarely considered explicitly. This paper explores the use of cost-effectiveness analysis to set priorities for research using the development of a schistosomiasis vaccine as an example. It then explicitly considers behavioural factors which might affect the accuracy of the calculations. A 'product profile' for the new technology is derived which can be used by developers as a target to aim at. To ensure that the vaccine would be more cost-effective than the currently preferred option for the control of schistosomiasis, chemotherapy based on praziquantel, researchers need a vaccine which has sufficient duration of protection to be delivered as part of the regular childhood immunization programme me. The cost of adding it to existing vaccination schedules should not be more than US$4.30 per child in excess of the cost of one round of chemotherapy. It should, ideally, have an efficacy over 80%. These results, however, depend on a number of cultural and behavioural factors which are often ignored in cost-effectiveness studies. For example, low rates of school attendance would increase the cost of contacting children for a chemotherapy programme and increase the relative attractiveness of a vaccine. For chemotherapy to be effective, children also need to comply each year for a number of years. Falling rates of compliance over time would reduce the effectiveness of chemotherapy and increase the attractiveness of a vaccine. But on the other hand, even though a vaccine may still be more cost-effective than chemotherapy at relatively low levels of vaccine efficacy, if mothers perceived the vaccine to be ineffective and refused to bring their children for vaccination, the success of the entire childhood immunization programme could be threatened.

Different approaches to modeling the cost-effectiveness of schistosomiasis control

The limited economic resources available for health care in developing countries necessitates the involvement of cost analysis in the planning of any control intervention. A number of studies have undertaken cost-effectiveness analysis of schistosomiasis control, and the methodologies utilized in both cost and effectiveness evaluation are discussed. In attempting to relate cost to effectiveness, most studies have utilized static models expressing effectiveness in terms of coverage (drug delivery) or cure rate (infection prevalence reduction). These immediate output measures do not consider the long-term impact of control nor the effect on disease. An alternative approach is to use a model of the transmission dynamics of the parasite to permit evaluation of the long-term impact of control. An example of a population dynamic approach to cost-effectiveness analysis that can assess the impact of treatment on infection and disease due to the intestinal nematodes is presented to illustrate the potential of this approach in modeling the cost-effectiveness of schistosomiasis control.

Community-based approach to schistosomiasis control

With few exceptions, efforts to control schistosomiasis have relied upon ongoing community cooperation with "outsiders' rather than creating within the community the capacity and means for carrying out ongoing disease control measures with minimal external support. Offered as a useful model is a program in Kaele subdivision, Extreme North Province, Cameroon designed to establish and integrate within the primary health care (PHC) system the control of urinary schistosomiasis, hyperendemic in the region. At the community level, and with minimal dependence upon external resources, culturally appropriate and effective health education was instituted, the capacity to diagnose and treat schistosomiasis was created, diagnosis and drug therapy (praziquantel) was made available conveniently and at low cost, and, on a very limited basis, snails were controlled. Efforts were made to build upon and strengthen existing community structures and institutions rather than create new ones. The impact of the interventions was measured in terms of changes in knowledge and behavior, prevalence and intensity of infection, utilization of health services, and the ability to finance the control activities within the context of a generalized cost recovery system. Program successes and failures are discussed, as well as lessons learned and their implications.