The effects of selected neglected tropical diseases on economic performance at the macrolevel in Africa

BACKGROUND

Neglected tropical diseases (NTDs) such as leprosy, lymphatic filariasis (LF), schistosomiasis and onchocerciasis are endemic in several African countries. These diseases can lead to severe pain and permanent disability, which can negatively affect the economic productivity of the affected person(s), and hence resulting into low economic performance at the macrolevel. Nonetheless, empirical evidence of the effects of these NTDs on economic performance at the macrolevel is sparse. This study therefore investigates the effects of the above-mentioned NTDs on economic performance at the macrolevel in Africa.

METHODS

The study employs a panel design with data comprising 24 to 45 African countries depending on the NTD in question, over the period, 2002 to 2019. Gross domestic product (GDP) is used as the proxy for economic performance (Dependent variable) and the prevalence of the above-mentioned NTDs are used as the main independent variables. The random effects (RE), fixed effects (FE) and the instrumental variable fixed effects (IVFE) panel data regressions are used as estimation techniques.

RESULTS

We find that, an increase in the prevalence of the selected NTDs is associated with a fall in economic performance in the selected African countries, irrespective of the estimation technique used. Specifically, using the IVFE regression estimates, we find that a percentage increase in the prevalence of leprosy, LF, schistosomiasis and onchocerciasis is associated with a reduction in economic performance by 0.43%, 0.24%, 0.28% and 0.36% respectively, at either 1% or 5% level of significance.

CONCLUSION

The findings highlight the need to increase attention and bolster integrated efforts or measures towards tackling these diseases in order to curb their deleterious effects on economic performance. Such measures can include effective mass drug administration (MDA), enhancing access to basic drinking water and sanitation among others.

An Updated Economic Assessment of Moxidectin Treatment Strategies for Onchocerciasis Elimination

BACKGROUND

Concerns that annual mass administration of ivermectin, the predominant strategy for onchocerciasis control and elimination, may not lead to elimination of parasite transmission (EoT) in all endemic areas have increased interest in alternative treatment strategies. One such strategy is moxidectin. We performed an updated economic assessment of moxidectin- relative to ivermectin-based strategies.

METHODS

We investigated annual and biannual community-directed treatment with ivermectin (aCDTI, bCDTI) and moxidectin (aCDTM, bCDTM) with minimal or enhanced coverage (65% or 80% of total population taking the drug, respectively) in intervention-naive areas with 30%, 50%, or 70% microfilarial baseline prevalence (representative of hypo-, meso-, and hyperendemic areas). We compared programmatic delivery costs for the number of treatments achieving 90% probability of EoT (EoT90), calculated with the individual-based stochastic transmission model EPIONCHO-IBM. We used the costs for 40 years of program delivery when EoT90 was not reached earlier. The delivery costs do not include drug costs.

RESULTS

aCDTM and bCDTM achieved EoT90 with lower programmatic delivery costs than aCDTI with 1 exception: aCDTM with minimal coverage did not achieve EoT90 in hyperendemic areas within 40 years. With minimal coverage, bCDTI delivery costs as much or more than aCDTM and bCDTM. With enhanced coverage, programmatic delivery costs for aCDTM and bCDTM were lower than for aCDTI and bCDTI.

CONCLUSIONS

Moxidectin-based strategies could accelerate progress toward EoT and reduce programmatic delivery costs compared with ivermectin-based strategies. The costs of moxidectin to national programs are needed to quantify whether delivery cost reductions will translate into overall program cost reduction.

Economic evaluations of onchocerciasis interventions: a systematic review and research needs

OBJECTIVE

To provide a systematic review of economic evaluations that has been conducted for onchocerciasis interventions, to summarise current key knowledge and to identify research gaps.

METHOD

A systematic review of the literature was conducted on the 8th of August 2018 using the PubMed (MEDLINE) and ISI Web of Science electronic databases. No date or language stipulations were applied to the searches.

RESULTS

We identified 14 primary studies reporting the results of economic evaluations of onchocerciasis interventions, seven of which were cost-effectiveness analyses. The studies identified used a variety of different approaches to estimate the costs of the investigated interventions/programmes. Originally, the studies only quantified the benefits associated with preventing blindness. Gradually, methods improved and also captured onchocerciasis-associated skin disease. Studies found that eliminating onchocerciasis would generate billions in economic benefits. The majority of the cost-effectiveness analyses evaluated annual mass drug administration (MDA). The estimated cost per disability-adjusted life year (DALY) averted of annual MDA varies between US$3 and US$30 (cost year variable).

CONCLUSIONS

The cost benefit and cost effectiveness of onchocerciasis interventions have consistently been found to be very favourable. This finding provides strong evidential support for the ongoing efforts to eliminate onchocerciasis from endemic areas. Although these results are very promising, there are several important research gaps that need to be addressed as we move towards the 2020 milestones and beyond.

Equity and efficiency in the scaled-up implementation of integrated neglected tropical disease control: the health economics protocol of the COUNTDOWN multicountry observational study in Ghana, Cameroon and Liberia

INTRODUCTION

Worldwide, millions of individuals are affected by neglected tropical diseases (NTDs). They are frequently the poorest and most marginalised members of society. Their living conditions, among other things, make them susceptible to such diseases. Historically, several large-scale treatment programmes providing mass drug administrations (MDAs) were carried out per single disease but over the last decade there has been an increasing trend towards co-implementation of MDA activities given the resources used for such programmes are often the same. The COUNTDOWN multicountry studies focus on scaled-up implementation of integrated control strategies against four diseases: lymphatic filariasis, onchocerciasis, schistosomiasis and soil-transmitted helminthiasis. The objective of the COUNTDOWN economic study is to assess the multicountry implementation of control interventions in terms of equity, impact and efficiency.

METHODS

The health economic study uses different analytical methods to assess the relationship between NTDs and poverty and the cost-effectiveness of different large-scale intervention options. Regression analysis will be used to study the determinants of NTD occurrence, the impact of NTDs on poverty, factors that hinder access to MDAs and the effect of NTDs on quality-of-life of those affected, including disability. Cost-effectiveness analyses of various integration methods will be performed using health economic modelling to estimate the cost and programme impact of different integration options. Here, cost-effectiveness ratios will be calculated, including multivariate sensitivity analyses, using Bayesian analysis.

ETHICS AND DISSEMINATION

Ethics approval has been received both at the Liverpool School of Tropical Medicine and in all participating countries. Results of the various substudies will be presented for publication in peer-reviewed journals.

STUDY DATES

1 July 2016 to 30 June-October 2019.

Feasibility of utilizing the SD BIOLINE Onchocerciasis IgG4 rapid test in onchocerciasis surveillance in Senegal

As effective onchocerciasis control efforts in Africa transition to elimination efforts, different diagnostic tools are required to support country programs. Senegal, with its long standing, successful control program, is transitioning to using the SD BIOLINE Onchocerciasis IgG4 (Ov16) rapid test over traditional skin snip microscopy. The aim of this study is to demonstrate the feasibility of integrating the Ov16 rapid test into onchocerciasis surveillance activities in Senegal, based on the following attributes of acceptability, usability, and cost. A cross-sectional study was conducted in 13 villages in southeastern Senegal in May 2016. Individuals 5 years and older were invited to participate in a demographic questionnaire, an Ov16 rapid test, a skin snip biopsy, and an acceptability interview. Rapid test technicians were interviewed and a costing analysis was conducted. Of 1,173 participants, 1,169 (99.7%) agreed to the rapid test while 383 (32.7%) agreed to skin snip microscopy. The sero-positivity rate of the rapid test among those tested was 2.6% with zero positives 10 years and younger. None of the 383 skin snips were positive for Ov microfilaria. Community members appreciated that the rapid test was performed quickly, was not painful, and provided reliable results. The total costs for this surveillance activity was $22,272.83, with a cost per test conducted at $3.14 for rapid test, $7.58 for skin snip microscopy, and $13.43 for shared costs. If no participants had refused skin snip microscopy, the total cost per method with shared costs would have been around $16 per person tested. In this area with low onchocerciasis sero-positivity, there was high acceptability and perceived value of the rapid test by community members and technicians. This study provides evidence of the feasibility of implementing the Ov16 rapid test in Senegal and may be informative to other country programs transitioning to Ov16 serologic tools.

As onchocerciasis control programs succeed and transition to elimination efforts, different diagnostic tools are needed. The goal of this study was to determine if integrating the Ov16 rapid test is feasible based on acceptability, usability, and cost. A study was conducted in 13 villages in southeastern Senegal in May 2016. Community members were invited to participate in a demographic questionnaire, a rapid test, a skin snip biopsy, and an acceptability interview. Technicians were also interviewed and a costing analysis was conducted. Out of 1,173 participants, 1,169 (99.7%) agreed to the rapid test while 383 (32.7%) agreed to skin snip microscopy. The rapid test result was reactive in 2.6% of those tested, while none of the skin snips were positive. Community members thought the rapid test was performed quickly, was not painful, and provided reliable results. If no one had refused skin snip microscopy, the total cost would have been around $16 per person tested for either method. In this area with little if any remaining onchocerciasis, there was high acceptability and perceived value of the rapid test. This study suggests that implementing the Ov16 rapid test in Senegal is feasible and these findings may be informative to other country programs.

Benchmarking the Cost per Person of Mass Treatment for Selected Neglected Tropical Diseases: An Approach Based on Literature Review and Meta-regression with Web-Based Software Application

Background

Advocacy around mass treatment for the elimination of selected Neglected Tropical Diseases (NTDs) has typically put the cost per person treated at less than US$ 0.50. Whilst useful for advocacy, the focus on a single number misrepresents the complexity of delivering “free” donated medicines to about a billion people across the world. We perform a literature review and meta-regression of the cost per person per round of mass treatment against NTDs. We develop a web-based software application (https://healthy.shinyapps.io/benchmark/) to calculate setting-specific unit costs against which programme budgets and expenditures or results-based pay-outs can be benchmarked.

Methods

We reviewed costing studies of mass treatment for the control, elimination or eradication of lymphatic filariasis, schistosomiasis, soil-transmitted helminthiasis, onchocerciasis, trachoma and yaws. These are the main 6 NTDs for which mass treatment is recommended. We extracted financial and economic unit costs, adjusted to a standard definition and base year. We regressed unit costs on the number of people treated and other explanatory variables. Regression results were used to “predict” country-specific unit cost benchmarks.

Results

We reviewed 56 costing studies and included in the meta-regression 34 studies from 23 countries and 91 sites. Unit costs were found to be very sensitive to economies of scale, and the decision of whether or not to use local volunteers. Financial unit costs are expected to be less than 2015 US$ 0.50 in most countries for programmes that treat 100 thousand people or more. However, for smaller programmes, including those in the “last mile”, or those that cannot rely on local volunteers, both economic and financial unit costs are expected to be higher.

Discussion

The available evidence confirms that mass treatment offers a low cost public health intervention on the path towards universal health coverage. However, more costing studies focussed on elimination are needed. Unit cost benchmarks can help in monitoring value for money in programme plans, budgets and accounts, or in setting a reasonable pay-out for results-based financing mechanisms.

Advocacy around mass treatment for the elimination of selected Neglected Tropical Diseases (NTDs) has typically put the cost per person treated at less than US$ 0.50. Whilst useful for advocacy, the focus on a single number misrepresents the complexity of delivering “free” donated medicines to about a billion people across the world. Given the increasing focus of the NTD community on value for money and, in the context of universal health coverage, of the global health community on outreach beyond health facilities, there was a need for greater nuance. We performed the most comprehensive literature review and first regression analysis of differences between settings in the cost per person treated against six NTDs (excluding the cost of individual medicines). We considered more than ten possible drivers of cost. We found, for example, that the unit cost of treatment depends very much on the number of people treated (economies of scale). We then developed a web-based software application (https://healthy.shinyapps.io/benchmark/) that can be used to predict setting-specific unit costs against which programme budgets and expenditures or results-based pay-outs can be benchmarked.

Lymphatic filariasis and onchocerciasis prevention, treatment, and control costs across diverse settings: a systematic review

The control and eventual elimination of neglected tropical disease (NTD) requires the expansion of interventions such as mass drug administration (MDA), vector control, diagnostic testing, and effective treatment. The purpose of this paper is to present the evidence base for decision-makers on the cost and cost-effectiveness of lymphatic filariasis (LF) and onchocerciasis prevention, treatment, and control. A systematic review of the published literature was conducted. All studies that contained primary or secondary data on costs or cost-effectiveness of prevention and control were considered. A total of 52 papers were included for LF and 24 papers were included for onchocerciasis. Large research gaps exist on the synergies and cost of integrating NTD prevention and control programs, as well as research on the role of health information systems, human resource systems, service delivery, and essential medicines and technology for elimination. The literature available on costs and cost-effectiveness of interventions is also generally older, extremely focal geographically and of limited usefulness for developing estimates of the global economic burden of these diseases and prioritizing among various intervention options. Up to date information on the costs and cost-effectiveness of interventions for LF and onchocerciasis prevention are needed given the vastly expanded funding base for the control and elimination of these diseases.

Disease control priorities for neglected tropical diseases: lessons from priority ranking based on the quality of evidence, cost effectiveness, severity of disease, catastrophic health expenditures, and loss of productivity

BACKGROUND

In the context of limited health care budgets in countries where Neglected Tropical Diseases (NTDs) are endemic, scaling up disease control interventions entails the setting of priorities. However, solutions based solely on cost-effectiveness analyses may lead to biased and insufficiently justified priorities.

OBJECTIVES

The objectives of this paper are to 1) demonstrate how a range of equity concerns can be used to identify feasible priority setting criteria, 2) show how these criteria can be fed into a multi-criteria decision-making matrix, and 3) discuss the conditions under which this decision-making procedure should be carried out in a real-world decision-making context.

METHODS

This paper draws on elements from theories of decision analysis and ethical theories of fair resource allocation. We explore six typical NTD interventions by employing a modified multi-criteria decision analysis model with predefined criteria, drawn from a priority setting guide under development by the WHO. To identify relevant evidence for the six chosen interventions, we searched the PubMed and Cochrane databases.

DISCUSSION

Our in vitro multi-criteria decision analysis suggested that case management for visceral leishmaniasis should be given a higher priority than mass campaigns to prevent soil-transmitted helminthic infections. This seems to contradict current health care priorities and recommendations in the literature. We also consider procedural conditions that should be met in a contextualised decision-making process and we stress the limitations of this study exercise.

CONCLUSION

By exploring how several criteria relevant to the multi-facetted characteristics of NTDs can be taken into account simultaneously, we are able to suggest how improved priority settings among NTDs can be realised.

Economic evaluation of Mectizan distribution

The distribution of ivermectin has dramatically altered the nature of onchocerciasis control. Existing economic analyses of ivermectin distribution programmes show that these programmes have a highly beneficial impact. Most analyses have estimated the economic benefits in terms of increased labour productivity as a result of reductions in blindness, and in terms of additional land-availability because of a reduced transmission of the parasite. Economic evaluations of the Onchocerciasis Control Program (OPC) in West Africa have calculated a net present value - equivalent discounted benefits minus discounted costs - of $485 million for the programme over a 39-year period, using a conservative 10% rate to discount future health and productivity gains. The net present value for the African Program for Onchocerciasis Control (APOC) is calculated at 88 million US dollars over a 21-year time period, also using a 10% discount rate. Cost-effectiveness analyses of ivermectin distribution have found a cost of 14-30 US dollars per disability-adjusted life-year prevented - estimates comparable with other priority disease control programmes. However, the economic success of ivermectin distribution is sensitive to the fact that the drug itself has been donated free of charge. The market value of Merck's donations to the APOC for just 1 year considerably outweighs the benefits calculated for both the OPC and the APOC over the life of these projects. Pending the development of an effective macrofilaricide, the distribution of ivermectin will remain a public health priority into the foreseeable future.

Profitable gifts: a history of the Merck Mectizan donation program and its implications for international health

A unique public/private partnership situated around a pharmaceutical, Merck's Mectizan donation program stands out as an example of corporate philanthropy in the history of the pharmaceutical industry and provides insight into future public/private partnerships in public health. This paper considers the issues Merck faced in the decision to donate Mectizan (ivermectin) and in the subsequent development of the Mectizan donation program, delineating the moral and financial debates that arose within the company. Coming after almost 15 years of donation, this assessment of the program's strengths and shortcomings suggests how the pharmaceutical industry can better serve as a viable partner in improving international health.

Community-directed treatment with ivermectin in two Nigerian communities: an analysis of first year start-up processes, costs and consequences

OBJECTIVES

To determine the start-up processes, costs and consequences of community-directed treatment with ivermectin (CDTI) in two onchocerciasis endemic rural towns of Southeast Nigeria; namely Achi and Nike. The other objectives were to discover the community-financing mechanisms, local ivermectin distribution strategies and communities' organisational capacity to handle the programme.

METHODS

Structured questionnaires, informal interviews, observations, discussions with community members at general village assemblies and community outreach lectures were used at different stages of the study.

RESULT

The towns had the organisational capacity to implement the programme. Coverage with ivermectin was between 31-73% in Achi (mean = 58.6%), and 36.6-72% in Nike (mean = 61.95%). The unit financial costs were $0.17 in Nike and $0.13 in Achi, but the unit aggregate cost was $0.37 in Nike and $0.39 in Achi. When research costs were removed, the unit aggregate cost was $0.22 in Achi and $0.20 in Nike. Provider's financial costs and communities' non-financial costs were the biggest contributors to the aggregate cost. The cost would decrease in subsequent years since the research cost and parts of the mobilisation and training costs would not be incurred after the first year.

CONCLUSION

Governments and sponsors of CDTI should find means of continuously strengthening the programme and providing technical support to the communities. As both CDTI and communities are dynamic entities, continuous health education campaigns are needed to keep reminding the people of the benefit of long-term ivermectin distribution, together with the need for community ownership of the programme.

Onchocerciasis control in Nigeria: will households be able to afford community-directed treatment with ivermectin?

OBJECTIVES

To determine the level of affordability of community-directed treatment with ivermectin (CDTI) to households living in two onchocerciasis endemic Nigerian communities namely Toro in the north and Nike in the south.

METHODS

The proportion of the cost of treating people with ivermectin will deplete in average monthly/projected annual household expenditure on food and health care, and on average monthly and projected annual household income were respectively calculated and used to determine the level of affordability of CDTI. Questionnaires administered to heads of households or their representatives were used to collect information on the household expenditures and income. The suggested unit CDTI cost of $0.20 was used. However, as a test of sensitivity, we also used the unit cost of $0.056 which some community based distributors are charging per treatment.

RESULT

Using $0.20 as the unit treatment cost, this will consume less than 0.05% of average annual household income in both communities. It will equally deplete 0.05% of combined annual household expenditures on food and health care in both communities. However, using $0.056 as the unit treatment cost, then 0.02% of average annual household expenditure on health care, 0.01% average annual expenditure on combined health care and food, and 0.01% of average annual household income will be depleted.

CONCLUSION

The households living in both communities may be able to afford CDTI schemes. However, the final decision on levels of affordability lies with the households. They will decide whether they can afford to trade-off some household income for ivermectin distribution.

The community-directed, ivermectin-treatment programme for onchocerciasis control in Uganda--an evaluative study (1993-1997)

The first 5 years of a community-directed, ivermectin-treatment programme, to control onchocerciasis in 1805 endemic communities in 10 districts in Uganda, are evaluated. Each year, the desired treatment coverage of the population eligible to take invermectin (90%) was achieved in 42.6%-51% of the 1713 communities for which complete data were available; 67%-74.8% achieved 80% coverage. The annual cost per person treated with ivermectin (ACPTI) was much higher in the districts with small populations to be treated (< 15,000) than in those with large populations (> 40,000) (U.S.$0.40 v. U.S.$0.10 or less). The community members' acceptance of the programme was related to their attendance at health-education sessions (P = 0.009), and their participation in the mobilisation of other community members increased greatly when they were allowed to take part in the selection of the community-based distributors (CBD) and the choice of treatment sites. The overall target ratio of one CBD/71 families was attained by 1997. However, the failure of some trained CBD to participate in the treatment exercise prevented some communities achieving 90% treatment coverage. Providing CBD with cash incentives or externally derived incentives 'in kind' proved counter-productive whereas locally generated incentives 'in kind' were simply regarded as the normal obligations of the community. District health staff successfully integrated the programme with their other health commitments, but the involvement of CBD in other programmes proved detrimental to their performance. Other constraints identified were rebel insurgency in some areas, and abnormally heavy rains in hilly areas with poor roads.

Willingness to pay for community-based ivermectin distribution: a study of three onchocerciasis-endemic communities in Nigeria

OBJECTIVE

To determine the willingness to pay (WTP) for local ivermectin distribution in a community financing framework.

METHOD

Contingent valuation in three communities in Nigeria, using randomly selected household heads. WTP was elicited using a bidding game, and for collecting information on the households' socio-economic status, level of knowledge, priority ranking and perception of risk of contracting the disease, structured questionnaires were used. Ordinary least squares (OLS) multiple regression analysis was used to analyse factors associated with WTP.

RESULTS

Between 92.1% and 93.3 % of respondents were willing to pay amounts ranging from 5 Naira (US$ 0.06) to 100 Naira (US$ 1.25) (median: 20 Naira, US$ 0.25) in the three communities, more than three times the modelled unit direct cost of distributing ivermectin by the communities themselves. Occupation of the respondent, marital status, average monthly expenditure on health care, manifestations of onchocerciasis, the type of savings scheme embarked on by the respondent, age-group, level of education and type of property were statistically significant (P < 0.05) variables affecting WTP.

CONCLUSION

This study shows that there is WTP for local ivermectin distribution in the three study communities, and that it should be assessed before instituting community-directed treatment with ivermectin.

Control of onchocerciasis: challenges for the future

The control of onchocerciasis has grown over the last two decades to attain global dimensions. This rapid growth poses challenges that are technical and managerial in nature. Appropriate control measures have to be applied to eliminate the disease as a worldwide, public-health problem and prevent the problem recurring. Novel tools and innovative approaches, both for control and surveillance activities, will have to be developed. The health systems of the affected countries need not only to be directly involved in control activities but also to direct operations and have adequate resources to run them successfully.

Delivery systems and cost recovery in Mectizan treatment for onchocerciasis

The efficiency of on-going delivery systems and cost recovery in Mectizan (ivermectin, MSD) treatment for onchocerciasis are reviewed. The search is on for an effective system of Mectizan delivery, involving drug procurement, delivery from port to districts and distribution to eligible persons, which can be sustained by the endemic countries for many years. The mechanisms for procuring and clearing the drug at the ports, and the drug's integration into the existing delivery systems of each national health service, need to be improved. Although large-scale treatments by mobile teams or community-based methods evidently achieve high and satisfactory rates of coverage, they also incur high recurrent costs which have to be covered by external partners and are not sustainable by national health services. Cost-sharing is considered an important factor in a sustainable delivery system and community-directed treatment, in which the community shares the cost and ownership of local distribution and is empowered to design and implement it, is likely to be more cost-effective and sustainable.

Economic impact of onchocerciasis control through the African Programme for Onchocerciasis Control: an overview

This note overviews several studies that have been conducted on the economic impact of onchocerciasis (river blindness) control through the African Programme for Onchocerciasis Control (APOC). A cost-benefit analysis of the APOC concludes that the programme is highly cost-effective. The economic rate of return (ERR) is 17% if benefits are considered in accordance with the stated objective of the programme (i.e. the achievement of long-term, sustainable, ivermectin-delivery systems). However, the cost-benefit analysis significantly under-estimates the net benefits from the APOC, since it considers, for ease of quantification, only the reduction in blindness as the principal benefit accruing from control activities. Recent studies, summarized here, have shown that there may be substantial benefits (in terms of enhanced productivity, increased household-level welfare, and reduced health-related expenditure, for instance) resulting from the reduction of the skin-related symptoms associated with the disease.

Farm land size and onchocerciasis status of peasant farmers in south-western Nigeria

Concern is being raised about the economic impact of the non-blinding strain of onchocerciasis, since half of those affected with onchocerciasis in Africa live in the forest zones where the non-blinding form is prevalent. WHO's TDR programme has embarked on multi-country studies on the social and economic effects of onchocercal skin disease (OSD). Baseline data from one site, the Ibarapa Local Government Area of Oyo State, Nigeria, is presented here. Farmers were screened for signs and symptoms of onchocerciasis including palpable nodules, reactive skin lesions and self-reported severe itching. Those having two or more of these conditions were classified as having severe OSD. A matching group of farmers without any of the signs or symptoms formed a control group. Women in the area either did not farm or held only one small plot. Land size comparisons were undertaken with 51 pairs of male farmers matched for age and location within 23 small hamlets bordering the Ogun River. Farmers with OSD had significantly less farmland under cultivation (9117 m2) than those with no OSD (13850 m2). The farmers with OSD did not appear to have alternative income strategies to compensate and, consequently, they had a lower value of personal wealth indicators (e.g. iron sheet roofing, motorcycle) than those without OSD. One can conclude that although the effect of forest strain onchocerciasis is less dramatic than of the blinding from, the disease poses an important economic threat in the region.

[Coffee tree cultivation and the social history of onchocerciasis in Soconusco, Chiapas state, Mexico]

Due to the social and ecological changes that have taken place in the region of Soconusco, Chiapas, Mexico, the coffee tree growth economy (established in the latter part of the last century) has been an important factor in the transmission of onchocerciasis. The optimum ecological conditions for the growth of the coffee tree coincide with those of the disease's growth rate vector; the mobilization of migrant workers for the cultivation and gathering of coffee beans, plus changes in the natural environment, are elements which explain the disease's distribution in the different regions. The origin of the disease in Chiapas may be due to the migration of coffee plantation workers from Guatemala in search of land in which to settle. Social changes occurring after the Agrarian Distribution (land distributions that occurred in 1918 and 1940) caused an intensification and modernization in the areas of cultivation which in turn caused a decline in the disease's growth rate vector. This, together with standard of living improvements and control measures against the disease, explain why the problem in these regions has decreased considerably. The use of ivermectin as a new therapy paves the way for better disease control in the future. Nevertheless, in the smaller locations occupied by middle and poor class farmers, where coffee bean cultivation is just commencing and still in a rudimentary form, onchocerciasis and other diseases continue to present serious health problems.

A critical re-examination of the economics of blindness prevention under the Onchocerciasis Control Programme

This article is a critical re-examination of the recent cost-effectiveness analysis of the Onchocerciasis Control Programme (OCP) in West Africa, undertaken by Prost and Prescott in 1984. We use the same approach, namely, measuring effectiveness of the programme by the number of healthy years of life added by the prevention of blindness. This work focuses on certain technical aspects of the data used for estimating parameter values in the cost-effectiveness calculations. Through examination of available data and the relationships between certain key variables, we estimate values that differ substantially from Prost and Prescott for the population at risk, the incidence and prevalence of onchocercal blindness, and the years of healthy life lost due to blindness. Our final results suggest that depending on the discount rate that the OCP is 7-40 times more costly as measured by discounted years of productive life added than measles immunisation. These results are in contradiction to Prost and Prescott's estimation that the OCP was more cost-effective than measles immunisation. We, however, feel that our results do not demonstrate that OCP is an inefficient use of resources. Rather, they call into question the methods used and the relevance of comparing measles immunisation and onchocerciasis control. In a subsequent article, we hope to deal directly with these conceptual problems by presenting separate humanitarian and economic cost-effectiveness measures.

The economics of blindness prevention in Upper Volta under the Onchocerciasis Control Program

This paper proposes a new approach to the economics of blindness prevention under the Onchocerciasis Control Program in Upper Volta. It differs from previous economic analyses of onchocerciasis control in three important respects. First, it uses empirical data as the basis of an estimate of the epidemiological effectiveness of the intervention. Second, it focuses on the prevention of permanent disability and premature death due to onchocercal blindness as the major health improvement attributable to onchocerciasis control. Third, it emphasizes cost-effectiveness rather than cost-benefit analysis. This limitation is imposed by the difficulty of undertaking a comprehensive assessment of the benefits of onchocerciasis control. In particular, the extent to which control of partial visual impairment and infection without ocular involvement would increase the effective supply of labor, and also the extent to which control would increase the effective supply of land by inducing new settlement in the river valleys, have not been clearly established. The cost-effectiveness approach is limited because it foregoes the opportunity provided by cost-benefit analysis to compare the relative desirability of investing in onchocerciasis control with alternative investments in other sectors. However, it does permit useful judgments to be made about the relative efficiency of allocating scarce resources to onchocerciasis control compared to other possible investments within the health sector. For this purpose, an illustrative comparison is made with estimates of the cost-effectiveness of measles immunization.