| Opportunities for Control of Dracunculiasis (1982) |
Control of dracunculiasis is clearly desirable even though the disease is rarely fatal. Control efforts must be considered in terms of the societal burden of illness and disability attributable to the infection, length of time control efforts would be required, their likelihood of success, and the net additional investment needed to carry them out.
This chapter discusses alternative approaches for reducing dracunculiasis incidence in endemic villages. Much of the text is devoted to activities other than provision and improvement of water supply systems, because workshop participants recognized that numerous reports and manuals dealing with general issues of rural water supply are being produced elsewhere. Activities directed solely at dracunculiasis can easily be Justified in areas where protected water supplies will not be available or adequately supplied to populations at risk for some time. Comparisons of costs estimated for each type of control activity proved exceedingly difficult to make, because in most cases these efforts should be organized (albeit with centralized coordination) as temporary missions assigned to agencies already responsible for multipurpose programs .
Careful studies of the costs to society of the disease have not been prepared, but available literature suggests a global loss of marketable goods of between $300 million and $1 billion a year. The values attached to suffering, loss of household production, and reduced educational opportunities have not been assessed at all but probably approach those attributed to marketable goods. If these rough calculations are correct, the benefits of disease control would be at least U.S. $500 million a year. According to estimates prepared by Fredrick Golladay, a workshop participant, at present interest rates, a successful program to eradicate the disease globally would justify an investment of at least $6 billion or, alternatively, about $150 per person at risk.(1
Public health authorities in countries or regions where dracunculiasis is endemic will be able to plan continuing surveillance and control strategies once data gathered during the problem assessment phase have been analyzed. The surveillance system and control activities adopted will depend on available resources and willingness of other public agencies to share costs and personnel. The scope of such activities could include conducting periodic surveys, giving priority for safe water supply to endemic villages, and establishing an ongoing case reporting system and mounting a multi-approach elimination program.
A dracunculiasis control strategy might consist of any one or a combination of the following approaches: (1) provision of protected sources of drinking water, (2) health education of the population at risk, (3) vector control of cyclops, and (4) treatment of victims of the disease. Training of control workers would be needed for any strategy. Figure 10 illustrates the points of intervention in the Dracunculus life cycle that correspond to control approaches. A surveillance system provides the epidemiologic feedback needed to direct program resources toward areas most in need and to measure progress in achieving program objectives. Manpower and supplies may come from many different sources, but they should be coordinated by one central office.
Quantifiable national program objectives should be established and tailored to specific conditions in local endemic areas. These objectives should be set by an interministerial policy group, including representatives of health, water, education, agriculture, planning, and finance sectors. Such quantifiable objectives should include measures for process (changes in levels of training, educational activities, distribution of pesticide, rates or priorities in providing safe water, etc.), impact (changes in levels of knowledge, beliefs, practices, and cyclops populations), and outcome (changes in disease incidence, prevalence or disability rates), and should specify the time period in which change is expected to occur.
Workshop participants believe that the goal of elimination of dracunculiasis is feasible at the national level. Sustained control activities applied to specified endemic areas, together with surveillance, should result in the documented disappearance of the disease within several years.
The remainder of this section discusses the advantages and disadvantages of each potential intervention and suggests ways of organizing each.
Provision Of Sources Of Safe Drinking Water
The most effective means of eliminating dracunculiasis is to provide sources of safe drinking water, i.e., sources that are free of infected cyclops. The presence of dracunculiasis indicates that a community is using unprotected surface water supplies or step wells as primary sources of drinking water--sources that are probably also used for washing and bathing. The burden of other water-related diseases is hence likely to be high, although it may be masked by the dramatic presentation of dracunculiasis.
Safe sources of drinking water can be provided in several ways. In selecting an appropriate method, the following factors should be considered: availability of raw water sources in adequate supply to meet demand; socioeconomic factors; and political, legal, and institutional constraints. Protected sources of drinking water must be located in accord with wishes of villagers or they will not be used and maintained.
Options for providing sources of safe drinking water range from relatively simple and inexpensive modification of existing sources for personal or family water supplies, to sophisticated piped systems engineered for collection, treatment, and distribution of water. The latter systems require a commitment of capital for construction and adequate resources for maintenance and operation to ensure reliable performance on a continuing basis and are therefore not appropriate in all situations.
Some households may have unedged wells that permit runoff to drain back into the drinking water. This type of well may be protected from dracunculiasis infection at relatively low cost by adding a concrete rim that slopes outward. A dramatic reduction in dracunculiasis incidence was reported in northern Nigeria in 1948 after concrete-lined wells with sloping aprons were installed (White et al. 1972:75).
One currently underexploited source of safe water is rainwater that is collected and stored during the rainy season by households or communities for use during dry periods. However, in regions with extended dry seasons this method may not be feasible. Selected villages might receive potable water in tanker trucks at the height of the dry season.
Groundwater may be considered safe for drinking if it comes from a protected dug well or spring. Examples of protected wells include dug wells that are lined and covered, with or without pumping equipment, and tube wells.
Options for Improving Unprotected Sources of Drinking Water
Some degree of protection from dracunculiasis may be obtained through physical or environmental alteration of unprotected surface water sources used for drinking. Possibilities include (1) dredging or silt removal to permit shoreline access to deeper water, and (2) construction of fingerdikes extending from shore to deep water. Both of these efforts should be accompanied by erection of a barrier such as a retaining wall that prevents water users from entering the source. Surface contamination can be reduced by installation of a pumping mechanism and by use of infiltration galleries or equipment for conventional treatment (e.g., slow sand filters).
Alternatively, individuals can treat the water using one or a combination of the following methods:
- Filtration through cloth, sand, nylon bolting silk, or other locally available filtration media
- Clarification--use of a coagulating agent such as aluminum sulfate followed by filtration
- Boiling/disinfection (because of cost, in time and materials, generally not a viable option)
Table 5 outlines the various control options for protected and unprotected water sources and compares them on a qualitative basis.
A well-planned health education program is an essential component of any effort to control or eliminate dracunculiasis. The Indian Guinea Worm Eradication Program, for example, has developed some prototype health education and training materials for use in that country (National Institute of Communicable Diseases 1982). The potential efficacy of health education efforts against dracunculiasis was documented in a recent study by Akpovi and his colleagues (1981) in Nigeria.
Rural villagers are not likely to change their behavior unless they believe the benefits to be gained from adopting new practices outweigh the physical and psychological costs of abandoning traditional ones. Their belief in the efficacy of a new approach for preventing dracunculiasis may need to be strengthened through a successful demonstration in the first year of control activities. Health education of populations affected by dracunculiasis must be integrated into all aspects of control efforts. Villagers' involvement in decision making relevant to control operations must be secured from the outset in order to improve their chances of succeeding.
Health Education Strategies
Three mayor educational strategies or techniques can be used in conjunction with dracunculiasis control efforts:
1. Mass communication
2. Community (popular) organization
3. Instruction or training of individuals and small groups
These strategies vary in degree of effectiveness and resource requirements, depending on which control effort is being implemented. The message delivered by each strategy will also vary with the desired objective and the anticipated audience. For example, television programs or news articles about dracunculiasis may create a favorable political climate for a national elimination campaign among wealthier urban dwellers but would probably not be seen by people in affected villages. Radio programs and cassette tapes would be more likely to reach the population at risk, but even these techniques would be more effective when used as an integral part of control efforts. They would increase awareness of the problem but would probably not increase understanding of the disease to any appreciable extent.
The primary objective of health education efforts is to secure the active participation of the populations at risk in every phase of control activities. Health education objectives specific to each control option are shown in Table 6. The appropriateness of the various education strategies to each of the control options is discussed below:
TABLE 6 Health Education Objectives Associated with Control Options
Health Education Objectives
Physical protection of water sources
* 1. Participate in the planning and installation of new or improved supplies.
* 2. Care for and maintain installations and their surroundings.
* 3. Keep an adequate supply of spare parts.
** 4. Use only the new or improved source of water.
+ 5. Report new cases.
+ 1. Filter and/or boil water.
++ 2. Avoid contact with ponds when blisters appear and throughout patency period.
+ 3. Avoid drinking from contaminated surface sources.
+ 4. Drink water only from protected sources.
+ 5. Report new cases.
* 1. Use only treated water.
* 2. Treat surface sources regularly and properly.
* 3. Keep chemicals in stock.
+ 4. Participate in surveillance.
+ 5. Report new cases.
Prevention and treatment
++ 1. Seek and obtain treatment.
++ 2. Persist with treatment.
+ 3. Report new cases.
** Water carriers
+ Individual residents
++ Patent case
Physical Protection of Water Sources
Mass communication is useful in spreading information about the need to protect wells and springs and the need to use such safe sources exclusively once they are available. Ways of protecting those wells and springs can be taught in small group sessions.
Community organization is essential for participation in planning, installation, and maintenance of water supplies; site selection; selection of trainees for maintenance; collection of funds for installation, materials, and maintenance; and the organization of work teams.
Personal Preventive Measures
Mass communication can be used to inform the public about correct methods of boiling and filtering water and about using protected water sources and avoiding contaminated sources, and to urge people with patent infections not to enter sources of drinking water. Such measures may find easier acceptance if alternative laundry, bathing, and sanitary facilities are provided, maintained, or repaired. In some cultures people enter surface waters to defecate.
Community organization is useful in providing social support for filtering and/or boiling of drinking water, for preventing contamination of ponds, for facilitating cooperative purchase of filters, and constructing alternative sources of water for personal and household needs.
Instruction is needed for people in affected villages in the proper type and use of filters, boiling (a few minutes is sufficient), and sanitary handling of clean drinking water.
Prevention and Treatment
Mass communication can be used to inform the public of the risk of dracunculiasis and the possibility of prevention. Individual and small group discussions can emphasize the location of treatment centers and encourage individuals to seek early treatment, so as to avoid complications and prolonged disability. The same communication methods are available as indicated above.
Community organization can help to identify individuals needing treatment, establish new treatment centers, provide supplies to dispensaries for care of dracunculiasis cases, and facilitate access to care for those disabled by the disease.
Mass communication efforts can be used to bring about awareness of the extent and severity of dracunculiasis and the relationship of the disease to contaminated water, and to urge consumers to carry out the measures suggested in Table 6. Efforts might include radio or television in some areas, poster campaigns, study groups, folk media (drama, festivals, folklore), and pop culture (comics, photonovellas).
Community organization is useful in collecting baseline epidemiologic data, in providing social support for behavioral change in use of water for drinking, in selecting individuals for training in application of chemicals, in collecting funds for materials, and in support of trainees.
Vector Control Of Cyclops
Transmission of dracunculiasis occurs only if a surface water supply supports a population of cyclops, a proportion of which are infected by D. medinensis larvae. The disease may be prevented by ensuring that people drink only water that is free of infected cyclops. A variety of technical options is available for either eliminating cyclops from water used for drinking or ensuring that the cyclops are not infected by the dracunculiasis larvae. The effectiveness of these options requires cooperation from the people at risk. The level of water treatment and/or protection needed to control dracunculiasis is less than that required to halt transmission of waterborne viral and bacterial diseases, although measures taken to render drinking water safe from Dracunculus medinensis may improve the quality of drinking water with respect to other pathogens as well.
Chemical measures to control or eliminate cyclops may be used when existing contaminated drinking water sources either cannot be made safe immediately or cannot be eliminated from use. When an unsafe source is converted to a safe source (e.g., when a physical barrier is constructed), chemicals should be used in conjunction with such measures in order to eliminate any still-infected cyclops. They should also be used when an existing safe source becomes a hazard naturally or because of mechanical breakdown. If chemical treatment is carried out effectively, it may not be necessary to continue it for a period longer than 2 years.
Available Chemical Compounds
At present, a few chemical compounds are considered potentially effective against cyclops in controlling dracunculiasis: temephos (Abate), Hightest Hypochlorite, and niclosamide. Temephos is by far the preferred available compound for this purpose. Further research and testing are needed before the use of niclosamide in cyclops control can be recommended.
- Effective at low dose (1 mg/liter), as shown in field tests conducted in India
- Low mammalian toxicity
- Residual effect (4-6 weeks)
- Easy to apply
- Various Abate formulations can be purchased and shipped from American Cyanamid in Italy (Cyanamid Italia, S.p.A., Casella Postale A. 95100, Catania, Italy, tel. 591-555). A l: sand granule formulation is the formulation of choice because of ease of application.
- Low cost
- Has uses for control of other vectors such as Aedes and Culex mosquitoes, Simulium larvae
- Can be held in stock in tropical climates for as long as 3 years without deterioration.
- Technical-grade temephos is no longer available for resale. (The current policy of American Cyanamid is to sell the formulated product only.)
- Health or sanitation infrastructure is necessary to make the required visits to villages. Alternatively, a literate, respected person in each affected village (e.g., the schoolteacher) could be taught application and safety procedures.
- Low mammalian toxicity
- Effective against other disease-causing organisms
- Free chlorine residual required to kill cyclops (2 mg/liter). Villagers may refuse to use it if they perceive a bad taste or smell from excess chlorine.
- Applications may have to be frequent, depending on the reappearance of cyclops.
Application of Chemical Compounds to Water Sources
The text that follows relates only to temephos, which is the preferred available compound.
Frequency and Timing of Applications
1. As certain seasonal frequency of case distribution.
2. Treat all surface drinking water sources at least 1 month before peak incidence and repeat every 6 weeks until incidence is at minimum (i.e., 3 or more applications may be required to suppress the cyclops population).
How to Apply Chemical
1 Collaborate with community (inform and consult with community leaders).
2 Measure the average length, width, and depth of each water source used for drinking and calculate the volume of water to be treated.
3 Calculate correct quantity of chemical to be applied at a concentration of 1 gram of active ingredient per cubic meter of water (1 mg/liter).
4 Distribute uniformly over water body either manually or mechanically.
Monitoring of Safety
1 In the case of a massive overdose of temephos, any obvious adverse side effects in the population (e.g., nausea, vomiting, bronchospasm, abdominal pain, diarrhea, weakness) should be reported promptly.
2 Be prepared to deal with apprehension of community if there is a coincidental, unrelated outbreak of illness.
1 Keep a record of nature, number, dimensions, and water use patterns of all sources of drinking water.
2 Keep a record of applications to water bodies. For each application record the dimensions, and volume of water, quantity of chemical, and date of application.
3 Keep a record of presence of cyclops before and after treatment; record date of check.
4 Conduct an independent cross-check of sample of treated sources.
Management of Chemical Treatment at the Village Level
1 Temephos can be stocked at village level (or in each health unit, where appropriate).
2 Local health worker, schoolteacher, or other person can be trained to apply temephos and keep records. In certain endemic areas of West Africa, however, school holidays coincide with the peak transmission period and teachers may not be available.
3 Long interval (4-6 weeks) between applications requires that only one individual from each village be responsible for treatments.
NOTE: Breakdown of supplies or application for a brief period (e.g., 1 month) during the program will not greatly affect control efforts.
1 Management of inventory, procurement, and distribution is necessary at central, regional, and local government levels to ensure the availability of temephos during transmission season.
2 Transportation must be made available to deliver temephos to affected villages.
3 Evaluation of applications should be monitored by ministry of health personnel by periodic checks of records and through participation in control activities.
Documented experience with biological agents for cyclops control has involved only the use of predator fish. However, there have been no recent studies with fish species used previously - Gambusia, Barbus, and Rosbora. In general, many surface water sources are seasonal, have small volumes of water, and are scattered over wide areas. Biological control will probably be much less feasible than chemical treatment under these conditions. The requirements, advantages, and disadvantages of using fish to control cyclops are outlined in Table 7.
TABLE 7 Use of Fish to Control Cyclops
a. Bottom, column, and surface feeders are required.
b. Hatcheries at different locations are required for replacement.
c. Placement of fish in drinking water has to be culturally acceptable.
d. Fish selected should be unsuitable for human consumption and of no commercial value to village.
a. Cheap on short-term basis.
b. Compatible with environment.
c. Long lasting.
a. Replacement at intervals is required.
b. Maintenance of hatcheries involves cost.
c. Incomplete clearance of cyclops.
d. Not practical in small, temporary ponds.
Treatment Of Cases
The role of chemotherapy in the control of dracunculiasis is indirect and complementary to the main measures indicated above. Chemotherapy provides symptomatic relief and by doing so enhances community participation. Because it speeds up expulsion of the worm, chemotherapy may reduce transmission marginally and may shorten the period of disability.
Available drugs (thiabendazole, metronidazole, mebendazole, and niridazole) are not very effective against D. medinensis worms, and they are rather expensive. Because treatment requires more than one dose, they are difficult to administer to a rural population. Medical supervision is a prerequisite for chemotherapy with the available drugs, some of which have toxic effects. Moreover, none of the available drugs prevents dracunculiasis reinfection, nor has any drug been shown to be effective against early stages of the parasite in humans.
Prevention and Treatment of Secondary Bacterial Infection
Victims of dracunculiasis should be taught and encouraged to keep the wounds as clean as possible by washing periodically with soap and water and applying a clean dressing, if possible. Systemic or topical antibiotics can be used to treat secondary bacterial infection. Most important is to ensure adequate immunization against tetanus. Analgesics such as aspirin may provide temporary relief from the pain caused by the emerging worm.
Patients with soft tissue infections (e.g., open ulcers, adjacent cellulitis) can be managed in outpatient facilities by paramedical workers, who can give instructions about use of cleansing compresses, dressings, and bedrest. Oral penicillin (400,000 units 3 times daily for adults) for 5-7 days is generally adequate. Patients with more complicated dracunculiasis (e.g., sepsis, tetanus, limb contractures) will require hospitalization for appropriate treatment and rehabilitation. Contact between a paramedical worker and someone suffering from the disease also affords an opportunity to explain why the affected limb should not be immersed in a source of drinking water.
Each of the approaches for controlling dracunculiasis (e.g., filtering water prior to drinking, killing cyclops with temephos, installing a piped water system) requires training of people involved in control efforts (control workers) and in education programs. Decision makers should be made aware of the need for a systematic approach to training workers for dracunculiasis control (for example, through national workshops). Fortunately, personnel are often available who have acquired similar training and experiences while working in other disease control programs (e.g., tuberculosis, leprosy, malaria). Such individuals might be retrained to meet dracunculiasis control needs and then serve as instructors for training activities at the district level.
Training Goals for Control Workers
The goals stated below are relevant to all approaches aimed at preventing dracunculiasis, with some variations. Although each goal is elaborated specifically for dracunculiasis control efforts, it should be noted that the underlined general statements could serve equally well as goals for most disease control and primary health care programs. It is assumed that most staff assigned on a temporary or part-time basis to dracunculiasis control efforts will be drawn from public health or water and sanitation agencies. Such control workers (administrators, planners, and other employees) should be able to:
- Acquire appropriate technical skills. This may include, for example, the ability to store, measure, and apply pesticides properly; to determine cyclops density in contaminated water; and to maintain a spare parts inventory.
- Establish rapport with target populations. Technical agency staff should establish a basis for continuing collaboration with the target population so as to assure lasting results from the program.
- Actively involve the population in all stages of the program. Collection of accurate baseline data requires participation by target populations. Likewise, community participation in program planning, implementation, and evaluation will enhance program effectiveness and measurability of outcomes.
- Transfer appropriate technical skills. Unless basic technical skills are acquired by local people, there is no assurance of continued operation' maintenance, and repair of recommended improvements and additions to water sources. Without those skills villagers will remain dependent on outside resources, which are at best difficult to guarantee.
- Use appropriate communication techniques. Choice of appropriate communication techniques requires knowing how new information is incorporated and diffused within the target population.
- Adapt the program to local situations. Field staff must be able and allowed to modify activities to suit local practices, so as to assure their acceptance, use, and maintenance.
- Form linkages with existing services. To prevent unnecessary competition and wasted resources through overlap, the agents of the various organizations (agricultural and rural development, education, health, public works) working with local populations need to develop ways of mutually supporting each other.
Operational Research Issues
Research pertaining to control of dracunculiasis is being pursued in a few universities in India and Nigeria. The Organisation Centrale Contre les Grandes Endemies (OCCGE) is also sponsoring applied research on different control methods in climatically different zones of French-speaking West Africa. National authorities in endemic countries should consider carefully the different options for control, selecting those that seem most appropriate and practical. Where different approaches are used in different areas, operational research issues associated with each approach should be identified and studied early in the control program. Study results can then assist in modifying control efforts as they are expanded to cover the entire affected population. Topics that may need to be investigated in some countries include:
- Efficacy of filtering devices and materials for drinking water and their acceptance by the target population
- Cost and efficacy of cyclops control using temephos in different (representative) ecological situations
- Evaluation of effect of different health education techniques (i.e., mass communication, community participation, or individual and small group instruction) on knowledge, attitudes, and practices regarding dracunculiasis
- Efficacy and cost of different combinations of control approaches, as tested in several dissimilar villages
- Relative efficiency of alternative surveillance systems (e.g., passive reporting to health clinic versus active case searching by community member)
- Comparison of different training and supervision methods for control workers (e.g., workshop versus individual instruction)
- Evaluation or monitoring of national dracunculiasis control activities in West Africa.
1 According to Golladay, calculation of the economic loss attributable to dracunculiasis is constrained by the absence of data on the number of cases and the characteristics of victims. If one accepts that 10-48 million people are at risk (see Overview of Dracunculiasis, above), that 10-30 percent of these people become infected annually, and that 40 percent of the victims are disabled for 1-3 months, then the annual loss of work time ranges from 400,000 to 17,280,000 person-months. While a few of the victims are children, the overwhelming majority are of working age. Per capita incomes in the affected areas range from about $200 a year in India to over $1,000 in Ivory Coast. However, production per working adult is about three times these amounts since only about half the population is of working age and approximately one-third of this number is working in the home or is bearing children. Moreover, the disease strikes during the peak period of agricultural labor requirements, so that most of a crop is lost rather than only the average production of 1-3 months. The foregoing implies that the loss in production due to dracunculiasis ranges between $210 million and $3 billion a year; a range of $300 million to $1 billion appears likely to represent the true loss.
If for purposes of analysis one assumes that the annual loss is $500 million and that the present value of benefits is discounted at 8 percent, then global elimination would justify an expenditure of at least $6 billion. Even with the extreme assumption that 40 million people are presently at risk, this analysis suggests that on narrowly economic grounds an expenditure to eliminate the disease of up to $150 per person at risk would be justified.
2 Extensive data on Abate toxicity has been collected during more than 10 years of its use in the West African Onchocerciasis Programme. See WHO Doc. OCP/EAC/80.1, Onchocerciasis Control Programme in the Volta River Basin Area. Report of the first meeting of the Expert Advisory Committee, September 1980, pp. 8-9.
3 In February 1983, American Cyanamid supplied the following list prices:
- 1% sand granule formulation packed in 25-kg drums = US $1.90 fob per kg
- Abate 500 E.C. formulation in 20-lifer drums = US $15.69 per lifer
- Abate 200 E.C. formulation (used in Onchocerciasis Control Programme in West Africa) in 60-lifer drums = US $9.95 per lifer.