In 1986 the World Health Organization (WHO) designated dracunculiasis (guinea worm disease) as the next disease scheduled to be eradicated (by 1995) after smallpox. Dramatic improvement in national and intemational surveillance has played a key role in the global eradication campaign, which was initiated at CDC in 1980. About 3 million persons are still affected by the disease annually, with adverse effects on their health as well as on agricultural production and education. Over 100 million persons are at risk of having the disease in more than 20,000 villages in India, Pakistan, and 17 African countries. At least one nationwide, village-by-village search to detect all villages with endemic dracunculiasis and count cases is recommended at the outset of each national campaign, followed by monthly reporting by village-based health workers in the targeted villages during the implementation phase. Rapid dissemination of the results of the surveillance is critical. Intensive case detection and containment-with rewards for reporting of cases-are most appropriate near the end of each campaign. Cameroon, Ghana, India, Nigeria, and Pakistan have pioneered the various surveillance methods for this disease in recent years. Methods for conducting surveillance of dracunculiasis and other important diseases must continue to be developed and improved as countries now believed to be free of dracunculiasis prepare to apply to WHO for certification of elimination of dracunculiasis.
Dracunculiasis (guinea worm disease) has been the subject of a global eradication campaign that was initiated at CDC in 1980 in connection with the beginning of the International Drinking Water Supply and Sanitation Decade (1981-1990). This eradication effort was first endorsed by the World Health Assembly in 1986, just before the Global 2000 project of the Carter Center began to take a leading role in the campaign in collaboration with CDC. The 1991 World Health Assembly officially set the global target of achieving eradication of dracunculiasis by the end of 1995-a target that African Ministers of Health, representing the overwhelming majority of countries that still have endemic drancunculiasis, had already set for themselves as of 1988 (1). In 1989 the international Task Force for Disease Eradication agreed that dracunculiasis and poliomyelitis can become the next diseases to be eradicated after smallpox (2).
Dracunculiasis (caused by the parasite Dracunculus medinensis) is currently endemic in parts of India, Pakistan, and 17 African countries (Benin, Burkina Faso, Cameroon, Central African Republic, Chad, Cote d'lvoire, Ethiopia, Ghana, Kenya, Mali, Mauritania, Niger, Nigeria, Senegal, Sudan, Togo, and Uganda), where over 100 million persons are at risk of having the infection (Figure 1) 3,4). Humans contract the infection by drinking water from stagnant open sources, such as ponds, that contain small copepods or "water fleas" that harbor the immature stage of the guinea worm. The copepods become infected when persons with mature worms emerging through their skin enter the water, thus allowing the adult female worms to deposit thousands of larvae, which are ingested by copepods. The parasites mature in humans in a year and then emerge through the skin (usually of the foot or leg) to begin the cycle anew (Figure 2). People do not develop immunity to the infection, and there is no known animal reservoir of the parasite that infects humans.
This disease is a substantial public health concern because it occurs during the planting or harvest season, when it incapacitates one-third or more of some village populations simultaneously-for periods ranging from weeks to months. Since it affects mainly children and working-age adults, it has a severe negative impact on the health, agricultural production, and school attendance of affected populations ( 1).
Status of Surveillance Efforts
When the eradication campaign began, surveillance for dracunculiasis had traditionally been even more poorly conducted than that leading to the routine reporting of most diseases. The main reasons for this are
* almost all persons who have dracunculiasis acquire it in remote rural areas,
* the disease itself makes it difficult or impossible for many of its victims to walk or travel, and
* there has never been any treatment to cure the affliction and thus serve as an incentive for patients to seek medical attention at clinics, hospitals, or dispensaries where their condition might be recorded for reporting to authorities.
In an area of Rajasthan, india, in 1978-1979, for example, not one of 985 patients examined during a survey of villages had visited a health center (5). More recently, in Mali, researchers found that 1,111 cases of dracunculiasis had actually occurred in 68 villages they investigated late in 1989, but only two cases had been noted in routine reporting to public health authorities for the same year. However, when authorities decide to conduct surveillance for dracunculiasis, the obvious manifestation of the disease, which involves the emergence of a long worm through the patient's skin, is a unique characteristic that facilitates accurate reporting even by persons without formal training.
STRATEGIES AND METHODS
Surveillance for dracunculiasis has improved greatly over the past decade in the course of the eradication campaign. Different types of surveillance are appropriate at different stages of national dracunculiasis eradication programs (6). Four such stages are apparent.
* The mature female worm pierces the skin of the lower leg, causing an ulcer.
* When the ulcer comes in contact with water, the female worm discharges larvae into the water.
* Cyclopoid copepods (small fresh-water crustaceans) become infected by ingesting the larvae. Humans drink the water contaminated with the infected copepods.
* The ingested larvae mature in humans in 1 year.
First, at the beginning of an eradication program, a nationwide, village-by-village search for dracunculiasis is necessary.
* Second, during the implementation phase, village-based monthly reporting of cases is most helpful.
* Third, in the final "case-containment" phase, rapid detection and containment of all cases are of paramount importance.
* Finally, when the disease has disappeared or is thought to have been eradicated, special measures are required to obtain reliable evidence that the disease is not still being transmitted; at the same time effective surveillance for other priority diseases and conditions is begun.
So far, all these methods except the last have been used in different national programs to eradicate dracunculiasis. These methods and the results of their application are described below. Village-by-village Search
The nationwide village-by-village search for cases of dracunculiasis was pioneered by the Indian Guinea Worm Eradication Program (GWEP), in emulation of similar searches conducted during the latter stages of the Smallpox Eradication Program (7). The Indian GWEP subsequently used searches at 12-month, 6-month, then 4-month intervals in areas known to have endemic disease as the main means of monitoring and evaluating progress in the campaign to eradicate dracunculiasis.
This method is strongly recommended as perhaps the single most important first step in initiating a dracunculiasis eradication program 8,9). Although routine reports, published studies, and postal surveys can provide valuable leads for tracking the disease and confirming its existence in parts of the country, there is no substitute for conducting a village-by-village search nationwide, at least once, to ascertain quickly the full extent of the disease's distribution-including the location and the intensity of local transmission.
The nationwide searches require mobilization of a large number of public health and other workers for about 1-4 weeks, so that all villages in the country can be visited quickly. The shorter the period of the search, the more likely are requests to borrow personnel for this temporary service to be granted. Questionnaires are brief, uniform, and pretested. "Recognition cards" featuring color photographs of patients with typical emerging worms-and the name(s) of the disease in local languages or dialects-are also used to enhance the accuracy of case finding. The searchers-who may include personnel from family planning, malaria, immunization, agricultural extension, Peace Corps, and other programs-are carefully trained and supervised. When searchers enter a village, their first question is whether that community has had at least one case of dracunculiasis during the period in question. If the answer is no, they go on to the next village. If the answer is yes, they complete the rest of the questionnaire. Detection of all villages where a case of dracunculiasis has occurred (as defined by WHO: "an individual exhibiting or having a recent [about 1 year] history of a skin lesion with emergence of a guinea worm") 10), usually in the previous 12 months, is the first priority of the search. Determination or estimation of the actual incidence of cases during the period in question is second priority. Determination of point prevalence of the disease at the time of the search is much less important.
To be maximally useful, a provisional summary of the results of the search for cases should be prepared by those in charge of the national case search and made available to other officials within the Ministry of Health, the Ministry of Water, participating donor agencies, WHO, and other national and international partners in the eradication effort within 4 weeks of the completion of the survey. Those in charge of the national case search should consider making a brief report to WHO for publication in the Weekly Epidemiological Record. At a later date, a national conference should be convened by the Ministry of Health to formally present and publicize the results of the national case search.
As villages with endemic drancunculiasis are identified, one or more residents of each such village are designated to provide monthly reports of cases in the village to the next-level supervisor. Such residents are usually selected by the villagers or designated by the village leader(s). If a village already has a resident primary health-care worker or equivalent, that person is assigned responsibility for reporting cases of dracunculiasis each month. Usually, however, the remote villages that have dracunculiasis do not yet have such primary health-care workers. Village-based reporters may be volunteers or be paid a nominal amount in cash or in kind, depending on national and local policies and resources.
With village-based reporters, training and supervision are key factors. Such persons are taught how to conduct household visits within the village each month, record cases of dracunculiasis in a register for the village, report the information to a health-outreach team that may visit the village periodically, or report the information from the case register each month directly to the nearest primary health outpost. Depending on local circumstances, they may also provide simple dressing of patients' wounds, convey relevant health education messages, or dispense and demonstrate use of cloth filters for household use in preventing the disease. They should report at the agreed-upon intervals even if no new cases have occurred.
Cameroon, Ghana, Nigeria, and Pakistan have pioneered village-based reporting for dracunculiasis. An important contributory measure at this stage is to make reporting of dracunculiasis officially mandatory.
This method is appropriate a) when cases are few and elimination of dracunculiasis from a country or subnational geographic area appears to be imminent and b) in instances in which there has been importation of cases into areas that had not had endemic dracunculiasis. Case containment was first described for use in dracunculiasis eradication in Pakistan early in 1990 (11,12). It has since been adapted for use in Cameroon and India.
The key to the surveillance element in this method is to detect each case of dracunculiasis as soon as possible after it becomes patent, to prevent any further transmission associated with that case. Specific quantifiable standards are established for each stage of the process, e.g., to detect each new case within 24 hours of emergence of the worm, to report each new case to the next-level supervisor within 24 hours, and the like. Eventually, a premium could be placed on detection of cases at the pre-eruptive blister stage, before infected persons have had any opportunity to contaminate local sources of drinking water.
In Pakistan and India, cash rewards have been used and advertised widely as a means of increasing the sensitivity of surveillance at this stage of the program. Such rewards are paid to any villager, health worker, or patient with dracunculiasis who reports the first case in a village (Pakistan, 1991) or who first reports any case of dracunculiasis (India).
Verifying the Absence of Dracunculiasis
In several countries (Central African Republic, Gambia, Guinea, Iran, Saudi Arabia), dracunculiasis has apparently disappeared or been deliberately eliminated in the past 10-15 years. WHO has indicated that, to be certified as being free of dracunculiasis, countries that once had endemic disease will have to provide evidence that they have detected no indication of transmission of dracunculiasis for at least 3 years, despite having conducted effective surveillance programs specifically aimed at detecting any such transmission (13). Because dracunculiasis used to be much more widespread than it has been recently, more than 65 countries in Asia, Africa, and the Americas will require some form of official certification from WHO that dracunculiasis no longer occurs within their national boundaries.
Methods of conducting such surveillance for dracunculiasis while simultaneously conducting surveillance for other priority diseases or conditions (e.g., poliomyelitis) are being developed so that assistance agencies and countries that once had endemic dracunculiasis can make optimal use of scarce resources. Development of model systems for combining surveillance for dracunculiasis with surveillance for other diseases in countries that no longer have endemic dracunculiasis is now being considered in Gambia, Guinea, and several other countries. Poliomyelitis is one example of a disease for which good surveillance is an increasingly important priority and for which such surveillance could be successfully combined with surveillance for dracunculiasis. Other examples include diseases targeted by the Expanded Program on Immunization, diarrheal diseases, and onchocerciasis.
Each of the first three countries to conduct searches after India's initial effort produced unexpected results. In Pakistan, the national search found in 1987 that the actual area that continued to have endemic dracunculiasis was substantially smaller than authorities had believed, as was the total estimated number of cases (Figure 3). In Nigeria, fewer cases were found in the first search in late 1988 than the most recent estimates had indicated (653,000 vs. 2.5 million), but the number established through the search was still much higher than the 4,000-5,000 cases that had been reported each year up to that time. Moreover, the level of specificity of data on the intensity of endemicity and location of cases was far greater than had previously been available for dracunculiasis or any other disease in Nigeria. (This first search in Nigeria involved visits to an estimated 80% of the country's 90,000 rural communities, at a cost of approximately $100,000.) In Ghana, the numbers of cases found were substantially higher than most national authorities had expected, even though increasingly detailed surveys and public mobilization in the years immediately preceding the first search had already led to substantially larger annual totals of reported cases (Figure 4).
India still conducts village-by-village searches of communities in areas with known or suspected endemic dracunculiasis three times a year, as the main basis for surveillance in that country's GWEP (Figure 5). Ghana and Nigeria conducted two and three annual searches in 1989-1990 and 1988-1990, respectively. The third search in Nigeria was limited to villages with known or reported endemic disease and also included providing health education or other control measures in some villages (Figure 6) (14). Both countries, which along with Pakistan and Uganda are assisted directly by Global 2000, shifted to monthly village-based reporting of cases in 1991.
At present, most of the remaining countries with endemic dracunculiasis have completed at least one nationwide village-by-village search for cases, with financial assistance provided by the United Nations Children's Fund (UNICEF) (Figure 7). Searches were still under way in Mali and Uganda at the beginning of 1992, while Chad, Ethiopia, Kenya, and Sudan have not yet begun their first such search. Such searches in 1990-1991 have provided the most accurate and detailed picture ever available on the distribution of dracunculiasis and on the actual numbers of cases and affected villages in countries with endemic disease. The previously hidden bulk of endemicity now stands almost completely revealed (Figure 8).
Almost from the beginning of the GWEP in Pakistan, data collection has permitted month-by-month tracking of the program's progress (Figure 9). As the Ghanaian and Nigerian GWEPs shifted to this form of surveillance in 1991, they began to receive similar monthly feedback of progress based on control measures carried out 12 months earlier. Results are not yet available for the program in Nigeria, but the rates of monthly reporting from the >5,000 villages in Ghana known to have endemic dracunculiasis (within 1 month of the end of the reporting month) have increased from 60.5% of endemic villages in April 1991 to 82.8% in November 1991.
As implemented in Pakistan in 1990, this method of surveillance and control of cases produced results that were less satisfactory than expected. Indices in 1990 suggested that over 85% of cases were detected and contained within 24 hours of emergence of the worm, and a survey conducted late in 1991 found that a large majority of residents in villages with endemic dracunculiasis knew of the reward for reporting the first case in a village. However, there also were strong indications that in the village with the highest incidence of cases in the country (Ganju in North West Frontier Province), a number of cases were not detected by the program in 1990, and hence proper containment measures were not applied. Overall, reported cases were reduced only 36% in Pakistan in 1991 from the level in 1990 (Table 1).
Provisional data indicate that similar case-containment measures produced reductions of 54% in both Cameroon and india in 1991 from the levels in 1990 Table 1).
As used in several national GWEPs, the nationwide village-by-village search has proven to be a valuable tool for determining rapidly the status of dracunculiasis endemicity in countries with endemic disease. In addition to providing indispensable baseline epidemiologic knowledge for appropriate planning, monitoring, and evaluation of the GWEP, the results of such national searches are also an invaluable resource for mobilizing national and international decision makers in support of the program. A realistic national plan of action for eliminating dracunculiasis from a country cannot be prepared without the kind of detailed information on the scope of the national problem that such a search produces.
On occasion, the potential value of such searches has been greatly impaired because of delays in dissemination of the results. Such delays (as long as 12 months after completion of the search itself) have sometimes occurred because of poor communications or because of efforts to conduct "complete" or "definitive" analyses before releasing any of the data. For example, one country completed its national case search in 1990, but results were not made known outside the country until a year later. One country conducted its search over a 2-year period and never during that time provided periodic provisional updates of the search results. At other times, the attempted use of computers has delayed rather than facilitated even preliminary analysis of search results (e.g., total number of cases and villages with endemic dracunculiasis found in the country) because of delays in entry of data into the computer, missing spare parts, or other technical problems. In such situations, it is important to recall that the main purpose of obtaining such data is the use of information to help improve the lives of the persons affected as quickly as possible and that less than two decades ago national Smallpox Eradication Programs routinely managed even larger amounts of data promptly without computers.
The nationwide searches for dracunculiasis have been used to gather surveillance data simultaneously about urinary schistosomiasis in Ghana and about family planning in Nigeria, as well as to provide an opportunity for provision of vaccinations to children in previously unreached populations in Nigeria.
Although the village-by-village searches are ideal for quickly determining the extent of dracunculiasis in countries with endemic disease and have been used to monitor progress annually in India (since the early 1980s), Nigeria (1988-1990), and Ghana (1989-1990), village-based monthly reporting is preferable once a program has been implemented. Comparison of monthly figures against the previous year's monthly figures is an even more powerful tool for monitoring the program and motivating program workers and others than are annual search data. The more intensive focus on villages that actually have dracunculiasis also is logistically simpler than trying to reach all villages in the country. Even if subsequent annual village-by-village searches are limited to villages known to have endemic dracunculiasis, village-based surveillance workers still offer the additional advantage of being able to provide control measures rapidly as cases appear.
Most developing countries express a commitment to providing primary health care to as many of their citizens as possible as the main means of achieving "health for all by the year 2000." Village-based health workers are often included as a part of such schemes in theory-and less often in practice-especially in the more remote villages. The village-based surveillance workers in GWEPs embody such envisioned activities, although they may start out with a much narrower mandate, i.e., dracunculiasis reporting and control. Such experienced workers are a potentially valuable resource for broader use as primary health-care workers for disease surveillance and control in their villages after they complete their assignment for dracunculiasis eradication, and sometimes even while they are still working in the eradication program.
In countries where dracunculiasis has already been or is almost eradicated, it would be very costly and inefficient to undertake surveillance for dracunculiasis alone to meet the requirement for certification of elimination. The need for rapid development of systems suitable for conducting reliable surveillance for dracunculiasis simultaneously with other diseases is now urgent and must be stressed.
The net result of the increasingly complete surveillance for dracunculiasis over the past decade has been to establish the eradicability of dracunculiasis even more firmly than had generally been believed in earlier years. The distribution of the disease in areas that continue to have endemic disease is now clearer, and the total number of cases remaining is lower than had been previously postulated on the basis of earlier passively reported information.
The authors thank Ms. Renn Doyle for preparing the figures and table and for other assistance in preparing this manuscript for publication.
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