Dracunculiasis eradication: target 1995.

Substantial progress has been achieved over the past 3 years by the campaign to eradicate dracunculiasis. The target of eradication by 1995 has been set by the African Regional Office of the World Health Organization and accepted by the United Nations Children's Fund (UNICEF) and the United Nations Development Program. India and Pakistan continue to reduce their cases of the disease dramatically. In Africa, Ghana and Nigeria conducted national village-by-village searches in 1988-1990 and, between them, found greater than 800,000 cases of the disease. Most African countries have now prepared national plans of action, appointed national coordinators, and intend to use UNICEF's assistance to conduct national searches by the end of 1990. An international donors' conference held in 1989 facilitated major new assistance for the initiative by UNICEF, the United Nations Development Program, the United States Agency for International Development, the Japanese International Cooperation Agency, the Peace Corps, the American Cyanamid Company, and DuPont. The World Health Organization held a meeting early in 1990 to draft criteria and recommend the process for certifying achievement of elimination of dracunculiasis in formerly endemic countries. The major remaining obstacles to eradication of dracunculiasis by 1995 are civil wars in northeastern Africa and the apathy of some national and international officials.

Survival of Schistosoma mansoni in the human host: estimates from a community-based prospective study in Puerto Rico.

Changes over time in the prevalence and intensity of Schistosoma mansoni infection were measured by serial quantitative stool examinations using the modified Ritchie concentration technique in a 9-year prospective study of an endemic Puerto Rican community with a population of about 1,000 persons. The complete interruption of transmission was achieved by snail control during the 2nd year of the study, in February 1973. Annual stool specimens were obtained from all willing community residents. In addition, from 27 of these residents 10 consecutive stools were collected in each of 3 years: 1973, 1976, 1977. After a chemotherapy campaign with oxamniquine in 1980, only eight of these 27 persons remained untreated. Ten consecutive stools were collected from seven of these untreated individuals in 1981. We calculated the rate of decline (beta) in geometric mean egg count in the cohort of 27 over 5 years and in the subcohort of seven over 9 years. Similarly, beta was calculated from the change in the single annual stool counts in 528 persons providing data for all of the first 6 years of the study. Estimates of the average life-span (-1/beta, in a model assuming constant rate of death) of the adult S. mansoni with 95% confidence intervals are for the cohort of 27, 5.5 years (4.0 to 9.1), for the cohort of seven, 37 years (8.0 to infinity), and and for the cohort of 528, 35 years (16 to infinity).(ABSTRACT TRUNCATED AT 250 WORDS)

Dracunculiasis eradication: almost a reality.

The idea of a global campaign to eradicate dracunculiasis was first proposed by the Centers for Disease Control and Prevention in 1980, during the advent of the International Drinking Water Supply and Sanitation Decade (IDWSSD) (1981-1990). In 1981, the Steering Committee of the IDWSSD adopted eradication of dracunculiasis as a subgoal of their efforts to provide safe drinking water to unserved populations. In 1988, African ministers of health voted to eradicate dracunculiasis by the end of 1995, a target date that was endorsed by UNICEF in 1989 and the World Health Assembly in 1991. Although nine of 18 endemic countries, India (1980), Pakistan (1987), Nigeria and Cameroon (1988), Ghana (1989), and Mauritania, Benin, Burkina Faso, and Togo (1990) completed national searches for cases of the disease, only four countries, India (1983), Pakistan (1988), Ghana (1989), and Nigeria (1989), actually started eradication programs during the 1980s. The remaining 14 endemic countries began their eradication programs between 1991 and 1995. At the end of 1996, dracunculiasis had not been entirely eradicated, but its incidence had been reduced by 95%, from an estimated 3.2 million cases in 1986 to 152,805 cases in 1996. Sudan reported a total of 118,578 (78%) of the 152,805 cases of dracunculiasis reported during 1996. Insufficient funding and the civil war in Sudan continue to be the major obstacles to overcome. A primary aim of the eradication program in 1997 is to seek to ensure that all cases of dracunculiasis outside of Sudan are contained. In Sudan the challenge is to pursue all appropriate control measures in all accessible areas as vigorously as possible until political circumstances allow access to all of the remaining affected areas.

Dracunculiasis eradication: March 1994 update.

Substantial progress has been realized in the global campaign to eradicate dracunculiasis by the end of 1995 since a previous review of the subject was published in this journal a year ago. All known endemic countries are now engaged in the eradication effort, and one or more control measures are now in place in 93% of endemic villages. Despite improved surveillance for the disease, the number of reported cases of the disease has been reduced by 41% (to about 221,000), and the number of known endemic villages has been reduced by 28% (to about 16,500) in the past year. Priorities for national eradication programs in 1994 include increasing the use of vector control and intensifying the case containment strategy in endemic villages. It is still possible to achieve the eradication target of December 1995, but greatly intensified efforts this year will be required to do so.

Dracunculiasis eradication: beginning of the end.

Beginning with the International Drinking Water Supply and Sanitation Decade (1981-1990), an increasingly broad coalition of international and bilateral agencies, organizations, private companies, and other institutions have joined forces to eradicate dracunculiasis (Guinea worm disease). From an estimated annual incidence of 10 million persons just before the campaign began, the remaining incidence of cases is now less than two million. More than 23,000 villages are known to be endemic. All 18 countries where the disease is still endemic have completed or begun nationwide searches to identify endemic villages, except Kenya. Dracunculiasis is nearly eradicated in Asia, where Pakistan found only 23 cases in 1992, and India found 1,081 cases. Cameroon and Senegal are close to achieving eradication in Africa, where the two formerly highest endemic countries, Nigeria and Ghana, reduced their combined total of cases from approximately 820,000 in 1989 to less than 240,000 in 1992. Much remains to be done, however, in francophone West Africa and especially in East Africa. The most serious current obstacles to eradicating dracunculiasis by 1995 are the civil war in Sudan, apathy of some national and international health officials, and inadequate funding for the campaign.

Dracunculiasis eradication: delayed, not denied.

By the end of 1998, Asia was free of dracunculiasis (Guinea worm disease), with Pakistan, India, and Yemen having interrupted transmission in 1993, 1996, and 1997, respectively. Transmission of the disease was also interrupted in Cameroon and Senegal during 1997. Chad reported only 3 cases during 1998. Dracunculiasis is now confined to only 13 countries in Africa. The overall number of cases has been reduced by more than 97% from the 3.2 million cases estimated to have occurred in 1986 to 78,557 cases reported in 1998. Because the civil war in Sudan remains the major impediment to eradication of dracunculiasis, the interim goal is to stop all transmission outside that country by the end of 2000. The most important operational need now is for national programs to improve the frequency and quality of supervision of village-based health workers in order to enhance the sensitivity of surveillance and effectiveness of case containment.

The Boqueron Project after 5 years: a prospective community-based study of infection with Schistosoma mansoni in Puerto Rico.

The Boqueron Schistosomiasis Project is a prospective community-based study of Schistosoma mansoni infection after the interruption of transmission by nonchemotherapeutic control measures. The study methods and the parasitologic results of the first five annual stool surveys are described in this report. In the first year, 1972, among 904 inhabitants (88% of the total population) the prevalence of infection was 40%, and the geometric mean intensity of infection among positives was 16.1 eggs per gram (epg). Snail control was begun in early 1973 with molluscicides and habitat modification. Intensive monitoring every 2 weeks revealed only 63 noninfected Biomphalaria glabrata in the community during the subsequent 4 years. The incidence of new infectins among people negative in all previous surveys dropped from 17% in 1972 to 1% in 1974 and has remained negligible since then. Among young children and newborn, only four new infections (all less than 5 epg) were found after the first control year. Despite this low rate of transmission, prevalence only decreased from 37% to 34%, and the population geometric mean fecal egg output has not substantially changed in a cohort of 528 individuals examined in each of the six annual surveys. Possible reasons for the minimal change in parasitologic status are discussed and include water contact behavior outside the community and changes in laboratory techniques. Data from the first 5 years of the study suggest that in a population where mean intensity of infection with S. mansoni is low, further decreases in prevalence and intensity of infection occur slowly. The implications for control programs based on nonchemotherapeutic measures are discussed.

Evaluation of UNICEF/Arab Republic of Egypt/WHO schistosomiasis Control Project in Beheira Governorate.

We evaluated the UNICEF/Government of Egypt/WHO Schistosomiasis Control project in 2 districts of Beheira Governorate of the Nile Delta during 3 weeks in February 1988. The project, begun in 1983, was focused on reducing prevalence, intensity, and morbidity due to schistosomiasis by providing diagnosis and treatment with praziquantel to schoolchildren. Schools were visited twice. Following the completion of the school surveys, the program was extended into the community. Chemotherapy was delivered by mobile and static teams. The evaluation indicated that, with respect to accuracy of diagnosis, record-keeping, and coverage of targeted populations, project tasks were performed exceedingly well by highly motivated, well-supervised mobile teams. Static teams in rural health centers were less successful in providing diagnosis and chemotherapy to village populations. We resurveyed 6 randomly selected schools to assess the impact of chemotherapy. Overall, the prevalence of Schistosoma mansoni infection was reduced from 60.3% to 24.8% between the first and second surveys (approximately 1 year apart) and was still lower (41.1%) than initial levels up to 3 years after the last treatment with praziquantel. The percentages of those with greater than or equal to 34 S. mansoni eggs/slide using the Kato-Katz technique showed a marked and prolonged decrease (17.1% to 0.3% to 2.2%). The prevalence of S. haematobium infection dropped from 37.6% to 5.5% and was still 9.9% at the time of the evaluation. The percentages of those with greater than or equal to 50 S. haematobium eggs/10 ml urine dropped less dramatically (17% to 4.4% to 11.9%). Mobile teams conducting vigorous chemotherapy programs targeted at schoolchildren can have long-lasting benefits in terms of prevalence and intensity.

1983 Nile Delta schistosomiasis survey: 48 years after Scott.

To determine whether the sharply declining Schistosoma haematobium infection rates in parts of the Nile Delta could be generalized to the entire region, and to update the status of S. mansoni infection rates, a large scale survey was undertaken in 1983 in 70 of the 71 districts of the Nile Delta. In a house-to-house survey, greater than 91% of the sample population of 16,675 participated by providing stool and/or urine specimens which were examined qualitatively by Kato thick smear and sedimentation techniques, respectively. After the 1935 survey by Scott, the prevalence of S. mansoni appeared to change little, from 33% in 1935 to 39% in 1983, but a more sensitive diagnostic technique in 1983 strongly suggested that the actual prevalence had decreased between the 2 surveys. In contrast, the prevalence of S. haematobium infection decreased from 56% to 5%, with a similar decline in all 8 governorates. The dramatic decline in S. haematobium prevalence has been accompanied temporally with a sharp decrease in the population density of Bulinus truncatus. S. mansoni has become the predominant human schistosome species in the Nile Delta.

Aedes aegypti in Puerto Rico: environmental determinants of larval abundance and relation to dengue virus transmission.

In order to understand adquately the dynamics of vector-borne disease, one must understand how and why vector populations change over time. We describe a long-term, cooperative study of seasonal fluctuation in populations of the Aedes aegypti mosquito in Puerto Rico. During each month of the first 3 years of the project, A. aegypti was found breeding in all five communities studied. Mosquito density was positively correlated with rainfall, the relationship being more marked in the dry, south-coastal part of the island. Discarded tires and animal watering pans were the two most common larval breeding sites. In general, houses in Puerto Rico harbor more potential A. aegypti breeding sites than those in other tropical locations, probably because Puerto Rico is relatively more affluent.

Dengue in Puerto Rico, 1977: public health response to characterize and control an epidemic of multiple serotypes.

The largest and most extensive documented dengue epidemic in Puerto Rico struck an estimated 355,000 Puerto Rican residents from July-December 1977. The mixed epidemic of dengue types 2 and 3 coincided with a Caribbean pandemic of dengue type 1, first introduced into the western hemisphere in early 1977 and into Puerto Rico in the fall of that year. Health officials assembled a team to assess the epidemic and mounted a campaign to end it. Attempts to monitor the incidence and spread of dengue were confounded by simultaneous co-circulation of influenza virus, underscoring problems in formulating public health strategies dependent on nonspecific clinical and epidemiologic case criteria, and the need for rapid and reliable diagnostic capabilities. Despite co-circulation of multiple dengue serotypes, a risk factor associated with severe and fatal dengue hemorrhagic fever (DHF) in Southeast Asia, hospital and death certificate surveillance disclosed no cases of DHF in Puerto Rico. The epidemic serves as a reminder that when preventive measures are impossible or infeasible, developed countries with high living standards may be susceptible to large scale epidemics of infectious diseases.

Assessment of schistosomiasis in the Dominican Republic.

Active transmission of intestinal schistosomiasis is currently limited to the southeastern part of the Dominican Republic. A population-based stool survey in 1980 detected 4 asymptomatic individuals among 114 selected at random in 2 towns and a rural community in El Seibo Province. The distribution of the transmitting snail, Biomphalaria glabrata, considerably exceeds that of Schistosoma mansoni, extending to the National District and capital city of Santo Domingo and well into certain central valley provinces. There is evidence that transmission sites have shifted during the past three decades because of urban development, molluscicidal activities and, perhaps, introduction of competing mollusks. In spite of intermittent control activities, the combination of domestic and recreational use of streams with consequent fecal contamination, and the extended distribution of B. glabrata indicates that the potential for new transmission foci is as great today as it was 10 years ago. This potential transmission of S. mansoni is a continuing threat to public health in the Dominican Republic.

The efficacy of oxamniquine in acute schistosomiasis: a clinical analysis of 28 treated patients.

During the summer of 1980, acute Manson's Schistosomiasis occurred in 28 pediatric patients, swimming in two ponds with no watershed connections between them, in the rural area of Juncos and Cidra, Puerto Rico. Clinical and immunological events were studied and Oxamniquine (Vansil, Pfizer) was administered to all of them and followed closely for 3 years. Fever and general malaise recorded in 93% of the patients, diarrhea and abdominal pain in 68% and urticaria or facial edema in 64%. Hepato and/or splenomegaly was recorded in 71% of them. Twenty seven of the patients had evidence of immunoserological activity against adult schistosomal antigens (GASP and PSAP). Two patients had intense immunologic activity, even before the recovering of fresh Schistosoma mansoni eggs in their stool. This was a response to GASP and PSAP antigens. When they started passing fresh eggs of schistosoma and COP (Circumoval Precipitation Test) turned positive, their clinical status worsened and antibodies to GASP antigen increased two fold. The oviposition phase elicited a strong antibody and immunological reaction with significant eosinophilia and cross reaction was observed between adult schistosomal and egg shell antigens. Severe clinical manifestations were seen in spite of low egg excretion. Oxamniquine was effective in obtaining a coprological cure and in altering the immunologic response as compared with other untreated groups in literature.