Fewer parasites in paradise

The Seychelles Heart Study II

Frequency and impact of autosomal dominant polycystic kidney disease.

Results of upper gastrointestinal segment endoscopies in Seychelles,1990-1994

Fewer parasites in paradise: achievements and future perspectives of the Seychelles Intestinal Parasites Control Program

L. Savioli, MD, MP, DTM&H, Schistosomiasis and Intestinal Parasites, Division of Control of Tropical Diseases, World Health Organization

Abstract

Intestinal parasitic infections in the Seychelles have been perceived as a public health problem for decades. A Control Program strategy to reduce morbidity and eventually transmission of intestinal parasites was initiated in 1993 and has been implemented successfully. The management of the program has been integrated since the beginning into the well established primary health care system and the control activities have been performed through the existing health facilities. The strategy adopted was based on periodic chemotherapy of schoolchildren, intense health education in close collaboration with the Ministry of Education, joint improvement of sanitation and safe water supply. An overall reduction in prevalence of intestinal parasitic infections of 53% was one of the targets achieved through this joint effort after three years of activities. The intensity of Ascaris lumbricoides and Trichuris trichiura infection was reduced by 92% and 62%, respectively. This integrated approach in concert with the political commitment and limited operational costs is a warranty for the future sustainability of the control activities. Future control strategies are tailored to the results of evaluation surveys and are targeted to the identified high risk areas. The Seychelles Program can be seen as a model in other developing countries, as an example of intersectoral collaboration and optimal use of resources.

Introduction

Intestinal parasitic infections were the prime mover of the first public health program in the history of the Seychelles. In 1925 hookworm infections were recognized as a public health problem and mass deworming campaigns were promoted until 1931 together with construction of public latrines. Schools and teachers were actively involved in the campaigns. This approach was successful in reducing hookworm prevalence from 90% to 41% (1). However, the lack of continuity together with misuse of anthelminthic drugs and the poor participation of the community were responsible for the persistence of intestinal parasitic infections.

Intestinal parasitic infections are presently recognized as a major health problem by the Ministry of Health (MOH) and also by teachers of the Ministry of Education (MOE) and families. Ascaris lumbricoides, Trichuris trichiura, hookworms, Strongyloides stercoralis and the protozoa Giardia intestinalis and Entamoeba histolytica are responsible for morbidity in the young and in the adult population (2,3).

The MOH in collaboration with the MOE, with technical support from the World Health Organization (WHO) and financial support by the German Pharma Health Fund (GPHF), started in 1993 the Seychelles Intestinal Parasites Control Program (SIPCP) with the objective of reducing intestinal parasitic infections to a level which no longer constitutes a public health problem (4). The strategy adopted is based on periodic chemotherapy of schoolchildren with mebendazole 500 mg, intense health education in close collaboration with the MOE, joint improvement of sanitation and safe water supply. The achievements of the SIPCP in the years 1993-1996, an evaluation of the cost in view of future self-sustainability and the future perspectives of the Program activities are discussed in the present paper.

Subjects and methods

SIPCP objectives, management and implementation

The general objective of the Program was the reduction of intestinal parasitic infections to a level which no longer constitutes a public health problem. The operational objectives within three years were: (a) to reduce the intensity (expressed in eggs per gram of feces) of A. lumbricoides infections by 60%, of T. trichiura and hookworm infection by 30% in school age children; (b) to reduce in the target population of prevalence of S. stercoralis infections by 30%; (c) to reduce in the target population of prevalence of amebiasis by 40%; (d) have children represent the main target group, as they are more heavily infected, they suffer most from morbidity due to these infections and they are the most important source of infection(5,6). Furthermore they can be easily reached in schools and health services can be easily delivered by the teachers and health staff.

The Primary Health Care (PHC) system is well established in the Seychelles (7) and the program has been integrated from the beginning into the local health structure. The program has been implemented as a special program, now under the Division of Disease Prevention and Control. The program activities are coordinated by a Program Manager with technical support from the Clinical and Public Health Laboratories, Health Education Unit and Epidemiology Unit. The School Health nurses and Environmental Health officers are responsible for the control activities (health education, treatment campaigns, evaluation surveys) in their Health Centers (HC) catchment area, in close collaboration with the teachers.

Special courses on stool quantitative diagnostic techniques (Kato-Katz) and concentration techniques (formol ethyl-acetate) were organized for the laboratory technicians from hospitals and HC. Nurses and EHOs and Social Education teachers were trained in the prevention and control of intestinal parasitic infections.

Control activities comprised periodic chemotherapy with antheminthics and health education. Mebendazole (500 mg) tablets, given as a single dose, was the anthelminthic chosen by the Ministry of Health for the periodic chemotherapy in schoolchildren (8). Children have been dewormed every four months and the treatment was delivered by teachers under the supervision of health staff.

Print media (newspapers, posters, leaflets) and electronic media (radio, television, audio-visual aids) were extensively used to increase public information and awareness on intestinal parasites control. Since the start of the program, preventive measures on intestinal parasites were included in the school curriculum. Mobile health team (environmental health officers, school health nurses), in collaboration with Social Education teachers, organized sessions and disseminated health messages in all schools. The radio advertised the program's activities and general preventive methods. TV and national newspaper were also involved in advertising chemotherapy campaigns. A video on prevention and control of intestinal parasitoses produced in Seychelles, was widely distributed in the schools, health centers and through the local TV. Leaflets and posters on the prevention and control of intestinal parasitic infection were designed in Creole and printed locally. Program activities in 1992-1996 are summarized in Table 1.

Parasitological surveys

A first survey (survey 1) to collect baseline data on prevalence and intensity of intestinal parasitic infections was implemented before the beginning of control activities. Fecal samples from 5% of all school-children were examined by the Kato-Katz technique to identify and count helminth eggs and by the formol-ethyl acetate concentration technique to detect protozoa and S. stercoralis larvae (9). Quality control was performed at central level by re-examining randomly 10% of the total slides. The same children were interviewed with a questionnaire to evaluate the knowledge on intestinal parasitic infections before intervention. Between June and July 1993, 338 pregnant women attending the anti-natal clinics had also their stool examined for helminths and protozoa and their haemoglobin tested (survey 2). All the subjects found positive for intestinal helminths were treated with mebendazole 500 mg as a single dose and those positive for S. stercoralis or intestinal protozoan infections were referred to the Health Centers for appropriate treatment.

Two parasitological evaluations after one year (survey 3, after 3 chemotherapy campaigns) and after two years (survey 5, after 6 chemotherapy campaigns) from the start of the Program were performed in schoolchildren. A second parasitological evaluation was also carried out in the pregnant women population after two years (survey 4), to monitor the expected reduction in prevalence and intensity in the population. The surveys design was identical, in order to obtain comparable data.

Data from the parasitological examination together with name, age, sex, weight and height of the person examined, were recorded on a form and entered in a microcomputer for statistical and epidemiological analysis using the Epiinfo package. The intensity of infections with A. lumbricoides, T. trichiura, and hookworms were measured indirectly as egg counts. Mean egg counts were calculated as arithmetic means of all children examined and expressed as eggs per gram of feces (epg). Chi-square test was used to compare prevalence rates and mean egg counts were compared with Student's t-test.

Results

Results from the evaluation survey in 1996, showed that the cumulative prevalence of intestinal parasites in the schoolchildren population dropped from 60.5% to 28.6%. There was a significant decrease for any of the parasites, except for Giardia, particularly evident for Ascaris (from 17.7% to 3.7%), Trichuris (from 53.3% to 21.5%), hookworm (from 6.3% o 1.6%) and E. histolytica (from 4.6% to 2.8%). The intensity of infections, expressed as mean of eggs per gram (epg) of feces, was reduced by 92%, 62% and 82% of the baseline mean epg for Ascaris, Trichuris and hookworm, respectively. The prevalence of S. stercoralis was reduced by 64%. The results are summarized in Table 2.

a) The eggs per gram of feces are expressed by arithmetic mean.

*) P <0.001 for difference in cumulative prevalence between 1993 and 1995.

Results from the surveys in pregnant women are shown in Table 3. There was a significant reduction in prevalence (from 44.4 to 15.1%) and intensity (reduction by 90%, 75% and 73% of the baseline intensity for hookworm, Ascaris and Trichuris infection, respectively). In addition, 7% of women had hemoglobin less than 10 g/dl, but only 1% had hemoglobin less than 8 g/dl. No correlation was found with the low intensity of hookworm infections.

a) The eggs per gram of feces (epg) are expressed by arithmetic mean.

b) P <0.001 when comparing survey 1 with survey 5.

The distribution of intestinal parasitic infection by region is summarized in Table 4.

The cost of the intervention and the evaluation of the program in 1995 was 0.22 US $ per person treated, and 0.06 US $ per person if considering the whole Seychelles population. The costs were distributed as follows. The cost of a treatment campaign (20,000 children)was 1,200 US $; the cost of drug (mebendazole) per child was 0.03 US $; the cost of drug delivery per child was 0.03 US $; the total cost per child treated was 0.06 US $; the cost of an evaluation survey (1,000 children) was 900 US $; the cost per child protected was 0.045 US $. In terms of the estimated program (intervention + evaluation) cost, the cost per child treated (3x/yr) was 0.22 US $. Program costs in 1993-1996 are shown in Table 5.

Discussion

The objectives of the program were met after one year of control activities. It has been proved that the Program is highly cost-effective: US$ 0.22 cost per child treated (3x/yr) is a relatively low cost, compared with a budget for health per person in the Seychelles of 280 US $ in 1994. The estimated budget for the implementation of the activities and the running cost of the Program up to the years 2000 is approximately US$ 5,000 per year. The Ministry of Health should be able to sustain the control activities after the end of the external financial support. In spite of the partial success of the control program, it is important that the objectives are maintained in the long term. This can be facilitated by the sustainability of the Program but can only be achieved through a strong political commitment.

The Program has had an impact also to reduce parasitic infections in the adult untreated population, through a reduction in transmission of intestinal parasitic infections, by preventing the contamination of the environment with infected human feces. Additional benefits achieved by the Program enabled to:

identify high-risk areas where cumulative prevalence is still high (East, West, South Mahé, Praslin and La Digue),

build-up technical capabilities of laboratory staff. The sensitivity and specificity of parasitological diagnosis has improved and the concentration techniques has been introduced for routine examination in the Central and in the Cottage hospitals,

increase management and epidemiological skills at the central level,

promote coordination among health centers, central hospital laboratories and epidemiology unit.

reinforce and promote health education in the schools and in the community,

promote preventive measures in the community, change in health behavior, and create the demand for seeking periodic anthelminthic treatment,

improve the coordination within sectors from the MOH and increase the collaboration with the MOE and other Ministries and Organizations (Local Government, Environment, Finance and Communication, Public Utilities Corporation),

sensitize the other Ministries involved in improving sanitation and safe water supplies.

 

Although the prevalence and intensity of intestinal parasites has been dramatically reduced, there are some areas where the cumulative prevalence is still high. East Mahé for Ascaris and Trichuris, West Mahé for hookworm and Strongyloides, South Mahé and Praslin/La Digue for Giardia and E. histolytica infection are the regions where increased efforts in control activities are needed. In areas with low prevalence, however, the interval between treatments in schoolchildren may now be prolonged and chemotherapy may be administered every six months. Mebendazole 500 mg tablets should be available in the Health Centers for the treatment of the general population, on the basis of symptoms and clinical diagnosis and not only upon parasitological diagnosis.

Rural communities at higher risk of infection with intestinal parasites should be identified. In such communities a parasitological survey will be carried out. Treatment will be given if necessary and efforts will be coordinated to improve sanitation and safe water supplies will be made in liaison with Local Government. Examples could include the farming community at Val d’Endor, the inhabitants of Silhouette Island, the communities in Mont Plaisir and Salazie on Praslin. Areas where the coverage of latrines and the use of safe water supply is still not universal, will be targeted in conjunction with Environmental Health, and relevant Ministries and Government Organizations.

Health education sessions should continue in the schools, involving also the Parent and Teachers Association, and through the Media. Training refreshing courses to the laboratory staff should be held periodially to maintain the standard in the parasitological diagnosis. Training sessions should include also other health staff (e.g. Environmental Health Officers, School Health Nurses).

Among other key issues, multisectoral collaboration is the key to success and has to be actively developed and maintained. Monitoring and evaluation activities should be implemented to see if the targets will be maintained. Epidemiological surveillance should be established by examining a sample of about 1,000 schoolchildren at yearly intervals to assess the trend of prevalence and intensity of intestinal parasitic infections as an indicator for morbidity. Pregnant women, attending ante-natal clinics for the first visit should be surveyed every two years to monitor the possible reduction of the infection in the adult not-treated population as a result of effective control in the school-age group. Hospital laboratory records from outpatients and inpatients stool samples should be analyzed every year to look for possible pockets of infections and to monitor the trend of intestinal parasitic infections in the general population.

As part of the evaluation, a sample of schoolchildren will be interviewed with the same questionnaire by which the children were interviewed before the start of the program, to assess the improvement in knowledge and awareness on prevention and treatment of intestinal parasitic infections. To evaluate the coverage and improvement of sanitation and housing, the adult population which recently moved in new settlements (e.g. Roche Caiman) will be studied to assess the prevalence and intensity of intestinal parasites. Interviews will be carried out to inquire about the type of household and sanitary facilities available in the previous households. A second parasitological survey will be performed after 12 months.

With regards to the evolution of the Program it is expected that the continuation as a special Program will not be cost-effective in the long term. It is suggested that the Program is integrated into a MOH ongoing Program, giving it its contribution of public health experience, managerial skills and training of personnel in pre-service and in-service programs. The future of SIPCP should be decided according to the needs and priorities of the Ministry of Health. It would be prudent, in defining the timing and process of any reorganization, to ensure that the focus on intestinal parasites that the Program, in its present form, has been able to ensure, is not prematurely withdrawn.

The SIPCP is an example of effective control of a public health problem, through the existing health care facilities. The program has facilitated the collaboration between MOH and MOE and other Ministries for the control of communicable and non-communicable diseases. The SIPCP can be seen as a model for other developing countries, in which this comprehensive approach can be an opportunity to reinforce their health system, and can became the entry point for controlling other communicable diseases. In this respect, it is envisaged to promote the contact and collaboration with neighboring countries with similar problems (Indian Ocean Islands, Pacific Ocean Islands).

Acknowledgments

We are most grateful to the staff of the Ministry of Health of Seychelles. In particular we thank Mr. C. Decommarmond, Mr. P. Palmyre, and the dedicated laboratory technicians of the central hospital and health centers; the statistic and epidemiology staff; the school health nurses, the environmental health officers; the nurses in charge of the ante-natal clinics; and the teachers for their enthusiastic participation in this study. Special thanks to Dr N. Wickremesinghe for his most useful comments and guidance. The Seychelles Intestinal Parasites Control Program is financially supported by the German Pharma Health Foundation through WHO.