Value of individual household water supplies in the maintenance phase of a schistosomiasis control programme in Saint Lucia, after chemotherapy*

Bulletin of the World Health Organization, 60 (4): 583 - 588 (1982) Value of individual household water supplies in the maintenance phase of a schistosomiasis control programme in Saint Lucia, after chemotherapy* P. JORDAN,' G. 0. UNRAU,2 R. K. BARTHOLOMEW,3 J. A. COOK,4 & E. GRISTS Between 1970 and 1975, the incidence of new Schistosoma mansoni infections was reduced in 5 villages after each household wasprovided with its individual watersupply and community laundry shower units were made available. In 1975, 1976, and 1977 chemo- therapy with oxamniquine was offered to personsfound to be infected. Transmission was reducedfurtherand remained at a low levelfor the next 4years, with no sign ofan increase in spite of the reservoir of infection remaining after therapy and a poor level ofsanitation in the villages. Thus, properly maintained water supplies appear to be effective in maintaining trans- mission at a low level during the maintenance phase of a schistosomiasis control pro- gramme, after chemotherapy. Sporadic new infections must be anticipatedamong children, but these will probably be of low intensity and associated with minimal morbidity. The effect on transmission of Schistosoma mansoni ofproviding each household with its own water supply has been studied in five villages in Richefond valley in Saint Lucia (1-3). Between 1970 and 1975, the incidence of new infections among 0-10-year-old children fell from 31% to 12.6%, overall prevalence fell from 52% to 38%, intensity of infection fell by 50%, and the contamination potential was reduced by 68%. After stool surveys of all age groups in 1975 and 1976, chemotherapy was offered to persons then ex- creting S. mansoni ova; in 1977 all other untreated persons who at any time had been found infected were offered treatment. No further control was carried out but the transmission pattern was followed for 4 years to assess the effect of individual household water sup- plies on transmission in the consolidation phase of the control programme, after chemotherapy. * From the Research & Control Department, Castries, Saint Lucia. ' Director, Research & Control Department, Castries, Saint Lucia. Present address, to which reprint requests should be sent: Department of Parasitology, National Institute of Medical Re- search, Mill Hill, London, England. ' Formerly Engineer, Research & Control Department. 3 Formerly Laboratory Supervisor, Research & Control Depart- ment. 4 Formerly Physician, Research & Control Department. 5 Formerly Cost Analyst, Research & Control Department. THE STUDY AREA The five experimental villages in which each house- hold was provided with its own water supply have been described elsewhere (1, 4). With a total popu- lation of approximately 2000, they are located on the south side of the Richefond valley, on the eastern side of Saint Lucia. When the project started, one village-Grande Ravine-was situated at the end of a dirt road; as a result ofdevelopment over the past 10 years the village is now on a tarmac loop road, off the main road through the valley. The other four villages have changed little and population density has been static. Owing to increases in the price of oil and the result- ant rise in the cost of electricity for pumping water, the Grande Ravine system was connected, in 1979, to a new gravity-fed water supply on the northern side of Richefond valley. This water is of better quality than that originally distributed, and resulted in much lower maintenance costs, required less electricity for pump- ing, and enabled a few additional houses, above the economic level for pumping water, to be supplied. The main system providing Grande Riviere, Thomazo, and Morne Panache is also dependent on electricity, and modifications are in hand to provide a gravity-fed water supply. 4209 -583 P. JORDAN ET AL. In August 1980, Hurricane Allen completely de- stroyed the Grande Ravine laundry unit and the power lines to the Thomazo pumping station. Water supplies were interrupted for 7 weeks and ground-water was the only source available. Although rain was not a marked feature of the hurricane it was probably suf- ficient to "flush out" snails and the 1981 survey gives no indication oftransmission having taken place while supplies were interrupted. In earlier reports on this project, reference was made to comparison settlements on the northern side of Richefond valley. These villages are not referred to in the present communication as, with development, they became less suitable for comparison purposes; data from them will be reported elsewhere. MATERIALS AND METHODS Chemotherapy Treatment campaigns were organized as previously described (5). In 1975, children and adults were given oxamniquine at a dose of 15 mg/kg of body weight; later this was increased to 20 mg/kg for children. Parasitological studies Stools from children aged 0- 14 years were collected by annual house visits; stools from persons of all ages were collected in 1977 and for final evaluation in 1981. A sedimentation concentration was used for qualitative examination for helminth ova. If the quantity of stool was sufficient, those found with S. mansoni ova were quantitatively examined by a fil- tration staining technique (6) with a lower limit of sensitivity of 10 eggs per gram; in about 2% of cases, there was insufficient stool and the Kato technique was used. Quality control has been maintained by the method described by Bartholomew & Goddard (7). Cochran's method for combining 2 x 2 tables was used for significance tests of prevalence and incidence by age groups at different surveys (8). Sanitation and water usage In a survey of the standard of sanitation in the area, the type of latrine in each house was noted. In an enquiry into usage of water, householders were asked whether they still went to the river in spite of having their own household water supply. Cost analysis Detailed costs of maintaining water supplies and of the chemotherapy campaigns were kept. RESULTS Chemotherapy In 1975, out of 1340 persons examined, 512 were found to be infected, and were offered treatment; 95% accepted. In 1976, of 377 found to be infected Table 1. Incidence of new S. mansoni infections in children apparently negative at the first of two surveysa 1974/75b 1977/78c 1978/79 1979/80 1980/81 Age at No. % No. % No. % No. % No. % survey examined positive examined positive examined positive examined positive examined positive 0- 2 49 0 36 2.8 31 3.2 25 0 22 0 3- 5 85 7.1 63 3.2 72 2.8 40 7.5 35 0 6- 7 63 19.0 51 5.9 45 2.2 31 12.9 36 5.6 8-10 70 20.0 88 10.2 74 6.8 50 6.0 55 1.8 11 -13 41 41.5 64 9.4 71 7.0 39 2.6 39 10.3 0- 13 308 15.9 302 7.0 293 4.8 185 5.9 187 3.7 a No. examined = number of children found S. mansoni negative at the first of two surveys. % positive = the proportion of those examined who were found S. mansoni positive at the second of two surveys. b Last year before chemotherapy was offered. c Treatment was offered after the 1977 survey. 584 SCHISTOSOMIASIS CONTROL only 777o accepted treatment. In 1977, the final year of the campaign, 95 were treated bringing the total treated to 841 persons. Parasitology Data for the incidence of S. mansoni infections for the year prior to the first chemotherapy campaign (1974/75) (i.e., at the end of a 4-5 year period of evaluating the effect of individual household water supplies on the control of transmission) and for the years following the last campaign (1977/78) are shown in Table 1. The fall in incidence from 15.9% in 1974/75 to 7.0%7 in 1977/78 reflects the reduced con- tamination of the environment after chemotherapy. Transmission did not increase in the subsequent years. Changes in prevalence, intensity of infection, and contamination potential are shown in Table 2. Similar rates of prevalence were found in males and females. As has been reported elsewhere, in longitudinal studies the cooperation of the people decreases with time (10), and in the 1981 survey (the fourteenth) only 47% and 57%o of males and females, respectively, provided stools for examination. Overall prevalence declined from 38% in 1975 to 13%o in 1977, and to 8% in 1981. While the intensity of infection of those infected did not change, contamination was reduced by 78%o between 1975 and 1981. Compared with the figure at the start of control programme in 1970, there was a 9207o reduction in the level by 1981. Changes in the frequency distribution of different intensities of infection are shown in Table 3 and the past S. mansoni histories of those found to be infected in 1981 are shown in Table 4. One-third of these people were known to have been infected previously. The apparently new cases were mainly among children, most of whom had had several previous negative stools (Table 4). The new cases among adults, who had had fewer previous negative stools, may not have been truly new cases. Table 2. Changes in prevalence of S. mansoni infections, intensity of infection, and contamination potential in Saint Lucia 1975 1977 1981 Age group No. % GM egg No. % GM egg No. % GM egg (years) examined positive outputa examined positive outputa examined positive Output" 0-4 208 6.7 13 140 2.1 105 1.0 5-9 278 22.7 17 230 10.9 18 169 3.0 10 10-14 232 50.0 17 227 19.4 12 176 11.4 16 15-19 144 59.7 19 98 20.4 22 81 19.8 16 20- 29 144 60.0 23 117 17.1 29 80 15.0 25 30-39 91 56.0 15 88 16.0 17 , 74 12.2 26 40-49 94 40.4 14 73 11.0 67 10.4 50- 59 74 40.5 14 59 10.2 13 53 3.8 11 60 75 38.6 15 71 11.3 46 2.2 0- 14 718 26.9 17 597 12.1 14 450 5.8 17 > 15 622 51.3 17 506 15.0 19 401 11.7 Contamination potentialb 6389 2106 1412 % Reduction in contami- nation - 67% 33% Cumulative reduction 67% 78% ° Geometric mean of egg output/ml of faeces. b Sum of products of prevalence and GM egg output. 585 P. JORDAN ET AL. Table 3. Changing pattern of frequency distribution of intensity of infection as the control programme progressed Egg load (eggs/ml of faeces) No. % Year examined 6 50 51 - 100 101 - 200 201 -400 > 400 negative 1970 966 35.1 8.0 7.5 3.3 1.8 44.3 1975 1340 34.0 2.5 1.2 0.4a 61.9 1977 1103 11.9 0.8 0.4 0.3a 86.6 1981 851 7.2 1.2 0.1 b 91.5 a > 201 eggs/ml of faeces. b > 101 eggs/ml of faeces. Table 4. History of S. mansoni infections in the 73 persons found to be infected in 1981 Age No. previously positive No. No. No. group previously not previously of (years) Not treated Treated negativea examined immigrants Total 0-4 - - - - _ _ 5-9 1 - 412,3,4,5) - - 5 10-14 3 4 7(3,4,5,6,7,9, 11) 7 2 23 15_19 5 4 1 (1) 1 1 12 20-29 6 - 1 (3) 4 3 14 30-39 4 2 1 (1) 2 - 9 40-49 2 2 2(1,2) - 1 7 50-59 - 1 - 1 - 2 >60 1 - - - - 1 22 13 16 15 7 73 a The figures in parentheses represent the number of negative stools obtained previously from each individual. Engineering 0 The costs of maintaining the water supplies over the 4-year period are summarized in Table 5. The savings in pumping (electricity) costs for Grande Ravine once a gravity-fed system had been installed are noteworthy -as are the increasing electricity costs for the Thomazo pump. Transportation costs reflect the increase. in fuel prices, and rising labour costs show the effects of inflation. High labour costs from 1978 to 1980 were due to work on clearing a heavy deposit in the pipeline of the Grande Ravine distribution system. The cost of rebuilding the Grande Ravine laundry shower unit when it was destroyed by Hurricane Allen, was borne by the USAID relief organization. Minimal repairs (US$ 212) elsewhere were carried out by the department. Sanitation and water usage In a survey of 306 houses, 67%To had pit latrines, 3%o had septic tanks, and 30%o either had no latrine or the occupants used an open pit for faecal disposal. Nearly 1O0o of householders admitted to going back to the river periodically to obtain water or to bathe in spite of having a household water supply. DISCUSSION Chemotherapy campaigns can rapidly reduce the prevalence of S. mansoni infections, the intensity of infection, and the contamination potential but a con- siderable reservoir of infection will remain (9), and, with a poor level of sanitation and inadequate water 586 SCHISTOSOMIASIS CONTROL Table 5. Comparison of annual maintenance costs (US$) of water supply system (US$1 = EC$2.7) 1977/78 1978/79 1979/80 1980/81 Electricity G. Ravine 763 50% 263 39% 77 49% 67 57% Thomazo 4055 5%4286 7704 9773 Materials and equipment 986 10% 724 6% 893 5% 861 5% Labour 3394 35% 5855 50% 7049 43% 6389 37% Emergency work 200 2% 404 3% - 212 1 % Other costs 320 3% 224 2% 530 3% 81 < 1% Total 9718 100% 11756 100% 16253 100% 17383 100% Payment for water 221 362 431 336 Transportation 940 2233 3009 3997 Cost per person 5.22 6.81 9.42 10.52 supplies, transmission may continue-as it did else- where in Saint Lucia (10). In these circumstances, transmission can be controlled by routine focal mollusciciding (11), or repeated therapy of children (perhaps at 2- 3 year intervals) may be an alternative maintenance phase strategy (10). The results of the present study indicate that in Saint Lucia the provision of adequate, safe, house- hold water supplies, with laundry shower units, can be an effective strategy in the follow-up phase of control after chemotherapy. The finding contrasts with results from another area where a community water supply failed to prevent a resurgence of transmission (10). In the study reported here, only about two-thirds of the population offered stools for examination in the 1977 survey, and, in addition, many known to have been infected at that time did not accept chemo- therapy. In view of this, and the low level of sani- tation-inadequate latrines in 30%o of the houses and infrequently used pit-latrines in the others-con- tinued and possibly increasing transmission would have been expected. There was, however, no evidence of any increase; the 3.7qo incidence rate for 1980/81 is the lowest recorded from the area but is not significantly different from the 1978/79 level. Thus, while there may have been a downward trend, incidence may now have become established at a new low level. During the 4- 5 years in which the value of the water system was evaluated, the incidence fell from 31% to 11.3%o in 3 years, but in the next 2 it failed to decline further (3). The contamination potential in 1981 was only 8% of the pre-control level. The chance of snails being in- fected is therefore much reduced, but children will be exposed to sporadic infection as they play and fish in the rivers. In most cases any infections acquired will be of low intensity-though this is not always the case (10). In order to reduce to a minimum the chance of renewed transmission after the 1981 survey, all in- fected but previously untreated persons were offered therapy. Two-thirds accepted treatment, and although many of those who did not may have lost their infections since being first diagnosed, 22 of 73 found infected at the 1981 survey failed to accept treatment. Regrettably, in spite of personal and radio appeals, the response to the 1981 survey was the poorest ever with only 50% participation; the potential for continued transmission thus remains, but a rapid increase appears unlikely as long as individual water supplies are maintained. The original water scheme was installed to test the concept that well established customs -such as wash- ing in rivers-could be changed by health education and the provision of adequate, reliable, and con- venient water supplies. At the time, cost was not the prime consideration, but with inflation, and since the system has been handed over to Government, the need for a more economic policy during the maintenance phase has become obvious. Electricity costs were re- duced considerably when the distribution system to one settlement was changed to a gravity-fed system; such systems with long pipelines are likely to be more economical (and reliable) than short lines dependent on pumping. 587 588 P. JORDAN ET AL. When evaluated between 1970 and 1975 household water supplies provided in these 5 villages were shown to reduce transmission. They appear now to be effective in keeping it at a low level. While the provision of water supplies is unlikely to be a primary method of schistosomiasis control, such supplies are being provided for other medical and social reasons in many developing countries and their role in the control of this disease should not be overlooked. ACKNOWLEDGEMENTS The Research & Control Department is supported by the Rockefeller Foundation of New York, the Medical Research Council of the United Kingdom (through the Overseas Development Administration-scheme A-C 2108), and the Government of Saint Lucia. The authors acknowledge the support of field teams, microscopists, and nursing staff. RESUME UTILITE DE L'APPROVISIONNEMENT INDIVIDUEL DES MENAGES EN EAU DANS LA PHASE D'ENTRETIEN DU PROGRAMME DE LUTTE CONTRE LA SCHISTOSOMIASE A SAINTE-LUCIE APRES LE TRAITEMENT CHIMIOTHERAPIQUE Apres que la fourniture d'un approvisionnement indi- viduel en eau A chaque m6nage eut r6duit dans 5 villages de Sainte-Lucie la transmission de Schistosoma mansoni de 31,0% a 12,6% (chez les enfants Ag6s de 0- 10 ans), un traitement chimioth6rapique a 6t6 offert a toutes les personnes trouv6es infect6es en 1975, 1976 et 1977. On a administr6 de l'oxamniquine a une dose de 15 mg/kg de poids corporel; en 1976, la dose pour les enfants a ete aug- ment6e A 20 mg/kg. Apres le traitement chimiotherapique, l'incidence des cas nouveaux a ete encore r6duite et au cours des 4 ann&es suivantes (1977 - 81) elle a vari6 entre 4% et 7% seulement par an. La chimioth6rapie a r6duit les taux de pr6valence, qui etaient en 1975 de 26,9% et 51,3% pour les enfants et les adultes respectivement, aux taux de 12,1% et 15% en 1977. Au cours des 4 ann6es suivantes, il s'est produit une nouvelle reduction a 5,8% et 11,7%. Compar&e avec les donnees de 1975, la contamination potentielle vers 1981 6tait r6duite de 78% (et de 92% par rapport au chiffre relev6 avant le programme de lutte). Etant donn6 le bas niveau d'assainissement dans les villages et le reservoir d'infection subsistant apres le traite- ment chimioth6rapique, une certaine transmission pouvait encore etre pr6vue. Vers 1981 il y avait encore quelques cas nouveaux d'infec- tion chaque ann6e, principalement chez les enfants; toute- fois, l'intensit6 de l'infection demeurait basse. Des cas sporadiques d'infection apparaitront sans nul doute dans l'avenir, mais aussi longtemps que les approvisionnements individuels d'eau dans les menages seront ad6quatement entretenus, il semble improbable qu'une breche importante se produise dans la lutte contre la schistosomiase. Le co(t de l'electricite utilis6e pour le pompage de l'eau dans ces villages a plus que doubl6 pendant la p6riode 1977 - 81, mais des 6conomies substantielles ont te r6alisces lorsque fut construit pour desservir un village un systeme de distribution fonde sur la gravit6. Etant donn6 I'augmentation continue des coOts de construction, il est improbable que les approvisionnements en eau soient installes essentiellement comme m6thode de lutte contre la schistosomiase, mais dans cette d6cennie internationale de l'eau potable et de l'assainissement leur utilit6 potentielle ne doit pas etre ignor6e, d'autant plus qu'ils semblent se r6v6ler efficaces au cours de la phase d'entretien apres le traitement chimioth6rapique. REFERENCES 1. UNRAU G. 0. Bulletin of the World Health Organiz- ation, 52: 1 - 8 (1975). 2. JORDAN P. ET AL. Bulletin ofthe WorldHealth Organiz- ation, 52: 9- 20 (1975). 3. JORDAN P. ET AL. Bulletin ofthe World Health Organiz- ation, 56: 965-973 (1978). 4. DALTON P. Bulletin ofthe World Health Organization, 54: 587 - 595 (1976). 5. COOK J .A. ET AL. Americanjournal oftropical medicine and hygiene, 26: 887 - 893 (1977). 6. BELL D.R. Bulletin of the World Health Organization, 29: 525 - 530 (1963). 7. BARTHOLOMEW R.K. & GODDARD M. Transactions of the Royal Society of Tropical Medicine and Hygiene, 56: 309- 312 (1978). 8. SNEDECOR G.W. & COCHRAN G. Statistical methods, 6th ed., Ames, Iowa State University Press, 1967, p.253. 9. JORDAN P. ET. AL. Transactions of the Royal Society of Tropical Medicine and Hygiene, 74: 493 - 500 (1980). 10. JORDAN P. ET AL. Americanjournal oftropical medicine and hygiene, 31: 103- 110 (1982). 11. BARNISH, G. ET AL. Transactions ofthe Royal Society of Tropical Medicine and Hygiene, (in press, 1982).