Selective population chemotherapy among schoolchildren in Beheira governorate: the UNICEF/Arab Republic of Egypt/WHO Schistosomiasis Control Project.

Research/Recherche Selective population chemotherapy among schoolchildren in Beheira governorate: the UNICEF/Arab Republic of Egypt/WHO Schistosomiasis Control Project A. El Malatawy,' A. El Habashy,2 N. Lechine,3 H. Dixon,4 A. Davis,5 & K. E. Mott6 Selective population chemotherapy using a single dose of praziquantel (40 mg per kg body weight), which was offered to 29 365 schoolchildren in Abu El Matameer and 40 241 in Abo Homos districts, Beheira governorate in the Nile delta, reduced the prevalence of schistosomiasis from 75.4% to 40.9% (reduction of 45.8%) and from 80.5% to 30.8% (reduction of 61.7%), respectively. Of those with only S. mansoni infection, 10.6% before treatment and 1.7% one year later had more than 800 eggs per gram of faeces. The prevalence of S. haematobium in Abu El Matameer was reduced from 35.4% to 7.4% after a single treatment. Infections with both S. mansoni and S. haematobium were reduced by more than 90% after one year. These reductions in prevalence and intensity of schistosomiasis in the face of continuing transmission and water contact augur well for the future role of chemotherapy in control programmes. Introduction Praziquantel has been shown to have high cure rates against Schistosoma mansoni and S. haematobium infections in clinical trials and small community- intervention studies (1, 2); its effectiveness to reduce both the intensity of infection and the morbidity has been confirmed in different endemic areas (3). Some 1 Assistant Programme Officer (Training), UNICEF, Cairo, Egypt. 2 Former District Medical Officer, Abu El Matameer, Beheira, Egypt (deceased). 3 Former District Medical Officer, Abo Homos, Beheira, Egypt (deceased). 4 Chief, Epidemiological and Statistical Methodology, Health Situation and Trend Assessment, World Health Organization, Geneva, Switzerland. 5 Formerly Director, Parasitic Diseases Programme, World Health Organization, Geneva, Switzerland. 6 Chief, Schistosomiasis and other Trematode Infections, Division of Control of Tropical Diseases, World Health Organization, Geneva, Switzerland. Requests for reprints should be sent to Schistosomiasis Control, World Health Organization, 1211 Geneva 27, Switzerland. Reprint No. 5246 studies have found that, after treatment, the egg negative rate and the reduction in intensity of infec- tion, as measured by faecal egg counts, have not been as high or persistent in children as among adults (4, 5). As the large-scale use of chemotherapy in national control programmes increases, opera- tional research studies are essential to evaluate the effectiveness of treatment and to determine the appropriate regimen for a maximum impact on mor- bidity. Since most national control activities lack both human and financial resources to support costly, detailed field research, the available data must be used for evaluation as well as for operational deci- sions on where to increase or decrease control efforts. In 1983 UNICEF, WHO and the Department of Endemic Diseases of the Egyptian Ministry of Health collaborated jointly in a large-scale schistosomiasis control project. The object was to determine the prev- alence and intensity of S. mansoni and S. haemato- bium infection among schoolchildren in two districts of Beheira govemorate in the Nile delta of Egypt and to assess the impact of selective population chemo- therapy using a single dose of praziquantel. Bulletin of the World Health Organization, 70 (1): 47-56 (1992) © World Health Organization 1992 47 A. El Malatawy et al. Materials and methods Study areas. The districts of Abu El Matameer and Abo Homos in Beheira govemorate are situated about 20 km apart, some 40 km southeast of Alexandria and 150 km northwest of Cairo (see Fig. 1). Their populations numbered 160 000 and 217 822, respectively in 1987. Both districts are major irrigated agricultural areas to the west of the main channel of the Nile river. Schistosomiasis has been recognized as a major public health problem in the Nile delta, the Beheira governorate being the site of previous operational research activities conducted by WHO (6). Preparatory phase. In January 1983, during an Area Development workshop with community leaders in Abu El Matameer, schistosomiasis was recognized Fig. 1. Map showing location of study areas in Abu El Matameer and Abo Homos. WHO Bulletin OMS. Vol 70 199248 Selective population chemotherapy against schistosomiasis in Egypt by the public as the most important problem for intervention in the development phase. At the com- munity's request an operational research project was undertaken to evaluate the selective treatment of schoolchildren in this district and in a neighbouring district, Abu Homos, after one year. Baseline data were obtained from Ministry of Health reports on the distribution and prevalence of schistosomiasis. WHO conducted a five-day workshop for Ministry of Health staff and technicians. Subsequently over 400 staff and technicians were trained in the districts. The training emphasized basic laboratory techniques, organization of efficient surveys and supervisory skills. Methods. Both urine and faecal specimens were col- lected on the same day. If there was no gross haema- turia in the urine specimen, a chemical reagent strip (Hemastix, Ames-Miles Laboratories) was used to assess microscopic haematuria. If the latter was negative, a single random 10 ml sample of urine was syringe-filtered through a 20 HD Nytrel filter (UGB, Panissieres, France). After one drop of Lugol's solu- tion was added to the filter, it was examined micro- scopically. If S. haematobium eggs were present, they were counted up to 50 and recorded; larger numbers were not counted and recorded as 50+ eggs. The Kato-Katz cellophane thick-smear technique for faecal examination was used. A single sample from each stool specimen was examined microscopically within 24 hours of preparation. The microscopists recorded the actual number of S. mansoni eggs observed in each sample up to 34 eggs. After completion of the examinations, all infect- ed persons were treated, usually the next day, with a single dose of praziquantel (40 mg per kg of body weight). Treatment was given in anticipation of the known peak transmission between June and August. Thus, the timing of treatment between October and May was designed to permit the maximum period of reduced risk of re-exposure to infection. Throughout this project, the health communication activities were intensive among school teachers, religious leaders, community officials and lay groups. No snail control, water supply and sanitation interven- tions were implemented during the period of this study. Operations. All diagnosis and treatment surveys in the community were carried out by mobile teams and static teams in the rural health units. Each mobile team consisted of 9 persons (a physician, 2 micros- copists, 2 clerks, 1 community worker, 2 laboratory aides and a driver). Four mobile teams executed the community surveys in each district. Each static team was located in a rural health unit, with 4 persons (a physician, nurse, laboratory technician and a health aide). There were 48 static teams, 22 in Abu El Matameer and 26 in Abu Homos. In each district one physician and 3 senior labo- ratory technicians supervised the mobile and static teams. During the school surveys one supervisor was attached to each mobile team. Four staff members in each district health office received the school survey summary record forms from the mobile teams and checked these against the individual record forms. The data were further analysed and tables were pre- pared from the individual record forms. School surveys. Each mobile team prepared a time- table for the surveys of schools in their operational area. The operational objective was for each team to prepare Kato slides from faecal specimens of 400 schoolchildren each day and to examine 200 slides per day. Thus examination and treatment of 400 chil- dren required two working days. The schedule of school surveys was as follows: Abu El Matameer First survey: October 1983 to May 1984 Second survey: October 1984 to May 1985 Abu Homos First survey: October 1984 to May 1985 Second survey: October 1985 to May 1986. Community surveys. These began in Abu El Matameer in 1985 and in Abu Homos in 1986. The community surveys were done jointly by the mobile and static teams. Remote villages were surveyed only by mobile teams. Results School surveys In Abu El Matameer. During the first survey 29 365 children (99% coverage) were examined in 83 schools with an overall prevalence of 75.4% (Table 1). The prevalence of S. mansoni infection was over 90% in the schools of one council area where all S. haematobium infections were associated with S. mansoni (Zawiet Sakr). The prevalence of double infections was always higher than single infections with S. haematobium in all council areas except El Tahrir. The prevalence was higher in boys than in girls except in Zawiet Sakr where the overall prevalence was highest in the district. El Tahrir, the council area with the lowest prevalence of S. mansoni and the highest prevalence of S. haematobium, had the highest prevalence of intestinal helminths (16.5%), more than twice that observed in the other council areas (range, 2.7-8.2%). One year after treatment, 31 084 children were examined in 86 schools with an overall prevalence of 40.9% (Table 2). The prevalence of S. haematobium WHO Bulletin OMS. Vol 70 1992 49 A. El Malatawy et al. Table 1: Prevalence of schistosomiasis infection in schoolchildren at the first survey (October 1983 to May 1984), by sex and council area in Abu El Matameer district, Beheira governorate No. of No. positive for: Council area schools Sexa No. examined S. mansoni S. haematobium Both Total Abu El Matameer 14 M 4547 2489 (54.7) b 82 (1.8) 238 (5.2) 2809 (61.8) town F 2377 1187 (48.9) 37 (1.6) 65 (2.7) 1289 (54.2) T 6924 3676 (53.1) 119 (1.7) 303 (4.4) 4098 (59.2) Koum El Farag 17 M 4140 3100 (74.9) 109 (2.6) 607 (14.7) 3816 (91.2) F 1231 956 (77.7) 31 (2.5) 109 (8.8) 1096 (89.0) T 5371 4056 (75.5) 140 (2.6) 716 (13.3) 4912 (78.0) El Nomariah 12 M 3759 2397 (63.8) 147 (3.9) 854 (22.7) 3398 (90.4) F 1367 827 (60.5) 70 (5.1) 298 (21.8) 1195 (87.4) T 5126 3224 (62.9) 217 (4.2) 1152 (22.5) 4593 (89.6) Zawiet Sakr 12 M 3106 2810 (90.5) 0 (0. ) 205 (6.6) 3015 (97.1) F 964 877 (90.8) 0 (0.0) 69 (7.2) 946 (98.1) T 4070 3687 (90.6) 0 (0.0) 274 (6.7) 3961 (97.3) El Tahrir 28 M 5332 1375 (25.8) 920 (17.2) 873 (16.4) 3168 (59.4) F 2542 616 (24.2) 392 (15.4) 390 (15.3) 1398 (55.0) T 7874 1991 (25.3) 1312 (16.7) 1263 (16.0) 4566 (58.0) All areas 83 M 20 884 12 171 (58.3) 1258 (6.0) 2777 (13.3) 16 206 (77.6) F 8481 4463 (52.6) 530 (6.2) 931 (11.0) 5924 (69.8) T 29 365 16 634 (56.6) 1788 (6.1) 3708 (12.6) 22 130 (75.4) a M (males), F (females), T (total). b Figures in parentheses are percentages. infection was reduced from 6.1% to 2.5%, and that year (see Table 5). The overall reduction of double of double infections from 12.6% to 1.1%. The prev- infections was greater than 90% in all village coun- alence of single S. mansoni and double infections cils. The reduction of S. mansoni infections in this was highest in males while the prevalence of single school population was only 33.9%. The reduction of S. haematobium infections was highest in females. single S. mansoni infections was least (12.2%) in El A single treatment with praziquantel resulted in Tahrir, the village council with the highest initial a reduction in overall prevalence of 45.8% after one prevalence of single S. haematobium and double Table 2: Prevalence of schistosomiasis infection in schoolchildren at the second survey (October 1984 to May 1985), by sex and council area in Abu El Matameer district, Beheira governorate No. of No. positive for: Council area schools Sexa No. examined S. mansoni S. haematobium Both Total Abu El Matameer 15 M 4846 1195 (24.7) b 3 (0.06) 6 (0.1) 1204 (24.8) town F 2853 522 (18.3) 1 (0.04) 1 (0.04) 524 (18.4) T 7699 1717 (22.3) 4 (0.05) 7 (0.09) 1728 (22.4) Koum El Farag 17 M 4316 2421 (56.1) 3 (0.07) 7 (0.2) 2431 (56.3) F 1338 711 (53.1) 1 (0.07) 1 (0.07) 713 (53.3) T 5654 3132 (55.4) 4 (0.07) 8 (0.1) 3144 (55.6) El Nomariah 13 M 4058 2057 (50.7) 79 (1.9) 142 (3.5) 2278 (56.1) F 1615 772 (47.8) 28 (1.7) 42 (2.6) 842 (52.1) T 5673 2829 (49.9) 107 (1.9) 184 (3.2) 3120 (55.0) Zawiet Sakr 13 M 2947 1615 (54.8) 0 (0.0) 0 (0.0) 1615 (54.8) F 1072 535 (49.0) 0 (0.0) 0 (0.0) 535 (49.0) T 4019 2150 (53.5) 0 (0.0) 0 (0.0) 2150 (53.5) El Tahrir 28 M 5056 1255 (24.8) 428 (8.5) 100 (2.0) 1783 (35.3) F 2983 528 (17.7) 236 (7.9) 31 (1.0) 795 (26.6) T 8039 1783 (22.2) 664 (8.3) 131 (1.6) 2578 (32.1) All areas 86 M 21 223 8543 (40.2) 513 (2.4) 255 (1.2) 9311 (43.9) F 9861 3068 (31.1) 266 (2.7) 75 (0.8) 3409 (34.6) T 31 084 11 611 (37.4) 779 (2.5) 330 (1.1) 12 720 (40.9) a M (males), F (females), T (total). b Figures in parentheses are percentages. WHO Bulletin OMS. Vol 70 199250 Selective population chemotherapy against schistosomiasis in Egypt Table 3: Prevalence of schistosomiasis infection in schoolchildren at the first survey (October 1984 to May 1985), by sex and council area in Abo Homos district, Beheira governorate No. of No. positive for: Council area schools Sexa No. examined S. mansoni S. haematobium Both Total Abo Homos 22 M 6655 2137 (32.1) b 1226 (18.4) 1452 (21.8) 4815 (72.4) town F 3362 858 (25.5) 613 (18.2) 387 (11.5) 1858 (55.3) T 10 017 2995 (29.9) 1839 (18.4) 1839 (18.4) 6673 (66.6) Gawad Hosny 13 M 3591 1670 (46.5) 351 (9.8) 952 (26.5) 2973 (82.8) F 1576 675 (42.8) 192 (12.2) 317 (20.1) 1184 (75.1) T 5167 2345 (45.4) 543 (10.5) 1269 (24.6) 4157 (80.5) Koum el Kanater 11 M 3025 877 (29.0) 619 (20.5) 1090 (36.0) 2586 (85.5) F 1022 304 (29.7) 219 (21.4) 262 (25.6) 785 (76.8) T 4047 1181 (29.2) 838 (20.7) 1352 (33.4) 3371 (83.3) Demissna 13 M 2792 982 (35.2) 529 (18.9) 901 (32.3) 2412 (86.4) F 1528 501 (32.8) 346 (22.6) 346 (22.6) 1193 (78.1) T 4320 1483 (34.3) 875 (20.3) 1247 (28.9) 3605 (83.4) Boutros 9 M 1563 621 (39.7) 200 (12.8) 541 (34.6) 1362 (87.1) F 452 155 (34.3) 75 (16.6) 160 (35.4) 390 (86.3) T 2015 776 (38.5) 275 (13.6) 701 (34.8) 1752 (86.9) Berket Ghatas 7 M 2564 696 (27.1) 384 (15.0) 1080 (42.1) 2160 (84.2) F 994 224 (22.5) 173 (17.4) 327 (32.9) 724 (72.8) T 3558 920 (25.9) 557 (15.6) 1407 (39.5) 2884 (81.0) Bessintawy 17 M 5040 1631 (32.4) 818 (16.2) 2299 (45.6) 4748 (94.2) F 1940 617 (31.8) 406 (20.9) 762 (39.3) 1785 (92.0) T 6980 2248 (32.2) 1224 (17.5) 3061 (43.8) 6533 (93.6) Balakter 13 M 3086 1136 (36.8) 646 (20.9) 882 (28.6) 2664 (86.3) F 1051 317 (30.2) 275 (26.2) 180 (17.1) 772 (73.5) T 4137 1453 (35.1) 921 (22.3) 1062 (25.7) 3436 (83.1) All areas 105 M 28 316 9750 (34.4) 4773 (16.9) 9197 (32.5) 23 720 (83.8) F 11 925 3651 (30.6) 2299 (19.3) 2741 (23.0) 8691 (72.9) T 40 241 13 401 (33.3) 7072 (17.6) 11 938 (29.7) 32 411 (80.5) a M (males), F (females), T (total). b Figures in parentheses are percentages. infections. The overall reduction in prevalence was higher among females than males (50.4% vs. 43.4%). In Abo Homos. During the first survey in 1985, 40 241 schoolchildren were examined with an over- all prevalence of 80.5% (Table 3). The highest prev- alence of single S. mansoni infections was in the vil- lage council, Gawad Hosny, with the lowest prevalence of S. haematobium infection. In three vil- lage councils with a school population of 14 585 the prevalence of double infections was higher than the prevalence of either of the single infections. Bessintawy village council had the highest overall prevalence (93.6%) and the highest prevalence of double infections (43.8%). After a single treatment with praziquantel 47 183 schoolchildren were examined from 108 schools and the overall prevalence was 30.8% (Table 4). The prevalence of S. mansoni infection was higher than either S. haematobium infection alone or double infections. The village councils with the highest overall prevalence after treatment had the highest prevalence of double infections. The council area with the lowest overall prevalence, Abo Homos town, also had the lowest prevalence of single S. mansoni infections. The overall reduction in prevalence after one year was 61.7% (Table 5). Double infections were reduced by 89.2%. The lowest overall reductions in S. mansoni infections occurred in the schools of the three village councils where the initial prevalence of double infections was higher than either of the single infections. The highest reduction of overall preval- ence and either type of single infection occurred in Abo Homos town. As in Abu El Matameer, the reduction among females was greater than among males for all infections (69.3% vs. 58.8%). Sex ratio. In both Abu El Matameer and Abo Homos, 70% of those examined were males. Although the prevalence of infection was higher in Abo Homos than in Abu El Matamee, there were several important epidemiological similarities: among the schoolchildren, in decreasing order, the prevalence of single S. mansoni infections was highest, followed by double infections and single S. haematobium infections. WHO Bulletin OMS. Vol 70 1992 A. El Malatawy et al. Table 4: Prevalence of schistosomiasis infection in schoolchildren at the second survey (October 1985 to May 1986), by sex and council area in Abo Homos district, Beheira governorate No. of No. positive for: Council area schools Sexa No. examined S. mansoni S. haematobium Both Total Abo Homos 23 M town F T Gawad Hosny 13 M F T Koum el Kanater 11 M F T Demissna 13 M F T Boutros 10 M F T Berket Ghatas 7 M F T Bessintawy 17 M F T Balakter 14 M F T All areas 108 M F T 7191 1060 (14.7) b 489 (6.8) 214 (3.0) 4106 11 297 4163 1944 6107 3364 1291 4655 3242 1839 5081 2143 601 2744 3152 1289 4441 5650 2254 7904 3810 1144 4954 32 715 14 468 47 183 347 (8.4) 1407 (12.4) 1213 (29.1) 395 (20.3) 1608 (26.3) 747 (22.2) 191 (14.8) 938 (20.2) 731 (22.5) 272 (14.8) 1003 (19.7) 604 (28.2) 108 (18.0) 712 (25.9) 821 (26.0) 235 (18.2) 1056 (23.8) 1519 (26.9) 506 (22.4) 2025 (25.6) 924 (24.2) 177 (15.5) 1101 (22.2) 7619 (23.3) 2231 (15.4) 9850 (20.9) 150 (3.6) 639 (5.7) 223 (5.4) 79 (4.1) 302 (4.9) 369 (11.0) 84 (6.5) 453 (9.7) 262 (8.1) 120 (6.5) 382 (7.5) 102 (4.8) 17 (2.8) 119 (4.3) 306 (9.7) 98 (7.6) 404 (9.1) 315 (5.6) 141 (6.3) 456 (5.8) 308 (8.1) 76 (6.6) 384 (7.8) 2374 (7.3) 765 (5.3) 3139 (6.7) 39 (0.9) 253 (2.2) 137 (3.3) 33 (1.7) 170 (2.8) 142 (4.2) 20 (1.5) 162 (3.5) 92 (2.8) 27 (1.5) 119 (2.3) 65 (3.0) 6 (1.0) 71 (2.6) 185 (5.9) 47 (3.6) 232 (5.2) 206 (3.6) 49 (2.2) 255 (3.2) 240 (6.3) 23 (2.0) 263 (5.3) 1281 (3.9) 244 (1.7) 1525 (3.2) a M (males), F (females), T (total). b Figures in parentheses are percentages. In both Abu El Matameer and Abo Homos, the prevalence among boys was higher than among girls. The reduction in double infections was higher than the reduction in either single infection or overall prevalence, thus after treatment the prevalence of double infections was less than either of the single infections. Table 5: Percentage reductions in prevalence of schistosomiasis infection in schoolchildren be- tween surveys, by sex, in Abu El Matameer and Abo Homos S. haema- S. mansoni tobium Both Total Abu El Matameer: Males 31.0 60.0 91.0 43.4 Females 40.9 56.4 92.7 50.4 Total 33.9 59.0 91.3 45.8 Abo Homos: Males 32.3 56.8 88.0 58.8 Females 49.7 72.5 92.6 69.3 Total 37.2 61.9 89.2 61.7 Intensity of S. mansoni infection. At the first survey among those with only S. mansoni infection, 10.6% had more than 800 eggs per gram of faeces and one year after treatment the prevalence of infections of this same intensity was only 1.7% or a reduction of 84% (Table 6). After treatment, 66.2% of the remaining infections were less than 100 eggs per gram of faeces as compared with 34.2% before treat- ment. Table 6: Intensity of schistosomiasis infection (eggs per gram of faeces, epg) among children with only S. mansoni in both districts No. No. <100 100-799 .800 Surveya examined positive epg epg epg 1 69 606 30 035 10 257 16 612 3186 (34.2) b (55.3) (10.6) 2 78 267 21 461 14 215 6883 363 (66.2) (32.1) (1.7) a For dates of surveys 1 and 2, see Tables 1 to 4. b Figures in parentheses are percentages of the number posi- tive. WHO Bulletin OMS. Vol 70 1992 1763 (24.5) 536 (13.0) 2299 (20.4) 1573 (37.8) 507 (26.1) 2080 (34.0) 1258 (37.4) 295 (22.8) 1553 (33.4) 1085 (33.5) 419 (22.8) 1504 (29.6) 771 (36.0) 131 (21.8) 902 (32.9) 1312 (41.6) 380 (29.5) 1692 (38.1) 2040 (36.1) 696 (30.9) 2736 (34.6) 1472 (38.6) 276 (24.1) 1748 (35.3) 11 274 (34.5) 3240 (22.4) 14 514 (30.8) 52 Selective population chemotherapy against schistosomiasis in Egypt Table 7: Prevalence of haematuria (assessed visually and by reagent strip test) and S. haematobium (S.h.) infection by filtration in schoolchildren in both districts (including single and mixed infections) No Haematuria (%) 2 50 eggs/ S.h. positive examined Visually Strip test 10 ml (%) (%) Abu El Matameer: Survey 1 a 29 365 5.2 22.5 2.2 18.7 Survey 2 31 084 1.4 3.2 0.07 3.6 Reduction (%) 73.1 85.8 96.8 80.7 Abo Homos: Survey 1 40 241 6.6 15 9.8 47.2 Survey 2 47 183 0.9 1.9 0.8 9.9 Reduction (%) 86.4 87.3 91.8 79.0 Both districts: Survey 1 69 606 6.0 18.1 6.6 35.2 Survey 2 78 267 1.1 2.4 0.5 7.4 Reduction (%) 81.7 86.7 92.4 79.0 a For dates of surveys 1 and 2, see Tables 1 to 4. Haematuria and S. haematobium infection. At the first survey in Abu El Matameer the prevalence of haematuria detected by reagent strips was higher than the prevalence of S. haematobium infection by filtration (Table 7). During the first survey in Abo Homos, the overall prevalence of S. haematobium infection (including haematuria) was 47.2% vs. 18.7% in Abu El Matameer. In both districts, one year after treatment the prevalence of gross haema- turia was reduced from 6.0% to 1.1%. In the same period the overall prevalence of haematuria detected by reagent strips was reduced from 18.1% to 2.4%. The overall prevalence of S. haematobium infection was reduced from 35.2% to 7.4%. The overall rates of gross haematuria and the prevalence of heavy infections (2 50 S. haematobium eggs per 10 ml of urine) were of the same order of magnitude before and after treatment. Community surveys Between 1985 and 1986, 86 512 persons were exam- ined in Abo Homos (31.8% of the total population), and 97 923 persons in Abu El Matameer (66.2% of the total population). The overall prevalence in both communities was 73.5%. In Abu El Matameer the peak prevalence was in the 25-44-year-old age group; in Abo Homos the 15-24-year-old age group was the most affected (Table 8). Among 0-5-year- olds the overall prevalence was nearly twice as high in Abu El Matameer as in Abo Homos. In contrast to the school surveys, the distribution of S. mansoni and S. haematobium infections in the two communities was different in all respects except that the prevalences of both infections (separately and together) were similar between males and females (Table 9). The prevalence of S. mansoni and the proportion of heavy infection (> 800 eggs per gram of faeces) was highest in Abu El Matameer. -The prevalence of S. haematobium was highest in Abo Homos, 1.8% vs. 0.08%. The prevalence of double infections was 9.6% in Abo Homos as com- pared to 0.9% in Abu El Matameer. In the Abu El Matameer communities S. manso- ni was found in 98.2% of those infected; 0.8% were S. haematobium infections and 1.0% were double infections. Among the Abo Homos communities Table 8: Prevalence of schistosomiasis, by age group, in the communities of Abu El Matameer and Abo Homos Abu El Matameer Abo Homos Both districts Age group (years) Examined Positive Examined Positive Examined Positive 0-5 7359 4590 (62.4) a 8578 3102 (36.2) 15 937 7692 (48.3) 6-14 21 327 16 673 (78.2) 27 872 17 913 (64.3) 49 199 34 586 (70.3) 15-24 27 401 24 873 (90.8) 24 636 17 087 (69.4) 52 037 41 960 (80.6) 25-44 26 237 23 902 (91.1) 14 352 9652 (67.3) 40 589 33 554 (82.7) . 45 15 599 11 969 (76.7) 11 074 5732 (51.8) 26 673 17 701 (66.4) Total 97 923 82 007 (83.7) 86 512 53 486 (61.8) 184 435 135 493 (73.5) a Figures in parentheses are percentages. WHO Bulletin OMS. Vol 70 1992 53 A. El Malatawy et al. Table 9: Prevalence of schistosomiasis infection, by sex, in community surveys in Abu El Matameer and Abo Homos S. mansoni S. haematobium No. No. > 50 eggs/ Positive Total Sex examined negative Positive > 800 epga Positive 10 ml for both positive Abu El Matameer: Male 51 684 8084 (15.6) b 42 780 (82.8) 4358 (8.4) 349 (0.7) 46 (0.1) 471 (0.9) 43 600 (84.4) Female 46 239 7832 (16.9) 37 731 (81.6) 3916 (8.5) 297 (0.6) 32 (0.1) 379 (0.8) 38 407 (83.1) Total 97 923 15 916 (16.3) 80 511 (82.2) 8274 (8.4) 646 (0.7) 78 (0.1) 850 (0.9) 82 007 (83.7) Abo Homos: Male 45 216 15 814 (35.0) 21 381 (47.3) 2074 (4.6) 3347 (7.4) 1020 (2.3) 4674 (10.3) 29 402 (65.0) Female 41 296 17 212 (41.7) 18 107 (43.8) 1598 (3.9) 2338 (5.7) 550 (1.3) 3639 (8.8) 24 084 (58.3) Total 86 512 33 026 (38.2) 39 488 (45.6) 3672 (4.2) 5685 (6.6) 1570 (1.8) 8313 (9.6) 53 486 (61.8) Both districts: Male 96 900 23 898 (24.7) 64 161 (66.2) 6432 (6.6) 3696 (3.8) 1066 (1.1) 5145 (5.3) 73 002 (75.3) Female 87 535 25 044 (28.6) 55 838 (63.8) 5514 (6.3) 2635 (3.0) 582 (0.7) 4018 (4.6) 62 491 (71.4) Total 184 435 48 942 (26.5) 119 999 (65.1) 11 946 (6.5) 6331 (3.4) 1648 (0.9) 9163 (5.0) 135 493 (73.5) a Eggs per gram of faeces (epg). b Figures in parentheses are percentages. 73.8% of infections were due to S. mansoni, 10.6% to S. haematobium and 15.5% were double infec- tions. Discussion In this highly endemic area the prevalences before treatment were higher than previously reported (7, 8). In the past S. haematobium was the predomi- nant species in the Nile delta. This study has confirmed the dominance of S. mansoni infection as reported from other areas of the delta (9, 10). Abu El Matameer district is further to the west of the main Nile river channels and S. haematobium is almost absent from this district. This study was designed to assess the effective- ness of chemotherapy using praziquantel in "worst case" conditions which are the rule rather than the exception in most endemic countries. Aside from dif- ferences in the epidemiology of schistosomiasis be- tween endemic countries most control programmes are similar in their lack of coordination of snail control, water supply provision, and sanitation implementation. Thus the following aspects of this operational research activity would be anticipated to mitigate against the effectiveness of praziquantel during the study: - only schoolchildren were treated and this cohort represented only about 70% of school-age boys and 30% of school-age girls; - no coordinated snail control was conducted; - no improvement in sanitation or water supply was initiated; - treatment of the non-school population (adults and children) was incomplete. One year after a single treatment with prazi- quantel the prevalence of schistosomiasis was re- duced by more than 40% in both districts. More sig- nificantly, the prevalence of heavy S. mansoni infec- tions (> 800 eggs per gram of faeces) was reduced by 84%. This reduction was accompanied by a shift in the distribution of the high and medium egg count classes to egg counts below 100 eggs per gram of faeces in those who remained infected. These results are similar to those obtained in other large-scale intervention studies using selective population chemotherapy (3-5). Although in clinical trials the egg-negative rates for S. mansoni infections at 6 months or one year after treatment with praziquantel were consistently about 75-85% and slightly higher for S. haemato- bium infections (1), in large scale interventions these figures have been much lower (4, 11). These differ- ences may be due to constant reinfection, different diagnostic techniques and quality control and timing of chemotherapy in relation to transmission. In operational control programmes a 40% reduction in prevalence at one year is the minimal acceptable reduction. If a lower reduction is reported a detailed review of operational procedures, quality control of microscopy, drug storage and supply, and drug expiration dates is warranted. The reduction in prevalence of S. haematobium was proportionally greater than the reduction of S. mansoni infection. This reduction was such that sub- sequent interventions concentrated on stool examina- tion and urine examinations were not done. During the past 20 years a gradual reduction in the preval- ence of S. haematobium has been noted in the Nile delta. This has been variously attributed to reduction in the Bulinus populations related to perennial irriga- tion and reduced silting after the Aswan dam WHO Bulletin OMS. Vol 70 199254 Selective population chemotherapy against schistosomiasis in Egypt construction; and to emphasis by the Ministry of Health on diagnosis and treatment of S. haemato- bium because of the ease of diagnosis and public recognition of haematuria as a sign of infection. Thus the dramatic reduction in S. haematobium can- not be attributed to praziquantel alone but also to the reduced risk of reinfection. The impact of appropri- ate timing of treatment cannot be evaluated in this study since no transmission variables were assessed. The correlation between the prevalence of gross haematuria and heavy infections, as assessed by microscopy before and after treatment, found in this study confirms observations made elsewhere (11). On the other hand, the correlation between micro- haematuria, as detected by the chemical reagent strips, and the presence of S. haematobium eggs in the urine was inconsistent. The reason for this dis- crepancy is not known but confirms the necessity of evaluating indirect techniques in each endemic area rather than assuming the validity of extrapolation from other areas. The community surveys have shown that the prevalence of infection among adults was higher than among schoolchildren. Treatment was given during the survey and the effect of the single treat- ment was evaluated and is reported elsewhere.a Quality control and adequate supervision have increased the reliability of the results and confidence in allocation of resources based on the data. Fur- thermore the feasibility of reliable data collection, processing and analysis in operational research pro- grammes by minimally trained staff was confirmed (12). Thus, in areas with low prevalence after treat- ment, the interval of re-examination and retreatment can be extended and the use of the rural health units' laboratories to provide diagnosis and treatment on routine consultation can be expected to be sufficient for maintenance of the reduction in prevalence and intensity of infection achieved by the mobile teams. The impact of chemotherapy in this study may have been enhanced by (1) the high coverage of the target school-age population, (2) the timing of treat- ment after the peak of transmission in an area where transmission is definitely seasonal, (3) the treatment of the target population within a short period of time rather than over a long interval, and (4) the high standard of quality control of microscopy which assured reliable diagnosis of the infection. The results of this operational research augur well for the future of large-scale chemotherapy in the control of schistosomiasis. a El-Malatawy, A. An integrated approach to schistosomiasis control. Unpublished document, UNICEF, Cairo, 1989. Note. This project was subsequently independently evaluated and the results 3-5 years after the last treatment confirm those in this short-term report (see Spencer, H.C. et al. Evaluation of UNICEF/Arab Republic of Egypt/WHO Schistosomiasis Control Project in Beheira govemorate. American journal of tropical medicine and hygiene, 42: 441-448 (1990)). Acknowledgements This study was successfully completed because of the dedication and motivation of the health workers in the rural health units of Abu El Matameer and Abo Homos, Beheira governorate. The project was initiated by Mr Rolf Kruger, UNICEF Representative, in response to the expressed needs of the communities concerned, and was continued under his successor, Mr E.J. Lannert. The sup- port of Dr Said El Makaway, Director General of Health, Beheira governorate, and Dr Saleh El Hak, Under- Secretary of Health, Ministry of Health of Egypt, is grate- fully acknowledged. This publication is dedicated to the late Dr Ahmed El Habashy, Chief Medical Officer, Abu El Matameer district, and the late Dr Nagy Lashine, Medical Officer, Abo Homos district. Their personal qualities as public health workers and community leaders were recognized beyond the areas where they worked. They both died while active- ly engaged in the front line of schistosomiasis control; they are sadly missed and we hope that others will follow to continue the fight. Resume Chimiotherapie selective chez des 6coliers du Gouvernorat de Beheira: le projet UNICEF/Republique Arabe d'Egypte/OMS de lutte contre la schistosomiase L'article decrit la methodologie d'intervention et la prevalence et l'intensit6 des infestations a Schistosoma mansoni et a S. haematobium chez les 6coliers de deux districts du Gouvernorat de Beheira dans le Delta du Nil, en Egypte, avant et apres traitement par le praziquantel. Dans le district d'Abu El Matameer, 29 365 enfants (couverture 99%) ont 6te examines dans 83 6coles au cours de l'enquete r6alisee avant traitement; la pr6valence totale de la schistoso- miase due a S. mansoni et/ou a S. haematobium 6tait de 75,4%. Un an apres chimioth6rapie selec- tive, 31 084 enfants ont ete examin6s dans 86 ecoles. La pr6valence totale de la schistosomiase 6tait alors de 40,9% (soit une baisse de 45,8%). A Abo Homos, 40 241 6coliers ont ete exami- n6s lors de 1'enquete avant traitement; la pr6va- lence totale de la schistosomiase 6tait de 80,5%. Un an plus tard, 47 183 ecoliers ont e exami- n6s et la prevalence totale 6tait de 30,8% (soit WHO Bulletin OMS. Vol 70 1992 55 A. El Malatawy et al. une baisse de 61,7%). Lors de la premiere enquete r6alis6e avant traitement chez les ecoliers des deux districts infest6s uniquement par S. mansoni, 10,6% avaient plus de 800 ceufs par gramme de selles. Un an apres le traitement, la pr6valence de ces infestations massives n'6tait plus que de 1,7%, soit une r6duction de 84%. La diminution globale des infestations doubles par S. mansoni et S. haematobium 6tait superieure a 90%. Dans les deux districts, un an apres le traite- ment, la pr6valence de l'hematurie clinique etait pass6e de 6,0% a 1,1%, la pr6valence globale de l'hematurie d6celee par bandelettes r6actives de 18,1% a 2,4%, et la pr6valence de l'infestation a S. haematobium de 35,4% a 7,4%. Lors des enquetes portant sur 1'ensemble de la communaut6, 86 512 personnes ont ete exami- nees a Abo Homos (31,8% de la population tota- le), et 97 923 personnes a Abu El Matameer (66,2% de la population totale). La pr6valence totale de la schistosomiase dans ces deux com- munaut6s 6tait de 73,5%. Dans cette 6tude, l'impact de la chimioth6ra- pie peut avoir ete renforc6 par: 1) la forte couver- ture de la population cible d'age scolaire, 2) le moment du traitement, apres le pic de transmis- sion dans une r6gion ou la transmission est net- tement saisonniere, 3) le traitement de la popula- tion cible sur une courte p6riode plut6t que sur une p6riode 6tendue, et 4) le niveau 6leve de contr6le de la qualit6 de l'examen microscopique, qui garantissait un diagnostic fiable de l'infesta- tion. Nous concluons que les r6sultats de cette recherche op6rationnelle augurent favorablement des op6rations de chimioth6rapie a grande echel- le dans la lutte contre la schistosomiase. References 1. WHO Technical Report Series No. 728, 1985 (The control of schistosomiasis: report of a WHO Expert Committee). 2. Kardaman, M.W. et al. Treatment with praziquantel of schoolchildren with concurrent Schistosoma man- soni and S. haematobium infections in Gezira, Sudan. Journal of tropical medicine and hygiene, 88: 105-108 (1985). 3. Gryseels, B. et al. The relevance of schistosomia- sis for public health. Tropical medicine and parasito- logy, 40: 134-142 (1989). 4. Gryseels, B. et al. Two-year follow-up of Schistosoma mansoni infection and morbidity after treatment with different regimens of oxamniquine and praziquantel. Transactions of the Royal Society of Tropical Medicine and Hygiene, 83: 219-228 (1989). 5. Etard, J.F. et al. Schistosoma haematobium infec- tion in Mauritania: two years of follow-up after a tar- geted chemotherapy - a life-table approach of the risk of reinfection. Parasitology, 100: 399-406 (1 990). 6. Farooq, M. & Nielsen, J. The epidemiology of Schistosoma haematobium and S. mansoni infec- tions in the Egypt-49 project area. 1. Sampling tech- niques and procedures for measuring the preval- ence of bilharziasis. Bulletin of the World Health Organization, 35: 281-291 (1966). 7. Doumenge, J.P. et al. Atlas of the global distribu- tion of schistosomiasis. Talence, Presses Univer- sitaires de Bordeaux, 1987, p. 47. 8. Kessler, P.N. et al. Report of an independent eva- luation mission on the National Bilharzia Control Program in Egypt, 1985 (abridged version). Trans- actions of the Royal Society of Tropical Medicine and Hygiene, 81 (Suppl.): 1-57 (1987). 9. El Alamy, M.A. & Cline, B.L. Prevalence and inten- sity of Schistosoma haematobium and S. mansoni infection in Qalyub, Egypt. American journal of tropi- cal medicine and hygiene, 26: 463-469 (1977). 10. Abdel Wahab, M.F. et al. Changing patterns of schistosomiasis in Egypt 1935-1979. Lancet, 2: 242-244 (1979). 11. Savioli, L. et al. Control of morbidity due to Schistosoma haematobium on Pemba island: use of selective population chemotherapy in schools to identify high-risk localities. Transactions of the Royal Society of Tropical Medicine and Hygiene, 83: 805-810 (1989). 12. Dixon, H.G. Data management in schistosomiasis control programmes. Tropical medicine and parasi- tology, 38: 209-215 (1986). 56 WHO Bulletin OMS. Vol 70 1992