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Am. J. Trop. Med. Hyg., 62(2)S, 2000, pp. 35–41 Copyright 䉷 2000 by The American Society of Tropical Medicine and Hygiene

THE EPIDEMIOLOGY OF SCHISTOSOMIASIS IN EGYPT: ISMAILIA GOVERNORATE Z. M. NOOMAN, A. H. HASAN, Y. WAHEEB, A. M. MISHRIKY, M. RAGHEB, A. N. ABU-SAIF, S. M. ABAZA, A. A. SERWAH, A. EL-GOHARY, A. SAAD, M. EL-SAYED, AND M. FOUAD Departments of Medicine, Community Medicine, Radiology, Parasitology, and Clinical Pathology, and Clinical Epidemiology Unit, Faculty of Medicine, Suez Canal University, Ismailia, Egypt

Abstract. A multi-stage stratified sample of 12,515 individuals from 1,941 households in 42 villages in the Ismailia governorate of Egypt were surveyed for schistosomal infection. A subset of 2,390 subjects were surveyed for morbidity by physical and ultrasonographic examination. The prevalence of Schistosoma mansoni infection in rural Ismailia was 42.9% and the geometric mean egg count (GMEC) was 93.3 eggs/gram of stool, with considerable variability between communities. Prevalence and intensity peaked in the 20–30-year-old age group and was higher in males than in females. Prevalence and intensity of S. haematobium was very low: 1.8% and 3.5 ova/10 ml of urine GMEC, respectively. Canal water exposure risk factors for S. mansoni infection were males bathing (odds ratio [OR] ⫽ 2.2), females washing clothes (OR ⫽ 1.9), and children playing or swimming (OR ⫽ 2.3). Presence of inhouse piped water supply and latrine lowered infection rates (P ⬍ 0.001 and P ⫽ 0.002, respectively). Histories of S. mansoni infection (OR ⫽ 1.6) or treatment (OR ⫽ 1.5) and blood in feces (OR ⫽ 3.5) were associated with infection. Hepatomegaly (16.0%) was more frequently detected than splenomegaly (3.6%) by physical examination, with both being more frequent in older age groups. Splenomegaly, but not hepatomegaly, was associated with presence of S. mansoni ova in stools (OR ⫽ 1.4) and the community burden of infection (P ⫽ 0.02). Ultrasonographically detected hepatomegaly, splenomegaly, and periportal fibrosis (PPF) were detected in 43.0%, 17.4%, and 39.7% of the subjects, respectively. The higher grades of PPF were rare. Ultrasonographically detected splenomegaly, not hepatomegaly, was associated with S. mansoni infection, community burden of infection, and PPF. Risk factors for PPF were the same as for S. mansoni infection. There was a marginal association of PPF with infection and none (P ⫽ 0.33) with the intensity of infection in individuals or in the community. We conclude that in rural Ismailia, S. haematobium infection is rare but the prevalence and intensity of infection with S. mansoni is high. The risk of infection is associated with environmentally detected factors and behaviors. Hepatosplenic morbidity attributable to S. mansoni infection is low, presumably because of the favorable effect of wide application of praziquantel therapy. The Schistosomiasis Research Project-supported Epidemiology 1, 2, 3 (EPI 1, 2,3) Project’s goals were to provide epidemiologic information about schistosomiasis in Egypt to assist the Egyptian Ministry of Health to more effectively control schistosomiasis in the country.1 The EPI 1, 2, 3 project had three objectives: 1) to measure the prevalence and intensity of infection and study the changing pattern of Schistosoma haematobium and S. mansoni transmission in 9 representative governorates, 2) to identify factors causing variation in prevalence and intensity of schistosomiasis among villages; and 3) to describe the public health impact of schistosomiasis morbidity and identify its determinants. The use of abdominal ultrasonography to study randomly selected subjects provided much of the data for the third objective. Reported herein are the results from Ismailia governorate, which is situated mostly on the west side of the Suez Canal in the eastern part of the Nile Delta, as shown in Figure 1 of Hussein and others in this series.2 The rural inhabitants, representing 53% of the total population of 544,000 individuals according to the 1986 census, represent 0.9% of the rural population in Egypt. The main source of drinking and irrigation water is the Ismailia Canal, which branches from the Nile River. Certain geographic and demographic features differentiate Ismailia governorate from the prevailing pattern in the Delta and Upper Egypt. Partly agricultural and partly desert, it lacks the usual compact village structure prevalent in the Nile Valley. Instead, most villages are small hamlets (ezbas), each consisting of 100–200 households. The population is rather heterogeneous, having moved from various regions during the digging of the Suez Canal.

SUBJECTS AND METHODS

The sample selection, designed to achieve the objectives, was made by multi-stage probability selection.2 Children less than 5 years old were excluded from these studies by protocol. However, this exclusion was not absolute. The total sample was 12,515 individuals from 1,941 households in 3 villages and 39 ezbas. Physical and ultrasonographic examinations was performed upon 2,390 subjects living in 400 households. The interview technique for collecting sociodemographic, environmental, and medical data has been described in detail.2 Quantitative microscopic counting of Schistosoma ova in stool using a modified Kato technique and urine using the Nuclepore (Pleasanton, CA) filter technique was performed as described.3 Physical and ultrasonographic examinations were performed by specially trained physicians.4 Risk factors for infection were evaluated according to whether S. mansoni was present in the stool. Risk factors for morbidity were evaluated according to whether periportal fibrosis (PPF) was detected during abdominal ultrasonography. The burden of S. mansoni in communities was calculated by using the mean log(x ⫹ 1) transformed ova count of the community sample. Special data forms were developed in Arabic and English to enter data on microcomputers using Epi-Info 5.01b (Centers for Disease Control and Prevention, Atlanta, GA). After checking and correcting the data files, analysis was performed using Survey Data Analysis (SUDAAN) software.2 Further analysis was performed after transformation to SPSS/PC ⫹ 4.01 (SPSS, Inc., Chicago, IL). This software was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs).

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TABLE 1 Odds ratio and 95% confidence limits for risk factors or markers for infection with Schistosoma mansoni in Ismailia Governorate* Risk factor

Demographics Age groups (years) 0–10 11–20 21–35 36–55 ⬎55

Total in group

Infected No. (%)

Odds ratio

Confidence limits

2,504 2,095 1,709 1,098 381

855 1,128 811 406 152

(34.1) (53.8) (47.5) (37.0) (39.9)

2.25 1.74 1.13 1.28

2.00–2.53 1.54–1.98 0.98–1.31 1.03–1.60

Gender Female Male

4,035 3,755

1,457 (36.1) 1,897 (50.5)

1.81

1.65–1.98

Domicile Village (ⱖ500 houses) Ezba (⬍500 houses)

1,198 6,592

229 (19.1) 3,125 (47.4)

3.81

3.28–4.44

1,840 1,543

759 (41.3) 941 (61.0)

2.23

1.94–2.56

Washing (females) No Yes

2,276 1,556

685 (30.1) 691 (44.4)

1.86

1.62–2.12

Playing (children ⬍15 years old) No Yes

1,780 1,520

531 (29.8) 759 (49.9)

2.35

2.03–2.71

3,935 2,311

1,493 (37.9) 1,133 (49.0)

1.57

1.42–1.75

Prior treatment of schistosomiasis No Yes

4,754 2,286

1,874 (39.4) 1,115 (48.8)

1.46

1.32–1.62

History of blood in stools No Yes (total) ⬍15 years ⱖ15 years

6,157 707 270 437

2,518 441 182 259

(40.9) (62.4) (67.4) (59.3)

2.40 3.49 1.83

2.04–2.81 2.68–4.55 1.49–2.24

History of abdominal pain No Yes ⬍15 years ⱖ15 years

4,889 1,959 826 1,133

2,142 808 327 481

(43.8) (41.2) (39.6) (42.5)

0.90 0.99 0.81

0.81–1.00 0.84–1.17 0.70–0.93

Hepatomegaly in MCL (by PE) No Yes ⬍15 years ⱖ15 years

6,543 1,247 440 807

2,791 563 194 369

(42.7) (45.1) (44.1) (45.7)

1.11 1.25 0.99

0.98–1.25 1.02–1.53 0.85–1.16

Splenomegaly (by PE) No Yes ⬍15 years ⱖ15 years

6,632 237 52 185

2,835 120 29 91

(42.7) (50.6) (55.8) (49.2)

1.37 1.94 1.03

1.06–1.78 1.12–3.37 0.80–1.33

Ultrasonography Hepatomegaly in MCL No Yes ⬍15 years ⱖ15 years

1,029 686 293 393

440 324 140 184

(42.8) (47.2) (47.8) (46.8)

1.20 1.45 1.03

0.99–1.45 1.08–1.96 0.80–1.33

Exposure to canal water Bathing (males) No Yes

Clinical findings History of schistosomiasis No Yes

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TABLE 1 Continued Risk factor

Total in group

Infected No. (%)

Odds ratio

Confidence limits

Hepatomegaly in MSL No Yes ⬍15 years ⱖ15 years

1,350 364 153 211

586 178 78 100

(43.4) (48.9) (51.0) (47.4)

1.25 1.56 1.05

0.99–1.57 1.09–2.23 0.78–1.43

Splenomegaly No Yes ⬍15 years ⱖ15 years

1,403 314 61 253

584 182 34 148

(41.6) (58.0) (55.7) (58.5)

1.93 1.81 1.93

1.51–2.48 1.07–3.07 1.44–2.58

Periportal fibrosis No Yes (ⱖ3 mm) ⬍15 years ⱖ15 years Grade I (3–⬍5 mm) Grade II (5–⬍7 mm) Grade III (⬎7 mm)

1,011 666 137 529 618 44 4

424 331 70 261 306 21 4

(41.9) (49.7) (51.1) (49.3) (49.5) (47.7) (100.0)

1.37 1.49 1.29 1.36 1.26

1.12–1.67 1.02–2.16 1.00–1.67 1.11–1.66 0.69–2.31

* MCL ⫽ midclavicular line; PE ⫽ physical examination; MSL ⫽ midsternal line.

RESULTS

Epidemiologic findings. Of 12,515 individuals surveyed, adequate data on stool examination were available from 7,790 subjects, with a dropout rate of 36.0%. A better response was obtained in clinical and ultrasound examination, where the response rate was 91.0%. The overall prevalence of S. mansoni infection in the study population was 42.9%, ranging from 12.3 to 71.3%, in the 42 communities. The overall intensity of infection (geometric mean egg count [GMEC]) in the governorate was 93.3 eggs/gram of stool, ranging from 44.7 to 168.3 (Figure 1). The OR of infection in those living in smaller communities in comparison with larger communities was 3.8 with a 95% CI of 3.3–4.4 (Table 1). When results of all communities were pooled, the age- and sex-related prevalence and intensity of S. mansoni infection followed the classical pattern of a rapid increase to a peak in those 11–20 years old and remained high in older age groups (Figure 2). Males showed a higher (OR ⫽ 1.8) prevalence of infection than females in all age groups, 50.5% and 36.1%, respectively (Table 1 and Figure 2). Infection with S. haematobium was detected in only 1.8% (range ⫽ 0–9.9%) of the population and the GMEC was 3.5 ova/10 ml of urine, ranging from 1 to 501. Infection with S. haematobium was not analyzed further in this report. Exposure to canal water was associated with a higher risk TABLE 2 Relationship of some environmental characteristics of dwellings with the presence of Schistosoma mansoni infection in at least 1 member of the household Characteristic

Tap in Zereeba Latrine

Frequency

r

P

33.0% 57.8% 90.1%

⫺0.597 0.459 ⫺0.474

⬍0.001 0.003 0.002

for S. mansoni infection, i.e., bathing for males (OR ⫽ 2.2), washing clothes and utensils for females (OR ⫽ 1.9), and playing or swimming in canal water in children ⬍15 years old (OR ⫽ 2.3; Table 1). Environmental factors related to certain characteristics of the dwelling were studied as risk factors for infection by S. mansoni (Table 2). There was a negative correlation between presence of piped water in the house and the number of houses in that community with at least one member of the household infected with S. mansoni (r ⫽ ⫺0.60, P ⬍ 0.001). Only 33% of the houses had a piped water supply for domestic use. The presence of a latrine inside the house also showed a negative correlation with infection (r ⫽ ⫺0.47, P ⫽ 0.002). Lodging farm ani-

FIGURE 1. Prevalence and intensity of Schistosoma mansoni infection in 42 communities in Ismailia Governorate. The solid bars represent the mean prevalence of infection in villages, the hatched bars represent prevalences in individual ezbas, the asterisks represent the mean intensity of infection in geometric mean egg count in each community, the solid vertical line represents the mean prevalence for all 42 communities, and the dashed vertical line represents the mean intensity of infection.

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TABLE 3 Odds ratio and 95% confidence limits for risk factors for morbidity as shown by periportal fibrosis with Schistosoma mansoni in Ismailia Governorate* Risk factor

Demographics Age groups (years) 0–10 11–20 21–35 36–55 ⬎55

Total in group

630 579 475 317 89

Morbidity No. (%)

73 221 265 191 55

Odds ratio

Confidence limits

(11.6) (38.2) (55.8) (60.3) (61.8)

4.71 9.63 11.57 12.34

3.50–6.33 7.11–13.05 8.30–16.12 7.54–20.19

Gender Female Male

1,092 999

381 (34.9) 424 (42.4)

1.38

1.15–1.64

Domicile Village (ⱖ500 houses) Ezba (⬍500 houses)

276 1,815

79 (28.6) 726 (40.0)

1.66

1.26–2.19

475 433

173 (36.4) 196 (45.3)

1.44

1.11–1.88

Washing (females) No Yes

586 440

174 (29.7) 180 (40.9)

1.64

1.26–2.13

Playing (children ⬍15 years old) No Yes

437 403

75 (17.2) 68 (16.9)

0.98

0.68–1.40

(36.3) (43.8) (44.6) (43.0)

1.37 1.41 1.32

1.12–1.67 1.11–1.80 1.03–1.69

1,017 691

305 (30.0) 343 (49.6)

2.30

1.88–2.81

Prior treatment of schistosomiasis No Yes

1,211 682

368 (30.4) 340 (49.9)

2.28

1.88–2.76

History of blood in stools No Yes ⬍15 years ⱖ15 years

1,712 225 88 137

635 106 17 89

(37.1) (47.1) (19.3) (65.0)

1.51 1.14 1.67

1.14–2.00 0.65–1.99 1.15–2.43

History of abdominal pain No Yes (total) ⬍15 years ⱖ15 years

1,307 621 247 374

506 231 40 191

(38.7) (37.2) (16.2) (51.1)

0.94 0.88 0.83

0.77–1.14 0.59–1.31 0.64–1.06

Hepatomegaly in MCL (by PE) No Yes ⬍15 years ⱖ15 years

1,737 354 112 242

656 149 17 132

(37.8) (42.1) (15.2) (54.5)

1.20 0.83 1.02

0.95–1.51 0.48–1.44 0.77–1.36

Splenomegaly (by PE) No Yes ⬍15 years ⱖ15 years

1,855 83 18 65

693 48 4 44

(37.4) (57.8) (22.2) (67.7)

2.30 1.35 1.84

1.47–3.59 0.44–4.18 1.08–3.14

Exposure to canal water Bathing (males) No Yes

Parasitologic findings S. mansoni infection No Yes ⬍100 ova/gram of stool ⱖ100 ova/gram of stool Clinical findings History of schistosomiasis No Yes

922 755 392 363

335 331 175 156

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TABLE 3 Continued Risk factor

Total in group

Morbidity No. (%)

Odds ratio

Confidence limits

Ultrasonography Hepatomegaly in MCL No Yes ⬍15 years ⱖ15 years

1,190 899 378 521

473 332 52 280

(39.7) (36.9) (13.8) (53.7)

0.89 0.63 0.97

0.74–1.06 0.44–0.90 0.77–1.22

Hepatomegaly in MSL No Yes ⬍15 years ⱖ15 years

1,620 467 185 282

622 181 30 151

(38.8) (38.8) (16.2) (53.5)

1.02 0.89 0.97

1.82–1.25 0.58–1.38 0.74–1.27

Splenomegaly No Yes ⬍15 years ⱖ15 years

1,707 384 72 312

530 275 38 237

(31.0) (71.6) (52.8) (76.0)

5.60 6.64 3.64

4.39–7.15 4.02–10.97 2.72–4.88

* MCL ⫽ midclavicular line; PE ⫽ physical examination; MSL ⫽ midsternal line.

mals in the house, i.e. presence of a Zereeba inside or attached to the house correlated with an increased prevalence of houses harboring infected persons (r ⫽ 0.46, P ⫽ 0.003). Clinical findings. Our interview data revealed an association between prior history of schistosomiasis (OR ⫽ 1.6) and prior treatment (OR ⫽ 1.5) and the presence of infection (Table 1). A history of blood in the stools was associated with S. mansoni ova (OR ⫽ 2.4). This association was more obvious in children (OR ⫽ 3.5). There was no association between a history of abdominal pain and infection with S. mansoni. Hepatomegaly detected by physical examination was present in 1 of every 6 of our study population; splenomegaly was less commonly detected (3.6%). Both findings were agerelated, being detected more frequently in older age groups. The prevalence of hepatomegaly in the community as detected by physical examination was not associated with the presence of S. mansoni ova in stools (OR ⫽ 1.1; Table 1),

FIGURE 2. Age (years)- and gender-adjusted prevalence and intensity of Schistosoma mansoni infection in Ismailia Governorate. GMEC ⫽ geometric mean egg count.

or correlated with the community burden of infection (r ⫽ 0.24, P ⫽ 0.06). Splenomegaly, on the other hand, was associated with the presence of S. mansoni ova in the stools (OR ⫽ 1.4; Table 1). Ultrasonographic findings. Abdominal ultrasonography demonstrated a high prevalence of hepatomegaly, splenomegaly, and PPF in our subjects. Hepatomegaly was measured in both the midclavicular and midsternal lines. Enlargement of the right and left lobes of the liver was demonstrated in 43.0% and 22.4% of the subjects, respectively. Splenomegaly was detected in 17.4% of the subjects. Periportal fibrosis, predominantly of grade I, was demonstrated in 39.7% of the subjects. Grades II (2.6%) and III (0.2%) were much less frequently encountered. The prevalence of these parameters increased with age (Figure 3). Males were slightly more likely to exhibit PPF than females (OR ⫽ 1.4; Table 3). Ultrasonographically detected splenomegaly

FIGURE 3. Age (years)-adjusted prevalence of ultrasound-detected right (midclavicular line [MCL]) and left (midsternal line [MSL]) lobe hepatomegaly, splenomegaly, and periportal fibrosis (PPF) in Ismailia Governorate.

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showed consistent associations with S. mansoni ova in stools (OR ⫽ 1.9), with ultrasonographically detected PPF (OR ⫽ 5.6; Table 3), and with the community burden of S. mansoni infection (r ⫽ 0.30, P ⫽ 0.04). The relationship of splenomegaly with PPF was greater in children than in adults (Table 3). However, ultrasonographically detected hepatomegaly of either lobes of the liver was not significantly associated with presence of S. mansoni infection, the intensity of infection, or PPF (Table 3). Some of the risk factors associated with S. mansoni infection were also associated with ultrasonographically detected PPF, e.g., exposure to canal water by males for bathing, or by females for washing clothes or utensils, a history of schistosomiasis, or prior treatment for schistosomiasis (Table 3). Periportal fibrosis was slightly more frequently (OR ⫽ 1.4) encountered in those infected with S. mansoni than in noninfected individuals. This association was more evident in children than in adults ⬎15 years old (Table 3). However, there was no correlation between detection of PPF and the intensity of infection in individuals (Table 3) and in communities (r ⫽ 0.074, P ⫽ 0.33). DISCUSSION

Our data indicated a rather high burden of S. mansoni infection among the rural population of Ismailia governorate with a prevalence of 43% and an average intensity of infection of almost 100 eggs/gram of stool. Pertinent to the interpretation of this observation, as well as of the influence of some of the risk factors, is the understanding of certain historical and geographic features peculiar to the Suez Canal region and its inhabitants. From the early 1950s through the late 1970s, this region was the seat of several military actions that had a devastating effect on the overall development of the region and led to mass emigration and evacuation of the inhabitants to the Nile valley. These events could have affected the epidemiologic features of schistosomiasis in several ways: 1) during their emigration to the high prevalence areas, mostly in the neighboring Nile Delta, the inhabitants were exposed to infection; and 2) there was a prolonged halt in the environmental and socioeconomic development of the region. This disruption of the infrastructure of the region has impacted upon living standards, e.g., only 33% of our surveyed dwellings had piped water in-house (Table 2). Our study is the first population-based survey of schistosomal infection in Ismailia governorate. In Sharkia governorate, bordering Ismailia, the overall prevalence of S. mansoni infection among the rural population in 1983 was reported to be 26%.5 A prevalence of 62% was reported in Abu-Hammad district, the nearest to Ismailia. More recently, the prevalence of S. mansoni infection was reported to be 21% and 38% in two rural communities in Ismailia in 1985 and 1989, respectively (Mousa IE, El-Zallat H, M.Sc. Theses, Faculty of Medicine, Suez Canal University). These fall within the range of a prevalence of 12–71% for S. mansoni reported in our communities. Our results indicate that our study population shared the phenomenon of the ‘‘fading away’’ of S. haematobium infection with the inhabitants of the Nile Delta region since the overall prevalence of infection with that species was less than 2%.5,6 Almost half of

our communities had no S. haematobium infection. In the two surveys conducted in two rural communities in Ismailia, the prevalence of S. haematobium infection was 15% and 3.6%, respectively (Mousa IE, El-Zallat H, unpublished data). Our findings also support the previously reported impact of environmental factors on the transmission of schistosomiasis.7 The prevalence of S. mansoni infection was considerably higher among inhabitants of small ezbas than in dwellers of larger communities. These larger villages are semi-urban communities with relatively better housing conditions than those prevailing in the small scattered hamlets where most rural inhabitants of Ismailia live. There were no differences in age or gender distributions between inhabitants of villages or ezbas. Further indication of the significance of housing characteristics in influencing the transmission of S. mansoni was demonstrated by the negative correlation of a protected water supply (water tap) in the dwelling and the probability of its inhabitants being infected with S. mansoni. Presumably linked with the latter observation is the well-known fact, again demonstrated by our investigation, that exposures to canal water during daily activities are risk factors for schistosomal infection.8 Rural inhabitants, therefore, frequent the canals for daily activities, becoming infected, largely out of their basic needs and a lack of convenient water supply in their homes. Previous studies indicated that knowledge about modes of transmission or complications of schistosomiasis had no effect upon prevalence or intensity of infection in the community.9 No significant effect of the level of education on prevalence of S. mansoni was observed in our study. All of these indicators point to the importance of environmental factors on the transmission of S. mansoni in Ismailia and provide support for improvement of sanitation and provision of a convenient protected water supply. A history of blood in stools was the only symptom associated, more in children than in adults, with S. mansoni infection among our subjects. Such an association has consistently been reported in community-based studies of S. mansoni in Egypt,7 Puerto Rico,9 and Zambia.10 The prevalence of hepatomegaly detected by physical examination approaches the 18% overall prevalence demonstrated in 1978 by clinical examination of 2,866 unselected subjects in five villages in Qalyub governorate (El-Alamy MA, cited in Pope and others11). This can be compared with a 27% prevalence of hepatomegaly in a survey of 537 inhabitants of a village in the center of the Nile Delta with a high (74%) prevalence of S. mansoni infection.7 Whereas hepatomegaly was reported to be associated with intensity of infection in some community-based studies in Africa,10 this relationship was evident only in younger members of a population in Egypt,12 and was not present in our study. In their evaluation of schistosomal morbidity, Pope and others conducted a hospital-based clinical study of 77 subjects selected on the basis of an egg count ⱖ100 eggs/gram of stool from Qalyub (Southern Delta).11 Hepatomegaly was present in only 26% of the subjects and they concluded that ‘‘despite the high intensity of S. mansoni, the degree of morbidity was not striking’’. Assessment of the prevalence of hepatomegaly in the community as an indicator of morbidity attributable to S. mansoni should take into consideration several confounding factors. In Egypt, histopathologic studies

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have demonstrated a progressive decrease in the percentage of chronic liver disease attributable to schistosomiasis from 71% in 1948,12 and 60% in 196313 to 16.6 in 1983 (Kamel I, Department of Pathology, Cairo University, unpublished data). Ismailia governorate has been included in the National Schistosomiasis Control Project since 1988 and praziquantel is freely dispensed to all individuals with detected schistosome ova in their urine or stools since that time. This clearly would reduce community morbidity due to schistosomiasis. Our ultrasonographic findings reach the same conclusions as those arrived at from physical examinations despite the obvious superiority of ultrasonography as a measure of liver and spleen size and its provision of data related to the liver pathology and portal circulation. There was no association between enlargement of liver and either prevalence or intensity of infection in the community. Splenomegaly, detected by ultrasonography five times as frequently as by physical examination, was consistently associated with both the prevalence and intensity of S. mansoni in individuals and in communities. Splenomegaly, therefore, as detected by either physical examination or ultrasonography, was a more reliable indicator of morbidity attributable to S. mansoni infection than measurement of liver size. This might be due to the relative ease of estimating splenomegaly and by the fact that whether it is caused by reticuloendothelial hyperplasia and/or portal hypertension, the spleen would only grow in size in chronic schistosomiasis, unlike the variation in the liver size in the different stages of hepatic pathology. Periportal fibrosis, as measured as intrahepatic portal tract thickening (PPT) of 3 mm or more, was present in more than 40% of our study population. Less than 3%, however, had the higher grades of PTT. The specificity of PTT as a measure of bilharzia PPF has only been conclusively demonstrated in the more severe grades by wedge liver biopsies from hospitalized patients undergoing surgery to relieve portal hypertension.14,15 There have been several reports that grade I PTT is not specific for schistosomiasis. However, community-based studies from Egypt16 and Brazil (Rocha R and others, Fourth International Conference on Schistosomiasis, FIOCRUZ, Rio de Janeiro, Brazil, unpublished data) have suggested the specificity of grade I PTT for schistosomal hepatic fibrosis may be poor. As measured in our study, PTT was slightly more frequent in individuals passing ova in their stools than in those with negative stool examinations, and there was no correlation between PPF and intensity of infection in the community.

Acknowledgments: We acknowledge the cooperation and support of the Administration and Secretariat of the Schistosomiasis Research Project and the assistance of Dr. G. Thomas Strickland in preparing and editing this manuscript. Dr. Nabiel N. H. Mikhail performed the analysis reported in Tables 1 and 3 and prepared the illustrations under the supervision of Dr. Mohamed H. Hussein. Financial support: This research was supported by the Egyptian Ministry of Health/Unite States Agency for International Developmentfunded Schistosomiasis Research Project, 263-0140.2, grants no. 0204-017 and 12-01-95.

Authors’ address: Z. M. Nooman, A. H. Hasan, Y. Waheeb, A. M. Mishriky, M. Ragheb, A. N. Abu-Saif, S. M. Abaza, A. A. Serwah, A. El-Gohary, A. Saad, M. El-Sayed, and M. Fouad, Faculty of Medicine, Suez Canal University, Ismailia, Egypt. Reprint requests: Schistosomiasis Research Project, Medical Services Corporation International, 1716 Wilson Boulevard, Arlington, VA 22209. REFERENCES

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