The epidemiology of schistosomiasis in Egypt: Summary findings in nine governorates

Health questionnaires and parasitologic examinations of urine and stool wer e evaluated from a stratified random sample of 89,180 individuals from 17,1 72 households in 251 rural communities in 9 governorates of Egypt to invest igate the prevalence of, risk factors for, and changing pattern of infectio n with Schistosoma sp, in Egypt. A subset, every fifth household, or 18,600 subjects, had physical and ultrasound examinations to investigate the prev alence of and risk factors for morbidity. Prevalence of S. haematobium in 4 governorates in Upper Egypt in which it is endemic ranged from 4.8% to 13. 7% and averaged 7.8%. The geometric mean egg count (GMEC) ranged from 7.0 t o 10.0 ova/ 10 ml of urine and averaged 8.1. Age stratified prevalence of i nfection peaked at 15.7% in the 10-14-year-old age group and decreased to 3 .5-5.5% in all groups more than 25 years of age. Age-stratified intensity o f infection peaked at approximately 10.0 ova/10 ml of urine in the 5-14-yea r-old age groups and was about half that in all,groups more than 25 years o f age. Males had higher infection rates and ova counts than females in all age groups. Schistosoma mansoni was rare in Upper Egypt, being consequentia l in only Fayoum, which had a prevalence of 4.3% and an average intensity o f infection of 44.0 ova/g of stool. Risk factors for S. haematobium infecti on were male gender an age <21 years old, living in smaller communities, ex posures to canal water; a history of, or treatment for schistosomiasis, a h istory of burning micturition or blood in the urine, and reagent strip-dete cted hematuria or proteinuria. The more severe grades (II and III) of ultra sonography-detected periportal fibrosis (PPF) were rare (15 of 906) in thes e schistosomiasis haematobia-endemic governorates. Risk factors for morbidi ty (ultrasonography-detected urinary bladder wall lesions and/or obstructiv e uropathy) were similar to those for infection, with the exception that ri sk progressively increased with age. Subjects with active S. haematobium in fections were 3 times as likely as those without active S. haematobium infe ctions to have urinary tract morbidity. The prevalence of S. mansoni in 5 g overnorates in Lower Egypt, where it is endemic, ranged from 17.5% to 42.9% and averaged 36.4%. The GMEC ranged from 62.6 to 93.3 eggs/g of stool and averaged 81.3. Age-stratified prevalence of infection peaked at 48.3% in th e 15-19-year-old age group, but averaged 35-45% in all groups more than 10 years of age. The intensity of infection was highest in the 10-14-year-old age group, and showed a range of 70-85 eggs/g of stool in those greater tha n or equal to 5 years of age. Males had higher infection rates and ova coun ts than females in all age groups. Schistosoma haematobium was rare in thes e governorates; Ismailia (1.8%) had the highest infection rate. Risk factor s for S. mansoni were male gender an age >10 years old, living in smaller c ommunities, exposures to canal water, a history of, or treatment for, schis tosomiasis or blood in the stool, detection of splenomegaly by either physi cal examination or ultrasonography, and ultrasonograghy-detected PPF The mo re severe grades (II and III) accounted for 463 (13.3%) of the 3,494 having ultrasonography-detected PPF. Risk factors for morbidity (ultrasonography- detected PPF) were similar to those for infection except that inhabitants o f smaller communities were not at increased risk. Active S. mansoni infecti on increased the odds ratio (OR) of having PPF by 1.37. In comparison with others with normal-size livers, subjects having hepatic enlargement in eith er the midclavicular line or the midsternal line detected by physical exami nation or ultrasonography had a reduced risk (ORs = 0.64-0.72) of PPF. The prevalences of lesions detected by ultrasonography were 23.7% for enlar gement of light lobe of the liver, 11.3% for enlargement of left hepatic lo be, 20.6% for splenomegaly, and 50.3% for PPF Schistosoma mansoni has almos t totally replaced S. haematobium in Lower Egypt and is spreading into Fayo um in Upper Egypt. The prevalence of S. mansoni in the Nile Delta remains h igh with moderate average intensities of infection in rural communities. He patic morbidity was less than expected and, with the exception of splenomeg aly, correlated poorly with active S. mansoni infections in individuals or in communities. The prevalence and intensity of infection with S. haematobi um was low in endemic Upper Egypt governorates. The prevalence of bladder a nd upper urinary tract morbidity were low but correlated with active infect ion. Hepatomegaly, splenomegaly, and PPF were common findings in rural comm unities in Egypt. They occurred 1.5-3.5 times as frequently in areas endemi c for schistosomiasis mansoni as in areas endemic for schistosomiasis haema tobia, and were not specific for the latter, since these ultrasonography-de tected lesions had no or marginal relationships with S. haematobium infecti on and morbidity.