2 Am. J. Trop. Med. Hyg., 62(2)S, 2000, pp. 2–7 Copyright  2000 by The American Society of Tropical Medicine and Hygiene EPIDEMIOLOGY 1, 2, 3: ORIGINS, OBJECTIVES, ORGANIZATION, AND IMPLEMENTATION TAHA EL-KHOBY, MOHAMED H. HUSSEIN, NABIL GALAL, AND F. DEWOLFE MILLER Schistosomiasis Research Project, Endemic Disease Control, Ministry of Health, Cairo, Egypt; Faculty of Medicine, Cairo University, Cairo, Egypt; School of Public Health, University of Hawaii, Honolulu, Hawaii Abstract. This supplement is a report on the Epidemiology 1, 2, 3 (EPI 1, 2, 3) investigation, its origins, evolution, and findings that were carried out over a period beginning in 1990 and ending in 1994 in Egypt. The large scope and size of the study, the largest to date on schistosomiasis in Egypt, was a rationale for publishing a supplement to document EPI 1, 2, 3 methods and results collectively in sufficient detail to serve as a reference for planning, designing, and analyzing future epidemiologic studies and evaluation of schistosomiasis control in Egypt. The 3 objectives of EPI 1, 2, 3 were to 1) determine the changing patterns of Schistosoma haematobium and S. mansoni, 2) investigate factors contributing to differences between villages in the Nile Delta, Middle Egypt, and Upper Egypt, and 3) investigate risk factors for morbidity. The objectives were addressed using standardized techniques, stool and urine examinations, clinical examinations (including abdominal ultrasound), and questionnaires on a selected sample of the populations of selected villages in 9 governorates in Egypt. Two species of human schistosomiasis are endemic in Egypt, Schistosoma haematobium and S. mansoni. Schisto- soma haematobium was discovered in Egypt in 1851 by Theodor Bilharz 1 and the schistosome life cycle was first described in Egypt by Leiper 2 in 1915. In fact, the manifes- tations of schistosomiasis were described by pharaonic Egyptians in papyri dating from 1500 BC, 3 and calcified schistosome eggs were recovered by Ruffer 4 from 2 Egyp- tian mummies of the 20th dynasty. Khalil and Azim 5 in 1937 demonstrated the remarkable impact of converting the ancient form of basin irrigation to perennial irrigation in Upper Egypt on the transmission of S. haematobium. More than two-thirds of Egypt had been converted to perennial irrigation by the 1930s, 3,6 and by the 1950s most of the arable land in the Egyptian Nile valley had been converted to perennial irrigation including much of old Nubia. El-Zawahry 7 reported that S. haematobium had increased strikingly in those areas of old Nubia where pe- rennial irrigation systems had been constructed. The Nile Delta, which has always had the largest popu- lation of rural Egyptians, had been converted to perennial irrigation before the turn of the century to grow cotton and schistosomiasis endemicity was at a peak when J. Allen Scott 8 conducted his now classic studies on ‘‘The Incidence and Distribution of the Human Schistosomes in Egypt’’ in the 1930s. Scott meticulously described the patterns of S. haematobium and S. mansoni infection throughout the coun- try. He was the first to fully map the disease in Egypt and showed that S. mansoni was restricted to the northern and central parts of the Nile Delta. Schistosoma haematobium was highly prevalent throughout the Nile Delta, where many were infected with both species, and continued to be highly prevalent in Upper Egypt as far south as the Assiut gover- norate. With some exceptions, Scott found that S. haema- tobium prevalence decreased to very low levels in the 3 southernmost governorates of Sohag, Qena, and Aswan. These 3 southern governorates had yet to be converted to perennial irrigation, except in isolated areas of sugar cane cultivation. Following Scott’s work, there was a gap of almost 2 de- cades before similar data were available. These data, origi- nating from an Egyptian Ministry of Health survey, were reported by Wright. 9 When compared with Scott’s data, as shown in Table 1, changes in the pattern of the 2 species were apparent. Both species had decreased in the Nile Delta, S. mansoni had increased in Giza, indicating future changes, and S. haematobium had decreased in Upper Egypt, except in Sohag, Qena, and Aswan. There were dramatic increases in these 3 governorates where land had been converted to perennial irrigation, details of which are shown in Table 2. Since that time there have been numerous studies in both Upper Egypt 10–25 and in the Nile Delta 26–49 that confirm the trend of decreasing S. haematobium in both of these regions, and a resurgence of S. mansoni throughout the Nile Delta with expansion into Upper Egypt. 3,9,20,21 It is within this con- text of changing patterns of schistosomiasis endemicity that Epidemiology 1, 2, 3 (EPI 1, 2, 3) was first conceived and is reflected in its 3 objectives; thus, its name. A comprehen- sive review of schistosomiasis epidemiology in Egypt re- mains to be published. ORIGINS AND OBJECTIVES The Schistosomiasis Research Project (SRP), sponsored by the Egyptian Ministry of Health and the United States Agency for International Development, was designed in 1985 and implemented in 1988. The SRP comprised 6 major research components, one of which was schistosomiasis ep- idemiology. 50 Within the epidemiology component, there was a number of separate, detailed, research activities. 51 The objective of the first epidemiologic research activity (EPI 1), based upon review of the available data at that time, 51 was to describe the changing patterns of prevalence and inci- dence of S. haematobium and S. mansoni infection, intensity of infection, and morbidity throughout the endemic areas of Egypt and investigate its causes. Operationally, EPI 1 was to describe the current pattern of both species and obtain estimates of prevalence and in- cidence (or related rates) from probability samples represen- tative of populations residing in the cultivated areas of the Nile Valley, including all of the Nile Delta and Middle and Upper Egypt. The Nile Valley, from Aswan north, makes up 8 of the 10 areas (excluding Sinai and Lake Nasser) char- acterized by the National Schistosomiasis Control Program