RESUME Nous avons réalisé une étude rétrospective dans 14 hôpitaux égyptiens entre janvier 1997 et décembre 1999 afin de déterminer l’incidence clinique annuelle de l’échinococcose kystique humaine. Parmi les 492 353 dossiers examinés, 133 (0,027 %) nouveaux cas d’échinococcose kystique humaine ont été recensés. Cinquante (50) de ces cas (37,6 %) ont été enregistrés dans les hôpitaux d’Alexandrie et de Matrouh, 33 (24,8 %) à l’hôpital cardiothoracique de Giza et 50 dans les hôpitaux d’autres régions. Le Gouvernorat de Matrouh avait la plus forte incidence clinique annuelle (1,34-2,60 pour 100 000) suivi par le Gouvernorat de Giza (0,80-1,16 pour 100 000). Environ un tiers des personnes affectées étaient âgées de 20 ans ou moins. Le foie et les poumons étaient les organes les plus touchés. Bien que l’Egypte soit un pays de faible endémicité de l’échinococcose kystique humaine, cette maladie peut représenter une préoccupation de santé publique dans les gouvernorats de Matrouh et de Giza.

Human cystic echinococcosis (CE) (cystic hydatidosis) is a chronic zoonotic disease that results from infection with the larval stage of the dog tapeworm, Echinococcus granulosus. The disease is highly endemic in most of the countries of the Mediterranean basin, including North Africa and the Middle East [1,2]. It has been reported as an important public health problem in Jordan, Libyan Arab Jamahiriya, Morocco, Tunisia, and Israel [3–7]. Thus, Egypt is surrounded by countries endemic for CE, and several publications have recognized the existence of human CE cases among Egyptians [8–10]. Furthermore, CE has been documented by veterinarians in slaughtered camels (4.3%) and sheep (0.33%) in Egyptian abattoirs [11,12]. There is, however, little medical awareness or information regarding the endemicity of human CE in the country.

In human CE, the liver is the main organ affected, followed by lung tissue, however, there is usually no direct parasitological evidence for the presence of cysts in organs or tissues. Indirect methods of diagnosis are, therefore, important and include imaging for detection of a space-occupying mass and serological techniques which require improved clinical and laboratory facilities [13]. Patients with hepatic CE frequently exhibit no symptoms because of the slow progression of the cysts [2]; therefore, they may only be discovered accidentally and frequently have complicated forms of the disease. Pulmonary hydatidosis may be fortuitously revealed during thoracic radiography. Surgery, chemotherapy (or a combination of both) and the PAIR technique (puncture, aspiration, injection, reaspiration) are the main forms of treatment of human CE [14,15].

Cystic echinococcosis is a disease of people living in rural areas, where pastoral livestock is predominant [10], but there appears to be no recognized area where CE transmission is intense in Egypt. Consequently, physicians in rural areas rarely consider CE in their differential diagnosis. Furthermore, medical administrations in rural areas are frequently inadequate and therefore consultation with experienced physicians is required. Cases with query diagnosis are usually referred to specialized Ministry of Health and Population (MOHP) hospitals or to major universities for conclusive diagnosis and intervention.

Accordingly, the objective of this retrospective study was to determine the annual clinical incidence of the disease in northern Egypt. In particular, we examined records in 14 hospitals, including university hospitals, MOHP specialized hospitals and referral hospitals covering the period January 1997 to December 1999.

The study was carried out at general and specialized hospitals of 3 universities (in Alexandria, Cairo and Giza governorates), the hospital of the Liver Institute (Menoufia University, in the Nile delta) and 10 MOHP hospitals (6 chest and 4 general referral). The MOHP hospitals are located in Cairo, the Nile delta, North Sinai, and Matrouh governorate in the north-western part of Egypt. We reviewed inpatient records from all sites for the period January 1997– December 1999. During the study period, with the exception of Kasr El Aini Hospital (Cairo University), none of the records were kept on computer, therefore, the medical records were searched manually by one of our teams. The review team consisted of a physician, who worked as project manager, along with 2 part-time health workers as reviewers. The physician was qualified for a minimum of 10 years. Each reviewer screened sets of 50 notes under supervision until they were judged to be fully conversant with the review process. Records that were suspected for CE were then reviewed by clinicians, who verified the final diagnosis.

As mentioned above, diagnosis of CE is usually based on imaging techniques with serological confirmation, and surgery, chemotherapy and the PAIR technique are the main forms of treatment. Hence, the criteria we used to assess the case records were indicative imaging techniques (X-ray, ultrasound, CT scan or MRI) or positive serological tests (indirect haemagglutination or enzyme-linked immunosorbent assay), along with treatment of the case with chemotherapy (albendazole), surgery or PAIR, and histopathology records of cysts or aspiration fluid. Sex, date of admission, date and place of birth, cyst location, and whether the infection was new or recurrent were recorded for all CE cases. We maintained patient confidentiality by using initials only for individual identification. Multiple admissions for the same patient were identified from admission dates, initials, age, sex and only the first admission of such cases was included in the analysis.

Since it was not feasible to include all hospitals and clinics that perform thoracic and abdominal surgery in each region covered in the study, we adjusted the annual clinical incidence of recorded cases to estimate adjusted incidence. This was done by dividing the recorded CE cases by the number of beds in the hospitals we studied then multiplying the outcome by the total number of hospital beds in each governorate.

A total of 492 353 patient files were examined and 133 accumulated new cases of human CE were recorded from 14 hospitals examined for the period January 1997 to December 1999 (Table 1). Giza Chest Hospital showed the highest CE rate for total admissions (0.096%–0.160%) followed by Menoufia Liver Institute (0.026%–0.088%).

Table 2 shows the estimated annual clinical incidence (per 100 000 population) of CE for each governorate, based on 2.1% annual growth rate of estimated resident population in 1996. Matrouh governorate had the highest annual incidence, followed by Giza governorate. The calculated rates for Matrouh governorate were significantly higher than Giza governorate in years 1998 (Matrouh 1.97/100 000, Giza 0.80/100 000; c2 = 7.27, P = 0.013) and 1999 (Matrouh 2.60/100 000, Giza 1.00/100 000; c2 = 3.99, P = 0.040). The estimated annual clinical incidence of CE did not differ significantly within each governorate from one year to another except in Cairo governorate, where the incidence increased significantly from 0.05/100 000 in 1997 to 0.27/100 000 in 1999 (c2 = 4.59, P = 0.03).

All age groups and both sexes were well represented among patients with CE (Table 3). Approximately one third (45 cases) of the CE cases were £ 20 years of age. Of these, 19 (42.2%) were from hospitals in Giza governorate and 18 (40.0%) from hospitals in Alexandria and Matrouh governorates.

Of the 133 cases of human CE, 79 (59.4%) people had surgical interference. Of these, 18 (22.8%) cases had been confirmed pathologically. The remaining 54 (40.6%) cases received medical treatment; they were diagnosed based on serological tests and imaging techniques.

Hydatid cysts occurred most commonly in the liver and the lungs, either singly (54 and 52 respectively) or in conjunction with other organs (24 and 11 respectively). A total of 24 cases involved infection in > 1 organ (Table 4).

Egypt is recognized to be endemic for parasitic diseases such as schistosomiasis, filariasis and amoebiasis. Cystic echino- coccosis, however, is not currently a well-known medical condition, nor is it considered to be of public health importance; it is not a notifiable disease and there are no surveillance data available for the country. Our study was carried out to determine whether infection with CE represents a public health threat to residents of certain areas and to identify regions with high parasite transmission. Our data clearly confirm the low endemicity of the disease in northern Egypt, however the data indicate that the incidence of CE was relatively high in the western governorate of Matrouh, near the Libyan border, decreasing towards the east, and virtually disappearing in the most easterly parts of the country.

The calculated CE incidence for Giza governorate was unexpectedly high. Several factors could account for this finding. Firstly, major hospitals like Cairo University hospitals, located in Giza, do not just serve residents of Giza governorate: as there are no hospitals specialized in treating hydatidosis, patients seeking high quality medical care would choose hospitals such as these, which are known for good diagnosis and intervention. One of the limitations of our study is that the geographic location of residence and occupation at the time of admission were not always recorded in the files of many patients. Thus, some of the CE patients at hospitals in Giza could have been residents of other regions. Secondly, there is a large market for camels imported from Sudan (where the disease is prevalent) in Imbaba, Giza, where camels are kept before being slaughtered in an abattoir in the vicinity. Haridy, Ibrahim and Morsy reported that 4.0%–7.5% of camels slaughtered in Egypt had CE lung infection [11], and Ibrahem and Craig recorded a prevalence of 48% in Libyan camels [16]. It is possible that camels play an important role in the epidemiology of echinococcosis and hydatidosis in Giza governorate. Finally, since Giza Chest Hospital showed the highest incidence of CE, using such a figure for the assessment of the overall incidence rate for this region could have resulted in overestimation of the calculated incidence for Giza governorate.

In general, retrospective hospital surveys have been criticized for not providing precise estimates of disease incidence as not all hospitals in a particular region or district are included in the study, and the population is calculated rather than based on actual census. Furthermore, retrospective hospital survey data on human CE cannot give an accurate picture of the prevalence of infection. A certain number of cases are not seen in hospitals because the infection is asymptomatic or does not require surgical intervention, and some data are not available in the files. However, despite such limitations, careful examination of hospital records provides a useful indication of infection expressed as annual rate of hospital cases. It can give an indication of the public health importance of a disease and, when done continuously over many years, detects regional changes in incidence of infection [17].

In this study, we used a formula based on number of hospital beds to correct for the underestimation of annual rates for hospitals that were not included in the survey. It was of especial interest that Matrouh governorate, which is adjacent to the Libyan border, had the highest annual incidence. The Libyan Arab Jamahiriya is known to have a high prevalence of human CE [5].

In conclusion, this study proved highly useful in determining the annual incidence of hospitalized CE cases. It identified 2 areas, Matrouh and Giza governorates, where the disease could be of public health importance and CE should perhaps be a notifiable disease in these regions.

The authors wish to thank the administration authorities of the hospitals included in the study for their cooperation throughout the study period. The study was supported by the European Commission’s Scientific and Technological Cooperation with Developing Countries (INCO-DC) programme, No. IC18CT980354.