A survey of the prevalence of bilharziasis has been made in the Egypt-49 Project Area, part of the Beheira province of Egypt with an area of 422 km(2) and a population of nearly 250 000 in 552 villages. The area has been classified into four divisions-Rural (Agricultural), Urban (Industrial), Reclamation (Resettlement) and Control, and subdivided into 23 sections bounded by irrigation canals or drains. Between April 1962 and March 1963, 11 944 individuals from 2573 households in 96 villages were examined.An over-all 5% two-stage cluster sample was obtained in each division, except in the Reclamation Division, where, because of the sparse population, a 10% systematic sample was used. The age and sex distributions of the samples were representative of those of the population as a whole. Larger villages tended to be over-represented, but there is no evidence that bilharziasis prevalence is related to village size.Bilharziasis was diagnosed by the detection of eggs in faeces or urine; details of the procedures are given. Examination of single samples, as in this study, leads to an underestimate of the extent of infection, by about 20% for S. mansoni infections and about 13% for S. haematobium; this fact has to be borne in mind in interpreting the prevalence data obtained.

Adolescent↗

PubMed1966

The epidemiology of Schistosoma haematobium and S. mansoni infections in the Egypt-49 project area. 2. Prevalence of bilharziasis in relation to personal attributes and habits.

The over-all uncorrected prevalence rates of bilharziasis determined in this survey were-Control Division, 59.5%; Rural and Reclamation Divisions, 35.9%; Urban Division, 21.0%. There are significant differences in rates of infection between sections within a division, between adjacent villages and even between different parts of one village. Prevalence increases rapidly with age up to about the age of 14 years, declines somewhat up to the age of 40 years and then remains fairly constant at a rate of about 30%; the age-group 0-8 years should provide the most sensitive group for the assessment of control measures. S. mansoni infection is acquired more slowly than S. haematobium infection during childhood and is more persistent among adults.Except for the youngest age-group, bilharziasis rates are higher in males than in females, but more detailed analysis shows that this is true only for farmers and farm labourers and for those who swim. In respect of occupational categories, farmers and farm labourers, with prevalence rates of 50.6% and 41.6%, respectivelx, bear the brunt of the infection, since they constitute 48% of the population, although fishermen (60.4%) and boatmen (52.0%) have higher infection rates.Differences in bilharziasis rates can also be related to differences in religion, educational attainment and domestic habits (swimming, washing clothes, utensils and cattle) according to the opportunity provided for contact with polluted water. Swimming, because of the thorough exposure to possible schistosome infection that it provides, is one of the most important activities involved in the transmission of bilharziasis.

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PubMed1966

The epidemiology of Schistosoma haematobium and S. mansoni infections in the Egypt-49 project area. 3. Prevalence of bilharziasis in relation to certain environmental factors.

The influence of the size and location of communities in relation to the different types of watercourse, the availability of a protected water supply, types of housing and the presence of other sanitary facilities on the prevalence of bilharziasis in the Egypt-49 project area has been studied. There is no direct relationship between the size of village and the prevalence of bilharziasis. Main drains and distributaries are potent sources of infection and, in terms of the total population exposed, distributaries play the most significant role in the transmission of infection. Of the other factors, the availability of a protected water supply seems to have the greatest effect on the prevalence. Although the presence of a latrine in the dwelling does not of itself influence the extent of schistosome infection, which is caught from polluted water, the installation of latrines assists in the cultivation of healthy habits, thereby lessening the prevalence not only of bilharziasis but also of certain other infections.

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PubMed1966

Assessment of severity of disease caused by Schistosoma haematobium and S. mansoni in the Egypt-49 project area.

The impact of bilharziasis on a community has been evaluated in terms of the stages and grades of severity of the disease; egg counts in faeces and urine were correlated with the clinical severity. At the time this study was carried out, the over-all prevalence of S. haematobium infection was 37.6%, that of S. mansoni infection 29.8% and that of mixed infections 17.1%.Of 579 people examined, 292 (58.2%) were excreting schistosome eggs. All except one person were classified as Stage III-asymptomatic, 122 (41.8% of those infected); mild, 74 (25.3%); moderate, 89 (30.5%); severe, 6 (2.1%). The remaining person was classified as Stage IV (moderate). Mixed infections produced a higher proportion of symptomatic cases (74.8%) than either infection alone (58.2%), and S. haematobium (57.1%) a higher proportion than S. mansoni (37.8%). The percentage of symptomatic cases was highest in those aged 10-14 years, who also had the highest prevalence of infection.On average, the egg output per infection was in the range 32-63 eggs for S. haematobium infections and 4-7 for S. mansoni in unit measure of urine and faeces, respectively. For S. haematobium infections, alone and in mixed infections, mean egg output increased with the severity of clinical symptoms. For S. mansoni infections, no such relation was established.It is concluded that the criteria of severity should be made more objective and that more satisfactory methods of determining egg counts should be adopted in an attempt to obtain more direct evidence of the validity of regarding egg count as a measure of worm load.

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PubMed1965