Risk Of Schistosomiasis Research Articles

Diagnosis of schistosomiasis japonica in Chinese schoolchildren by administration of a questionnaire

This paper describes a rapid, simple, cost-effective questionnaire for screening school-aged children at risk for Asian schistosomiasis in China. Five hundred and thirty-two children, aged 8–14 years, were selected from 3 schools in an area moderately endemic for Schistosoma japonicum in Hunan province. The questionnaire, comprising 15 multiple-choice questions, was administered by teachers in order to collect both ethnographic and epidemiological data relevant to current S. japonicum infections. This was followed by Kato-Katz thick smear stool examinations, miracidium hatching tests, and soluble egg antigen-enzyme linked immunosorbent assays in order to validate the efficacy of the questionnaire approach. The results from a combination of all 3 procedures indicated that the overall schistosomiasis prevalence in the 3 schools was 29·9% ( 138 472 ). Six risk factors (episodes of diarrhoea, frequency of water contact, school grade attained, weakness, past history of S. japonicum infection(s), and whether a subject had been previously treated for schistosomiasis) in the questionnaire were determined by logistic regression to be highly statistically significant predictors of individual current infection. The sensitivity (93·7%), specificity (91·9%) and low cost ( c. US$ 0·6/true positive case) associated with the 6 variables model make the questionnaire approach a very useful diagnostic tool for screening marshland and lake communities at high risk for schistosomiasis in China before selective treatment with praziquantel or diagnostic follow-up. An even simpler 3 variables ‘yes/no’ model was derived from the questionnaire and found to be nearly as good at predicting individual infection (sensitivity 86·2% and specificity exceeding 97·6%) and extremely simple to use. If validated in other ecological settings in China the questionnaire, modified or as presented here, could be adopted by the national schistosomiasis control programme.

Questionnaires in the screening for Schistosoma mansoni infection: a study of socio demographic and water contact variables in four communities in Brazil.

The use of questionnaires has been recommended for identifying, at a lower cost, individuals at risk for schistosomiasis. In this study, validity of information obtained by questionnaire in the screening for Schistosoma mansoni infection was assessed in four communities in the State of Minas Gerais, Brazil. Explanatory variables were water contact activities, sociodemographic characteristics and previous treatment for schistosomiasis. From 677, 1474, 766 and 3290 individuals eligible for stool examination in the communities, 89 to 97% participated in the study. The estimated probability of individuals to be infected, if they have all characteristics identified as independently associated with S.mansoni infection, varied from 15% in Canabrava, to 42% in Belo Horizonte, 48% in Comercinho and 80% in São José do Acácio. Our results do not support the hypothesis that a same questionnaire on risk factors could be used in screening for S.mansoni infection in different communities.

Prevalence and epidemiology of Schistosoma mansoni and S. haematobium infection in two areas of Egypt recently reclaimed from the desert.

Projects are being carried out in many regions of Egypt to reclaim land from the desert for agriculture. This paper presents findings from a baseline epidemiologic study conducted in 1992 in two newly reclaimed areas near Ismailia, Egypt. In the first area, just east of the Suez Canal, 40.0% of the residents tested positive for Schistosoma mansoni and 1.7% tested positive for S. haematobium, while in the second area, 15 km southwest of Ismailia, 49.3% tested positive for S. mansoni and 3.3% tested positive for S. haematobium. The intensities of S. mansoni infection were moderately high, with a geometric mean egg count of 76 eggs/gram of feces among positive individuals in the first area, and 100 eggs/gram of feces in the second area. When compared with a previous study conducted in 1985, the prevalence of S. mansoni infection in the first area has increased from 21.7% to 42.1% among settlers in the last seven years, while that of S. haematobium has decreased from 7.8% to 1.7%. These trends may result from changes in irrigation practices or other alterations in the local environment. There is a risk of schistosomiasis becoming a major public health problem in reclaimed areas if adequate control measures are not taken.

Temperature Data from Satellite Imagery and the Distribution of Schistosomiasis in Egypt

Polar orbiting environmental satellites operated by the National Oceanographic and Atmospheric Administration acquire daytime and nighttime thermal infrared measurements of the earth's surface around the world at a spatial resolution of 1.1 km. Day-night pairs of this imagery from the Advanced Very High Resolution Radiometer (AVHRR) were processed to produce temperature maximum, temperature minimum, and diurnal temperature difference (dT) maps of the lower Nile River valley. Nile delta subsets of the dT maps for August 16, 1990 and February 14, 1991 were analyzed in detail. Values of dT at specific locations were derived using the median of 5 x 5 pixels centered on the latitude and longitude of 41 survey sites listed in 1935, 1983, and 1990 schistosomiasis surveys of the Nile Delta. A Spearman correlation coefficient matrix revealed an inverse relationship between site dT values for August 16, 1990 and February 14, 1991 and prevalence of Schistosoma mansoni in the 1935 and 1983 surveys. For S. haematobium, a positive association of site dT values and prevalence was seen for 1935 only. A significant association was observed between 1935 S. mansoni prevalence and that observed in 1983 and 1990; S. haematobium prevalence in 1935 was not correlated with the later surveys. The results suggest that AVHRR thermal difference maps reflect regional hydrologic conditions that can be used as a predictor of environmental risk of schistosomiasis for control program management.

Community-Based Questionnaires and Health Statistics as Tools for the Cost-Efficient Identification of communities at Risk of Urinary Schistosomiasis

Self-administered questionnaires, distributed by existing administrative channels to village party chairmen, head-teachers and schoolchildren, showed good diagnostic performance for the qualitative assessment of urinary schistosomiasis endemicity. At a cost 34 times below that of the WHO-recommended parasitological screening strategy, the schoolchildren's questionnaire allowed the screening of 75 out of 77 schools of a rural Tanzanian district in six weeks, and the exclusion of schools not at high risk for urinary schistosomiasis with over 90% confidence. The headteacher and party questionnaires made it possible to assess the perceived importance of a spectrum of diseases and symptoms, among which was schistosomiasis. The priority rank of schistosomiasis control was strongly correlated with the prevalence rate of the disease in the community. The questionnaires also looked for the prioritization of health among other community issues and thus contributed important information for planning at district level. Standardized monthly disease reports, sent by all primary health services, were also analysed. They allowed a zonal schistosomiasis endemicity classification.

Knowledge attitudes and practices in relation to schistosomiasis in a rural community

A knowledge attitudes and practices survey of sanitation, water supplies and schistosomiasis was carried out in a rural schistosomiasis endemic area of Zimbabwe. Questionnaires were administered to 349 households. No latrines were present in 61% of households and information on use, likes and dislikes was collected. Most drinking water was collected from sources presenting no risk of schistosomiasis whereas most washing activities were carried out at sites presenting such a risk. Schistosomiasis was thought to be a problem in the community by over 50% of households and 79% gave haematuria as a symptom of the disease. There was a correlation between the washing site and the reported presence of schistosomiasis in the family.

Diagnosis of Schistosomiasis

To the Editor.— In the article entitled "Acute Schistosomiasis Among Americans Rafting the Omo River, Ethiopia" Istre et al1describe very clearly the features and natural course of "Katayama syndrome." They state that this stage occurs withSchistosoma mansoni and Schistosoma japonicuminfections. This syndrome has also been described inSchistosoma haematobiuminfections.2-4 This stage of the disease is usually considered to run a benign course, but more serious and varied manifestations may be present. Cardiac and cerebral complications have been described,2,3as well as features of the Henoch-Schonlein syndrome.3As the risk of schistosomiasis may now have to be seriously considered for visitors and American residents who have traveled abroad, it is well to note that examination of rectal mucosal biopsy specimens often leads to earlier diagnosis than stool and urine studies. This method of diagnosis is also very reliable inS haematobium, and, in

Acute Schistosomiasis Among Americans Rafting the Omo River, Ethiopia

An outbreak of acute schistosomiasis occurred among a group of adventurers who took part in a rafting expedition on the Omo River in Ethiopia in November 1981. Six (55%) of the 11 members of the expedition experienced Schistosoma mansoni infection confirmed by stool examination. Five of these six had symptoms compatible with acute schistosomiasis. Eosinophilia was the most frequent sign of infection (five of six), and fever, the most common symptom (four of six). Despite medical evaluations, illnesses had remained undiagnosed until January 1982. This outbreak should alert physicians to the risk of schistosomiasis among travelers to this part of Africa and the difficulty of correct diagnosis early in the course of the disease.