Showing papers in "Bulletin of The World Health Organization in 1991"

Effects of improved water supply and sanitation on ascariasis diarrhoea dracunculiasis hookworm infection schistosomiasis and trachoma.

Abstract: A total of 144 studies were analysed to examine the impact of improved water supply and sanitation facilities on ascariasis, diarrhoea, dracunculiasis, hookworm infection, schistosomiasis, and trachoma. These diseases were selected because they are widespread and illustrate the variety of mechanisms through which improved water and sanitation can protect people. Disease-specific median reduction levels were calculated for all studies, and separately for the more methodologically rigorous ones. For the latter studies, the median reduction in morbidity for diarrhoea, trachoma, and ascariasis induced by water supplies and/or sanitation was 26%, 27%, and 29%, respectively; the median reduction for schistosomiasis and dracunculiasis was higher, at 77% and 78%, respectively. All studies of hookworm infection were flawed apart from one, which reported a 4% reduction in incidence. For hookworm infection, ascariasis, and schistosomiasis, the reduction in disease severity, as measured in egg counts, was greater than that in incidence or prevalence. Child mortality fell by 55%, which suggests that water and sanitation have a substantial impact on child survival. Water for personal and domestic hygiene was important in reducing the rates of ascariasis, diarrhoea, schistosomiasis, and trachoma. Sanitation facilities decreased diarrhoea morbidity and mortality and the severity of hookworm infection. Better water quality reduced the incidence of dracunculiasis, but its role in diarrhoeal disease control was less important than that of sanitation and hygiene.

Etiology of acute diarrhoea among children in developing countries: a multicentre study in five countries.

Abstract: A 2-year etiological survey of acute diarrhoea in children aged 0-35 months who were attending treatment facilities was carried out using a standardized protocol in five hospitals in China, India, Mexico, Myanmar, and Pakistan. A total of 3640 cases of diarrhoea and 3279 age- and sex-matched controls were studied; about 60% of the patients were aged less than 1 year and 60% were male. An enteric pathogen was detected in 68% of the cases and in 30% of the controls. In all the study centres, the pathogens most strongly associated with disease were rotavirus (16% of cases, 2% of controls), Shigella spp. (11% of cases, 1% of controls) and enterotoxigenic Escherichia coli (16% of cases, 5% of controls). Rotavirus was commonest among 6-11-month-olds, accounting for 20% of all cases in this age group; 71% of all rotavirus episodes occurred during the first year of life. Shigella spp. were commonest among those aged 12-23 months and 24-35 months, accounting for 22% and 27% of the cases, respectively. The proportion of cases that yielded no pathogen was inversely related to age, being highest (41%) among infants below 6 months of age and lowest (19%) among those aged 24-35 months. These results suggest that microbe-specific intervention strategies for the control of childhood diarrhoeal diseases in developing countries should focus on rotavirus, Shigella spp. and enterotoxigenic E. coli.

Bacterial indicators of risk of diarrhoeal disease from drinking-water in the Philippines.

Abstract: Inadequate measures of water quality have been used in many studies of the health effects associated with water supplies in developing countries. The present 1-year epidemiological-microbiological study evaluated four bacterial indicators of tropical drinking-water quality (faecal coliforms, Escherichia coli, enterococci and faecal streptococci) and their relationship to the prevalence of diarrhoeal disease in a population of 690 under-2-year-olds in Cebu, Philippines. E. coli and enterococci were better predictors than faecal coliforms of the risk of waterborne diarrhoeal disease. Methods to enumerate E. coli and enterococci were less subject to interference from the thermotolerant, non-faecal organisms that are indigenous to tropical waters. Little difference was observed between the illness rates of children drinking good quality water (less than 1 E. coli per 100 ml) and those drinking moderately contaminated water (2-100 E. coli per 100 ml). Children drinking water with greater than 1000 E. coli per 100 ml had significantly higher rates of diarrhoeal disease than those drinking less contaminated water. This threshold effect suggests that in developing countries where the quality of drinking-water is good or moderate other transmission routes of diarrhoeal disease may be more important; however, grossly contaminated water is a major source of exposure to faecal contamination and diarrhoeal pathogens.

Diabetes in adults is now a Third World problem. The WHO Ad Hoc Diabetes Reporting Group.

Abstract: Since 1988, WHO has been collecting standardized information on the prevalence of diabetes mellitus and impaired glucose tolerance (IGT) in adult communities worldwide. Within the age range 30-64 years, diabetes and IGT were found to be absent or rare in some traditional communities in Melanesia, East Africa and South America. In communities of European origin, the prevalences of diabetes and IGT were in the range of 3-10% and 3-15% respectively, but migrant Indian, Chinese and Hispanic American groups were at higher risk (15-20%). The highest risk was found in the Pima Indians of Arizona and in the urbanized Micronesians of Nauru, where up to one-half of the population in the age range 30-64 years had diabetes. The prevalence of total glucose intolerance (diabetes and IGT combined) was greater than 10% in almost all populations, and was within the range 11-20% for European and U. S. white populations. However, the prevalence of total glucose intolerance reached almost 30% in Arab Omanis and in U. S. blacks and affected one-third of all adult Chinese Mauritians, migrant Indians, urban Micronesians and lower-income urban U. S. Hispanics. In Nauruans and Pima Indians, approximately two-thirds of all adults in the age range were affected. These results lead to three important conclusions. (1) An apparent epidemic of diabetes has occurred--or is occurring--in adult people throughout the world. (2) This trend appears to be strongly related to life-style and socioeconomic change. (3) It is the populations in developing countries, and the minority or disadvantaged communities in the industrialized countries who now face the greatest risk.(ABSTRACT TRUNCATED AT 250 WORDS)

Levels and risk factors for perinatal mortality in Ahmedabad, India.

Abstract: To estimate levels and determinants of perinatal mortality, we conducted a hospital-based surveillance and case-control study, linked with a population survey, in Ahmedabad, India. The perinatal mortality rate was 79.0 per 1000, and was highest for preterm low-birth-weight babies. The case-control study of 451 stillbirths, 160 early neonatal deaths and 1465 controls showed that poor maternal nutritional status, absence of antenatal care, and complications during labour were independently associated with substantially increased risks of perinatal death. Multivariate analyses indicate that socioeconomic factors largely operate through these proximate factors and do not have an independent effect. Estimates of attributable risk derived from the prevalence of exposures in the population survey suggest that improvements in maternal nutrition and antenatal and intrapartum care could result in marked reductions of perinatal mortality.

Epidemiological evidence from Zaire for a dietary etiology of Konzo, an upper motor neuron disease.

Abstract: A clear association between seasonal outbreaks of a paralytic disease called konzo and toxic effects from consumption of insufficiently processed bitter cassava roots has been demonstrated in Bandundu region, Zaire. A community-based survey of 6764 inhabitants identified 110 live and 24 dead konzo-affected persons with a history of isolated non-progressive spastic paraparesis of abrupt onset. The start of these annual outbreaks of konzo in 1974 coincided with the completion of a new tarmac road to the capital, which facilitated the transport of cassava and made it the main cash crop. The extensive cassava sales encouraged the consumption by the peasant families of roots that had not been adequately processed; frequent acute cyanide intoxications resulted when the naturally occurring cyanogens in the roots were eaten. The disease mainly appeared in the dry season when there was high consumption of insufficiently processed cassava and the diet lacked supplementary foods with sulfur-containing amino acids which promote cyanide detoxification. These results, which confirm the earlier findings in East Africa, show that, owing to the high cyanide and low sulfur dietary intake, there is an increased risk of konzo outbreaks in cassava-growing areas during periods of adverse agro-economic changes.

Pricing, distribution, and use of antimalarial drugs.

Abstract: Prices of new antimalarial drugs are targeted at the "travellers' market" in developed countries, which makes them unaffordable in malaria-endemic countries where the per capita annual drug expenditures are US$ 5 or less. Antimalarials are distributed through a variety of channels in both public and private sectors, the official malaria control programmes accounting for 25-30% of chloroquine distribution. The unofficial drug sellers in markets, streets, and village shops account for as much as half of antimalarials distributed in many developing countries. Use of antimalarials through the health services is often poor; drug shortages are common and overprescription and overuse of injections are significant problems. Anxiety over drug costs may prevent patients from getting the necessary treatment for malaria, especially because of the seasonal appearance of this disease when people's cash reserves are very low. The high costs may lead them to unofficial sources, which will sell a single tablet instead of a complete course of treatment, and subsequently to increased, often irrational demand for more drugs and more injections. Increasingly people are resorting to self-medication for malaria, which may cause delays in seeking proper treatment in cases of failure, especially in areas where chloroquine resistance has increased rapidly. Self-medication is now widespread, and measures to restrict the illicit sale of drugs have been unsuccessful. The "unofficial" channels thus represent an unacknowledged extension of the health services in many countries; suggestions are advanced to encourage better self-medication by increasing the knowledge base among the population at large (mothers, schoolchildren, market sellers, and shopkeepers), with an emphasis on correct dosing and on the importance of seeking further treatment without delay, if necessary.

Influence of deltamethrin treatment of bed nets on malaria transmission in the Kou valley, Burkina Faso.

Abstract: A 3-year entomological study was carried out on the transmission of malaria in a village of 900 inhabitants in a rice-growing area of Burkina Faso. In the study area inhabitants use bed nets to protect themselves from mosquito bites. In the first year of the study, baseline data were collected; in the second year, the village was divided in two parts and all the bed nets in the southern part were sprayed with deltamethrin (25 mg/m2); and in the third year, all the bed nets in both parts of the village were sprayed. The inoculation rate was estimated by hand collection of mosquitos on human volunteers who were not protected by bed nets. The overall inoculation rate in the first year was 55 infected bites per person and was higher in the southern than in the northern part of the village. During the second year the rate increased to 70 bites per person on average (but was slightly lower than this in the southern part of the village). During the third year, the inoculation rate fell to three infected bites per year, i.e., a reduction of 94% compared with the first year. This reduction arose primarily because of a marked decrease in the sporozoitic index and a lower density of vectors. Thus, use of pyrethroid-impregnated bed nets by all members of the community appears to be a major tool in preventing transmission of malaria.

Duration of immunity following immunization with live measles vaccine : 15 years of observation in Zhejiang Province, China

Abstract: The duration of immunity following measles vaccination of 2882 immunized children has been investigated in a closed region of China for 15 years. A total of 1002 of the children were treated as primary immunization subjects, and 1547 as reimmunization subjects. These two cohorts were not in contact with known wild measles virus over the whole observation period, and the results obtained probably reflected the antibody responses to measles vaccine alone. The remaining 333 vaccinees came into contact with wild measles virus, and this permitted evaluation of the protective effect of the measles vaccines tested: 4 children experienced very mild clinical measles, and 329 experienced subclinical infection, including 12 who had had undetectable haemagglutination-inhibition antibodies for 9-10 years. These results indicate that the immunity induced by successful primary immunization may persist for at least 15 years. Within this period, a second dose of vaccine only induces low antibody responses which decrease rapidly to their original levels. This provides strong evidence that the immunity produced by primary immunization is long-lasting. However, there were some indications that reimmunization might produce better effects if live attenuated measles virus were used with a longer interval between doses.

Estimation and projection of adult AIDS cases: a simple epidemiological model.

Abstract: Many HIV/AIDS (acquired immunodeficiency syndrome) models have been developed to help our understanding of the dynamics and interrelationships of the determinants of HIV (human immunodeficiency virus) spread and/or to develop reliable estimates of the eventual extent of such spread. These models range from very simple to very complex. WHO has developed a simple model for short-term projections of AIDS, details of which are presented here along with results obtained using the model to estimate and project AIDS cases for the USA, sub-Saharan Africa, and south/south-east Asia. WHO has also developed, based on the model described in this paper, a computer program (Epi Model), which will enable the user to easily change the values of any of the variables required by the WHO model.

Rapid, low-cost, two-step method to screen for urinary schistosomiasis at the district level: the Kilosa experience.

Abstract: The operational and diagnostic performance of a two-step method for the cost-effective screening of urinary schistosomiasis was investigated in the Kilosa District of east-central Tanzania. In the first step a simple questionnaire was administered to 15,073 primary schoolchildren by their class teachers over a 4-week period. The answers to the questionnaires had a high negative predictive value for schistosomiasis, and this permitted the safe exclusion of schools where the risk of the disease was low. In the second step, the head-teachers of the 49 high-risk schools and of 26 low-risk schools were instructed on the use of reagent sticks to detect haematuria. Each head-teacher then performed this test on 80 children selected at random in their schools (5750 children were screened within 6 weeks). Crosschecks of the results in 18 schools confirmed the reliability of the head-teachers' testing and their findings were therefore used to prepare an epidemiological map of the district and to arrange for treatment of positive children. This two-step approach relied entirely on the existing school system and permitted screening of a rural district of area 15,000 km2 (population, 350,000) over a 4-month period at a cost of only US$3000.

Transmission of HIV, hepatitis B virus, and other bloodborne pathogens in health care settings : a review of risk factors and guidelines for prevention

Abstract: This article discusses the risk factors for HIV hepatitis B virus (HBV) and other blood-borne pathogen transmission in the health care setting and the specific guidelines for its prevention Reports confirmed that the transmission of HIV HBV as well as other blood-borne pathogens in health care settings have caused considerable public health concern and constitute infectious hazards in certain settings Transmission of blood-borne pathogens were believed to be from patient to patient patient to health care and rarely from health care worker to patient Although the risk of infection is certainly real it is largely preventable it may occur due to the use of unscreened blood for transfusion the use of improperly sterilized medical and dental equipment accidental punctures with contaminated needles and exposures to non-intact skin or mucus membrane to infectious materials The risk of transmission depends on the dose of pathogen contaminated and the frequency or probability of exposure to infectious material General guidelines for the prevention of transmission in the health care settings are given including the concept of "universal precautions" the need for adequate supplies of sterile equipment; the reduction of unnecessary injections and transfusions; and the appropriate use of hepatitis B vaccine In addition areas of research and development are highlighted to provide both the health care workers and the patients an improved understanding on the risks of transmission of these blood-borne pathogens

Principles of measles control.

Abstract: WHO's Expanded Programme on Immunization has significantly helped to reduce global morbidity and mortality from measles. Recently, some African countries with high vaccine coverage levels have reported measles outbreaks in children above the current target age group for immunization. Outbreaks such as these are to be expected, unless close to 100% of the population are immunized with a vaccine which is 100% effective. Success of an immunization programme requires identification of the distribution and ages of susceptible children and reduction of their concentration throughout the community. Priority should be given to urban and densely populated rural areas. In large urban areas, high coverage of infants must be achieved soon after the age at which they lose their maternal antibodies and become susceptible. This will be facilitated by the introduction of high-dose measles vaccines which can be given at 6 months of age. Where measles incidence is increasing among children aged over 2 years, immunization of older children may be considered during contacts with the health care system, or at primary school entry, if this does not divert resources from immunization of younger children. Health workers should be informed of the predicted changes in measles epidemiology following immunization. The collection, analysis and use of data on measles (vaccine coverage, morbidity and mortality) should be improved at all levels of the health care system in order to monitor the immunization programme's overall impact, identify pockets of low coverage, and allow early detection of and response to measles outbreaks.

Comparative evaluation of 36 commercial assays for detecting antibodies to HIV.

Abstract: Summarized are the results of an assessment of the major operational characteristics of 36 commercially available assays for detection of antibodies to human immunodeficiency virus type 1 (HIV-1) and/or type 2 (HIV-2). For this purpose, 20 enzyme-linked immunosorbent assays (ELISAs), 11 simple immunoassays with visual reading, four supplemental assays, and one discriminatory assay were assessed using a panel of 537 sera (65% of which were of African, 26% of European, and 9% of South American origin); the prevalence of HIV-1 was 39.1% and of HIV-2, 15.7%. The following operational parameters of the assays were investigated: ease of performance; suitability for use in small blood collection centres; sensitivity and specificity; positive predictive values at different prevalences; inter-reader variability for simple assays whose results were read visually; the proportion of indeterminate results; and, for some of the ELISA assays, delta-values, as quantitative measures of sensitivity and specificity. The results will be of use to health policy decision-makers, managers of national AIDS prevention and control programmes, directors of blood banks, and laboratory specialists in the selection of appropriate HIV antibody assays.

Strategies for dracunculiasis eradication.

Abstract: In 1991 the Forty-fourth World Health Assembly declared the goal of eradicating dracunculiasis (guinea worm disease) by the end of 1995 This article summarizes the recommended strategies for surveillance and interventions in national dracunculiasis eradication programmes It is based on personal experience with dracunculiasis programmes in Ghana, Nigeria and Pakistan Three phases are described: establishment of a national programme office and conduct of a baseline survey; implementation of interventions; and case containment The relevance of dracunculiasis eradication activities to strengthening of primary health care in the three countries is discussed briefly Similar strategies would help eradicate this disease in the remaining endemic countries

Increase in mortality associated with blindness in rural Africa.

Abstract: Forty-seven persons were identified with visual impairment (visual acuity of 6/60 or less in their better eye) during a population-based survey in 1986 of eye disease in three villages in central Tanzania. Four years later, 41 (87%) of them and 70 (82%) of 84 age-, sex-, and village-matched controls with normal functional vision (visual acuity 6/18 or better in the better eye) were traced, and those who were still alive were re-examined. The remainder were reported to be alive but had moved to other villages. Deaths among those aged 40-79 years amounted to 10 among the 37 visually impaired and 7 among the 70 sighted controls. This gave an excess mortality rate (odds ratio) of 3.33 times (1.03-11.04, 95% Cl) among the visually impaired compared to their age-matched controls. The excess mortality rate for visually impaired women was 4.11 (0.72-25.5) and 2.71 (0.50-15.2) for visually impaired men. Nine out of 25 with vision of less than 3/60 in their better eye had died. The higher mortality rate among the visually impaired suggests that, in this environment, blindness is not only associated with considerable disability but is also associated with a shortened life expectancy, especially for women.

Maternal anthropometry for prediction of pregnancy outcomes: Memorandum from a USAID/WHO/PAHO/MotherCare meeting

Abstract: The memorandum is an abbreviated version of a prepared report on maternal anthropometry which summarizes the general recommendations of a consensus of 50 experts on field applications and priority research issues in developing countries. Consensus was reached at a meeting on Maternal Anthropometry for Prediction of Pregnancy Outcomes held in Washington D.C. in April 1990. 15 general recommendations are identified for field applications and research priorities. Specific recommendations differentiating field applications from research priorities are provided for prepregnancy weight weight gain in pregnancy height arm circumference and weight for height and body mass index. For example the discussion of arm circumference indicates that it is useful as an indicator of maternal nutritional status in nonpregnant women because of its correlation with maternal weight or weight for height. During pregnancy it is useful as a screen for risk of low birth weight (LBW) and late fetal and infant mortality. Maternal arm circumference has been found to be stable during pregnancy in developing countries and is independent of gestational age. Field applications involve the use 1) to assess the nutritional status of pregnant and nonpregnant women 2) to screen women at risk of poor maternal stores postpartum because it reflects maternal fat and lean tissue stores for instance 3) to screen women and refer to facilities for a more thorough assessment of nutritional risk and 4) to assess the extent of undernutrition in an area particularly for surveillance. Community level workers especially birth attendants (TBAs) should be trained and have access to arm circumference tapes. The technology is simple enough also for use by women in the home. Cutoff points for assessing biological risk are fairly consistent across developing country populations and range between 21-23.5 cm. Routine monitoring during pregnancy is not necessary because the changes are too small to detect. Where prepregnancy weight is unavailable and weight is monitored arm circumference may serve as a proxy for prepregnancy weight. All women of childbearing age should be measured. Research priorities are to explore the functional significance with women of difference body compositions (fat versus lean upper arm) the relationship to pregnancy related outcomes arm changes relative to stages throughout the reproductive period and to weight changes different instruments such as color-coded tapes or 1 tape for arm measurement and uterine height combinations of different measurements the relationship with prepregnancy weight and the development of arm circumference in weight gain charts as a proxy for prepregnancy weight.

Adverse reactions to sulfa drugs: implications for malaria chemotherapy.

Abstract: National adverse drug reaction registers in Sweden and the United Kingdom provided data on the type, severity and frequency of reported adverse reactions attributed to sulfa drugs. Reactions to the ten principal drugs were examined in terms of their half-lives and usual indications for use. Of 8339 reactions reported between 1968 and 1988, 1272 (15%) were blood dyscrasias, 3737 (45%) were skin disorders, and 578 (7%) involved the liver. These side-effects occurred with all types of sulfa drugs investigated, although at different relative rates, and 3525 (42%) of them were classified as serious. The overall case fatality rate (CFR) was 1:15 serious reactions, and was highest in patients with white blood cell dyscrasias (1:7). Drugs with longer elimination half-lives had higher CFRs, particularly for fatalities after skin reactions. In Sweden, the estimated incidences of serious reactions were between 9 and 33 per 100,000 short-term users of sulfa drugs (two weeks), between 53 and 111 among those on malaria prophylaxis, and between 1744 and 2031 in patients on continuous therapy. For dapsone, the incidence appeared to increase with higher doses. Our results indicate that sulfa drugs with short elimination half-lives deserve to be considered for use in combination with proguanil or chlorproguanil for malaria chemotherapy and possibly prophylaxis. The smaller risk of adverse reactions associated with lower-dose dapsone suggests that it should also be evaluated as a potentially safe alternative.

Measles epidemic in Harare, Zimbabwe, despite high measles immunization coverage rates.

Abstract: Despite rapidly increasing measles immunization coverage in Harare city, measles remains endemic, and regular outbreaks occur. The most recent occurred in 1988, when the measles immunization coverage was 83%. We have carried out a retrospective study of the clinical and epidemiological features of this outbreak to assess whether the present immunization policy needs to be changed. Of 4357 cases of measles seen at primary health care centres and hospitals in Harare during the outbreak, 1399 (32%) were severe or involved complications that required hospital admission. The peak incidence occurred among under-2-year-olds, followed by that among 5-7-year-olds. Poor nutritional status was significantly more frequent among children who were hospitalized and among those who died. A total of 59% of all cases aged 9-59 months had documented evidence of measles immunization. The most frequent complications, which occurred most often among under-5-year-olds, were diarrhoea with dehydration, pneumonia, laryngotracheobronchitis, and convulsions, which together affected 56% of hospitalized cases. The hospital case fatality rate was low (1.43%). In Harare, measles transmission remains a problem, despite high measles immunization coverage rates; the failure rate for the standard Schwarz measles vaccine also appears to be high. There is a need to reduce the number of measles cases among under-9-month-olds and young children. Further studies into alternative measles vaccines and schedules are required.

The Risk and Dynamics of Onchocerciasis Recrudescence after Cessation of Vector Control

Abstract: Using a computer simulation study, we have investigated the risk and dynamics of onchocerciasis recrudescence after stopping vector control, in order to provide guidelines for operational decision-making in the Onchocerciasis Control Programme in West Africa (OCP). For this purpose, we used the microsimulation model ONCHOSIM to predict for periods of 9-15 years of vector control the ensuing risk and dynamics of recrudescence in an onchocerciasis focus. The model was quantified and validated using OCP evaluation and field research data. A range of plausible values was determined for important confounding parameters, i.e., vector biting rate, variation in exposure between individuals, parasite life span, and the relation between skin microfilarial load and vector infection. Different model quantifications were used in order to take account of the possible confounding effect of these parameters on the prediction of recrudescence. In the absence of immigration of infected humans or invasion by infected flies, the model predicts that 14 years of full-scale vector control are required to reduce the risk of recrudescence to less than 1%. The risk depends, in particular, on the vector biting rate, and this has implications for the planning of post-larviciding surveillance. Recrudescence will be a relatively slow process, and its rate will depend on the duration of vector control. Even if vector control were stopped too early, i.e., after 12-13 years in a highly endemic area, it would take more than 20 years before the intensity of infection in the community would reach levels of public health importance.

Experimental chemotherapy of Trypanosoma cruzi infection: persistence of parasite antigens and positive serology in parasitologically cured mice.

Abstract: Mice infected with Trypanosoma cruzi, but parasitologically cured after specific chemotherapy, continued to exhibit positive indirect immunofluorescence serological tests 3-6 months after the therapy. Treatment of trypanosome antigens with monospecific antisera produced in rabbits, and examination by immunoelectron-microscopy following peroxidase labelling disclosed the presence of membrane deposits in cell processes in the spleens of the mice. Similar deposits were observed in the external membranes of T. cruzi amastigotes in the spleens of acutely infected mice, but not in normal control mice. No reaction occurred in tissues not previously treated with the monospecific anti-T. cruzi serum. Positive cells in treated and cured mice, as well as in the not cured or untreated control mice, were located in germinal centres of the splenic white pulp and presented long and branching cytoplasmic processes, which are indicative of dendritic cells of the lymphoid follicles of the spleen.

Geographical and socioeconomic factors relating to the distribution of Schistosoma mansoni infection in an urban area of north-east Brazil.

Abstract: A study was carried out in Santo Antonio de Jesus, a town in Bahia State, north-east Brazil, to determine the relationship between various biological, socioeconomic, behavioural, and geographical factors and the prevalence and intensity of Schistosoma mansoni infection. The town's population was around 45,000 and the study was targeted at all children born in 1970-71 who were living in the town at the time of the survey (August-November 1984). An extensive questionnaire was used to collect information on each child and on family and household conditions; samples of stools were also taken for examination (Kato-Katz method). A survey of water snails was also carried out and information on the distribution of their breeding sites was plotted on a map of the area. The overall prevalence of S. mansoni infection was 31.0%. Several variables that reflected different aspects of the population's way of life were strongly associated with the prevalence and the intensity of infection. Some of the findings are valuable for understanding the mechanisms involved in the occurrence of schistosomiasis and its distribution in urban locations as well as for defining high-risk groups, all of which are important for planning control strategies.

Evaluation of a computerized field data collection system for health surveys.

Abstract: A customized field data collection system (FDCS) has been developed for a hand-held computer to collect and check questionnaire data. The data quality, preparation time, and user acceptability of the system were evaluated during a malaria morbidity survey in Bakau, the Gambia. Eight field-workers collected data with either the FDCS or on paper questionnaire forms in alternate weeks over a 6-week period. Significantly fewer item errors occurred with the FDCS, and by the end of the survey period interview times were significantly less with the FDCS than with the paper and pencil questionnaire. Advanced appropriate technology may have a useful role in providing accurate and rapid information, particularly in overcoming bottlenecks in data processing, and in obviating the need for costly expertise and equipment. In developing countries this could help to improve the quality of data on health care.

Indoor spraying with the pyrethroid insecticide lambda-cyhalothrin: effects on spraymen and inhabitants of sprayed houses.

Abstract: In March 1990 a study was carried out in the village of Kicheba, United Republic of Tanzania, in which the pyrethroid insecticide lambda-cyhalothrin was sprayed on all the internal surfaces of houses and other shelters at a coverage of about 25 mg of active ingredient per m2. Every day for 6 days, 12 spraymen and 3 squad-leaders were interviewed about symptoms of overexposure to the insecticide. Each sprayman used up to 62 g of lambda-cyhalothrin over 2.7-5.1 hours every day. All the spraymen complained at least once of symptoms that were related to exposure to lambda-cyhalothrin, the commonest being itching and burning of the face, and nose or throat irritation frequently accompanied by sneezing or coughing. Facial symptoms occurred on non-protected areas only. The symptoms were experienced at various times after the beginning of exposure and disappeared before the following morning. The number of subjects affected and the duration of their facial symptoms were proportional to the amount of compound sprayed. A sample of individuals was interviewed 1 day and 5-6 days after their houses had been sprayed. One woman, who entered her house 30 minutes after the end of spraying, complained of periorbicular itching, but this lasted only a few minutes. No other significant, insecticide-related adverse effect was reported by the inhabitants of the sprayed houses.

Plasmodium falciparum and P. malariae epidemiology in a West African village.

Abstract: Transmission of Plasmodium falciparum and P. malariae was studied in a village in Burkina Faso. Consecutive captures of mosquitos were organized twice a month over a year and the species of the mosquitos identified. Also, the prevalences and densities of Plasmodium spp. were determined every 2 months in a sample of children who lived in the village. Anopheles gambiae, A. funestus, and A. nili were the local vectors, but only the first two played a predominant role in both P. falciparum and P. malariae transmission. The parasitological sporozoite index (SI) was 4.48% for A. gambiae and 4.22% for A. funestus. The immunological SIs were higher: 5.82% of A. gambiae were infected with P. falciparum and only 0.16% with P. malariae; the corresponding proportions for A. funestus were 6.45% and 0.41%. Transmission of Plasmodium spp. by A. gambiae was important during the rainy season (July-October) and by A. funestus at the beginning of the dry season (September-November). Each child in the study village could receive about 396 P. falciparum-infected bites per year but only 22 of P. malariae. The P. falciparum parasite indices were maximum during the middle of the rainy season (August), while those for P. malariae reached a peak during the dry season (February).

Prevalence of infections and their risk factors in geriatric institutions: a one-day multicentre survey.

Abstract: This one-day prevalence survey of 1919 patients (74% females and 44% aged greater than or equal to 85 years) in nine geriatric hospitals, six of them located in France and three in Switzerland, indicated a high prevalence of infections in elderly institutionalized patients (infection rate: 18.7% in males and 15.4% in females). The risk factors for infection were identified and the relative risks assessed. Prevention of infections in geriatric wards should be one of the goals of every care-giver. A low rate of infection in elderly inpatients is thus likely to be associated with care of good quality.

Presence of enteric viruses in freshwater and their removal by the conventional drinking water treatment process.

Abstract: A review of results published in English or French between 1980 and 1990 was carried out to determine the levels of indigenous human enteric viruses in untreated surface and subsurface freshwaters, as well as in drinking water that had undergone the complete conventional treatment process. For this purpose, the conventional treatment process was defined as an operation that included coagulation followed by sedimentation, filtration, and disinfection. Also assessed was the stepwise efficiency of the conventional treatment process, as practised at full-scale facilities, for removing indigenous viruses from naturally occurring freshwaters. A list was compiled of statistical correlations relating to the occurrence of indigenous viruses in water.

Surveillance of patients with chronic ulcerative colitis. WHO Collaborating Centre for the Prevention of Colorectal Cancer.

Abstract: In chronic ulcerative colitis, the object of surveillance is prevention of cancer or at least prevention of death from cancer by diagnosis at an early curable stage or by detection at a pre-malignant phase. Patients must be informed about their cancer risk as well as the limitations of endoscopic surveillance and the availability of surgical alternatives. Physicians must bear in mind the risks, benefits and costs of surveillance procedures. Patients at greatest risk of cancer for whom endoscopic surveillance is warranted are those with extensive colitis of greater than 8 years duration. Colonoscopy should be performed every 1 to 2 years at which time multiple biopsies are obtained from every 10-12 cm of normal-appearing mucosa. Targeted biopsies should also be obtained from areas where the surface appears raised as a broad-based polyp, low irregular plaque or villiform elevation, or from an unusual ulcer, particularly one with raised edges, or from a stricture. Typical inflammatory polyps need not be sampled. Colectomy is recommended in the presence of multifocal high-grade dysplasia if confirmed by an experienced pathologist. The identification of a mass lesion associated with any degree of overlying dysplasia is also a generally accepted indication for colectomy, while persistent low-grade dysplasia without a mass is somewhat more controversial. Recently introduced biomarkers may replace or supplement dysplasia in surveillance programmes as well as provide new information about malignant transformation.

A reassessment of risk factors for neonatal tetanus.

Abstract: A hospital-based case-control study was conducted to further examine the risk factors for neonatal tetanus (NNT) in the North-west Frontier Province of Pakistan. Three control infants were concurrently evaluated for each of 102 consecutively diagnosed NNT cases hospitalized over an 8-week period. Application of clarified butter (ghee) during the first few days of life was shown to be a significant risk factor, confirming our previously reported finding. However, the risk appeared to be limited to ghee made in the home from cow's milk. The tool used to cut the umbilical cord was again refuted to be a risk factor; application of topical antibiotics conferred significant protection. Multivariate analysis of the matched data showed that delivery by persons with academic training (physicians, nurses, and lady health visitors) was also protective. Mothers with a past history of NNT babies were shown to have a significantly increased risk, and accounted for more than one-third of all cases in the present study. The findings suggest possible ways to augment the effectiveness of NNT elimination programmes.

The epidemiology of yellow fever in Western Africa

Abstract: Observations made during the epidemics in Cote d'Ivoire (1982), Burkina Faso (1983), Nigeria (1986 and 1987) and Mali (1987), together with studies conducted in the last 10 years, particularly in Cote d'Ivoire, now make it possible, without calling into question the dynamics of yellow fever virus circulation in space and time, to redefine some features of the pattern suggested in 1977 and refined on a number of occasions up to 1983 The endemicity area is still the region of epizootic and enzootic sylvatic circulation, and contains the natural focus and the endemic emergence zone --The natural focus is no longer confined to the forest alone, now that transovarial transmission has been demonstrated --The endemic emergence zone is tending to become conterminous with the endemicity area on account of increasing deforestation Emergence in forest regions, due to Aedes africanus, is still few and isolated, unlike that observed in savanna regions where A furcifer is the major vector The different behaviour of these two vectors and their population dynamics determine the quality of the man-vector contact and are responsible for these two patterns of emergence --The emergence front limits the endemicity area in the north Its position varies and depends on annual rainfall patterns The epidemicity area, where the virus does not circulate before an epidemic and where the immunity status of unvaccinated populations is low, is geographically heterogeneous It consists of regions to the north of the emergence front and of towns anywhere It is characterized by high potentials for the development of A aegypti populations Only man can introduce the virus into this area Three types of epidemic are distinguished, depending on the vectors: --Urban epidemics resulting from transmission by a domestic vector These epidemics always occur within the epidemicity area, either in dry savanna (rural subtype) or in towns (urban subtype) The virus is introduced into the ecosystem by man Transmission is always strictly interhuman --Intermediate epidemics consist of two successive phases: first of all there is a series of endemic emergences, followed by interhuman transmission involving A aegypti These epidemics can only occur in the endemicity area --Sylvatic epidemics occur in villages, but only involve the sylvatic vectors They result from a conjunction of a very large number of emergences for which A furcifer is almost always mainly responsible, and occur in the endemicity area, usually close to the emergence front Transmission is never strictly interhuman, as the same vector populations are responsible for epizootic and epidemic transmission(ABSTRACT TRUNCATED AT 400 WORDS)