Methodological approaches in a baseline study of diarrhoeal morbidity in weaning-age children in rural Zaire

A community-based prospective study of diarrhoeal morbidity of weaning-age children in 18 geographically separate village clusters was conducted as the baseline phase of a controlled trial of a hygiene education intervention to reduce diarrhoeal diseases in rural Zaire. For 12 weeks trained interviewers collected information at weekly home visits about the diarrhoeal morbidity of 2082 children aged 3-35 months. Included in the analyses were 1914 children (92%) with 9 or more complete weeks of data. Mothers' reporting of the existence or otherwise of episodes appeared reliable, and more than 70% of children had at least one episode of diarrhoea during the 12-week study period, the mean number of episodes being 1.9 per child. Reporting of the start and termination of diarrhoeal episodes was, however, irregularly distributed among the 7 days between successive home interviews, with 36% of all episodes reported as starting on interview days, and 29% reported as ending the day before an interview: in each case, only 14% would have been expected. After adjusting for these reporting biases, 61% of the episodes lasted 2-4 days, but a number of very long duration were also reported, and the mean duration of the episodes was 4.8 days. Children, had, on average, 9.2 days of diarrhoea during the study period. Contrasts with previous characterizations of reporting error in diarrhoeal studies are noted.

Community-based hygiene education to reduce diarrhoeal disease in rural Zaire: impact of the intervention on diarrhoeal morbidity

BACKGROUND

Diarrhoeal disease is a leading cause of morbidity in young children in rural Zaire. Few diarrhoea prevention programmes have been implemented in Bandundu Province, where available data suggest an annual prevalence rate of 10%. The urgent need to reduce diarrhoeal morbidity in Zaire, together with the potential effectiveness and feasibility of hygiene education as a diarrhoea prevention strategy, led to the development of the present research project.

METHODS

A randomized, controlled trial of an education intervention to reduce diarrhoea through improved personal and domestic hygiene behaviours was conducted in 18 geographically separate village clusters (sites) in rural Zaire. For 12 weeks baseline information on the diarrhoeal morbidity of 2082 children aged 3-35 months was collected at weekly home visits, and structured observations of hygiene practices related to diarrhoea were made on a subset of 300 families. Intervention messages addressed disposal of animal faeces from the yard, handwashing after defecation and before meal preparation and eating, and disposal of children's faeces. Three months after the start of the intervention and exactly 1 year after the baseline studies, a second diarrhoeal morbidity study and a second observational study were conducted in order to evaluate the intervention.

RESULTS

Children in intervention communities experienced an 11% reduction in the risk of reporting diarrhoea during the peak diarrhoeal season, compared to controls (P < 0.025). The largest differences were seen among children aged 24-35 months, with those from intervention communities reporting significantly fewer episodes, shorter mean durations and hence fewer days of diarrhoea. There was some evidence that greater reductions in diarrhoea occurred in sites where the quality of the intervention, a scored measure of volunteer efficacy and community participation, was highest.

CONCLUSIONS

The results of this study suggest that hygiene education may be an effective approach to reduce the incidence and duration of diarrhoeal episodes in rural Zaire. Children aged 2 years appear to benefit the most. A Hawthorne effect of the education may contribute to diarrhoeal reductions.

Lack of association between vitamin A status and measures of conjunctival epithelial integrity in young children in northern Ghana

OBJECTIVE

To investigate the association between vitamin A status and conjunctival epithelial function in young children in rural northern Ghana and to consider whether impaired epithelial function was associated with increased measures of systemic infection in these children.

DESIGN

Children were selected from the Ghana Vitamin A Supplementation Trials' Child Health Study, a randomized, double-blind, placebo-controlled trial of the effect of vitamin A supplementation on morbidity. Treatment group and serum retinol concentrations were used as measures of vitamin A status, conjunctival impression cytology and tear IgA concentrations as measures of conjunctival epithelial integrity, and serum immunoglobulin and alpha 1-acid glycoprotein concentrations as indicators of chronic or acute systemic infection.

SUBJECTS

Children 13-64 months old.

INTERVENTION

60 mg retinol as retinyl palmitate every 4 months for 1 year.

RESULTS

Vitamin A status was not significantly associated with epithelial integrity nor with measures of systemic infection. Impaired conjunctival epithelial integrity was also not associated with increased systemic infection.

CONCLUSIONS

There was no evidence for a major role of improved epithelial integrity and function on the biochemical indices of chronic or acute systemic infection after vitamin A supplementation. These data support the observations in the main study that vitamin A supplementation did not improve conjunctival impression cytology nor decrease the prevalence of most morbidity symptoms.

Weaning in southern Brazil: is there a "weanling's dilemma"?

In Pelotas, Brazil, 400 newborns from low income families were followed-up until 26 wk of life to study the relationship between their feeding patterns and growth as modified by access to water and by diarrhea. Effects of access to water were the strongest among non-breastfed infants. In houses without indoor water taps, the weight gain of non-breastfed infants during the first 3 mo was approximately half that of partially or predominantly breastfed infants (P < 0.001). In houses with indoor water taps, non-breastfed infants' growth was similar to or exceeded that of predominantly breastfed infants from 2 mo. Predominantly breastfed infants' growth was similar in houses with and without water taps. Breastfed infants had less weight loss per day of diarrhea than non-breastfed infants during the first 4 mo and less diarrhea through 6 mo of life, particularly in houses without taps, in which diarrhea was most prevalent. The existence of a "weanling's dilemma" was approached by comparing the duration of the detrimental effects of not breastfeeding (i.e., 0-3 mo in this study) with the age at which breast milk alone becomes less than optimal for growth (i.e., at 5 mo). Because these two points did not coincide, we conclude that there is no "weaning's dilemma" in this population.

Diarrhoea--defining the episode

BACKGROUND

There is still no consensus on the appropriate definition of an 'episode' of diarrhoea, even though it has been shown that the choice of definition has a major impact on reported incidence rates. Previous work has focused on the observed distribution of illness episodes in time but has not attempted to determine whether the patterns observed depart from those expected by chance.

METHODS

A simple theoretical model of the distribution of illness episodes is developed, based on the concept of a 'trigger event'. The model incorporates elements relating to the duration of symptoms, inter-individual variation in incidence rates and seasonality. Appropriate parameters for the model are derived from two empirical datasets.

RESULTS

It is shown that short intervals between one aetiologically distinct period of diarrhoea and the next will frequently occur by chance, especially in circumstances where high incidence rates and within-child clustering of illness prevail. The duration of symptoms will have no effect on the length of intervals between periods of illness, and seasonality is unlikely to have a major impact. Over 10% of all non-initial trigger events might be expected to occur during the course of a pre-existing period of diarrhoea, and would not therefore be identified in a study based on reported symptoms.

CONCLUSIONS

The findings of previous studies, suggesting that 2 or 3 days without symptoms will generally mark a new episode of diarrhoea, are endorsed. Modelling the expected distribution of illness in time may help to highlight structural or analytical problems with empirical datasets.

Influence of demographic, socioeconomic and environmental variables on childhood diarrhoea in a rural area of Zaire

There have been very few longitudinal studies of diarrhoea morbidity in sub-Saharan Africa. This longitudinal study of children aged 3-35 months from 18 clusters of villages reports an annual incidence rate of 6.3 episodes per child in a rural area of Zaire, which is higher than a cross-sectional estimate previously obtained in the same district. The study confirms that a child's risk of diarrhoeal attack is associated with age, water quality and sanitation, parental education and household size. The findings suggest also that birth interval may be an important risk factor for diarrhoeal morbidity.

Influence of morbidity on serum retinol of children in a community-based study in northern Ghana

Serum retinol concentrations decrease during illness and thus may not accurately reflect the vitamin A status of populations with a high prevalence of illness. To quantify the contribution of illness to low serum retinol in a field study of children aged 6-59 mo in northern Ghana, serum retinol values were compared with two indicators of recent illness; symptoms reported by parents and acute-phase protein concentrations in serum. Serum retinol was not associated with symptoms of illness but showed a significant negative correlation with both alpha 1-acid glycoprotein (AGP) and serum amyloid A (SAA). Elevated AGP was associated with a 24% decrease in mean serum retinol. A large proportion of asymptomatic children had elevated AGP or SAA concentrations, suggesting that subclinical infections may have had important effects on serum retinol. A significant negative correlation between malaria parasite density and serum retinol indicated that malaria may have been one of the subclinical infections responsible. Measurement of AGP may improve interpretation of serum retinol data from populations with a high prevalence of morbidity.

Comparison of the causes and consequences of prematurity and intrauterine growth retardation: a longitudinal study in southern Brazil

A cohort of 5914 liveborns (99% of the city births) was followed up to the age of 4 years in Pelotas, southern Brazil. Besides the perinatal evaluation, the cohort children were examined again at mean ages of 11, 23, and 47 months. During each visit the children were weighed and measured and information on morbidity was collected. Also, multiple sources of information were used for monitoring mortality throughout the study. Of the babies with known gestational age, 9.0% were classified as intrauterine growth-retarded and 6.3% as preterm. Excluding those of unknown gestational age, 62% of low birth weight babies were intrauterine growth-retarded and 36% were preterm. Intrauterine growth retardation was statistically associated with maternal height, prepregnancy weight, birth interval, and smoking, whereas preterm births were associated with maternal prepregnancy weight and maternal age. Preterm babies had a perinatal mortality rate 13 times higher than that of babies of appropriate birth weight and gestational age and 2 times higher than that of intrauterine growth-retarded babies. Infant mortality rates presented a similar pattern, with the differentials being more pronounced during the neonatal than in the postneonatal period. In the first 2 years of life intrauterine growth-retarded children were at almost twice the risk of being hospitalized for diarrhea compared with appropriate birth weight, term children, while preterm children experienced only a slightly greater risk. For pneumonia, however, both groups of children were hospitalized significantly more than appropriate birth weight, term children. In terms of growth, despite their earlier disadvantage, preterm children gradually caught up with their appropriate birth weight, term counterparts.(ABSTRACT TRUNCATED AT 250 WORDS)

Breast-feeding, nutritional status, and other prognostic factors for dehydration among young children with diarrhoea in Brazil

Early identification of children at high risk of diarrhoea-associated dehydration would be of great value to health care workers in developing countries. To identify prognostic factors for life-threatening dehydration, we carried out a case-control study among under-2-year-olds in Porto Alegre, Brazil. Cases were 192 children admitted to hospital with moderate or severe dehydration, while controls were children matched to controls by neighbourhood and age, who experienced nondehydrating diarrhoea in the week preceding the interview. The following variables were significantly associated with an increased risk of dehydration, after adjustment for age and other confounding variables: absence of the father from the home; low paternal education level; young age; maternal age 25-29 years or less than 20 years; mother of mixed race; high birth order; short birth interval; low birth weight; stunting, underweight and wasting; lack of breast-feeding; presence of other under-5-year-olds in the home; families with 4-5 members; lack of antenatal care; less than three doses of diphtheria-pertussis-tetanus or poliomyelitis vaccine; previous admission to hospital; use of medicines during the fortnight prior to the episode; and living in an unclean home. The associations were particularly strong (P less than 0.001) for the child's age, birth weight and other anthropometric indicators, birth interval, and feeding mode. In terms of their sensitivity and specificity, however, these prognostic factors were not as effective as early signs and symptoms for predicting the outcome of the episode.

Is it possible to predict which diarrhoea episodes will lead to life-threatening dehydration?

Early detection of children who are likely to develop life-threatening dehydration as a consequence of diarrhoea would be of great value for health care workers in developing countries. We carried out a case-control study to compare the symptoms and signs observed on the first day of diarrhoea in two groups of 192 children aged under two years, in the Brazilian city of Porto Alegre. The cases were children admitted to a hospital with moderate or severe dehydration, and controls were children from the same neighbourhoods as the cases, who had diarrhoea which did not lead to hospital admission. The sensitivity and specificity of different clinical indicators were calculated. Alterations in thirst (82%), followed by six or more stools (71%), fever (60%), vomiting (58%) and loss of appetite (57%) had the highest sensitivities, whereas the specificities were largest for blood in the stools (97%), fever (78%) and vomiting (78%). Assuming that dehydration occurs in 5% of all episodes of diarrhoea, the use of fever as a screening criterion, or the use of vomiting, would select 24% of all children with diarrhoea, and capture about 60% of all episodes of dehydration. The combination of fever or vomiting would increase the proportion selected to 36%, and capture 75% of episodes of dehydration.

Pneumonia, diarrhea, and growth in the first 4 y of life: a longitudinal study of 5914 urban Brazilian children

The synergism between nutrition status and hospital admissions due to diarrhea and pneumonia was studied in a population-based birth cohort of greater than 5000 children in southern Brazil. Children were identified soon after birth in 1982, and data on nutrition status (weight and length) and hospital admissions were collected in 1984 and in 1986. Diarrhea admissions were stronger predictors of malnutrition than were pneumonia admissions, but malnutrition was a more important risk factor for pneumonia than for diarrhea. All associations were stronger in the first 2 y of life, although the early effect of severe diarrhea and pneumonia on nutrition status could still be detected in the fourth year of life.

The Imo State (Nigeria) Drinking Water Supply and Sanitation Project, 1. Description of the project, evaluation methods, and impact on intervening variables

A health impact evaluation was conducted in conjunction with the Imo State Drinking Water Supply and Sanitation Project in Nigeria. The project consisted of a package of water supply, sanitation, and health and hygiene education given by village-based workers. The evaluation was a quasi-experimental study covering pre-, peri- and post-intervention periods. Data were collected from 3 intervention and 2 control villages. Baseline surveys indicated that the intervention and control areas were similar with respect to most socio-demographic variables. Use of the improved water supply was high, although this was influenced by borehole-to-population ratios and household-to-borehole distances. Water collection time was consequently greatly reduced. Data from a small sample of households showed that borehole water became heavily contaminated during collection and storage, and that there was no significant change in consumption of water per person. Adults in 46% of household units in the intervention area were using ventilated improved pit latrines by the end of the study period. Use by young children (2-5 years old), however, was low. Limitations in the success of the health education component of the project were found. Although changes were found in knowledge, attitudes and practices related to water and sanitation, and in management of childhood diarrhoea, this occurred in both the intervention and control areas.

Case-control designs in the study of common diseases: updates on the demise of the rare disease assumption and the choice of sampling scheme for controls

In recent years the use of case-control designs has been extended to the study of common diseases. It has been shown that the rare disease assumption is not necessary, and that by a suitable choice of sampling scheme for controls, it is possible to obtain direct estimates of relative risk and relative rate, instead of relying on the odds ratio as an indirect estimate. The majority of papers addressing these issues are theoretical, and the arguments have been couched in mathematical terms. As such they are not readily accessible to many practising epidemiologists. This paper summarizes the discussion in a simplified manner. It describes the three different measures of relative incidence, namely the relative risk, the relative rate and the odds ratio, together with their corresponding case-control designs. The discussion is extended to show that the choice of the appropriate measure of relative incidence depends on the mode of action of the risk factor, as well as on characteristics of disease. We propose a classification scheme comprising five different categories of situation, and make recommendations regarding study designs for each.

Health impact evaluation of improved water supplies and hygiene practices in Sri Lanka: background and methodology

Between January 1987 and March 1988 a Health Impact Evaluation (HIE) of the Rural Water Supply and Sanitation Project (RWSSP) was conducted in Kurunegala District. Four related activities were undertaken: 6598 children were recruited into a case-control study of diarrhoea morbidity conducted in five hospitals; an additional 1649 children from the catchment areas of three of the five hospitals were recruited as a community comparison group; environmental microbiology was performed on water samples collected during 3092 visits to the homes of children recruited into the study; diagnostic stool microbiology was performed for 371 children with diarrhoea and 121 controls. In this paper the seasonality of reported diarrhoea and the socio-demographic characteristics and health-related behaviours of each study group are examined. Cases, clinic controls and the community comparison group were all drawn from the essentially rural settlements typical of the southern part of the dry zone of Sri Lanka. The majority of households in these settlements are Sinhalese buddhist, and the main economic activity is subsitence farming. There was some evidence of differences between the three groups, community recruits tending to come from larger and wealthier households than the children recruited at the hospitals. Issues arising in the design and analysis of this Health Impact Evaluation are discussed. In particular, potential sources of bias are examined and the question of validity investigated.

The Imo State (Nigeria) Drinking Water Supply and Sanitation Project, 2. Impact on dracunculiasis, diarrhoea and nutritional status

Morbidity due to dracunculiasis (guinea worm disease) and diarrhoea in persons of all ages, and nutritional status of young children, were used as health impact indicators in the evaluation of the Imo State Drinking Water Supply and Sanitation Project in south-eastern Nigeria. Data were collected using repeated cross-sectional surveys and longitudinal follow-up. The study area was found to have a low level of endemicity of dracunculiasis. While no impact could be demonstrated on overall period or point prevalence rates in the cross-sectional surveys, a prospective longitudinal survey showed a significant reduction in the percentage of person-fortnights positive for dracunculiasis in areas served by the project, while the control areas showed no such change. In the cross-sectional surveys it was found that, in the project villages, those persons drinking only borehole water had significantly lower period prevalence rates one year later than others. Moreover, those living further from the nearest borehole had higher rates of dracunculiasis. An impact of the project on diarrhoea morbidity was found only in limited sub-groups of the population. A greater association with water availability rather than quality was suggested for rates in young children. The prevalence of wasting (less than 80% weight-for-height) among children aged less than 3 years decreased significantly over time in all 3 intervention villages; there was no such decline in the control villages.

Childhood diarrhoea in Sri Lanka: a case-control study of the impact of improved water sources

Between January 1987 and March 1988 a case-control study of the impact of improved water sources on childhood diarrhoea was conducted in Kurunegala District, Sri Lanka. Two thousand four hundred and fifty eight cases of diarrhoea were recruited at five of the hospitals in the district. Another 4140 children presenting at the same hospitals with complaints other than diarrhoea were recruited as controls. Data from the five hospitals suggest that children in households drawing their drinking water from handpumps suffer 46% fewer episodes of diarrhoea than children in families using unprotected traditional sources (95% c. i. 29-59%), while children in families using protected traditional wells suffer 35% fewer episodes than children in families using unprotected traditional sources (95% c. i. 27-41%). There were, however, substantial differences between the different hospitals. Among children recruited at one of the hospitals, the reduction in diarrhoea rates associated with the use of improved sources was estimated to be 93% compared with an average of 18% for the other four hospitals. In common with other case-control studies conducted in Malawi and the Philippines, little evidence of confounding of the association between diarrhoea and water supply was observed. Our results suggest that, in Sri Lanka, the use of improved water supplies, including protected traditional wells, rather than unprotected traditional sources may lead to a substantial reduction in diarrhoea morbidity among children under five years of age.

Determinants of water quality, availability and use in Kurunegala, Sri Lanka

Between January 1987 and February 1988, 4590 homes of children under five years of age were visited in three areas of Kurunegala district, Sri Lanka and data were collected on water related practices. 60% of the population used protected wells, 30% used unprotected sources and 10% used handpumps on boreholes or piped supplies. 90% of households had a source less than 1 km away. Mean water consumption was above 25 litres per capita per day and did not correlate with the distance to source. Samples of drinking water were collected and faecal coliform levels were determined in samples of stored water from 3092 households and in samples from the water sources used by 1043 of these households. The absence or presence of organisms in each sample, and the geometric mean count in samples with organisms were used as indices of contamination. Both indices changed with season and varied between areas and between types of water source. The proportion of positive source samples was uniformly high with the exception of piped supplies and handpumps. The mean count was highest for unprotected sources. There was no evidence that ground water contamination occurred in boreholes. With stored samples, boiling appeared to reduce contamination markedly. The proportion of positive stored water samples was also lower with the use of different vessels for collection and storage, with storage inside the house, and with use of a storage container other than an earthenware pot. Because surface water pollution appears to be important it is proposed that headwalls and drainage aprons be built around unprotected sources. Faecal contamination at the source may have more public health significance than contamination of stored water. In this respect public hygiene may play an important role in reducing water pollution at handpumps or protected wells.

Disability from dracunculiasis: effect on mobility

A study was conducted in northeastern Imo State to define the disability and restriction of mobility associated with dracunculiasis. The study was part of an evaluation of the UNICEF-assisted Drinking Water Supply and Sanitation Project in Imo State, Nigeria. A sample of household units (100 in year 1, 195 in year 2) was visited every two weeks to determine who was affected by dracunculiasis and to characterize the extent of related disability. The average duration of symptoms was 12.7 weeks (range 3-29 weeks). Fifty eight per cent of all episodes of disease resulted in severe disability (with the individual unable to leave the compound) lasting a mean of 4.2 weeks (range 2-12). The mean period of severe disability was significantly higher for those aged 50 years and over than for those less than 50 years old. In the area studied, the disease occurred during the peak yam and rice harvest time and the period of preparation for the planting season. This is the first study to document systematically and prospectively the marked restriction of normal activity in affected individuals and the long duration of the disability. These findings can assist in improving estimates of the costs associated with dracunculiasis and of potential economic benefits if the disease were eradicated.

Community-based intervention trials

The randomized controlled trial has become the standard basis for the evaluation of new therapeutic agents and procedures (and for measuring the protective efficacy of new vaccines or for assessing the value of screening procedures). Patients, who have met the criteria for eligibility and have agreed to participate in the trial, are allocated on a random basis to the alternative therapies under consideration. In order to avoid possible bias in the handling or assessment of these groups, a double blind procedure is preferred; the therapy given is not known to those who administer it, to those who assess the course of the disease thereafter, nor to the patients themselves. There is an extensive literature on clinical trials covering their logic and history, modern developments and the many complex, often controversial, issues that such trials have provoked. Not all issues have been fully resolved but by and large the principle, the practice and the ethical concerns of clinical trials are worked out and firmly established.

Epidemiological studies of onchocerciasis in forest villages of Sierra Leone

Results are presented for five villages in the forest zone of Sierra Leone in which forest onchocerciasis was considered to be a significant health problem. All five villages were found to be hyperendemic and 85% (682/803) of persons were found to have at least one sign of onchocerciasis. The emergence of microfilariae from skin snips (iliac crest and/or canthus) or the presence of nodules accounted for 96.5% of all persons positive for onchocerciasis. The prevalence of nodules from all body sites was 70.5% and of elephantiasis, hanging groin and skin lesions (moderate and severe) was 0.4%, 0.3% and 5.3% respectively. Analysis of eye lesions (the most serious clinical manifestation of the disease) was restricted to persons aged 30 years and over since this gives a better indication of the public health importance of onchocerciasis than analysis in the overall population. This gave prevalence rates of onchocercal blindness of 4.5% (both eyes) and 2.8% (one eye only). Rates for the four potentially blinding eye lesions were sclerosing keratitis (4.1%), iritis (16.5%), optic atrophy (13.8%) and choroidoretinitis (14.4%). Rates in males were approximately twice as high as those in females.

Epidemiological studies of onchocerciasis in savanna villages of Sierra Leone

The overall prevalence of onchocerciasis was 78% and 73% in three villages of the woodland savanna of Koinadugu and four villages of the savanna-forest mosaic of Kambia respectively. The total number of persons examined was 611. In Koinadugu the prevalence of microfilariae of Onchocerca volvulus in skin snips from the iliac crest and canthus was 51.3% and 22.5% respectively while corresponding figures for Kambia were 52.2% and 19.3%. The pattern of clinical manifestations were similar in both districts, the overall rates for nodules, skin lesions (moderate and severe) and leg elephantiasis being 53.2%, 12.5% and 0.3% respectively. No cases of hanging groin were seen. The prevalence of onchocercal eye lesions was lower in the present surveys than in our own findings in Guinea or the findings of other investigators in the Guinea or Sudan savanna of West Africa. In the present study prevalences of the fourmain blinding eye lesions in persons aged 30 years or more were sclerosing keratitis (3.7%), iritis (8.7%), optic atrophy (14.2%) and choroidoretinitis (11.3%), and the prevalence of blindness was 4.2% (both eyes) and 2.0% (one eye). Males were more commonly affected than females. Further entomological studies are needed to elucidate the relative role played by the different cytospecies of Simulium damnosum s.l. in the transmission of onchocerciasis in the savanna of Sierra Leone.

Onchocerciasis in Sierra Leone.2: A comparison of forest and savanna villages

Very little of the original primary forest remains in Sierra Leone and the savanna is mainly woodland or a forest-savanna mosaic. The prevalence of microfilariae of Onchocerca volvulus, nodules and moderate or severe skin lesions was higher in forest than savanna villages. In forest villages the prevalence of microfilariae was 71.8% at the iliac crest, 36.6% (outer canthus), 12.8% (cornea) and 34.1% in the anterior chamber of the eye. Corresponding figures for the savanna villages were 51.9%, 20.5%, 5.6% and 21.8%. The overall prevalence of nodules in the forest and savanna was 70.5% and 53.2% respectively, while the prevalence of head and upper body nodules was 14.8% (forest) and 11.0% (savanna). The prevalence of moderate or severe skin lesions was 17.7% in forest and 13.0% in savanna villages. Lesions of the groin and scrotum were few in both zones. In persons aged 30 years or more the prevalence rates of severe eye lesions--sclerosing keratitis, iritis, optic atrophy and choroidoretinitis--were 4.3%, 16.1%, 13.9% and 14.8% respectively in forest villages. Corresponding figures for the savanna villages were 3.7%, 8.7%, 14.2% and 11.3%. Males were more commonly affected than females. At least one of these lesions was found in 32% persons in forest and 24% in savanna villages.

Onchocerciasis in Sierra Leone 3: Relationships between eye lesions and microfilarial prevalence and intensity

The relationship between severe onchocercal eye lesions (iritis, sclerosing keratitis, optic atrophy and choroidoretinitis) and (i) the prevalence and intensity of microfilariae (mf) of Onchocerca volvulus in skin snips from the iliac crest and outer canthus, and (ii) the prevalence of mf in the cornea and anterior chamber of the eye, was studied in 1414 persons from forest and savanna villages and 312 attenders at eye clinics. Ecologically the savanna of Sierra Leone more closely resembles the forest than the dry Sudan-savanna areas of West Africa, and in persons aged 30 years or more the combined prevalence of anterior segment lesions (iritis and sclerosing keratitis) was higher in the forest villages (20.6%) than in the savanna (12.7%). The higher loads of mf found in the forest compared to savanna villages could explain these results. Prevalence rates for posterior segment lesions (optic atrophy and choroidoretinitis) were 28.1% and 22.6% in the forest and savanna respectively. Although in villages from both zones there was a close association between mf in the anterior chamber and optic atrophy, other associations between posterior segment lesions and mf were either not significant or weak. In contrast, there was a strong association between anterior segment lesions and mf in the eye and the concentration of mf at the outer canthus. This association was stronger for iritis than for sclerosing keratitis.

Adult male all-cause, cardiovascular and cerebrovascular mortality in relation to ethnic group, systolic blood pressure and blood glucose concentration in Trinidad, West Indies

In a prospective survey of 1342 Trinidadian men aged 35 to 69 years at recruitment, age-adjusted mean blood pressures were highest in those of African descent, intermediate in Indians and mean of Mixed origin, and lowest in Europeans. Age-adjusted fasting blood glucose concentrations were highest in Indians and lowest in men of European descent. Relative risks of all-cause, cardiovascular and cerebrovascular mortality increased progressively with increasing systolic pressure, whereas for fasting blood glucose concentration the associations were U-shaped. No ethnic differences were apparent in relative risks. For systolic pressure, mortality from all-causes and cardiovascular diseases respectively were about two and three times higher at 180 mmHg or more than at pressures below 130 mmHg. For blood glucose, all-cause and cardiovascular mortality were about four times higher at fasting concentrations greater than 7.7 mmol/l than in the lowest risk group (4.2-4.6 mmol/l). All-cause population attributable mortality rates for systolic pressures of 130 mmHg or more were 1.3 to 2.8 times higher in Indian men than in other groups. For blood glucose in excess of 4.6 mmol/l, population attributable mortality was between 2.9 and 6.9 times higher in Indians than in other groups. The findings emphasized the high mortality in men of Indian descent, partly due to an apparent underlying predisposition to cardiovascular disease, and partly to their high prevalence of diabetes mellitus.

The bacteriological quality of traditional water sources in north-eastern Imo State, Nigeria

Monthly bacteriological water testing of traditional water sources (ponds, rivers, unprotected springs and traditional wells) used by five villages in northeastern Imo State, Nigeria, was conducted during the period January 1983 to August 1985. The membrane-filtration technique was used to detect faecal coliforms (FC) and faecal streptococci (FS). Evidence of faecal pollution was seen throughout the year for all water sources. During the study period, the monthly geometric mean counts per 100 ml of water (all sources combined) ranged from 760 to 17877 for FC and from 678 to 17394 for FS. The peak period of faecal pollution occurred during the transition between the dry and wet seasons and in the early wet season. During this peak pollution season (February-May), the geometric mean counts were 2.5-7.2 times higher than in the remaining part of the year for all source types except rivers, with ponds being the most heavily polluted. Preliminary findings on the sensitivity and specificity, in this tropical environment, of the standard membrane-filtration technique for enumerating FC are presented. The implications of the findings of this study for the environmental control of waterborne and hygiene-related diseases are discussed.