Diarrhoea and growth faltering in rural Zimbabwe.

OBJECTIVE: To assess the evidence that diarrhoea is an important cause of growth faltering in young children in developing countries. DESIGN: Prospective, longitudinal cohort study. SETTING: Worker's compounds on commercial farms in Shamva, rural Zimbabwe. SUBJECTS: 204 children < 12 months old were enrolled, 73 from birth. The median age at enrolment was 4 months. Eleven children died and 39 were lost to follow-up. INTERVENTIONS: Prospective weekly diarrhoea surveillance by farm health workers and monthly anthropometry. RESULTS: Growth faltering was severe, but there was little difference in average rates of growth between children with frequent diarrhoea and infrequent diarrhoea. The results of an interval-based data analysis were consistent with there being only a transient effect of diarrhoea on weight gain. Estimation of weight faltering following episodes of diarrhoea and the rate of return to the trend in the 9-14 month age range, indicated that weight loss associated with each episode was small (approximately 2%) and return to the child's trend was 90% complete within a month. At older ages than this, weight loss appeared to be less, and estimates were not statistically significant. CONCLUSIONS: These observations lend weight to the hypothesis that recurrent episodes of diarrhoea are not a potent cause of growth faltering in early childhood except in a small minority of largely catastrophic cases. Inadequate food intake is a more plausible explanation.

PIP: In Zimbabwe, health workers collected data on diarrhea incidence every week and anthropometric data once a month from 204 children aged less than 12 months to examine the association between diarrhea and growth faltering. 73 children were enrolled at birth. 148 children were followed throughout the entire study. 11 children died (8 because of diarrhea or protein-energy malnutrition). 39 children were lost to follow-up. The children's parents were farm laborers who lived on large-scale commercial farms in Shamva district. Diarrhea incidence peaked between 13 and 18 months. In 91% of attacks, the diarrhea was watery rather than bloody. 31 children had more than 9 diarrhea episodes (high diarrhea frequency). 25 had no more than 4 diarrhea episodes (low diarrhea frequency). There was little difference in the children's mean weight and mean length from 1 to 30 months of age between high and low diarrhea frequency subjects. The average loss of overall growth per diarrhea episode in the age range 9-23 months was 51 g and 0.18 cm. In the age range of 9-14 months, weight loss after the diarrhea episode was 2.3% of body weight, and 90% of the sudden weight decline below the child's trend was recovered in 30 days. Weight loss was less than 2.3% among older children. A 2.3% weight loss in an 8 kg child is 180 g. Assuming that diarrhea is responsible for the entire weight loss (about 66 g/episode), the reduction in overall growth is about 120 g (1.5%). The total energy needed to accumulate 120 g is 480 kcal; thus, a child would require an additional 2-3 kcal/kg/day (a small amount) to gain 120 g. These findings support the hypothesis that recurrent diarrhea episodes do not induce growth faltering except in a few cases. Inadequate food intake is a more plausible explanation.

A community-based study of acute respiratory infections among preschool children in Syria.

A longitudinal community-based study of the epidemiology of acute respiratory infections (ARI) in children less than 5 years old was carried out in a low income peri-urban area of Syria. A total of 1030 children were followed up by weekly morbidity surveillance for a period of 24 weeks, starting September 1989. The results revealed that, on average, a child suffered 3.4 episodes of ARI per 100 child-days at risk. The average prevalence of ARI was 23 per cent of time of observation. The peak age-specific incidence occurred in children 6-12 months old for cough/cold, and in children 0-5 months for pneumonia. Male children experienced higher incidence and prevalence of ARI. The most frequently reported symptoms were nasal discharge and cough.

Effect of pneumococcal vaccine on morbidity from acute lower respiratory tract infections in Papua New Guinean children.

The effect of a 14-valent pneumococcal polysaccharide vaccine on morbidity from acute lower respiratory tract infection (ALRI) was determined in a randomized double-blind controlled trial in children under the age of 5 years living in the Paupa New Guinea highlands. The vaccine did not protect against mild ALRI. Vaccine efficacy in the study as a whole was 28% for moderate/severe ALRI, which was not statistically significant though consistent with the significant effect on mortality. Children entered the trial in five separate cohorts 4 months apart. The incidence of disease and vaccine efficacy varied between cohorts and with age. There was no vaccine effect in the first cohort, which had a much higher proportion of older children. The effect was greatest and statistically significant among those groups encountering an epidemic of moderate and severe ALRI at a young age. It was therefore in children at the most vulnerable age in times of greatest incidence of disease that the vaccine had its most potent effect. It is postulated that the efficacy of pneumococcal vaccine is dependent on the predominant invading serotypes in the period after vaccination, the age at which children develop immunocompetence to specific vaccine serotypes, and the levels of naturally acquired specific immunity already present in children at the time of vaccination, and that for all of these conditions there will be a cohort effect.

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.

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.

Clinical signs and risk factors associated with pneumonia in children admitted to Goroka Hospital, Papua New Guinea.

This study examined the clinical signs and symptoms in 897 children aged under 5 years presenting with pneumonia to Goroka Hospital in the highlands of Papua New Guinea between June 1982 and July 1985. The usefulness of the signs in predicting severity of disease was determined and risk factors for severe disease were identified. While cyanosis and poor feeding were the strongest predictors of death, bronchial breathing, grunting, and nasal flaring also significantly increased the risk of dying. First-born children, children under 1 year of age, females, malnourished children, and children with symptoms for more than 7 days were at increased risk of severe disease and of dying. Fever alone did not increase the risk of dying unless it was present for more than 7 days. These clinical signs of severity and risk factors may be used to improve the efficiency of health education programmes, for both health workers and mothers, aimed at reducing childhood mortality from pneumonia.

Evidence for a 'memorized' home range in Anopheles farauti females from Papua New Guinea.

Evidence is presented that female Anopheles farauti Laveran released in an alien village dispersed more, in their first oviposition cycle after release, than females released in their village of capture. In a subsidiary experiment transporting the mosquitoes did not affect dispersal; wind speed or direction was not sufficient to account for the phenomenon. It is hypothesized that these permanent-pool breeding mosquitoes make appetitive long-range flights to oviposition sites. Mosquitoes blood-fed before midnight had a shorter oviposition cycle than those fed just before dawn. Nulliparous females, and those with well-defined ovariolar dilatations, predominated in the early evening whereas females that had oviposited recently were largely collected in the middle and later parts of the night.

Pneumococcal vaccine prevents death from acute lower-respiratory-tract infections in Papua New Guinean children.

In three double-blind placebo-controlled trials of pneumococcal capsular polysaccharide vaccines against death from acute lower-respiratory-tract infections (ALRI), children were vaccinated at 6 months to 5 years of age. The efficacy of the vaccines against ALRI as the sole cause of death was estimated at 59% in children vaccinated when younger than 5 years (p = 0.008) and 50% in children vaccinated when younger than 2 years (p = 0.043). Mortality from all causes was 19% less in the vaccinated group.

Density-dependent perception of triatomine bug bites.

Pots containing different densities of Rhodnius prolixus were strapped on to the upper and lower arms and legs of six human volunteers. Analysis of the volunteers' perception of the bugs' probing activity showed a clear linear trend of perception according to bug density. Comparison with other results suggests that in humans as well as other vertebrate hosts, density dependent irritation from the bug bites and consequent disturbance and interruption of bugs' feeding could provide the mechanism by which bug development and population density is normally regulated.

The incidence of eye lesions and visual impairment in onchocerciasis in relationship to the intensity of infection.

Data from follow-up surveys of onchocerciasis, conducted in the rain-forest and savanna areas of the United Cameroon Republic, are used to fit equations relating the incidence of eye lesions and visual impairment to microfilaria concentration in skin-snips. The incidence of lesions in those aged under 45 appears to be directly proportional to concentration, though the association is less clear in females over 25 in the savanna. The incidence of visual impairment appears also to be directly proportional to concentration among those under 45, but only in the savanna. Predictions of changes in incidence rates under transmission control are made, using hypothetical values for the rate of decline of infection. They are compared with reported incidence of lesions from the Onchocerciasis Control Programme: they are in good agreement for those aged under 30 years, but they understate the observed decline in older subjects.

The molluscicidal properties of Ambrosia maritima L. (Compositae). 2. Results from a field trial using dry plant material.

A field trial in Egypt of the plant molluscicide, Ambrosia maritima is described. Applications of 140, 70 and 35 mg/l-1 dry, whole plant were made to irrigation canals and drains in June. The treatment effect took between 1 and 5 weeks to become fully established. The reduction in the numbers of alive Biomphalaria alexandrina snails was generally more than 90% and was virtually the same at all treatment levels and in both types of watercourse. The snail population remained at a low level for at least 3 months until September-October. The possible use of a single, annual application in April or May in controlling snails throughout the main schistosomiasis transmission season in Lower Egypt is suggested.

Dynamics of Schistosoma haematobium infection in a Gambian community. I. The pattern of human infection in the study area.

The roles of some of the factors thought to be responsible for the characteristic relationship between age and the intensity and prevalence of Schistosoma haematobium infection have been investigated. In this initial report a study population in an area of intense infection is described, as are the methods used. Subsequent papers report the effect of interrupting transmission with molluscicide in part of the area and compare changes in egg count in this treated area with changes in an area where no intervention took place. These allow a consideration of age-specific rates of loss and acquisition of infection to be made. The intensity and prevalence of infection varied between villages both in the treated and untreated areas, but the relation of age to the pattern of infection was regardless of the level of infection in the villages. Over-all, the number of subjects and their pattern of infection was similar in both areas. The prevalence of infection tended to be higher in adult males than females but preliminary water contact observations suggest males are less exposed to infection. Observations over the three-year study period emphasize the extent of population movement in the study area and point to its importance in the planning of control measures.

Dynamics of schistosoma haematobium infection in a Gambian community. II. The effect on transmission of the control of Bulinus senegalensis by the use of niclosamide.

Niclosamide was used to interrupt transmission of Schistosoma haematobium by Bulinus senegalensis in seasonal rainwater pools for a period of three years. Snail populations were progressively reduced to approximately 1% of the numbers in untreated pools. There was little or no evidence of acquisition of new infection by children in the area during the period of intervention. The intensity of infection in a cohort of children initially under 10 years old followed for three years fell by more than 50%, while there was a ten-fold increase in a similar group in a nearby untreated area. The mean annual cost (1982) of control per head of the population protected was pound 0.50 (US $0.89).

Dynamics of Schistosoma haematobium infection in a Gambian community. III. Acquisition and loss of infection.

During a three-year period of effective control of Schistosoma haematobium transmission by molluscicide application the mean number of S. haematobium ova passed by subjects in the treated area fell in an exponential manner which suggested that the mean life span of the worm was 3.4 years. Parallel observations were made in a similar but untreated area. A comparison of the observations in these two areas suggested that in the untreated area subjects of all ages acquired infection during the course of the study. At the end of the study over 50% of the egg output in most age groups in the untreated area appeared to come from worms acquired during the preceding three years. There were substantial differences between age groups in the amount of infection acquired. Children, aged between eight and ten years at the end of the study, appeared to be passing perhaps a thousand times more ova from worms acquired during the preceding three years than were middle-aged subjects. Preliminary observations suggest that age- and sex-related differences in the pattern of water contact may not fully account for age- and sex-related differences in the rate of acquisition of infection and its prevalence. The probable significance of protective immunity in the epidemiology of schistosome infections is discussed.

The molluscicidal properties of Ambrosia maritima L. (compositae). 1. Design for a molluscicide field trial.

The composite plant, Ambrosia maritima is toxic to the snail intermediate hosts of schistosomiasis. A field trial was required to confirm this activity. A preliminary survey of irrigation canals and drains was conducted using two snail sampling methods. The results have been used to indicate the minimum number of watercourses which would have to be treated and the number of sampling stations per watercourse required to establish statistical significance in a kill of snails obtained from a molluscicide treatment.

The use of infectivity titrations for measurement of the viability of Entamoeba histolytica after cryopreservation.

An infectivity titration technique is described for the measurement of the viability of Entamoeba histolytica. Using this method an optimal cryopreservation technique has been developed. When amoebae from young cultures were equilibrated with 7.5% dimethylsulphoxide for 15 minutes at 37 degrees C, cooled to -100 degrees C at 1 degree C per minute, and stored in liquid nitrogen, 1 to 2% regularly survived after thawing rapidly at 37 degrees C and, on occasions, 10 to 12% survived.