Chlorination of Schistosoma mansoni cercariae.

BACKGROUND: Schistosomiasis is a water-based disease acquired through contact with cercaria-infested water. Communities living in endemic regions often rely on parasite-contaminated freshwater bodies for their daily water contact activities, resulting in recurring schistosomiasis infection. In such instances, water treatment can provide safe water on a household or community scale. However, to-date there are no water treatment guidelines that provide information on how to treat water containing schistosome cercariae. Here, we rigorously test the effectiveness of chlorine against Schistosoma mansoni cercariae. METHOD: S. mansoni cercariae were chlorinated using sodium hypochlorite under lab and field condition. The water pH was controlled at 6.5, 7.0 or 7.5, the water temperature at 20°C or 27°C, and the chlorine dose at 1, 2 or 3 mg/l. Experiments were conducted up to contact times of 45 minutes. 100 cercariae were used per experiment, thereby achieving up to 2-log10 inactivations of cercariae. Experiments were replicated under field conditions at Lake Victoria, Tanzania. CONCLUSION: A CT (residual chlorine concentration x chlorine contact time) value of 26±4 mg·min/l is required to achieve a 2-log10 inactivation of S. mansoni cercariae under the most conservative condition tested (pH 7.5, 20°C). Field and lab-cultivated cercariae show similar chlorine sensitivities. A CT value of 30 mg·min/l is therefore recommended to disinfect cercaria-infested water, though safety factors may be required, depending on water quality and operating conditions. This CT value can be achieved with a chlorine residual of 1 mg/l after a contact time of 30 minutes, for example. This recommendation can be used to provide safe water for household and recreational water activities in communities that lack safe alternative water sources.

Calcium, magnesium, iron, zinc and copper, compositions of human milk from populations with cereal and 'enset' based diets.

BACKGROUND: As breast milk is normally the only source of food in the early stages of life, the dietary levels of the essential elements in the milk of lactating mothers are significantly important. Ethiopia is a country of many nations and nationalities with distinct dietary habits. This variation in food habit may result in the variation of the nutritional quality of milk of lactating mothers who live in different part of the country, which in turn may affect the intake of nutrients by breast-fed infants. Therefore, a cross-sectional study of the levels of Ca, Mg, Fe, Zn and Cu in milk of mothers from societies with cereal and 'enset' based dietary habits was carried out to assess the influence of maternal diet on the levels of the elements in human milk. METHODS: Milk samples were collected from 27 voluntary mothers in Jimma and in 18 rural areas of Welkite. Breast milk samples were collected within four days postpartum and the concentrations of the elements were determined by using FAAS. RESULTS: Average concentrations (mg/L) of the elements determined in the milk of mothers from Jimma and rural Welkite respectively were: Ca (758 ± 107, 579 ± 168); Mg (22.6 ± 7.87, 30.5 ± 13.4); Fe (0.50 ± 0.08, 0.41 ± 0.17); Zn (2.3 ± 1.2, 2.49 ± 0.88) and Cu (0.28 ± 0.14, 0.16 ± 0.08). CONCLUSIONS: Milk samples from Jimma were found to have significantly higher levels of Ca and Cu than those of rural Welkite (P < 0.05). Breast milk Ca and Cu levels were thus found to be influenced by dietary intake.