Testing household disinfectants for the inactivation of helminth eggs on surfaces and in spills during pit latrine emptying

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Abstract

The lack of potable water, poor hygiene practices and inefficient sanitation systems in developing countries pose a risk to human health. Pit latrines aim to break the link between human faecal waste and human contact by serving as improved sanitation. The eThekwini Municipality has developed a programme that employs workers to empty pits every 3 to 5 years. This study aimed to find a cost-effective, easy way of disinfecting household surfaces and inactivating Ascaris eggs using household disinfectants, so that transmission of helminths is minimised when pits are emptied. Disinfectants tested in this study were based on sodium hypochlorite or carbolic acid. Experiments simulated inactivation of Ascaris eggs by wiping contaminated surfaces with disinfectants and by soaking small spills in disinfectants. Samples were processed using standard helminth egg enumeration methods for soil and sludge. Wiping of contaminated surfaces removed Ascaris eggs, facilitating egg transfer but not egg inactivation. Prolonged exposure to disinfectants, at concentrations of 50% and above, were required to inactivate eggs. Sodium hypochlorite-based disinfectants were the most successful for inactivation, whilst those based on carbolic acid were mostly ineffective. It is recommended that faecal sludge spills are soaked in a sodium hypochlorite-based disinfectant and contaminated surfaces be wiped with a sodium hypochlorite-based disinfectant-saturated cloth, which should then be soaked for 1 h in a similar disinfectant solution (50% dilution) to inactivate any eggs picked up on the cloth.

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Intraluminal pH of the human gastrointestinal tract.

J Fallingborg (1999)

After a short introduction (chapter 1) methods of measuring gastrointestinal pH are described in chapter 2. The methods are divided into intubation techniques and tubeless methods, and the advantages and disadvantages are discussed. Measurements with pH-sensitive, radiotransmitting capsules are highlighted, and methodological problems with these capsules are described. Chapter 3 concerns the gastrointestinal pH profile of healthy subjects. The intraluminal pH is rapidly changed from highly acid in the stomach to about pH 6 in the duodenum. The pH gradually increases in the small intestine from pH 6 to about pH 7.4 in the terminal ileum. The pH drops to 5.7 in the caecum, but again gradually increases, reaching pH 6.7 in the rectum. The physiological background of these pH values is discussed. Chapter 4 describes the effect of gastrointestinal pH on bacterial flora, absorption of vitamins and electrolytes, and on the activity of digestive enzymes. The pH-profile in children is described in chapter 5. The profile is identical with that of adults, and it is therefore concluded that the release of a drug from pH-dependent, controlled-release preparations is also probably identical with that of adults. Chapter 6 describes the correlation between certain diseases and the gastrointestinal pH. A resection of the colon and the creation of an ileostomy do not affect the pH of the remaining gut. An ileocaecal resection shortens the small intestinal transit time, increases pH of the proximal colon, but does not change the pH-profile of the small intestine. Chronic pancreatitis and cystic fibrosis seem to decrease pH of the proximal small intestine. Very low colonic pH values have been observed in severe active ulcerative colitis and in Crohn's disease, but the background and clinical implication of this phenomenon are not clear. Chapter 7 describes the modulating effect of diet and drugs on gastrointestinal pH. Diet primarily has an effect on the colonic pH, whereas drugs might affect both small intestinal and colonic pH. The different effects are described. Finally, chapter 8 summarizes the present knowledge about gastrointestinal pH, and future investigations are proposed.