Community perceptions of bloody diarrhoea in an urban slum in South Asia: implications for introduction of a Shigella vaccine.

Understanding local perceptions of disease causation could help public health officials improve strategies to prevent bloody diarrhoea. A cross-sectional survey was conducted in Dhaka, Bangladesh to elicit community beliefs about the causes of and prevention strategies for bloody diarrhoea. Between March and June 2003, we interviewed 541 randomly selected respondents. Overall, 507 (93%) respondents perceived that a vaccine could prevent bloody diarrhoea. If a vaccine provided lifetime protection, 445 (83%) respondents stated that they would opt to get the vaccine and would pay a median of $0·05 (range U.S.$0·01-0·15) for it, equivalent to <1% of their median weekly income. There was almost universal perception that an effective vaccine to prevent bloody diarrhoea was highly beneficial and acceptable. While respondents valued a vaccine for prevention of bloody diarrhoea, they were only willing to pay minimally for it. Therefore, achieving a high rate of Shigella vaccine coverage may require subsidy of vaccine purchase.

The localization of aluminium in the digestive gland of the terrestrial snail Helix aspersa.

The terrestrial snail Helix aspersa was exposed to food containing elevated levels of aluminium for up to 33 days and the digestive gland examined by light and electron microscopy and X-ray microanalysis. Four types of cell are found in the digestive gland, (digestive, excretory, calcium and thin) although aluminium was only found in the excretory cells. The aluminium was localised in the 'yellow' or excretory granules that are a characteristic feature of the excretory cells. Aluminium was only found in the granules of snails fed aluminium but there was no difference in the appearance of granules from control or aluminium-fed snails. The granules were large (up to 20 mum in diameter), irregularly shaped and electron-dense. Sulphur, phosphorus and calcium were detected in granules from all snails. The presence of sulphur may indicate protein residues. The amount of aluminium and phosphorus in the granules increased over the experimental period but the number of granules did not change. Levels of aluminium in the granules decreased when the snails were given control food. The role of the excretory granules in the localisation, detoxification and excretion of aluminium is discussed.

Accumulation and excretion of aluminium and iron by the terrestrial snail Helix aspersa.

1. The snail Helix aspersa was fed one 24 hr meal containing Al, Fe or both together in barley flour pellets. Accumulation and distribution within the digestive gland, kidney, crop and remaining soft tissues were examined over the subsequent 30 days using atomic absorption spectroscopy (A.A.S.). 2. The digestive gland contained significantly (P < 0.05) elevated levels of Al and Fe for 8 and 12 days. The digestive gland is the major sink for both Al and Fe in Helix. 3. The kidney rapidly accumulated Al and Fe but the increase was short-lived. The kidney may therefore be involved in the elimination of metal not incorporated into the digestive gland. 4. Iron was absorbed by the crop but Al was not. This may indicate a route of uptake of Fe into the digestive gland not shared with Al. 5. No obvious pattern of accumulation of Al and Fe were seen in the remaining soft tissues or the blood of Helix. 6. Aluminium is present in the faeces for 12 days suggesting that Al is released relatively slowly. 7. Presence of both Al and Fe in the feed induced a change in the pattern of accumulation in the digestive gland but not in the kidney, crop and remaining soft tissues. 8. The distribution of Al is discussed in relation to the suggestion that Al follows the ferretin pathway during accumulation.