Individual prevention is easy, and consists of always drinking clean, boiled or filtered water. There is at present a world eradication campaign, adopted as a sub-goal of the Clean Drinking Water and Sanitation Decade by the United Nations World Health Assembly in 1986 and 1989 (Cairncross et al., 2001). The first priority in any eradication campaign is to have accurate figures on the distribution and annual incidence of infection and this has required active surveillance, as the disease is rarely reported to health clinics: passive surveillance has been estimated as identifying only about 2.5% of infections. Annual national case searches have now been replaced by community-based surveillance, followed by case-containment strategies.
There are various possible interventions:
1. Provide a safe drinking-water supply (mains, tube wells or safe draw wells). Where piped water is supplied, the disease usually vanishes rapidly and it no longer exists anywhere in towns but this provision is too expensive for endemic rural areas. The most important control measure of the current effort is the provision of bore holes and hand-operated pumps, the funds being provided by governments, charities and international agencies. These have many other health benefits and are part of a general campaign, by UNICEF in particular, to provide safe drinking water to all developing countries during the next decade. Where bore holes are not feasible, traditional brick-lined draw wells with a parapet can be built by local communities, particularly if the initial hole is made by a mechanical digger. Large cisterns for storing rainwater are a useful adjunct for schools in some areas.
2. Boil or filter all drinking water. Boiling water for drinking is effective but not usually feasible, as firewood is in very short supply in most endemic regions. Water can be filtered and this is a short-term measure which is playing a large part in the current campaign. A monofilament nylon net with a standard pore size of 0.15 mm filters out cyclops, is not easily clogged and is long-lasting. Enough material to supply all endemic villages has been donated by the manufacturers.
3. Persuade or prevent all persons with an emerging female worm from entering drinking water ponds or step wells. The cooperation of the local population, particularly school children, in preventing contamination of the water sources is playing an important role in control campaigns, and trained village health teams have been set up in all endemic countries. Bandaging of the lesion at the beginning of patency helps to stop the patient from entering water, as well as preventing secondary infection.
4. Treat water sources with chemicals to kill cyclops. Chemical treatment of ponds is most useful towards the end of a campaign, when there are only a few cases left or where the provision of wells has not stopped transmission. The organophosphate temephos (Abate) can be safely added to potable water sources and will kill cyclops for up to 6 weeks at 1 ppm. Enough to treat ponds in endemic areas of Africa has been donated by the manufacturers.
Since the beginning of the eradication campaign, the disease has been certified as having been eliminated from Pakistan in 1994 and there have been no cases in India since 1996. In Africa, there has been a great fall in the number of cases in Ghana and Nigeria in the last 10 years (Figure 20.4) and active campaigns are also under way in Benin, Burkina Faso, Chad, Ethiopia, Ivory Coast, Mali, Mauritania, Niger, Kenya, Senegal, Sudan, Togo, Uganda and Yemen. In all these countries except Sudan, there are only a few limited foci left. The situation in Sudan, where 56 000 cases were reported in 1999, remains the most problematical. Thirty-seven countries where the disease has occurred in historical times have applied for certification of its absence.
It is to be hoped that by the next edition of this book, this chapter will be superfluous.
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