Schisto comes to town / by Rajendra Kumar Sarda

Schisto comes to town Rural people in the tropics catch schistosomiasis* as they farm, fish, swim, fetch water, wash and bathe. City-dwellers, who have less water contact and better sanitation, ought to be luckier. Instead, in slums and shanty-towns, more and more of them are getting the disease by Rajendra Kumar Sarda [J ntil the early 1960s, no-one knew of any schistosomiasis in the large towns and cities of developing countries. Now, surveys have revealed that it is not only present but on the increase. Addis Ababa, Dar es Salaam, Harare, Kampala, Kinshasa and Lusaka have all reported schistosomiasis as a public health problem in their inner-city areas. Cities in Latin America-Sao Paulo and Recife -are not immune. A number of factors have led to this spread of schistosomiasis in the urban environment, the most im- portant being rural-urban migra- tion. Cities in the developing world are increasing in population at 3.8 per cent a year, twice the rate of rural growth, as people from the countryside flock to town in search of white-collar jobs. The economic prospects they find there are very often dismal, and unemployment is widespread. To sustain themselves they start small farms along the rivers and streams, growing food crops. The only areas available to them for housing are on steep hillsides and in areas liable to seasonal flooding. Because they live in un- planned settlements they are rarely or inadequately supplied with wa- ter, while latrines are almost non- existent. These migrants introduce new sources of disease into pre- viously disease-free areas. Because of the overcrowded conditions, they have many health problems, including schistosomiasis. The urinary (bladder) form of schistosomiasis occurs along the Tanzanian coast where Dar es * See World Health, December 1984 WORLD HEALTH, June 1987 Salaam, the capital, suffers like other fast-growing cities from the great phenomenon of urbanisation. It has a large number of swampy depressions and lakes; a network of small streams and canals cut through the city, most of them draining off into the Indian Ocean via the Msimbazi creek. In Dar es Salaam the markets overflow with rice, maize, cassava and other food crops grown in the city. Farming is fast becoming a major occupation. In the 1981 national census, it emerged as the second most corn- mon profession in urban centres in Tanzania. The economic conditions are making food dearer, so people are going figuratively "back to the land". Dar es Salaam's population in- creased from 0.3 million in 1970 to 1.3 million in 1981. In the 1960s, planned settlements were set up on the outskirts of the city, but so many people came in that other, unplanned settlements have grown Schoolchildren line up for urine sample "cups". Tests will show whether schisto is prevalent in the community. Photo WHO/K. Mott up around them. All these areas, planned and unplanned, have been provided with water from outdoor public standpipes-largely satisfy- ing the need for clean water for domestic purposes-and pit latrines are in common use. Nevertheless, urinary schistosomiasis and fecal- borne infectious diseases are ram- pant amongst adults and children. Surveys made by the Parasitol- ogy Department of the Faculty of Medicine, University of Dar es Salaam, showed that the average prevalence of urinary schis- tosomiasis was 20 per cent in school-age children, though in some schools over half of the children are infected. The city has a population of 300,000 primary-school chil- dren; an estimated 60,000-and 27 very likely more-are infected. Over the years more adults, too, have been seen in the city's dispensaries suffering from schisto- somiasis. After the surveys, the Kigogo area was chosen for more detailed studies. The aim was to find out how schistosomiasis was transmit- ted and to examine the factors which bring the city population into contact with contaminated water. Located only three miles from the city centre, Kigogo has a popu- lation of 56,000. A meandering, all-year-round watercourse runs through the area: its water comes mainly from the textile factories at Ubungo as they discharge their wastes. Human waste from over- flowing pit latrines also enters the watercourse at several points. Snails, the intermediate hosts for schistosomiasis, have been found in abundance in this polluted stream. Rice and vegetables are cultivated extensively on both sides of it. The 28 Schistosomiasis control teams are now having to work close to some of the world's sprawling cities. Concrete slabs for doing the laundry help to stop the spread of this parasitic disease; women no longer have to stand in infested waterways. Photos W HO/Liba Taylor adults actually do the farming, but children of all ages help with vege- tation clearance, planting, weeding and harvesting. The water from the stream is diverted into shallow earth chan- nels which provide ideal conditions for the snails. Adults work barefoot, some channeling water into their shambas, others drawing water into a watering-can, all mak- ing contact with the contaminated water. All along the watercourse there are signs of defecation. Some residents have built several small water impoundments for fish- farming, so creating new sites of transmission. Dense masses of wa- ter hyacinth cover these impound- ments. Usually it is the children who are seen clearing the hyacinth. Over 55 per cent of them in this area suffer from urinary schis- tosomiasis already, and these new man-made reservoirs will make the disease increasingly prevalent. The construction of a new road from Kigogo to Magomeni has also created suitable habitats for the snails. The road had to cross a valley, so several bridges were built. Due to poor excavation and drainage, the surrounding areas became waterlogged. The people were quick to take advantage of this and started planting rice, but within a few months infected snails were found at these new sites. As a result of the poor drainage, the surrounding areas flood during the rainy season, which in several places makes it difficult to cross the valley without coming into contact with the contaminated water. The city's expanding population exerts pressure on all the social services, including clean and safe water. Dar es Salaam has frequent water shortages, or outright cuts, in the lower Ruvu water-plant supply. This has resulted in more people going to streams and ponds to do their washing and bathing. Our studies in the Kigogo area have shown that the community stand- pipes supplying safe water were adequate for some domestic needs; however, they did not prevent people going to contaminated water for bathing, laundry and recreation. Most women questioned about the standpipes said it was more com- fortable to carry their laundry to nearby streams than to carry the water home from the pipe. Swimming in the watercourse and the small fish impoundments was the most important water-con- tact activity throughout the year for the Kigogo children. With the adults, it was largely bathing, wash- ing clothes and farming that brought them into contact with con- W oRLD HEALTH, June 1987 Schistosomiasis (bilharziasis) is a water-borne parasitic disease affecting mainly developing countries. Over 200 million people are thought to be infected and 500-600 million more could catch it at any time. because of poverty, ignorance. poor hygiene. ·poor housing and lack of clean water and latrines. Most of these people live in r.ural areas in Asia, Africa. the Caribbean and Latin America. but urban schistosomiasis is now gaining ground. taminated water. The children in Kigogo and other areas of the city have no recreational facilities. Their former playing fields have either been cultivated or have had houses built on them. By itself, providing public stand- pipes for water and promoting sani- tation will not control schis- tosomiasis in cities located in en- demic areas. Studies in Kinshasa and in Dar es Salaam show that even when public taps are avail- able, human contact with contami- nated water is unavoidable. How- ever, research in the Caribbean island of St Lucia showed that when a public standpipe system was sup- plemented by laundry facilities and W oRLD HEALTH, June 1987 showers, schistosomiasis was suc- cessfully halted. In Zimbabwe too, the installation of simple concrete washing slabs reduced people's con- tact with contaminated water. (See World Health December 1984, pp. 24-26: refers to two articles.) In the last few years the strategy of schistosomiasis control has changed. Several safe and highly effective drugs are now available, Digging drainage ditches on the fringe of an African city. Unless they are carefully controlled, they can encour- age the spread of urinary schisto- somiasis. Photo WHO/H. Anenden and new low-cost methods of rapid diagnosis have been developed. The spread of schistosomiasis can be checked. In a city environment, the most effective places for diagnostic ser- vices and treatment are the urban health centres. Vigorous health education is necessary to influence people to change their behaviour to an alternative made possible by simultaneously providing commu- nal laundry, shower and sanitary facilities and recreation grounds for children. These measures will reduce many infections and other parasitic diseases, including schisto- somiasis. The demand for food in cities suggests that the construction of small dams must be increasing rapidly. More local government de- partments are now realising the health hazards involved and are encouraging preventive health measures. In the long term, how- ever, disease control needs to go hand in hand with better socio- economic conditions for those who live in both the rural and urban areas of the developing world. • 29