320 Parasitology Today, vol, Z no. I I, 1986

canis and Trichinella spiralis. These nematodes differ from schistosomes and most other biological systems in that of eight different lipid analogues tested only one, C~8-FI, actually inserted into the membrane. Quenching with trypan blue revealed that the probe was present in the outer monolayer of the membrane. FRAP studies showed the probe to be com- pletely immobile in adults, newborn larvae and infective larvae of T. spiralis and in the infective larvae of T. canis i°. (The surface properties of the newly fertilized Xenopus egg It are similar to those of the nematode membrane in that there is a similar selec- tivity and immobility of the lipid probe used.) Thus although nematodes exhibit lipid immobility, the nature of the surface appears to differ from that of schisto- somes, which is probably not surprising considering the different environments inhabited by these parasites.

Some exciting potential applications of FRAP and other fluorescence techniques in the field of parasitology are still waiting to be carried out. For instance, in malaria parasitized red blood cells it would be possible to measure not only lipid diffusion but also host and

parasite antigen diffusion in the erythro- cyte membrane. Many questions con- cerning the location and organization of parasite proteins in the red cell mem- brane could be addressed. Another area of investigation where FRAP would be useful is in the response of immune cells to various parasites. For example, sev- eral workers have measured the diffu- sion of defined molecules in the mem- brane of lymphocytes 12, macrophages i3 and neutrophils 14 on defined substrates, It would be possible to measure the diffu- sion of neutrophil or eosinophil molecules when the cells are attached to schisto- somes ~s or other large parasites, possibly giving information on why eosinophils appear to kill schistosomes in vitro whereas neutrophils do not ~ 6.

Acknowledgements: Our work was sup- ported by the Wellcome Trust and the Medical Research Council.

References I Axelrod, D. et al. (1976)Biophys.]. 16, 1055-

1069 2 Koppel, D,E. et al. (1976) Biophys. ]. 16, 1315-

1329 3 Bloom, J.A. and Webb, W,W. (1983) Biophys,J.

42, 295-305 4 Zagyanski, Y., Benda, P. and Bisconte, J.C.

(1977) FEBS Lett. 77, 206-208 5 Foley, M. etal. (1986)]. CellBiol. 103,807N]18 6 Stryer, L. (1978) Annu. Rev. Biochem. 47, 819-

846 7 Taylor, P.W. (1983) Microbiol. Rev. 47, 63 pp. 8 Bell, G.I., Dembo, M. and Bongrand, P. (I 984)

Biophys.J. 45, 1051-1064 9 KuseI,J.R. etaL(1984)Parasitology89,483-494

IO Kennedy, M. etal. (1986)inMofecularStrategies .of Parasitic Invasion (Agabian, N., Goodman, H. and Noguiera, N., eds) A.R. Liss inc. New York (in press)

II Dictus, W.J.A.G et al. (1984) Dev. Biol 101, 201-211

12 Leuther, M.D. et al. (1979) B~ochem Biophys. Res. Commun. 89, 85-90

13 Woda, B.A. et aL (1981)J. Cell Biol. 90, 705- 710

14 Hafeman, D.G. et aL ( 1982)]. Cell Bio194, 224- 227

15 Caulfleld, J.P, et al (I 980)J. Celt Biol. 86, 46-63 16 Vadas, M.A. et al. (1979) ] ImmunoL 122,

1228-1236

Michael Foley is at the Department o f Biochemistry, University o f Dundee, DD I 4HN, UK, John Kusel is at the Department o f Biochemistry, University o f Glasgow, G I2 8QQ, UK, and Peter Garland is now with Unilever Re- search Calworth Laboratory, Sharnbrook, Bed- fordMK44 ILQ, UK.

Health of the Urban Poor in Developing Countries

T. Harpham

"The urban poor are at the interface be- tween underdevelopment and industrializa- tion and their disease patterns reflect the problems of both. From the first they carry a heavy burden of infectious diseases and malnutrition, while from the second they suffer the typical spectrum of chronic and social diseases" l .

The rapid urbanization occurring in developing countries is now hitting the headlines. In the next 15 years the urban population of the developin~ world will increase by some 1.3 x I0 ° million to become 42% of the total. In Latin America it is more likely to exceed 75%. By the year 2000 there will be about 2.2 x l03 million people living in Third World cities. Almost 300 of these cities will have populations greater than I mil- lion. The urban poor (slum and shanty town dwellers; Fig. I) will often repre- sent 30-60% of the total city population. These uc-ban poor populations live in crowded, unsanitary conditions (Fig. 2a and b) which, compounded with prob- lems of poverty, lead to many health problems.

However, the specific health prob- lems of the urban poor populations rarely receive attention. Health policies and programmes are often based on a rural epidemiology, a rural social structure and a rural administrative framework, With the projected increase in urban poor populations, it is vital that more attention should be focused on this group by gov- ernments, municipalities, non-government organizations and international agencies.

A Wide Range of Diseases

Three groups of factors detrimental to health operate heavily against the urban poor t-3. The first includes low income, limited education, insufficient diet, over- crowding and limited protection from infectious diseases. The second relates to man-made conditions of the urban environ- ment, such as industrialization, pollution, traffic, stress and alienation. The third is the result of social and psychological instability and insecurity. In other words the urban poor suffer from both t~ditional and

'modem' heal~ problems - they get the worst of both wodds.

The excessive vulnerability of the urban poor and their exposure to pathogenic agents means that infec~ous diseases and malnutrition are severe heal~ problems in slums and shanty towns. Often an imported reservoir of infection is continually replenished by ruraJ-urban migration, which in turn reinforces local transmission of dis- eases such as malaria and filariasis.

Tuberculosis is prevalent in the slums and shanty towns of the developing world where infection is frequent and early in life. Malnutrition often occurs as both a cause and an effect of diarrhoeal diseases. The scarcity and contamination of water supplies and the lack of sanita- tion and appropriate sewage disposal make diarrhoeal diseases one of the most important health problems in poor urban areas. Disease incidence and mortality are also influenced by factors such as overcrowding poor housing condi- tions, density of insects and vermin, lack of rubbish disposal, poor personal hygiene, contamination of food, low literacy and in-

~)1986, ELsevier Science Publishers B.M, Amsterdam 0169~758/86/$02 00

Parasitology Today, voL Z no. I I, 1986 321

Box I. For many, poverty forms a barrier to the dream of a healthy life in the dry

The Dream: Health in the City

The Barrier: Poverty

Direct problems of poverty Environmental problems Psycho-~cial problems unemployment inadequate water and sanitation stress low income overcrowding alienation limited education poor housing instability

lack of land to grow food insecurity inadequate diet lack of rubbish disposal lack of breastfeeding traffic depression prostitution hazardous industries smoking

alcoholism infectious diseases abandoned children pollution accidents consumption of junk foods

appropriate weaning and other feeding prances. A variety of intestinal parasites is usually present, with Ascaris and Trichuris often at higher levels than in corresponding rural populations 4,5. High prevalence rates of preventable childhood infections such as measles, whooping cough (pertussis) and polio suggest that adequate coverage with immunization is a priority in such over- crowded communities.

The man-made conditions of the urban environment cause particular health prob- lems for the urban poor. Environmental pollution, which is a widespread problem for all urban people, affects the poorest more severely, because most of them live at the periphery where manufacturing, processing and distilling plants are often built, and where environmental protection is frequently weakest. In 1984 the escape of lethal gas in Bhopal, India, which led to the death of 2500 people, and a gas explo- sion in Mexico City demonstrated the vul- nerability of squatters who 'live next door to disaster '6.

Social and psychological problems as a result of political, economic and social instability form another group of health problems for the urban poor. The protec- tive structure of the local communities and extended family is generally replaced by the smaller 'nuclear' family unit on migra- tion to the city. Single parent households, often headed by a woman, are common; with the need for such women to work, the neglect of children is almost inevitable. The children may have to contribute to the family income, workhng under precari- ous conditions, exposed to accidents and abuse. UNICEF estimates that there may be up to 40 million abandoned children in Latin America and the Caribbean.

In contrast to the relatively stable and homogeneous rural village, the migrant to the city finds a society that is very heterogeneous, culturally and linguistically,

transient and mobile, opportunistic and restless. Pro~tu~on, venereal disease, depression, drug addiction and alcoholism are growing problems in poor urban areas.

The range of diseases of the urban poor is wide: from infectious diseases and malnutrition to chronic and social diseases. Useful 'tracer' diseases as indi- cators of change are (a) acute respiratory tract infections (including pneumonia and tuberculosis),~b) diarrhoea, (c) intestinal parasitic infections, and (d) nutritional problems.

T h e U r b a n H e a l t h M y t h

There is a long-standing myth that health conditions are worse in rural areas than in urban situations. In fact,

nutri~onal status, infant and child mortality and other health problems, are usually worse among poor city dwellers than in their rural counterparts 4,s,7-I°.

Studies comparing the health of urban poor and rural populations have usually found that there were more severely mal- nourished children in low income urban than in rural populations 7. The reasons for this are complex. Although in South East Asia and Latin America rural labourers largely depend on their landlords to pro- vide food, many rural families, especially in Africa, own a small piece of land where they can grow part of their food, or where harvest surpluses are available. This is gen- erally not possible for the poor in over- crowded cities. Although salaries in the cities are higher, so also are costs, with the result that the poor have a smaller prop- ortion of their income available for food. Furthermore, in the highly competitive city workplace, women are often forced to work in full- or part-time jobs (generally in the informal sector) to complement the family income or as the only family sup- port. Under such circumstances, women typ-ically have less time for food prepara- tJon and may resort to early weaning - leaving their infants in the custody of young children (Fig. 3) unable to prepare weaning food properly. They often have to dilute and divide a limited milk supply among many infants, and fall easy prey to adver- tisements for breast milk substitutes.

The general impression of urban advant- age over rural, as revealed by aggregate statistics on mortality also needs modifica- tion. Estimates of death rates for the under fives in six Latin American countries showed that only Bolivia and El Salvador had rural

Fig. I. Slums and shantytowns are often sited on swampy or in marshy ground or in inaccessible places where the land is not useful to other c/ty dwellers. This hillside slum in Lima, Peru, has no p/ped water - daily chores are difficult

x

o "I-

322 Parasitolo~/ Today, vol. 2, no. I I, 1986

childhood mortality clearly higher than the urban childhood mortalrb/8. In Brazil, the life expectancy of the urban poor of S~o Paulo and Belo Horizonte is below that of low income rural households, although mortality rates for upper income urban groups are lower than those of their rural counterparts 9. In the large slum areas of Port au Prince, Haiti, over 20% of infants die before one year of age and another 10% or more succumb in the second year; these mortality rates are almost three times those of the rural areas I°. However, these high mortality rates of the lower socio-economic classes of urban popula- tions are still more comparable to their rural counterparts than to the rates for upper class urban dwellers.

Other urban-rural differentials are highlighted by Coulibaly I t who found that the average annual incidence of tuber- culosis infection in the Ivory Coast was 1.5%, ranging from 0.5% in the rural areas to 2.5% in Abidjan. In the more deprived areas of Abidjan (Vridi and Koumani) the incidence reached 3% and affected much younger age groups. In Dakar, one-third of a peri-urban sample was positive for Ascaris, while only three cases in a sample of 400 were found in the rural areas 4. Similarly, Ascaris prevalence in Dube (part of Soweto in South Africa) was found to be seven times that in rural 'highveld' communities s.

Essentially, socioeconomic class seems to be a more discriminating factor than rural-urban residence in measuring health conditions. It is therefore important to look beyond the rural-urban dichotomy of poverty as indicated by various living conditions, and toward those socio- economic factors which transcend geo- graphical location.

The Myth of City Statistics

"The study of intra-urban differentials is in its infancy, so that people seldom realize that there are urban groups whose health conditions are in several ways worse than those of corresponding rural groups. Seldom do there exist in the rural areas the appalling conditions of extreme misery, destitution, environ- mental degradation and moral disrup- tion that affect huge populations in many large and intermediate cities of the developing world. Without wasting resources or burdening the system with unnecessary data, an effort must be made to delineate 'high risk' areas and population groups, and to provide minimum, purposeful, properly dis- aggregated information, that is sufficient to identify and illuminate the problems and to monitor change "j.

City health statistics usually tend to look much better than rural ones. Basta t2 has suggested that the reason is either because the squatter or slum inhabi- tants do not appear in the statistics (they are not 'official' residents of the city in many cases), or because their inclusion is. obscured by the enormous differences that exist between their status and that of the small, middle to high income parts of the city. Thus, a very misleading average becomes the basis of that city's stati~cs. Properly compiled information reveals a quite different and more truthful picture, but a systematic study of intra-urban dif-

ferentials in health has not yet been carried out anywhere in the developing world.

Drawing upon several projects, Basta 12 points out that many of the major cities of the developing world report infant mor- tality rates (IMR) of 75-90 per thousand live births, but amongst the urban poor these rates are far higher. In Manila, the IMR is three times higher in the slums than in the rest of the city, wrch the rates for tuberculosis nine times higher and with diarrhoea, malnutrition and anaemia two to three times more common. Again, in the 'bustees' of New Delhi the overall child mortality rate (0-5 years) is 221 per

Fig. 2. a - The location of houses on stilts in Recife, Brazil, makes sanitation very difficult b - Children washing in and taking water from stand pipes.

Z ,<, x ?

z <_ x

s

Parasitology Today, vol. 2, no. I I, 1985

Fig. 3. Children are neglected because mothers hove to work to supplement the family's income. Im fants are left in the care of other still-young children.

thousand but reaches twice that number amongst certain castes t2, and rates of mal- nutrition and vitamin deficiency were much higher in preschool children who came from slum areas 13. Similarly in Bombay H, mortality in the slum areas is 2-3 times that of the residential suburbs; in one slum the overall prevalence rate for leprosy was 22 per thousand compared to a city average of 7 per thousand. In Colombo, Sri Lanka, the IMR is significantly higher in the shanty towns than in the higher-income areas Is.

These health differences within cities are repeated elsewhere. In Singapore, for example, the prevalence of hookworm, Ascaris and Trichuris infections was 75% amongst slum dwellers compared to 32% amongst those in residential apartments 16. Again, studies of tuberculosis in Buenos Aires 17, malnutrition in Bogota 18, or diar- rhoeal diseases in Panama City 19 or Sa.o Paulo 20, all show a similar pattern of higher frequency amongst the poorer slum or shanty dwellers than those in better resi- dential areas. In S~o Paulo, neonatal deaths predominated over late infant deaths in the more affluent areas, while the reverse has been true for the periphery of the city.

While cardiovascular diseases remain the leading cause of death in all areas, they make up 20% of total deaths in the more affluent areas and only 10% in the periphery 19.

I n i t i a t i v e s

There are already good examples of small-scale initiatives (often by non- governmental organizations) aimed at im- proving the health of the urban poor. These were discussed at a workshop held in the summer of 1985 organized by OXFAM, UNICEF and the London School of Hygiene and Tropical Medicine. (Details of the case studies presented are available from the author.) It is poverty that is at the root of these health problems here. Any attempt at urban primary health care must therefore address the broader issues of poor housing, inadequate sanitation, urban malnutrition, the need for income genera- tion and the growing problem of aban- doned children. The urban environment is complex, often involving many different organizations or agencies, Collaboration between such agencies could be a first step

]>

323

towards improving the health status of the urban poor.

References I Rossi-Espagnet, A. (1984) Report No. 2499M.

WHO, Geneva 2 Ebrahim, G.J. (1984) in Basic needs and the

urban poor: the provision of communal services (P~chards, P.J. et at. eds) pp. 93-I 19, Croom Helm, London

3 Harpham, T., Vaughan, J.P. and Rifkin. S. (1985) EPC publication no. 5. London School of Hygiene and Tropical Medicine

4 Benyoussef, A., Cutler, J.L., Baylet, R. et al. (1973) Bull. WHO 49, 517-537

5 Richardson, N.J., Hayden-Smith, S., Bok- kenheuser, V. et al. (1968) S Aft. MeG. J. I, 46-48

6 Davis, I. (1984) The squatters who live next door to disaster. The Guardian Third World Review, 7th December

7 Lee, C. and Furst, B.G. (I 980) Differential indi- cators of hving conditions in urban and rural places of selected countries. Applied Systems institute, Washington DC

8 Puffer, R.R. and Serrano, C.V. (1973) Inter- American investigation of childhood mortality. Pan American Health Organization

9 de Cavalho, J.A. and Wood, C.H. (1978) Popu- lation and Development Review 4(3)

I 0 Rodhe, J.E. (1963) Why the other half dies: the soence of politics of chtld mortality in the third world. Assignment Children 61/62, 35-37

I I Coulibaty, N. (1981) Medecin Afrique Noire 28, 447-449

12 Basta, S.S. (1977) Ecol. Food Nutr. 6, I 13-124 13 Datta Banik, N.D. (1977) Ind J Pediatr. 44,

139-149 14 Bamasubban, R. and Crook, N. (1985) The

mortality toll of the cities: Emerging patterns of disease in Bombay. Economic and Political Weekly (Bombay) 20 (23) (June 8)

15 Cassim, J.K., Peries, T.H.R., Jayasinghe, V. et al. (1982) Development councils for participa- tory urban planning-Colombo, Sri Lanka. As- signment Children 57/58, 157-190

16 Kleevens, J.W.L (1966) Singapore MeG J. 7, 2-29

t7 Bianco, M. (I 983) Health and its care in greater Buenos Aires. Document SSH.HSR/83.1. WHO, Geneva

18 Mohan, R., Garcia, J. and Wagner, M.W. ( 1981 ) Staff Working Paper No. 447. World Bank, Washington

19 Kouray, M. and Vasquez, M.A. (I 979) Am J. Trop. Med Hyg 18, 936-94t

20 World Bank (1984) Staff Appraisal report, Brazil. 2nd Health Project. World Bank, Washington DC

Trudy Harpham is a Research Fellow at the Evaluation and Planning Centre for Health Care, London School of Hygiene and Tropical Medicine, London WC I E 7HT, UK. Her work is partly financed by OXFAM.