URBANIZATION AND HUMAN HEALTH

CHAPTER ONE

1.1                                                INTRODUCTION

Movements of people whether from rural to urban areas or from one country to another often alter the characteristic epidemiological disease profile and at the same time new disease appear or old ones reemerge. In the wake of industrial reform in the 1970s, mostly in developing countries, peasants started moving into towns with prosperity and better living conditions in mind slowly but steady there was growth in urban population.

Presently, the population of urban areas in developing countries is estimated at 3,000 million inhabitants (Houmsou, et al; 2000).  The world is becoming urban. The UN predicts that the World’ Urban population will almost double from 3.3 billion in 2007 to 6.3 billion in 2050. (Emilie et al; 2011). Most of this increase will be in developing countries. For the first time in history more than 50% of the world’s population lives in urban area. By 2050, 70% of the world’s population will be living in towns and cities.

Exponential urban growth is having a profound effect on global health. According to Dr Jacob Huaresan, the director world health organization’s centre for Health development based in kobe, Japan, “The world is rapidly urbanizing with significant changes in our living standards, lifestyles, social behaviour and health”.

Because of international travel and migration cities are becoming important hubs for the transmission of infectious diseases. Urban living continues to offer many opportunities including potential access to better health care, today urban environments can concentrate health risks and introduce new hazards.

1.2       DEFINITION OF URBANIZATION

Urbanization can be defined as the rapid and massive growth of cities. It is equally seen as the social process whereby cities grow and societies become more urban. It can be described as urban drift which is the physical growth of urban area as a result of rural migration and even suburban concentration into cities. It is closely linked to modernization, industrialization and the sociological process of rationalization. United Nations defines Urbanization as the movement of the people from rural to urban areas with population growth equating to urban migration.

       The rapid urbanization of the world’s population over the twentieth century is described in the 2005 Revision of the United Nation World Urbanization prospects report. The global proportion of urban population rose dramatically from 13% (220 million) in 1900 to 29% (732 million) in 1950 and to 49% (3.2 billion) in 2005.

The same report projected that the figure is likely to rise to 60% (4.9 billion) by 2030 (United Nation 2005).

According to the United Nation State of the world population report, (2O07) sometime in the middle of 2007, the majority of people world wide would be living in towns or cities for the first time in history. This is referred to as the arrival of the “urban millennium” or the tipping point. In regard to future trends, it is estimated that 93% of urban growth will occur in developing nations with 80% of urban growth occurring in Asia, and Africa. Urbanization rates vary between countries. The United States and United Kingdom have a far higher urbanization level than China and India.
Although most developed nations already show high rates of urbanization, tropical countries are experiencing a remarkable expansion of their urban agglomerations. The population of namely, Niger for example increased from 250,000 people in 1980s to almost 1 million today (Emilie et al; 2011). By 2050, the world’s urban population is expected to reach 6.3 billion. Almost all of this growth will be in low income regions. In Africa the urban population is likely to triple and in Asia it will be more than double (UN World Urbanization prospects, 2009)

Although Latin America became mostly urban in the early 1960s, sub-Saharan Africa remains mainly rural and is not expected to pass urban tipping point before 2030 (UN-HABITAT, 2011). Nearly half of the increase will be in small urban centers (less than 500,000 inhabitants), most mega-cities in Europe and Northern America will grow by less than 0.5%. High-growth rates are expected in Lagos of Nigeria, Dhaka of Bangladesh and Karachi of Pakistan. This world wide increase in urban population results from a combination of factors including natural population growth of rural urban migration, government policies, infrastructure development and other major political and Economical forces, including globalization.

1.2.1   URBAN: - There is no universally accepted definition of  urban. Some countries use a basic administrative definition (e.g. living in the capital city). Others use population measure (e.g. size or density) or functional characteristics (e.g. economic activities).

In industrialized nations, urbanization has contributed to an overall improvement of health and to a major shift in disease patterns towards a rise in chronic diseases. However, in many low income countries growth does not keep pace with the rise in urban populations. Many nations and municipal governments do not have the resources to cope with the steady influx of migrants or with the explosive demographic growth of urban centers. The urban sectors share of the poor is therefore on the rise. In Sudan and (Central African Republic, more than 94% of urban residents live in dismal conditions in shanty towns UN-HABITAT,2OO8).

In 2001, 924 million urban residents lived in slums and in formal settlements. This number is expected to double to almost 2 billion by 2030. Urbanization of low-income countries raise new health challenges for the international community. Several rural pathogens have adapted to urban environments and others have emerged or re-emerged in urban areas.

1.3       URBANIZATION AND HUMAN HEALTH

Movements of people whether from rural to urban areas or from one country to another often alter the characteristic epidemiological disease profile and at the same time new diseases appear or old ones reemerge. Such is the case of HIV/AIDS, tuberculosis, yellow fever, dengue, and many other parasitological diseases like amoebiasis. For example the large-scale migrations to Costa Rica in the 1980s, stemming from conflicts in other Central American Countries, produced a palpable increase in the prevalence of malaria and other parasitic diseases, especially along border area.

At the same time, Urbanization is associated with changes in diet and exercise that increase the prevalence of obesity with increased risk of type 11 diabetes and cardiovascular disease. Among migrants, mobility related risk include poverty, vulnerability to sexual abuse and exploitation and dangerous working conditions. Many of these conditions affect the most vulnerability segment of the population:-women, children and the elderly

Almost everyone who has taken course in epidemiology will have come across John snow” classic studies of choleria in London in the 1840s, with its attendant images of poor sanitation and contaminated waters. This history find a resonance in contemporary Concerns about the impact of cities and urbanization on health today. First there are the health and social problems of inner city areas of high income countries such as drug addiction, violence and HIV/AIDS.

Secondly there is concern about the health and welfare of the growing number of people in low and middle income countries that are living in urban areas many of whom are in what are classified as slums

Thirdly as reported by WHO (2007) is that increasing global urbanization is classed as a threat to public Health security as the unprecedented level of population agglomeration may facilitate the spread of epidemic disease.

Fourthly there is the plausible connection between urbanization and rising level of non - communicable diseases in low and middle income people.

Urbanization is a process of global scale, changing the social and environmental landscape on every continent. The world is rapidly urbanizing with significant changes in our living standards, lifestyles, social behaviour and health. While urban living continues to offer many opportunities, including potential access to better health care, today’s urban environments can concentrate health risk and introduce new hazard’s (Jacob, 2OO7). A Health challenges particularly evident in cities relate to water, environment, violence and injury and non-communicable diseases (Cardiovascular diseases, cancers, diabetes and chronic respiratory diseases).

In developing countries, population growth, rural-urban migration and development of the urban physical environment have facilitated the spread of many parasitic diseases such as malaria, amoebiasis, geohelminthiasis, filariasis, leishmaniasis, and trypanosomiasis. The increasing morbidity and mortality from these parasitic diseases have caused several negative consequences such as decreasing economic productivity, low performance in school and increasing medical costs (Houmsou et al 2O10).

Some of the health problems confronting million of rural migrants to slums, shanty towns and squatter settlements of developing countries need to be mentioned. According to a study by Crompton et al; (1993), about a third of the population of the cities in developing countries lives in slums and shanty towns. About half of the 7 million inhabitants of Dhaka, Bangladesh live in slums and only 6% of them have access to primary education and 3% to primary health care.

The prevalence of infections caused by Entamoeba histolytica and Giardia intestinalis and the prevalence and intensity of Ascaris lumbricoides and Trichuris trichiura infection may increase among the rural populations who are migrating to these urban and suburban settings owing to favourable conditions for transmission.

Urbanization can lead to environmental noise and air pollution, reduction of soil moisture, intensification of carbon- dioxide emissions, strain in the cities’ infrastructure, unplanned and congested residential areas, shortage of safe drinking water, and environmental changes which can affect food systems. Experts say that twenty percent of Europeans are subject to stress from noise. Air pollution also takes its toll on human health. Huge sums of money are spent on health care due to air pollution and many deaths resulting from respiratory diseases.

The reproductive system of pregnant women is especially vulnerable to environmental contaminants (Chelala, 2010). Each step in the reproductive process can be altered by toxic substances in the environment that increase the risk of abortion, birth defects, fetal growth and premature death. Many studies have shown that exposing pregnant women to carbon monoxide can damage the health of the fetus, (Chelala, 2010). In addition the developing fetus is susceptible to environmental factors for example through the mother’s exposure to toxic substances in the workplace. Children are especially susceptible to disease when they are born and develop in an environment characterized by overcrowding, poor hygiene, excessive noise, and lack of space for recreation and study. They suffer not only from hostile physical environment but from stress and other factors such as violence that such environments create. The pollutants that originate from motor vehicles particularly Nitrogen oxide, hydrocarbon, ozone, and particulate matter, account for a substantial proportion of air pollution in cities and serious impact on health. Land particles released as a result of gasoline combustion also pose a significant potential threat to children whose behavior and psychological development can be affected.

Most urban neighborhoods are crowded combined with poor sanitary condition and inadequate waste disposal which create conditions favourable to the spread of infectious diseases.

The rules, regulation and laws governing a particular city or country will be a reflection of the priority that the government attaches to providing good services and a healthy environment to the population.

Given the serious effects that urbanization can have on health, it is essential to include health considerations into policy making. Because many of the negative effects are suffered by the poor and minorities, it is equally essential to view the challenges incorporating consideration of social justice and equity. The Economic situation is a key determinant in the decision, resolve and capacity of the authorities to tackle environment problems effectively. As Herbert Giradet, an expert on urban sustainability has stated “if we are to continue to live in cities, indeed if we are to continue to flourish on this planet, we will have to find a viable relationship between cities and the living world, a relationship not parasitic but symbiotic or mutually supportive”.

1.4 POSITIVE AND NEGATIVE IMPACTS OF URBANIZATION
1.4.1   POSITIVE IMPACTS OF URBANIZATION

The urbanization process has marked effects on the natural and cultural environments, on housing arrangement and social networks, as well as on work and employment patterns, not only in the cities but also in the rural areas. Access to health care, social services and cultural activities are in many cases better in the cities.

The Urbanization promote market integration and globalization. Globalization means flow of economic capital, labour, goods and services, as well as ideologies across national borders.

The primary advantage of urbanization is that when population is concentrated in cities, people have less distance to travel to work and less distance to travel for most other purposes (such as shopping). An urban environment creates an opportunity for bigger and better community resources such as libraries, theatres, sports arenas etc. Big cities can afford things that small towns can’t other positive effects of urbanization includes jobs for people, wealth, and resources availability. Urban life can be rich and fulfilling since it is more diverse, stimulating and full of new opportunities. Individual and family mobility make it easier to escape from oppressive social relationships. Cities are sources of ideas, energy, creativity and Technology. They can for example foster enlightened congenial and multicultural living WHO (2005). The most prominent feature of urbanization is the difference in lifestyle.

Health wise, there are several examples of urban growth triggering the decline of infectious diseases. Air and water pollution which exist in many cities, can hinder vector proliferation. A study examining phiebotomies proliferation in Marrakech showed that urbanization generally decreased sandfly population (Emilie et al; 2011). Evidence for transmission of malaria has been found in most cities in sub-Saharan Africa but levels of transmission are generally lower in well planned urban area than in rural areas (Robert et al; 2003). Estimates predict that among the 0.6 billion people from Africa who are at risk of malaria, about 200 million are urban dwellers (Kaiser et al; 2004,). In urban environments, Anopheline vectors are less abundant and less likely to be infected with Plasmobium spp. Furthermore, urban dwellers experience reduced biting rates. Destruction of vector habitats, improved housing condition and improved access to preventive and curative measures all partly account for this decreased transmission. Other benefits of urbanization include improvement in Economy, growth of commercial activities, social and cultural integration, efficient services and resources of utilization.

1.4.2               NEGATIVE IMPACT OF URBANIZATION

The negative consequences of urbanization include poverty, overcrowding and diseases. Increased population leads to more waste garbage and by products.

Also Natural habitats are destroyed for housing purposes. Thirdly poor waste management causes the spread of diseases and pollution. Fourthly, food demand increases and more land needs to be cleared for food production. Fifthly high density of people can lead to conflicts and the quick spread of health problems as a result of over population’ it will be hard to find jobs for jobless ones.

In developing countries like Nigeria the migration of people to cities depletes the country side of the required labour force to grow the crops for national nutritional needs as well as export Jardel (1991).

Urbanization industrially produces pollution and acid rain it can cause loss of cultural identity and languages and homogenization. In summary, a range of economic, political, social, cultural and environmental factors are the effects of urbanization. Urbanization is encouraged socially and culturally through the media.

In the aspect of social-cultural impacts, cities have a strong socio-cultural impact on their surrounding rural areas. City life is depicted to be superior to rural life.

In the aspect of socio- economic impacts, as city grows, the cost of housing and infrastructure also grows, since there are less water, land and building material available and greater congestion problems. As a city decays in this way, governments often do not meet the service, needs of residents and urban development is dominated by private capital. Also unemployment grows, as do drug abuse, crime and homelessness.

The environmental impacts in urban large cities are waste management. Also air pollution results from over dependence on motorized transport and from burning of coal to supply energy. Water pollution results from poor sewage facilities and disposal of industrial heavy metals into water ways. Traffic congestion and noise pollution are major environmental impacts of large cities.

Finally there is increasing competition for facilities due to high standard of living in urban areas, which has triggered several negative effects such like slums and its consequences of overcrowding, lack of sanitation, poverty, illiteracy, unemployment and crime. Global warming, air pollution, water scarcity and pollution and loss of forest cover, agricultural land and depletion of wild life as a result of urban sprawl pose serious threats to the environment.

The challenges facing the world today is to minimize the negative effects and build the benefits. Infrastructure needs to be improved; opportunities should be created within rural areas to prevent migration to cities. (Kent et al; 2010).

1.5       WHAT IS PARASITIC INFECTION?

A parasitic disease is an infectious disease caused or transmitted by a parasite. It is a successful invasion of a host by an organism that uses the host for food and shelter. Some parasites do not cause diseases and are therefore termed free-living. Parasitic diseases can affect practically all organisms, including plants and animals. A parasite is organisms that live on or inside another organism (the host) and harms the host.

Although organisms such as bacteria function as parasites, the usage of the term “parasitic disease” is usually more restricted to diseases caused by protozoa, and helminthes (Nematodes, Trematodes, Cestodes) The three main types of organisms causing these conditions are protozoa (causing protozoan infections, helminthes (causing helminthiasis) and the ectoparasites. Protozoa and helminthes are usually endoparasites (usually living inside the body of the host) while ectoparasites usually live on the surface of the host.

CAUSES: Mammals can get parasites from contaminated food, water, insect bites and sexual contact etc.

Portal of entry includes the mouth by ingestion, through the skin by close contact (e.g. with pets) can lead to parasite infestation as dogs and cats are host to many parasites. Other risks that can lead people to get parasites are walking bare feet, inadequate disposal of feaces, lack of hygiene, close contact with some one who carries specific parasites, eating under cooked foods and meat. Insects and animals spread some parasitic diseases; mosquitoes for instance spread malaria, tsetse flies spread African trypanosomiasis (African sleeping sickness), Domestic animals spread beef and pork tape worms.

SYMPTOMS:

Symptoms of parasitic infections may not always be obvious, however, the symptoms vary widely, and many parasitic infections cause fever, fatigue, intestinal problems such as diarrhea, bowel obstruction (blockage of the intestines). Some of the symptoms caused by several worm infestation can include itching; abdominal pain, weight loss, increased appetite and vomiting. There may be sleeping problems, allergies, anaemia, aching muscles and joints, general malaise and nervousness.

The effects caused by parasitic diseases range from mild discomfort to death. Examples of nematode parasites, Necator americanus and Aucylostoma duodenal cause human hookworm infection which leads to anaemia and protein malnutrition. This infection affects approximately 740 million people in the developing countries including children and adults specifically in poor rural areas located in sub-Saharan Africa, Latin America, South-East Asia and China. Chronic hookworm in children leads to impaired physical and intellectual development, school performance and attendance are reduced, pregnant woman affected by a hookworm infection can also develop anaemia which results in negative outcome both for mother and the baby

Parasitic diseases are widely spread in Africa, South Asia and central and South America especially among children. Rural dwellers are more infected. Some Nations in these areas are too poor to take measures that could prevent parasitic infections- such as building water and sewage treatment plants, controlling mosquitoes, or providing adequate medical care. At the same time, in some places parasitic diseases make so many people weak, ill and unable to work that they slow economic development and help keep regions impoverished. Some parasites are found worldwide even in cooler climates and in wealthier nations, including the United States.

Many impoverished nations are undergoing urbanization which leads to crowding together into fast growing cities (slums) that may lack sewage treatment facilities. Row (untreated) sewage may be dumped into rivers whose water is also used for drinking, bathing, washing and cooking. Parasitic diseases spread easily in such conditions.

Some of the parasitic-infectious diseases inc1ude,
Trypanosomiasis, (African sleeping sickness), Amebiasis, Ascariasis, Babesiosis, Bed Bugs, infestation,  Blastocystis, Cercariasis (Swimmers’ itch), Chagas Disease, Cryptosporidiosis, Cyclosporiasis, Cysticercosis, Filariasis (Elephantiasis), Giardiasis, Hookworm infection, leishmaniasis, Lice infestation, Malaria, Onchocerciasis (River blindness), Pinworm infection, Schistosomiasis, Dipylidium infection (dog and cat flea tapeworm), Toxoplasmosis, Trichinosis, Trichomoniasis, Paragonomiasis,

The most common parasitic diseases include ascariasis, estimated to infect I billion people although it often does little damage. Secondly is malaria caused by Plasmodium spp. It is estimated to cause 300 million to 500 million illnesses a year and about 2 million deaths annually. About half of those deaths occur in children under 5years (WHO 2O10). Schistsome blood fluke spp. causes schistosorniasis which is estimated to cause 120 million illnesses.

Other parasite diseases that are estimated to cause a million or more cases of illness are Filariasis, amoebiasis, chagas disease, leishmaniasis and African sleeping sickness (trypanosomaniasis).

Parasitic infection can be diagnosed through laboratory analysis of specimen collected from infected victims. Such sample includes, blood, urine, stool, sputum, skin, CSF, Pleural fluid, etc.

The presence of parasites can be detected microscopically. However, immunodiagnostic technique and PCR techniques appears to be more sensitive.

PREVENTION:
-           Public authorities that build sewage and water   treatment

system play a major part in preventing these   diseases.

-           Controlling the insects (vectors) that spread same         parasitic

diseases also is important.

-           Educating people always on the need to wash their       hands

thoroughly after using the toilet and before handling food

C.D.C.(year 2010?)

1.6       PARASITIC INFECTION ASSOCIATED WITH URBAN

SETTING:
       Several rural pathogens have adapted to urban environments and others have emerged or re-emerged in urban areas. Some that were traditionally thought of as rural have adapted to the urban environment and are now common in cities. The heterogeneity in health of urban dwellers, increased rates of contact, and mobility of people results in a high risk of disease transmission in large urban populations. Cities become incubators where all the conditions are met for outbreaks to occur. However urban development has also reduced the transmission of other diseases (Emilie et al,2011).

According to (Bradley et al, 1998), many surveys have demonstrated a high prevalence of intestinal parasitic infections in children of slums, shanty towns and squatter settlements. It was discovered that the most frequently encountered intestinal parasites in urban communities include Entamoeba histolytica, Giardia lamblia (intestinalis), Ascaris lumbricoides and Trichuris trichura (Cromptom et al;1993).

Each of these species has a direct life cycle, being transmitted from human to human by the feaca-oral route during which cysts or eggs are discharged in human stools. Widespread contamination of the environment occurs and eventually infective stages are swallowed by new hosts. This is usually as a result of lack of sanitation, shortage of clean drinking water, poor standard of public and personal hygiene and inadequate health education. All these promote the spread of such parasites.

Intestinal parasitic infections persist and flourish wherever poverty, inadequate sanitation, insufficient health care and overcrowding are entrenched. Ascariasis is a mirror of socio economic status, a reflection of environmental sanitary practices and an indicator of the presence, or lack of health awareness and health education. (Crompton et al, 1993).

In the poor urban habitations, environmental factors promote the survival and transmission of intestinal parasites in urban slums.

Migration Influence: - several of the reflected tropical diseases that were once most common in rural, remote areas, are now frequently found in cities. Leishmaniasis is a growing health problem and rapid urbanization contributes to this increase (Desjeux; 2001)

In Kabul, Afghanistan, cases of cutaneous leishmaniasis increased from 14,200 in 1994, to 65,000 in 2002, and in uagadougou Burkina Faso, the incidence of cutaneous leishmaniasis increased from 28 cases in 1995, to 2375 in 2000. (Desjeux; 200l). Visceral leishmaniasis has become an important issue in several latin American cities including Teresina Belo, Horizonte, Sao Luis, and Salvado de Balia in Brazil. (Costa et al; 1990). Several other processes that contributed to the urbanization of this disease Include:

Rapid urban expansion: rapid urban expansion might bring populations into contact with zoonotic cycles established in adjacent rural areas. For example, cutaneus leishmaniasis has established itself in the periphery of Manus, Brazil, Bella-vista, Argentina, Marrakech, Morocco and Khartoum, Sudan (Barrette et al; 1989,) and Moroccan Ministry of Health (2005).

Secondly migrations have probably contributed to the urbanization of visceral leishmaniasis. In North East Brazil, prolonged draughts have triggered massive population movements towards the outskirts of large cities. Rural migrants settled in shanty towns and brought chickens, pigs and dogs with them, creating ideal conditions for the establishment of an urban transmission cycle (Desjeux; 2001). Similarly the emergence of visceral leishmaniasis in Khartoum in 1988 likely resulted from influx of people from Western Upper Province, Southern Sudan, who had fled the civil war in the South (De Beer et al; 1999). Poor sanitary conditions and changes in vector ecology also contributed substantially to the spread of visceral leishmaniasis and high sandflies were recorded in several cities (Costa et al; 2005).

    Chagas disease, the American trypanosomiasis, caused by the protozoa parasite T. cruzi affects 8 million people every year (Remme et al; 2OO6). This disease is transmitted by triatomine bugs that hide in walls, cracks and thatched roofs of rural households.

Chagas disease has long been thought of as a disease of rural areas, but several reports suggest the existence of transmission foci in urban and peri urban areas. According to (Albarracin Veizaga et al; 1999), in 1996, a sero epidemiological survey in Cochabamba, Bolivia, reported anti-T. cruzi antibodies in 12.5% of the inhabitants. Another survey showed that 22% of children from Cochabamba aged 5- 13 years were sero-positive for T. cruzi. (Levy et al; 2OO6).

In Urban settings, T. cruzi can also be transmitted via blood transfusion or organ transplants. In Latin American cities, between 1980 and 1989 1.3 - 51.0% of blood units intended for transfusion were infected with T. Cruzi (Schmunis;1991). Rural- to- Urban migrants have probably played an important part in the establishment of chagas disease in cities by transporting vectors from endemic rural areas to the peripheries of towns where they usually settle. Vector proliferation is associated with poor socio economic conditions, poor housing, and the presence of domestic animals in and around houses (Levy; 2OO6). Other neglected tropical diseases have adapted to the urban environment. Among the 1.2 billion people at risk of lymphatic filariasis, about 29% live in urban settings. In poor neigbourhoods in Nigeria, Brazil, and India, mismanagement of waste water, absence of sewage system and accumulation of waste, promote the proliferation of malaria and Wuchereria bancrofli vectors and increase biting rates (Terrenella et al; 2006).

Contrary to common perception on malaria transmission in urban settings, there is an improved health status of properly planned urban populations compared with rural populations in Africa as observed by many studies. For example, infant mortality rates and childhood mortality rates are lower in urban populations compared with rural populations, as shown by 59 national demographic and health surveys conducted in sub-Saharan African between 1988 and 2002. These same surveys showed that compared with those living in rural areas, mothers and children living in urban communities have better nutritional status indicators; fewer morbid events: increased vaccine coverage; better physical access to health services; and greater use of insecticide treated nets, (Monasch et al;2OO4).

The most extensive set of investigations on the effect of urbanization on malaria epidemiology was conducted by (Trape et al; 1980). In Brazzaville Congo, after a review of the demographical development of Brazzaville and previous malaria related entomological and parasite surveys, a series of papers were published that describe how the inhabitant of Brazzaville were subject to reduced anopheline biting rates (0 -7.36 versus 35 -96 bites per person per night compared with rural Congolese (Trape et al; 1987).

The above findings were corroborated in West Africa, for example Benin by (Akogbeto et al;1992), Burkina Faso by (Rossi et al; 1986), Ghana by (Coene; 1993) Niger by (Lebras et al; 1986) and Nigeria by (Awolola et al;2002).   In summary, there is clear evidence that urbanization affects anopheline species in the environment - diversity, numbers, survival rates, infection rates with P. falciparum and the frequency with which they bite people are all affected. So, fewer people acquired malaria infection, become ill and or die of its consequences in urban areas. The most common explanation is lower vector densities that result from a paucity of clean fresh water breeding sites.

However, the process of urbanization effects changes in indices of mosquitoes and malaria abundance not only by eliminating open space for breeding, but also by increasing pollution of the remaining breeding sites, thereby limiting the dispersion opportunities for adult mosquitoes with increased human densities, malaria exposure per capita also decreases (Smith et al;2OO4).

The qualitative evidence described above strongly indicates that urban population have access to better health, nutrition and services, and are at lower risk of malaria transmission than rural populations.

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