The physical environment of urban cities can promote
or hinder the proliferation and transmission of parasitic infections. The poor
and unhygienic conditions prevailing in many cities of the developing countries
encourage the transmission of parasitic infections via the air, food, water,
human waste or insect-vectors. For example outbreak of gastrointestinal and
skin infections is common in urban settings. Rates of certain epidemic
infections, such as acute diarrhea (the second biggest killer of children under
five years old worldwide) is very high in urban communities where there is lack
of sufficient housing, sanitation and clean water. (Harpham et al; 1991).
According to WHO, almost 137 million
people in urban
populations have no access to safe drinking water and more than 600 million urban dwellers do not have adequate sanitation. The situation is particularly alarming in congested cities of sub-Saharan Africa. In Nigeria for example, only 30% of residents in Ibadan have access to piped water and in Lagos only 90% of its 10 million residents have access to portable water (Satterth; 2O1O). Unsafe water sources and inadequate sanitation and hygiene are prime contributors to diarrhea infection and might lead to cholera endemicity (Guevart et al; 2006). The overall prevalence of diarrhea can be very high in cities as shown by data from northern Jakarta, Indonesia where prevalence is 50 per 1000 people (Agtini et al; 2OO5).
populations have no access to safe drinking water and more than 600 million urban dwellers do not have adequate sanitation. The situation is particularly alarming in congested cities of sub-Saharan Africa. In Nigeria for example, only 30% of residents in Ibadan have access to piped water and in Lagos only 90% of its 10 million residents have access to portable water (Satterth; 2O1O). Unsafe water sources and inadequate sanitation and hygiene are prime contributors to diarrhea infection and might lead to cholera endemicity (Guevart et al; 2006). The overall prevalence of diarrhea can be very high in cities as shown by data from northern Jakarta, Indonesia where prevalence is 50 per 1000 people (Agtini et al; 2OO5).
Inadequate sanitation also affects the transmission of
soil transmitted helminthiasis and intestinal parasites. Several surveys show a
high prevalence of intestinal parasites among children-for example, 52.8% in
Karachi Pakistan (Mehraj et al; 2008). In most urban settlements of the
developing countries where children comprise a high proportion of the
population, the impacts of parasitic infections are particularly heavy. Absence
of sewerage systems can lead to the proliferation of rodents, as in El
Salvador’s slums where rats carrying Leptospira interrogans proliferated
(De faria et al; 20O8). During the rainy season, open drainage gutters tend to
overflow, flooding streets and adjacent homes, and triggering out breaks of
leptopirosis.
The distribution of sewage contaminated vegetables
from urban gardens led to the propagation of cysticercosis in Mexico City
(Vasquez; 1996). However, (Ikeh et al; 2006) in their comparative
study of intestinal parasitism between rural and urban areas in North central
Nigeria reported that the common practice of emptying the watery portion of
filled septic tanks into the gutters, and burying the solid faecal waste in the
soil contributed to the high prevalence of intestinal parasites of the urban
centers. The watery portion eventually contaminated bodies of water used by
humans and the buried wastes contaminated underground surface water. This was a
very bad practice that affected the epidemiology of intestinal parasites in
those urban areas.
Management of solid wastes is another problem posed by
urbanization. The Asian Development Bank estimated that the waste quantities
generated by Indian cities will increase from 46 million tones in 2001 to 65
million tones in 2010. In rural areas, most waste is reused as compost,
burnt, or recycled to meet daily needs but in cities this is rarely possible
and when municipal service are deficient, waste piles up in empty lots and
street sides, leading to soil, air and water pollution. This might increase the
prevalence of diarrhea and intestinal parasitic infections (Moreas, 2007).
Accumulated wastes can also be a breeding site for
vectors. Phlebotomine Sandflies-the main vectors for leishmania parasites breed
in organic waste from human being and domestic animals. In Teresina, Brazil,
the risk of contracting visceral leishmaniasis is six times higher for people
living in houses with no regular rubbish collection than for people living in
houses with a regular rubbish collection(Costa et al; 2005).
Aedes spp mosquitoes
and Anopheles spp which are vectors for dengue, yellow fever,
chikungunya and malaria, have adapted well to the urban environment and often
breed in cans, plastic bottles and tyres (Hayes et al; 2OO3).
On the other hand, urbanization can positively impact
on vector - borne diseases. The expansion of urban areas can actually reduce
the prevalence of parasitic infections by destroying the breeding grounds of
some vectors (e.g. mosquitoes for malaria) (Trape et al; 1987). From the review of the demographical
development of Brazzaville and previous malaria related entomological and
parasite surveys, it revealed that inhabitants of Brazzaville were subject to
reduced anopheles biting rates (0-7.36 versus 35-96 (L
bites per person per-night), reduced transmission intensities of an APfEIR of 22.5 versus 250 infected bites per person per annum (i.e. urban versus rural) (Trape et al; 1987). (APfEIR is Annual Plasmodium falciparum entomological inoculation rate). The above findings were corroborated in West Africa like Benin by (Akogbeto et al; 1992), Burkina Faso by (Rossi et al; 1986). Ghana by (Appawu et al; 2OO4) and Nigeria by (Awolola et al. 2OO2). Therefore there is clear evidence that urbanization affects Anopheline species in environment. Diversity, numbers, survival rates, infection rates with P. falciparum and the frequency with which they bite people are all affected, so fewer people acquire malaria infection, become ill and or die of its consequences in urban areas. The reason is simply because of lower vector densities that result from a paucity of clean fresh water, breeding sites (Lindsay et al; 199O).
bites per person per-night), reduced transmission intensities of an APfEIR of 22.5 versus 250 infected bites per person per annum (i.e. urban versus rural) (Trape et al; 1987). (APfEIR is Annual Plasmodium falciparum entomological inoculation rate). The above findings were corroborated in West Africa like Benin by (Akogbeto et al; 1992), Burkina Faso by (Rossi et al; 1986). Ghana by (Appawu et al; 2OO4) and Nigeria by (Awolola et al. 2OO2). Therefore there is clear evidence that urbanization affects Anopheline species in environment. Diversity, numbers, survival rates, infection rates with P. falciparum and the frequency with which they bite people are all affected, so fewer people acquire malaria infection, become ill and or die of its consequences in urban areas. The reason is simply because of lower vector densities that result from a paucity of clean fresh water, breeding sites (Lindsay et al; 199O).
Housing conditions in urban centers are usually better
than in rural areas as a result of the use of concrete floors and walls to
build rather than houses built with leaves and mud. However, in many low-income
countries, poor resident of slums generally build their own dwellings from
flimsy, scrounged materials and with no concern for vector hygiene. In the
suburbs of Arequipa, peru, about half of the houses are infested with Triatoma
infestan, which transmits Trypanosoma cruzi (Levy et al; 2OO6). Infestans
were also found in peri-urban areas of Cochabamba, Bolivia (Albarracin et
al; 1999). Vectoral transmission of chagas disease has been documented in
the peri-urban shanty towns in many cities in Latin America. In metropolitan
Santiago, Chile 23% of the peri-urban substandard houses and 60% of the slums
were infested with Triatoma infestans and 15% of the captured
insects were infected by Trypanosoma cruzi, the causative agent of
chagas disease (Shenone; 1985).
Urban areas may also encroach on rural environment
where insects or arthropod vectors thrive facilitating exposure of increasing
numbers of urban inhabitants to infection.
THE
PROBLEM OF SLUMS
A slum, as defined by the United Nations agency
UN HABITAT is a run-down area of a city characterized by substandard housing
and squalor and lacking internal security. A United Nation expert group has
created an operational definition of a slum as an area that combines to various
extents the following characteristics-inadequate access to safe water,
inadequate access to sanitation and other infrastructured; poor structural
quality of housing. Over crowding and insecure residential status. (WHO, 2003)
Slums have posed a huge problem for developing nations because they are by
definition areas in which the inhabitants lack fundamental resources and
capabilities such as adequate sanitation, improved water supply, durable
housing or adequate living space.
While their physical forms vary by place and overtime,
slums are uniformly characterized by inadequate provision of basic
infrastructure_ and public services necessary to sustain health such as water,
sanitation and drainage. Buildings made of flimsy materials that are prone to
ignite, frequently collapse and offer scanty protection against the elements,
leaving resident vulnerable to injury, violence, illness, crime, and death.
Further since many of
these settlements are illegal, slum dwellers often have no official addresses and are commonly denied basic rights and entitlements like public education and health care. The characteristics and politics associated with slums equally vary from place to place.
these settlements are illegal, slum dwellers often have no official addresses and are commonly denied basic rights and entitlements like public education and health care. The characteristics and politics associated with slums equally vary from place to place.
It is usually characterized by urban decay, high rates
of poverty, illiteracy, unemployment, lack of personal/community land
ownership. They are commonly seen as “breeding grounds” for social problems
such as crime, drug addiction, alcoholism, high rate of mental illness and
suicide, high rate of diseases and malnutrition. The lack of services such as
routine garbage collection allows rubbish to accumulate in huge quantities. The
lack of infrastructure is caused by the informal nature of settlement and no
planning for the poor by Government officials. UNESCO reports that over 2
billion people in the world live in slums and that number is expected to double
by 2030(UNESCO, 2007) That means everyday approximately 250,000 children are
born into slums. That is 250,000 more children each day are denied access to
basic human rights such as health and clean water.
Recent years have seen a dramatic growth in the number
of slums as urban population has increased in the third world.
In April 2005, the director of UN-HABITAT stated that
the global community was falling short of the millennium Development Goals
which targeted significant improvements for slum dwellers and an additional
50million people have been added to the slums of the world in the past two
years (WHO, 2005).
According to a 2006 UN-HABITAT reports, 327million
people live in slums in commonwealth countries which Nigeria belong. Example of
slums in Nigeria are Maroko in Lagos, okpoko in Onitsha, mammy market Environs
etc
SANITATION
AND HYGIENE CHALLENGES IN SLUM:
Hygiene is commonly known as cleanliness or conditions
and practices that serve to promote or preserve health. A population that does
not take into consideration hygiene is at risk of infection and illness.
Improved housing, improved nutrition and improved hygiene are the essential
components for war against infectious diseases (Greene, 2OO1). Lack of
resources such as water, results in poor hygiene level, toilets cannot be
washed and there is not enough water to shower. This, however, promotes
parasitic infection. United Nations Habitat (2006) has described
sanitation and hygiene challenges in terms of poor basic services like access
to sanitation facilities and safe water source, the lack of water collection
service, poor rain water drainage system, poor infrastructure and absence of
electricity supply, substandard and inadequate houses overcrowding and
congestion. The cohabitation of different families and more single rooms (one
room unit in slum. Often shared by five or more people which they use for
cooking sleeping and living). The lack of path ways, the uncontrolled dumping
of water and polluted enrolments result to unhealthy living encouraging the
transmission of parasitic infection and their vectors such as malaria,
filariasis, schistosomiasis, amoebiasis, trypanosmiasis, leishmaniasis and
chagas disease etc. Houses may be built in dungeons locations which are
unsuitable for human settlement for example near waste disposal sites.
The living conditions in slums are often sub-human as
the denial of government services lead to children playing in gutters of human
feaces, houses mounted on heaps of trash and cesspools that serve as incubators
for infectious diseases.
According to (Bradley et al;1991) many surveys
have demonstrated a prevalence of intestine parasite infection in children of
slums, shanty towns and squatter settlements. Among them include Entamoeba histolytica, Giardia lamblia,
Ascaris lumbricoide, Trichuris trichuria and the less frequently
encountered one like Necator americanus.
According to (crompton
et al; (1993) the table below shows the Results from epidemiological
surveys of intestinal parasite infections in poor pen urban (slum) and urban
communities in developing countries.
Table 1:
Prevalence of intestinal parasite infections in poor peri-urban and urban
communities in some developing countries.
Prevalence
(%)
|
|
Amoebjasjs
|
Giardiasis
|
Ascariasis
|
Trichuriasis
|
|
Braganca
Paulista,Brazil Hyderabad ,India
|
7
9 |
13
32 |
30
35 |
39
- |
|
Kuala
lumpur.Malaysia
|
-
|
-
|
64
|
84
|
|
Nairobi)
kenya
|
41
|
30
|
82
|
60
|
|
Coatzacoakos)Mexico
|
-
|
-
|
55
|
55
|
|
Lagos,
Nigeria
|
8
|
-
|
68
|
72
|
|
Manila)Philippines
|
21
|
20
|
80
|
92
|
|
Freetown,
Sierra leone
|
-
|
27
|
43
|
81
|
Crompton et al, (1993)
Peri-Urban/Urban
Community And Country
About a third of the population in the cities of
developing countries lives in slums and shanty towns. In the year 2000 it was
estimated that the number will grow to 2200 million and by 2025 about 57% of
the population in developing countries will live in peri urban areas. (Crompton
et al; 1993) The prevalence of infections caused by Entamoeba histolytica and
Giardia intestinalis and the prevalence and intensity of Ascaris
lumbricoides and Trichuris trichura infection may increase among the rural population who
are migrating to these sub-urban settings owing to the favorable conditions for
transmission.
Urban consideration should therefore be given to improving
sanitation in slums and to treating periodically these populations to reduce
the worm burden especially in school age children (Crompton et al; 1993).
URBANIZATION
AND PROBLEM OF EPIDEMIOLOGY
The epidemiology of parasitic infection is usually
influenced by rapid urbanization, unplanned urbanization, uncontrolled
population growth, agricultural developments, socio-economic factors, disease
and vector control operation and health care delivery system.
Owing to population growth, poor level of hygiene and
increasing urban poverty, the urban environment in many developing countries is
rapidly deteriorating. Densely packed housing in shanty towns or slums and
inadequate drinking water supplies, carbage collection services and surface
water drainage system all combine to create favorable habitats for the
proliferation of vectors and reservoirs of communicable diseases. As a
consequence, vector-borne diseases such as malaria, lymphatic filariasis, and
dengue are becoming major public health problems associated with rapid
urbanization in many tropical countries. At the present time, the urban health
authorities in many countries are alarmed by the rise in vector-borne diseases
due to increased densities of vectors and other pests which present ever greater
burdens on their vector and pest control programs.
The escalation of diseases is closely related to
overcrowded urbanization, which is the result of population growth and rural to
urban migration taking place much faster than ever before since the dawn of
man. In many cities, slums and poor neighborhoods are spreading, with the
appalling living and working conditions, lack of safe drinking water and
sanitation. The exposure to emission from traffic and in many places, also from
factories is the daily burden of a rapidly growing proportion of city dwellers.
The
major urban arthropod vectors are those of dengue, malaria, filariasis, chagas
disease, plague and typhus. In addition most urban enviroment favours the
breeding of nuisance mosquitoes, cockroaches, mice and nuisance bird species.
According
to (Bradley et al; 1991) many surveys
have demonstrated a prevalence of intestine parasite infection in children of
slums, shanty towns and squatter settlements. Intestinal parasite infections
persist and flourish wherever poverty, inadequate sanitation, insufficient
health care and over crowding are entrenched. Ascariasis is a mirror of
socioeconomic 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 habitation, environmental factors promote the survival and
transmission of intestinal parasites.
However, a well planned urban setting usually records
reduced incidence of parasitic infection when compared to rural centers.