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close this bookA Guide to the Development of on-site Sanitation (WHO; 1992; 246 pages)
View the documentPreface
close this folderPart I. Foundations of sanitary practice
open this folder and view contentsChapter 1. The need for on-site sanitation
close this folderChapter 2. Sanitation and disease transmission
View the documentDiseases associated with excreta and wastewater
View the documentHow disease is carried from excreta
open this folder and view contentsChapter 3. Social and cultural considerations
open this folder and view contentsChapter 4. Technical options
open this folder and view contentsPart II. Detailed design, construction, operation and maintenance
open this folder and view contentsPart III. Planning and development of on-site sanitation projects
View the documentReferences
View the documentSelected further reading
View the documentGlossary of terms used in this book
View the documentAnnex 1. Reuse of excreta
View the documentAnnex 2. Sullage
View the documentAnnex 3. Reviewers
View the documentSelected WHO publications of related interest
View the documentBack Cover
 

Diseases associated with excreta and wastewater

Sources of disease

The inadequate and insanitary disposal of infected human faeces leads to the contamination of the ground and of sources of water. Often it provides the sites and the opportunity for certain species of flies and mosquitos to lay their eggs, to breed, or to feed on the exposed material and to carry infection. It also attracts domestic animals, rodents and other vermin which spread the faeces and with them the potential for disease. In addition it sometimes creates intolerable nuisances of both odour and sight.

There are a number of diseases related to excreta and wastewater which commonly affect people in the developing countries and which can be subdivided into communicable and noncommunicable diseases.

Communicable diseases

The major communicable diseases whose incidence can be reduced by the introduction of safe excreta disposal are intestinal infections and helminth infestations, including cholera, typhoid and paratyphoid fevers, dysentery and diarrhoea, hookworm, schistosomiasis and filariasis.

Table 2.1 lists some of the pathogenic organisms frequently found in faeces, urine and sullage (greywater).

High-risk groups

Those most at risk of these diseases are children under five years of age, as their immune systems are not fully developed and may be further impaired by malnutrition. The diarrhoeal diseases are by far the major underlying cause of mortality in this age group, accounting for some 4 million deaths each year.

In 1973, children in Brazil under one year of age totalled less than one-fifth of the population but suffered almost four-fifths of all deaths, while in the United States of America this age group represented 8.8% of the population and suffered only 4.3% of deaths (Berg, 1973).

There is no doubt that improving the sanitation within a community should lead to an improvement in health, but it is difficult to ascertain whether the impact would be direct or indirect. Often, provision of better sanitation is part of broader development activities within the community and, even if dissociated from improvement of the water supply, there are usually other factors that influence health which are introduced with sanitation changes, e.g., health and hygiene education (Blum & Feachem, 1983). The effect of these factors, such as increased handwashing or changes in attitudes to children's excreta, may be difficult to monitor and/or evaluate.

Table 2.1. Occurrence of some pathogens in urine,afaeces and sullageb

Pathogen

Common name for infection caused

Present in:

   

urine

faeces

sullage

Bacteria

 

Escherichia coli

diarrhoea

*

*

*

 

Leptospira interrogans

leptospirosis

*

   
 

Salmonella typhi

typhoid

*

*

*

 

Shigella spp

shigellosis

 

*

 
 

Vibrio cholerae

cholera

 

*

 

Viruses

 

Poliovirus

poliomyelitis

 

*

*

 

Rotaviruses

enteritis

 

*

 

Protozoa - amoeba or cysts

 

Entamoeba histolytica

amoebiasis

 

*

*

 

Giardia intestinalis

giardiasis

 

*

*

Helminths - parasite eggs

 

Ascaris lumbricoides

roundworm

 

*

*

 

Fasciola hepatica

liver fluke

 

*

 
 

Ancylostoma duodenale

hookworm

 

*

*

 

Necator americanus

hookworm

 

*

*

 

Schistosoma spp

schistosomiasis

*

*

*

 

Taenia spp

tapeworm

 

*

*

 

Trichuris trichiura

whipworm

 

*

*

 

a Urine is usually sterile; the presence of pathogens indicates either faecal pollution or host infection, principally with Salmonella typhi, Schistosoma haematobium or Leptospira.

b From Cheesebrough (1984), Sridhar et al. (1981) and Feachem et al. (1983).

Table 2.2 gives details for different countries of infant and child deaths (including deaths from diarrhoea), life expectancy at birth, and the levels of poverty in both urban and rural areas. In general, these data reflect an interactive relationship between poverty/malnutrition and children's health. In turn, this relationship may be related to the level of sanitation in the children's environment. For instance, the incidence of diarrhoeal disease in children is affected by poor personal hygiene and environmental sanitation, and also by reduced resistance to disease in malnutrition. Diarrhoea leads to loss of weight, which is normally transitory in the well nourished but more persistent in the malnourished. Repeated infections can lead to increased malnutrition which in turn increases susceptibility to further infection; this may be referred to as the diarrhoea-malnutrition cycle.

Table 2.2. Health indicatorsa

Country

Infant mortality rate per 1000 live births

Child mortality per 1000
(1-5 years)

Life expectancy at birth
(years)

Population below poverty line
(%)

 

1983

1985

 

1983

1985

Urban

Rural

Bangladesh

130

121

205

48

54

86

86

Ecuador

70

45

95

63

64

30

65

Finland

6

6

8

73

75

-

-

Haiti

130

125

190

53

54

55

78

India

110

114

165

53

54

40

51

Malaysia

30

17

41

67

70

13

38

Nepal

140

140

215

46

52

55

61

Papua New Guinea

75

72

105

53

50

10

75

Paraguay

45

30

65

65

65

19

50

Philippines

50

57

85

65

63

32

41

Sierra Leone

180

225

310

34

47

-

65

Thailand

48

12

60

63

63

15

34

Trinidad and Tobago

24

19

28

70

67

-

39

United Kingdom

10

12

12

74

73

-

-

 

a From UNICEF (1986); WHO (1987c).

Noncommunicable diseases

In addition to pathogen content, the chemical composition of waste-water has to be considered because of its effects on crop growth and/or consumers. The number of components to be monitored (e.g., heavy metals, organic compounds, detergents, etc.) is greater in industrialized urban areas than in rural areas. Nitrate content is important, however, in all areas because of the possible effects of its accumulation, in both surface and groundwater, on human health (methaemoglobinaemia in infants), and on the ecological balance in waters receiving run-off or effluent high in nitrates. Although the major human activity resulting in the increase of nitrate levels is the use of chemical fertilizers, poor sanitation or misuse of wastewater can contribute to or, in exceptional cases, be the major determinant of nitrate levels, particularly in groundwater.

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