Disease and sanitation

Action in low-income communities 

by Professor John Pickford of the Water, Engineering and Development Centre at Loughborough University of Technology.

It is often said that much of the disease in low-income countries is caused by bad water. Water-related diseases, so we are told, cause the deaths of many millions of children each year and occupy most of the hospital beds in developing countries. Diarrhoea in its various forms is a killer, as well as causing pain and suffering.

Water quality is unfairly blamed for all these problems. However, nearly all so-called water-carried diseases, from quick-killing cholera to uncomfortable stomach-ache, are really spread through poor hygiene and sanitation practices. Lack of sanitation may mean that water is contaminated but these diseases are also passed on in other ways. The diagram on page 2 shows some of the other ways in which diseases can be spread from the faeces of the infected person to other people.

The spread of disease

In Tanzania a medical officer told me about his investigations into the quite serious cholera outbreak in the mid-1970s. He had tried to work out how the infection spread. In one rural area a map marked with cholera cases showed clearly that all were along a stream used as water supply. Once the stream was polluted by cholera bacteria, people downstream were likely to be infected. But in Dar es Salaam (the capital city) he could find no connection between the epidemic and water. Here it seemed many women had contracted the disease while tending sick relatives and carrying out rites on those who had died. Their hands acted as the carrier.

Washing hands

In this example, as in many others, a lack of water for washing helped the spread of disease. Thorough washing of hands is so important in preventing the spread of infection. Washing with soap or ashes is best, but the essential thing for good health is to have enough water. Water for washing does not have to be of the same quality as drinking water.

Flies

Flies are also responsible for much of the spread of disease. Cockroaches are sometimes to blame too, but flies are the real villains. The trouble is that they like feeding on faeces. They can also travel long distances. Flies have spikes on their legs, so particles of whatever they feed on are carried away. If their food is faeces of someone suffering from a diarrhoea-type disease such as cholera (rare) or gastroenteritis (common), these particles may pass on the disease to others. Their next meal is quite likely to be on human food. So bits of faeces are left behind on food or drink which is to be eaten by people. The disease is passed on.

Disease spread through soil

Another route is in soil. This is very important for intestinal worms such as roundworms and hookworms. Children with roundworms often relieve themselves while crawling or playing in an unpaved compound. The faeces are likely to contain roundworm eggs. Even if someone cleans the compound, some eggs probably remain in the ground. Other children get some soil on their hands – children everywhere get dirty when playing. Then fingers go in mouths because children everywhere suck their fingers. The roundworms are passed on. One of the problems with roundworm eggs is that they remain infective for a very long time – many months. When children (or adults) with roundworms defecate on the ground near food crops, soil containing eggs can also easily get onto the crops many months later. Roundworms can then be spread through the food.

Disease spreads very easily

When particles of faeces from someone with a so-called ‘water carried disease’ are passed on by water, hands, flies or the ground, the disease may be transmitted to someone else. A tiny amount of faeces is enough. People excrete several thousand million micro-organisms every time they defecate. Most of these organisms are harmless, but it only requires a few of the dangerous ones for fresh infection.

The value of sanitation in preventing disease

The aim of sanitation is to block all these ways of spreading disease. This diagram shows how good sanitation prevents the micro-organisms in faeces from spreading disease.

It is important to reduce hand contact with faeces. Washing hands well after contact with faeces must go together with sanitation to reduce all risk of disease transmission. Washing hands is particularly important after cleaning a baby’s bottom. It is often wrongly assumed that the faeces of young children are harmless.