| Water purification, distribution and sewage disposal for Peace Corps volunteers |
|Section 7: Scope of disposal system projects in host communities|
Man is the reservoir of most of the diseases that destroy or incapacitate him. The faecal-borne infectious and infestations already mentioned are the cause of tremendous losses in death and debility. It is interesting to note that all these diseases are controllable through good sanitation, especially through sanitary excrete disposal.
In the transmission of these diseases from the sick, or from carriers of disease, to the healthy, the chain of events, as shown in Fig. 59 , is similar to that for many communicable diseases. In order to transmit disease, the following factors are necessary:
1. causative agent;
2. reservoir or source of infection of the causative agent;
3. mode of escape from the reservoir;
4. mode of transmission from the reservoir to the potential new host;
5. mode of entry into the new host;
6. susceptible host.
Channels of Transmission of Disease from Excreta
The absence of a single one of these six conditions makes the spread of disease impossible. As may be seen from the diagram in Fig. 59, there are many ways in which the causative agent of enteric disease reaches a new host. In different parts of the world, different modes of transmission may assume various degrees of importance: in some areas, water, food, and milk may be most important; in others, lies and other insects; and in still others, direct contact may assume a major role. What is most probable is a combination of all, and the sanitary worker must assume that this is the case and guard against all modes of transmission.