Survival of pathogenic micro-organisms and parasites in excreta, manure and sewage sludge.

The causative agents of many infectious diseases are excreted by the faecal route and also with other excretions or secretions of the body. Some pathogens are also excreted from clinically healthy animals, from those with latent infections and in cases of transmissible multifactorial diseases. In all types of livestock housing, the pathogens finally reach the floor with the installations for collecting manure as a solid or liquid. Under these conditions livestock owners do not realise that manure may contain pathogens, and therefore do not take precautions against possible spread of diseases by utilisation of manure. The pathogens do not survive very long in stored farmyard manure because of the temperatures and biological and biochemical activities prevailing in the middens. But the conditions in slurry are different because the temperature does not rise and biochemical activity is low. Therefore the pathogens survive for rather long periods in slurry. To avoid disease transfer by utilisation of manure and slurry as fertilisers, certain precautions are necessary and these are described in detail. The agricultural utilisation of municipal sewage sludge is common in many countries. However, these sludges contain pathogens which are excreted by the human population served by the sewers and sewage treatment plants. In the sewage purification processes most of the pathogens are reduced in number but not completely eliminated. They are enriched by sedimentation processes in the sewage sludge. To protect the livestock of farms utilising sewage sludge as fertiliser or for amending soils it is necessary to sanitise hygienically dubious sludges prior to their use. The epidemiological aspects of agricultural sludge utilisation are discussed and details of the available sanitation technologies are given.