Chapter 9 Pathogenic agents

This chapter describes the pathogens of humans, animals, and plants that may be present in organic wastes. The recycling of biological wastes by aerobic or anaerobic biotechnological treatment is necessary to protect the environment and to save natural resources. The recycling process may be conducted either in large-scale plants operated mostly in urban industrial areas, or in small plants operated primarily in the rural environment to improve the farmer's income. A relatively large number of pathogens are found in solid and liquid organic wastes and the most prevalent are bacteria, viruses, fungi, and parasites. Fungi present in wastes and materials used for composting are mainly of interest from the point of view of occupational health and phytohygiene. The presence of parasites or their infective stages in wastes or residues of plant, animal, or human origin depends on the nature of the wastes and the level of pretreatment. Parasites are of veterinary and medical importance if the raw materials used for composting are generated in wastewater treatment facilities or in slaughterhouses. Plant pathogenic parasites must also be considered, even if some of them are highly specialized on certain plants, which limit their epidemiological importance. Cyst-forming nematodes are the most relevant because these cysts may survive in the soil for several years.