The most important viral and bacterial, mycotic and parasitic diseases of laying hens accompanied by direct impairments of egg productiveness and egg quality in different housing systems

The most important viral, bacterial, mycotic and parasitic diseases of laying hens accompanied by direct impairments of egg productiveness and egg quality under the inclusion of the different housing system are listed and described. Especially bacterial and parasitic diseases of the laying hens preferably attain relevance under free range conditions because the conventional cage system does not offer soil as the habitat for bacteria and parasites. However, viral sceneries can occur in every housing system. Each disease of the laying hens is accompanied by decreases of egg productiveness. Sometimes the reduction of the egg quality is so distinctive that the changes may assume pathognomonic character. This article has to be associated to the previous reports about the ecology of infections and contamination of egos because these all together are adding to one epidemiological context. Finally, these are concerns of the consumer protection because the egg quality and other foods of poultry origin are dependent on this epidemiological context.