[The role of polyfactorial diseases in livestock husbandry in the Netherlands today and in the future (author's transl)].

The role of polyfactorial infectious diseases has increased as a result of the indstrial scale of livestock farming. Industrial livestock husbandry means keeping a single species of animal in large groups, optimum production on rational grounds being a concurrent object. Polyfactorial diseases are those diseases which are due to an infectious component and the clinical pictures of which are also determined to a considerable extent by the environment and by the animal itself. The problems associated with dysentery (Doyle), Atrophic rhinitis, Aujeszky's disease, Enzootic with nastitis, Chlamydia infection and Enzootic bronchopneumonia in cattle are discussed. In controlling these diseases, attention should not only be paid to the infectious component but also, and possibly to an even greater extent, to improvement of the environment and herd management. The view is advanced that efforts should be made to live with the disease. To stress a single measure is a technical error. Attempts should be made to improve the entire living environment of the animals by a number of measures. This requires constant expert supervision by the veterinarian. In supervising the health and welfare of farm animals, the veterinarian shluld be advised by the Provincial Health Services. These Health Services should be informed on possible or existing problems by post-mortem studies, serological studies and the study of secretions and excretions. Efforts should be made to ensure health control and health supervision in the entire field of livestock farming. It was pointed out that the hazards to attendants in livestock husbandry and the risks to consumers involved in the consumption of products of animal origin have been reduced to a minimum in 1976. Moreover, the risks are decidely smaller than those involved in keeping pets. Food poisoning caused by bacteria and bacterial toxins is a problem of hygiene rather than a problem of infection. From the point of view of prevention, improving hygienic conditions in the production, processing and manufacture of products of animal origin and altering particular eating habits should therefore be stressed.