The threat of emerging and re-emerging diseases in pigs
An emerging disease is the one that has appeared in a population for the first time, or that may have existed previously, but, is rapidly increasing in incidence or geographic range. The number of new diseases in swine, included under the scope of emerging or re-emerging diseases, has increased importantly during last 20-30 years. Most of them fall into the category of infectious diseases, since their transmissibility and maintenance into a population is favoured by a number of factors, including current intensive rearing practices and international trading (globalisation). In addition, the last 10 years have provided a significant increase in the knowledge of newly discovered infectious agents, mostly viruses, with a not yet very clear pathogenic effect in pigs. The objective of this review is to discuss the general and particular causes of the appearance of new diseases or novel presentations of already known diseases in pigs, as well as to discuss recently recognised infections with a virtually, as yet, unknown impact on the swine industry. Therefore, mechanisms of emergence and re-emergence of diseases and the duality of ‘disease and infection’ are discussed in general, and particularly for pigs.