Drivers for emerging issues in animal and plant health

Richardson, Jane; Lockhart, Caryl; Pongolini, Stefano; Karesh, William B.; Baylis, Matthew; Goldberg, Tony; Slingenbergh, Jan; Gale, Paul; Venturini, Tommaso; Catchpole, Mike; de Balogh, Katinka; Pautasso, Marco; Broglia, Alessandro; Berthe, Franck; Schans, Jan; Poppy, Guy

With pests and pathogens posing growing concerns with regard to plant, veterinary and human health, the disentangling of the underlying ecological disease dynamics has become a matter of attention. A historical perspective on agriculture, and more particularly livestock, shows that the long-term evolutionary pull is towards an ever increasing intimacy with the host, for pathogenic viruses, endoviruses and commensals. In animals, intimate pathogenic viruses may circumvent the outer defence lines, cause subclinical infection and yet infiltrate inner-body organs and vital systems, resulting in life-long infections that are vertically transmitted, selecting for greater host specificity. Host radiation thus appears more of a feature typical for opportunistic myxoviruses. However, given the enhanced ecological perturbation at the interfaces of the livestock, wildlife and human host domains, long-term interdomain and interspecies barriers are breaking down, permitting spillover and species jumps by pathogenic viruses. Livestock bacteria reside chiefly on the skin and mucosal tracts, supporting the host health rather than being harmful. Novel forms of clinical disease may appear when a bacterium succeeds in infiltrating inner-body environments, as seen recently in the Netherlands with the emergence of virulent Q fever in intensive goat dairy systems. Arguably more important is the evolution of new strains and toxins in the enteric tract environment of fast growing food animals. In particular, the use of antibiotics as growth promoters interferes with the functioning of the enteric tract microbiome, metabolism and immune system. Indeed, most modern livestock diseases and food safety challenges appear to be the result of an intensification process that has been driven too far.