Transboundary spread of pig diseases: the role of international trade and travel

Beltran-Alcrudo, Daniel; Falco, John R.; Raizman, Eran; Dietze, Klaas

Within global livestock production, the pig sector plays a key role in the provision of animal protein. Pork represents the most consumed meat from terrestrial animals, accounting for over 36% of global meat intake, and its growth has been steady over the past decades [33, 40] . The pork producing sector is characterized by a marked dichotomy of production systems, demonstrated by traditional small-scale and subsistence-driven production on the one hand, and industrialized pig farming with increasing vertical integration of the value chain on the other [32] . Despite the progressive growth in importance of these larger scale operations to meet the growing global pork demand, a large proportion of farmers engaged in pig production (about 43% of all pigs worldwide), particularly in the developing world, operate in small-scale settings, and are often not linked to formal markets [99] . Pig rearing is a very common and traditional practice in rural areas, representing an important source of meat for the population in the countryside and often generating valuable cash income. Pigs are also valued for their quick turnover, prolificacy, and their ability to convert household waste into protein, their manure to fertilize fields and fishponds, and their usefulness as a financial safety net. However, small-holder pig rearing is usually a secondary income for households, which means that there is often little incentive or resources to improve housing facilities and biosecurity in general, or adopt husbandry-related technologies. It becomes evident that these very different stakeholder groups, i.e. commercial versus backyard, may not have the same priority in investing and adjusting production practices to disease prevention and control measures [45] . Indeed, the backyard sector, characterized by low biosecurity, outdated husbandry practices and technologies, and a poor awareness and compliance with animal health regulations (outbreak reporting, movement control, certifications, vaccination, etc.) plays a major role in the introduction, spread and maintenance of most pig diseases [24] . China, hosting around 49% of the world's pig population, largely in low biosecurity systems, deserves particular attention [40, 118] .