Risk factors for emerging infectious diseases in aquaculture

Abstract

In the last few years, the global increase of aquatic animal production and farmed species has been associated with an increase in the numberand spread of infectious diseases. In 2002-2003, 62 cases of emerging diseases were reported in aquatic animals, two thirds in aquacultured species, mainly in Europe and Northern America. A disease is emerging when its incidence significantly increases in a given time,place and population. To emerge, a disease has to be introduced in a free zone or a free population, and animals must be exposed to favouring transmission factors. The risks of introducing new diseases are mainly associated to movements of infected animals (farmed or feral,dead or alive), contaminated farming gear or transport media, evolution of pathogens, and environmental factors: wild reservoirs, pollutants,climatic changes. Exposition factors allowing the emergence of an introduced disease include farming conditions, epidemiology ofthe diseases and movements of water and wild animals.