Publication Abstract

Aquatic animal transboundary diseases - challenges and threats

Peeler, E.J* VLA conference 3-5 September 2009

Over recent years aquatic animal transboundary diseases have seriously affected both farmed and wild populations. The main route of spread has been the movement of live animals for farming, the ornamental trade and food. The expansion of aquaculture has lead to farming new species and in new locations; inevitably this has resulted in disease emergence through pathogen interaction with wild populations. In some cases these new diseases have spread internationally (e.g. viral infections of shrimp). In particular, the translocation of non-native species has resulted in the spread of pathogens and parasites with very severe consequences for wild populations. The nematode Gyrodactylus salaris was introduced to Norway with Baltic Atlantic salmon from Sweden. The parasite decimated susceptible Norwegian salmon populations in rivers where it was introduced. Anguilloides crassus, a nematode infecting the swimbladder, was introduced to Germany with Japanese eels (Anguilla japonicus) imported for fattening, and rapidly spread throughout Europe. The parasite causes a debilitating condition in the native European eels (Anguilla anguilla) and is likely to have contributed to the collapse of eels populations. Crayfish plague spread throughout Europe with its non-susceptible natural host, the North America signal crayfish, resulting in the virtual elimination of native crayfish from large parts of Europe. The impact of transboundary diseases can be particularly severe since the new hosts have little or no immunity. In many cases the immune original host has established in the wild providing a reservoir of infection and further complicating control strategies. Since the movement of non-native aquatic animals drives disease emergence, by introducing putative disease agents to new naïve hosts, the ex-ante assessment of the disease risks is severely limited. Thus risk mitigation measures, improved disease detection and prompt internationally coordinated responses are vital.