The authors provide examples of emergency programmes which have been successful in eradicating or controlling certain diseases of aquatic animals. The paper is divided into four parts.

The first part describes the initial isolation of viral haemorrhagic septicaemia (VHS) virus in North America in the autumn of 1988 from feral adult chinook (Oncorhynchus tshawytscha) and coho salmon (O.kisutch) returning for spawning. The fish disease control policies at both State and Federal levels in the United States of America required quarantine and emergency eradication measures upon the finding of certain exotic fish pathogens, including VHS virus. The procedures for emergency plans, destruction of stocks and disinfection of facilities are described, as well as challenge experiments with the North American strains of VHS virus and the detection of the virus in marine fish species (cod [Gadus macrocephalus] and herring [Clupea harengus pallasi]) in the Pacific Ocean.

The second part of the paper outlines the aquatic animal legislation in Great Britain and within the European Union, in regard to contingency plans, initial investigations, action on the suspicion of notifiable disease and action on confirmation of infection. The legal description is followed by an account of an outbreak of viral haemorrhagic septicaemia in turbot (Scophthalmus maximus) in Great Britain, including the stamping-out process at the affected farm and investigations conducted to screen other farms in the vicinity for possible infection.

The third part provides a historical review of the build-up of infectious salmon anaemia (ISA) in Norway and the attempts to control the disease using legal measures in the absence of detailed knowledge of the aetiology, epizootiology, pathogenesis, etc. of the disease. The measures taken show that the spread of ISA can be controlled using restrictions on the movement of fish, disinfection procedures, etc. However, acceptance and understanding of the chosen strategy by the fish farmers is a pre-requisite to reach that goal. Finally, the paper summarises future needs for national and international legislation, including the development of standard approaches for control, the creation of appropriate infrastructures and a better understanding of the epidemiology of aquatic animal diseases.