EFSA’s scientific advice on aquatic species susceptible to certain diseases

The Animal Health and Welfare Panel (AHAW) of the European Food Safety Authority has reviewed the available scientific data on a number of fish and shellfish (mollusc and crustacean) species in order to identify their potential susceptibility to a list of 14 different diseases specified by the European Union[1].

Following a request from the European Commission, the Panel investigated whether species indicated in Directive 2006/88/EC should, in the light of new scientific evidence, no longer be considered as susceptible, or if species other than those already listed should also be considered as susceptible. The results of this work can serve as a basis for the Commission to update the list of susceptible species farmed in Europe and/or imported into Europe, and to help establish the most appropriate disease control measures.

The Directive defines susceptible species as “any species in which infection by a disease agent has been demonstrated by natural cases or by experimental infection that mimics the natural pathways”. However, it is difficult to scientifically demonstrate whether or not an experimental infection mimics the natural pathways. Furthermore, it is sometimes difficult to distinguish between infection by a disease agent and contamination. EFSA therefore developed a set of scientific criteria for assessing susceptibility, which was subsequently applied to both the existing list of susceptible species and to other species which could be susceptible to the listed diseases.

Scientists were able to single out various species whose susceptibility is demonstrated by clear scientific evidence[2] - referred to as Group I in the opinion - including some which are not currently part of the list [3]. The Panel recommends that the newly-identified susceptible species should be considered for possible inclusion in the list.

However, for a wide group of fish species - identified as Group II in the opinion - scientists were able to retrieve only partial evidence or no evidence at all suggesting susceptibility to specific pathogens[4]. The Panel recommends further studies to investigate the susceptibility of the species in Group II.

The scientific opinion published today identifies a wide range of species, representing many groups of aquatic animals, susceptible to the 14 diseases of fish, molluscs and crustaceans specified in the list. The results of the scientific review also identify many diseases - such as Epizootic Ulcerative Syndrome, Viral Haemorrhagic Septicaemia and White Spot Disease – to which a high number of species are susceptible.

Furthermore, scientists indicated that some species are susceptible not only to one but to several disease agents. Scientists stressed that these species are likely to present a higher level of risk with regard to the spreading of disease – for example when they are traded – than the species which are susceptible to only one disease.

The work was carried out by the AHAW Panel which gathered and reviewed the most up-to-date, peer-reviewed scientific literature in the field. In carrying out this work, Panel scientists, supported by external experts developed a set of scientific criteria to assess pathways for infection and the response to such infections in the various species. These criteria were applied to assess the susceptibility of the species.

[1] The diseases of aquatic animals are listed in Part II of Annex IV of EC Directive 2006/88. This directive on animal health requirements for aquaculture animals and products thereof, and on the prevention and control of certain diseases in aquatic animals, lists certain aquatic animal diseases and the fish species susceptible to those diseases and to act as a vector in the transmission of such diseases.
[2] These species were classified in Group I and are listed in Table 4, pages 24-25 of the Scientific opinion.
[3] These species are listed in Table 6, pages 28-29 of the Scientific opinion.
[4] These species were classified in Group II and are listed in Tables 5 and 7, pages 25-28 and pages 29-30 of the Scientific opinion.