Viral haemorrhagic septicaemia virus, infectious haematopoietic necrosis virus and HPR-deleted infectious salmon anaemia virus - Risk of introduction in free areas through fertilised eggs and gametes.

EFSA assessed the risk of introducing viral haemorrhagic septicaemia virus (VHSV), infectious haematopoietic necrosis virus (IHNV) and highly polymorphic region-deleted infectious salmon anaemia virus (HPR-deleted ISAV) into free areas through movement of fertilised eggs and gametes. No evidence of true vertical transmission of these viruses was found. However, viral contamination of the surface of fertilised eggs and gametes cannot be ruled out. Assuming full compliance with the recommendations in the new draft 4.Z chapter of the Aquatic Animal Health Code of the World Organisation for Animal Health, including individual testing of broodfish at stripping, the median probability of introduction following importation of fertilised eggs was 0.36% for VHSV and IHNV, and 0.4% for HPR-deleted ISAV. The median probabilities were reduced to 0.02% and 0.01%, respectively, if fertilised eggs were disinfected twice (as green and as eyed eggs) at origin. Additional disinfection upon arrival in the importing establishment reduced the median probability to 0.02% for all viruses with one disinfection at the origin, and to virtually zero when two disinfections were applied at the origin. The assessment also evaluated probability of introduction when only population testing before stripping is applied. Two disinfections at the origin plus one at destination also resulted in virtually zero probability of introduction. For gametes, individual testing of broodfish at stripping, along with the other risk mitigation measures recommended in the new chapter resulted in a probability of introduction ranging from 0% to 0.3%. Implementation of the measures included in the new draft 4.Z chapter is recommended to prevent the introduction of VHSV, IHNV and HPR-deleted ISAV when moving gametes and fertilised eggs from non-free to free areas. In addition, it is recommended that fertilised eggs are disinfected twice before being traded and, to further reduce the risk, also disinfected at the establishment receiving the imported materials.