Lack of Lumpfish (Cyclopterus lumpus) Susceptibility to the Infectious Salmon Anaemia Virus (ISAV) Using In Vivo Challenges.

Infectious salmon anaemia virus (ISAV) can cause disease and mortality in Atlantic salmon (Salmo salar). The virus is endemic in several regions including the Atlantic coast of Canada. Lumpfish (Cyclopterus lumpus) are increasingly utilised as cleaner fish to control sea lice levels in Atlantic salmon farms. With welfare concerns for both species, and the possibility of escaped fish, the objective of this study was to determine the susceptibility of lumpfish to ISAV. Lumpfish were exposed to two ISAV isolates (high and low virulence) through a cohabitation challenge (i.e., exposure to infected salmon) and through an intra-peritoneal challenge. Naïve salmon were exposed simultaneously to the same isolates tested to verify their virulence. In the cohabitation challenge, ISAV infection progressed as expected in the naïve salmon. ISAV was detected in a small number of lumpfish gill samples, but the lack of detection in other organs, e.g., heart, kidney, spleen, liver, and blood, suggests environmental contamination. Although two lumpfish blood samples tested positive in the later stages of the challenge, all other disease indicators, including a lack of anaemia, did not support potential for virus replication in lumpfish. Based on both exposure experiments, lumpfish do not appear to be susceptible to ISAV.