Survival of Paramoeba pemaquidensis on dead salmon: Implications of management of cage hygiene

Amoebic gill disease (AGD) is the most serious disease problem in Atlantic salmon aquaculture in Tasmania at present. Little is known however, about the sources or reservoirs of Paramoeba pemaquidensis, the causative agent of AGD. This study evaluated the possibility of mortalities being a reservoir of P. pemaquidensis that could infect live naïve fish as well as uninfected dead fish. Using Immunofluorescent antibody test (IFAT) for P. pemaquidensis on gill mucus smears it was determined that paramoebae remain on infected gills for at least 30 hours after death of the host and that during this time the number of paramoebae appear to increase. In addition it was established that paramoebae from dead infected fish can colonise the gills of previously uninfected dead fish thereby potentially increasing the bio-burden of paramoebae on infected farms.