Survival of Paramoeba pemaquidensis on dead salmon: Implications for 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 t he 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 naive fish as well as uninfecte d dead fish. Using Immunofluorescent antibody test (IFAT) for P. pemaquiden sis on gill mucus smears it was determined that paramoebae remain on infect ed 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 estab lished that paramoebae from dead infected fish can colonise the gills of pr eviously uninfected dead fish thereby potentially increasing the bio-burden of paramoebae on infected farms.