- The effect of anti-Paramoeba antibodies produced in sheep on Paramoeba sp., the causative agent of amoebic gill disease (AGD), was tested. Incubation of Paramoeba sp. with antiserum at a concentration of 20% or more effectively coated the Paramoeba with antibodies. The antiserum had no effect on Paramoeba sp. survival in vitro or on its ability to cause AGD in Atlantic salmon.