Proliferative kidney disease (PKD) is another huge impact disease, which commonly affected salmonids culture. The causative agent for this disease is a endoparasites called Tetracapsuloides bryosalmonae that require two live hosts to complete the life-cycle. The host required by T. bryosalmonae is in the bryozoan species rather than the annelids species in other parasitic pathogen. When the freshwater bryozoan such as Fredericella sultana is infected with T. bryosalmonae, they will release spores into the water, and consequently transmit the spores to the salmonid fish. The infection is commonly occurred in temperature more than 12ºC during the summer. Young and fingerlings are more susceptible to the infection than adults fish and mostly die from the infection. However, in certain cases when the fish recovered from the infection, they will be resistant to subsequent outbreak. The most obvious clinical sign observed for PKD disease on the fish include darkening of the skin, lethargy, fluid accumulation or (ascites), popeye and swelling of lateral body. Further histological analysis will show a significantly enlarged, greyish and blotchy shaped kidney, which confirmed the diagnosis of PKD.