Saprolegniasis is a major disease problem and of great concern for the aquaculture industry.It plays a serious threat to fish populations in natural habitats.It is a fungal disease caused by any of several species of water molds of the family Saprolegniaceae, in which Saprolegnia parasitica and Achyla bisexalis are the two most important oomycete fish pathogens.Due to the lack of efficient methods to control pathogenic Saprolegniaceae, there is a dramatic reemergence of saprolegniasis in aquaculture.