Prevalence and genetic analyses of Saprolegnia strains isolated from Nile tilapia farms at northern Egypt

This study was undertaken to investigate saprolegniasis outbreaks in Nile tilapia farms at northern Egypt and its linkage to the water quality parameters, besides, their genetic diversity across different farms and the induced ultrastructural lesions. Water quality parameters were recorded and a total of 200 Nile tilapia showing saprolegniasis like signs were collected from December 2017–March 2018 from three different regions at El-Manzala, Gamasa, and El-Sirw, located at northern Egypt. A significant increase was observed in salinity, where El-Manzala showed the lowest level lowest 0.25 g/L followed by Gamasa and El-Sirw at salinity levels of 3.5 g/L, and 2.15 g/L, respectively. The prevalence of saprolegniasis showed significant variations between different regions (P