First isolation of Streptococcus sp. from hybrid tilapia ( Oreochromis niloticus × O. aureus) in Saudi Arabia

The first documented epizootic of streptococcicosis has been recorded among cultured hybrid tilapia ( Oreochromis niloticus × O. aureus) in Saudi Arabia. Affected fish showed erratic swimming, melanosis, exophthalmia, haemorrhaging around the jaws and at the base of the pectoral and dorsal fins and tail, and the presence of ascitic fluid in the adbominal cavity. The causal agent was characterized biochemically, and identified as an α-haemolytic Streptococcus sp.