Epizootic ulcerative syndrome (EUS) or 'red spot disease' is a disease that can affect many species of fish. Red spot disease is known to be endemic in a number of waterways in NSW. In 2008 reports of red spot disease were confirmed in the Darling River. In 2009 it was confirmed in Port Stephens and the Clarence River and reported from the Richmond, Manning, Macleay and Tweed Rivers. In 2011 it was reported and confirmed in fish from Fullerton Cove in the Hunter River and Salt Creek on the Murray River.
In 2008 reports of ulcerated fish and confirmation of this disease in a number of estuaries including the Manning River in February, the Wisemans Ferry area of Hawkesbury River in March and in Myall Lakes occured in September. EUS was also reported from a number of mid-north coast NSW estuaries in 2008, including Macleay, Richmond, Clarence, Hastings and Wallamba Rivers. In addition to these coastal reports of red spot disease, fish sampled between Bourke and Brewarrina in the Darling River during May 2008 were also diagnosed with EUS.
EUS is caused by a fungus (Aphanomyces invadans) and shows as red lesions (sores) or deep ulcers. Secondary bacterial infections are often also associated with red spot disease.
EUS is reasonably common in NSW coastal catchments and has been previously reported in many freshwater catchments and estuaries throughout Australia, including NSW, Queensland, Western Australia and the Northern Territory. Many fish species are known to be susceptible to the disease including bony bream, silver scat, sole, bream, mullet, whiting, dusky flathead, silver trevally, eels and catfish.
Previous outbreaks of EUS have been associated with acid water run-off, particularly after heavy rain following a prolonged a dry spell, as well as other factors such as prolonged cold temperatures, crowding, and conditions associated with drought.
Healthy fish with no sign of EUS can still be caught and consumed by recreational fishers and caught and sold by licensed commercial fishers.
SEVERELY ulcerated fish should not be eaten (on advice from the NSW Food Authority)
DPI monitors the occurrence EUS, as well as other aquatic diseases. Please report any suspected occurrences of EUS to DPI so that consideration can be given to taking of samples for disease investigation.
Beginning of infection. Red spot lesions: Small area of reddening over single scale a ‘red-spot' (circled in red).
Moderately ulcerated fish: ‘Red-spot’ expands and deepens
Severely ulcerated fish: ulceration with loss of scales and skin, exposing underlying muscle.
Bony Bream from the Darling River at Bourke showing EUS lesion (picture R. Reece).