• Charles Sturt University researchers find parasite never before reported in Australia in 11 captivity-raised Murray cod
• Parasite is not known to harm humans, but does damage gills – a critical organ for fish
• The discovery has promoted a call for more research on parasites in aquaculture and in our native fish populations

The Charles Sturt University researchers were examining 46 Murray cod from a hatchery in south-east Australia when they noticed 11 of the fish had parasites attached to their gills.

Further microscopic examination identified the parasite from the genus of Dermocystidium, also known as Dermotheca.

Associate Professor Shokoofeh Shamsi (pictured above), the lead researcher for the study and a Senior Research Fellow in the Charles Sturt School of Animal and Veterinary Sciences and the Graham Centre for Agricultural Innovation, said this is the first recording of this parasite in Australia.

“We don’t have a lot of information about this particular parasite and its transmission pattern in Australia but genetically similar parasites are found overseas,” Professor Shamsi said.

“Those very similar parasites are not known to harm humans, but can have very harmful consequences for fish.

“While we were examining the infected fish, we noticed this parasite was inside cysts on the gills of the fish and there was damage to the gills where these cysts were attached.

“The damage this type of parasite can cause to the gills, a critical organ, is known to result in fish deaths, so we cannot rule out mass fish deaths being a result of this parasite.”

Further analysis of the gill structure by Professor Barbara Nowak from the University of Tasmania confirmed the damage caused by parasite.  

Professor Shamsi says more research is needed to better understand the extent of the distribution of the parasite.

“Dermocystidium easily infects many types of freshwater fish and even some amphibians, so it is possible other fish in our waterways are infected with the parasite,” Professor Shamsi said.

“The infected fish in our study were from a hatchery and given that hatcheries sell their fish to other hatcheries there is potential for this parasite to spread and cause mass fish deaths.”

She said the discovery also points to a need for further investigation of the impact of parasites on aquaculture and native fish populations

“Until more research is undertaken, the identity of introduced parasites and the potential impact on native fish health and biodiversity remains unknown,” she said.

Professor Shamsi was awarded a two-year Senior Research Fellowship by Charles Sturt to investigate the diseases caused by parasites in the Murray-Darling Basin.

A full report on the study conducted by Associate Professor Shokoofeh Shamsi and her research team is available on the ScienceDirect website.