Researchers have detected a high degree of a parasite, which can burrow into the gut of infected humans, in freshwater fish species across New South Wales.
The invasive parasite species, Eustrongylides excisus, was found in native fish, including Murray cod, galaxiids, and trout cod during a two-year study.
The research was a collaboration between Charles Sturt University (CSU), the Department of Primary Industries and Narrandera Fisheries.
Shokoofeh Shamsi, a professor in veterinary parasitology at CSU, said the fish were collected from Cataract Dam, near Sydney, and other waterways across New South Wales.
"We found this large worm inside the flesh of the fish, which is quite concerning because this is where usually people consume the fish," she said.
Professor Shamsi said further DNA research of the parasite revealed it was the same as parasites previously found to have killed native Australian birds.
"The worm actually got to their stomach and penetrated through the stomach, made a hole and went through the body cavity," she said.
"A lot of the time we found the parasite half inside the stomach, half inside the body cavity of the bird."
The research found the freshwater parasite completed its life cycle in three different animals.
"That includes a small invertebrate in the water, that we still don't know what it is, then it goes to the fish," Professor Shamsi said.
"Then when birds eat the fish, birds get the infection and when the bird defecates, the eggs of the parasite goes to the water, goes to the tiny invertebrates and the life cycle continues."
Risk to humans
Professor Shamsi said if humans consumed infected fish and became infected with the parasite, it could burrow in the gut and behave similarly to how it did in native birds.
"It usually penetrates the stomach or gastrointestinal tract of the body and is quite harmful," she said.
Professor Shamsi said there had been no known human deaths from the parasite.
She said it was unclear how many infections there had been in Australia, with most knowledge on the parasite coming from places such as the United States and Africa.
"The teaching of parasitology in Australian medical schools has declined significantly," she said.
"As a result of that, a lot of medical professionals and people who work in the diagnostic lab, they don't necessarily know about this parasite.
Preventing infection
Professor Shamsi said there were many different types of fish parasites that could infect humans, with typical symptoms consisting of stomach pain and vomiting.
But she said preventing infection from Eustrongylides excisus was "easy".
"All we have to do is make sure we cook fish and like any other food items, like vegetables, red meat or chicken, if you cook them properly you minimise or completely remove the risk of infection," she said.
"Although the parasite is quite dangerous it's easily preventable so there is no need to panic and we all can continue eating seafood."
