Officials provide update on parasite found in Elton Creek in the spring

ELTON — The parasite that was discovered within brook trout last April in Elton Creek has not caused any known cases of whirling diseases in the creek or other connected bodies of water, according to DNR Fish Culture Section Leader David Giehtbrock.

Giehtbrock said the DNR is still monitoring waterways connected to Elton Creek for signs of the parasite, known as myxobolus cerebralis, and that because April’s finding was the first known detection of the parasite in Wisconsin waters, the DNR does consider it a “grave concern.”

“We don’t understand if this parasite spreads to other bodies of water how it will affect those fish populations,” Giehtbrock said. “So when we don’t know where it is on the landscape or we haven’t detected its presence on the landscape for a long time — or ever in Wisconsin…we’re concerned about populations that have never seen it and are naive to an infection. If you look at science and the study of disease, you’ll see populations kind of develop immunities or they’re somewhat resistant eventually to things. Our populations are all naive to this parasite, and so that’s why it’s kind of concerning to us.”

Whirling disease affects fish such as trout and salmon, and in some states, such as Colorado, is thought to be a major cause in the reduction of certain fish populations.

The clinical signs of whirling disease, according to Giehtbrock, include odd behavior such as swimming in circles, or physical deformities such as a crooked spine. None of this behavior has been found in Elton Creek, or in Silver Moon Springs fish farm, where fish with the parasite were also detected.

“Wisconsin DNR, we went and looked at Elton Creek, which is the water source to the hatchery there, and we detected myxobolus in fish above and below the hatchery on that water body, Elton Creek. We did not detect fish showing clinical signs of disease, so that’s the distinction,” Giehtbrock said. “So what does that mean? I’m not sure what that means exactly, and I don’t think anybody does. Because there are populations of fish all over the country where myxobolus is present and as far as they can tell, it’s not causing significant effects on fish populations. Other locations, it is.”

He said samples have been collected from several regional water bodies, but results have not yet returned from the lab. Further collection is ongoing.

“When you’re testing for myxobolus presence or absence in a population, you collect fish by electrofishing,” Giehtbrock said. “You euthanize those fish, and then you bring them onto a table, and quite literally, you’re removing their heads for testing. Then you send those heads to a laboratory, where they’re examined. They’re basically looking at the cartilage in and around the head as the fish grows, and that’s where you can find the parasite, and that’s why the fish are whirling, because their skeletons are affected.”

According to Kelly Mella, a public information officer with the Wisconsin Department of Agriculture, Trade, and Consumer Protection (DATCP), the parasite was initially found during routine required testing for a fish health certificate at Silver Moon Springs.

“Upon finding the parasite, all the fish on this farm that were susceptible to the parasite were depopulated, after which the ponds and raceways were cleaned and disinfected prior to allowing for repopulation with susceptible species,” Mella said.

In an email, Jerome Winkel, Silver Moon Springs’ owner, wrote that DATCP determined the parasite likely originated from the surface waters of Elton Creek.

“Most likely it was brought in by migrating birds. The DNR has not previously been testing for it in state waters, so it is uncertain how long it has been around,” wrote Winkel, who also explained what became of the fish that were removed from Silver Moon Springs. “We were able to sell the trout live to other states that follow the USDA guidelines. We were able to sell the trout for human consumption, as the parasite has no effect on humans.”

Giehtbrock said the DNR has not continued to monitor Elton Creek itself simply because they know they would continue to find the parasite there.

“Myxobolus has a life cycle where they spend some time in the fish, and then they spend some time in the water, and then they spend some of their time in their life cycle inside of a tubifex worm,” Giehtbrock said. “A tubifex worm is a worm that’s common all over in water all over the state and in streams and ponds and lakes and such. So with that worm, the parasite just persists there, and that’s why you could remove all the fish, but you’d still have the parasite, because it would be found in the tubifex worms, and it’s virtually impossible to eliminate them. We couldn’t take actions as humans to eliminate it, so we don’t try.”