A Washington County judge has dismissed a ­grieving father's lawsuit contending that government should have warned of biological dangers in Stillwater's Lily Lake.

Judge Susan R. Miles wrote in her order that while she was sympathetic about 9-year-old Jack Ariola Erenberg's death in August 2012, she was powerless to create a remedy when none existed in law.

"Where, as here, the loss is caused by a natural condition found in the environment, ­neither the law nor public ­policy should place a burden on taxpayers to absorb the economic burden of harm," Miles wrote, granting defendants' motion to dismiss the case.

The boy, a Stillwater resident, died from a rare parasite after swimming in Lily Lake, which has a small beach. His death came two years after Annie Bahneman, 7, of Stillwater, also died from the Naegleria fowleri amoeba, which was traced to swimming in the same lake. The parasite, found in warm freshwater and soil, causes a rare but severe brain infection that is nearly always fatal.

Jim Ariola's suit alleged that after Annie died, the city of Stillwater, Washington County and the Minnesota Department of Health should have issued warnings of the ­amoeba's apparent presence in the lake and its potential for harm to protect his son.

Shallow water on the beach created "an artificial hot zone" where amoeba assumed a deadly, pathogenic form, ­attorney Roger Strassburg said in a September court hearing. He had filed suit a year ago, and said he will appeal Miles' ­dismissal order.

The suit claimed that excessive stormwater runoff from residences and streets surrounding Lily Lake, in the heart of Stillwater, warmed the water to an extent that the amoeba could thrive.

But Miles determined that the only dangerous condition that caused Jack's death was the amoeba.

"He was not killed by the city's improvements, the stormwater runoff, or increased phosphorous levels in Lily Lake. Rather, [Naegleria fowleri] entered Jack's nostrils, traveled up his nasal passages, killed his brain tissue, and caused the [infection] that led to his unfortunate death."

At a public meeting in Stillwater after Jack's death, a state health official said that many Minnesota lakes could have the parasite — particularly in prolonged stretches of summer heat — and that it can come and go unpredictably.

"It's not something that's quickly detectable, and it's not something that's going to be consistent," Jim Koppel, deputy commissioner at the agency, said then.

Lily Lake was closed to swimming after Jack died, but the Health Department said amoeba could be found in warm water anywhere, and swimmers should not assume that closing one lake meant others were safe.

Also cited in the Ariola suit, although not part of it, was the case of 12-year-old Hailee LaMeyer of Stacy, Minn., who died in 2008 after swimming in Fawn Lake near her home.

Miles wrote that no statute or ordinance requires Washington County or the state health agency to inspect water quality of any public lake for Naegleria fowleri. If government had a "special duty" to protect Jack in such a manner, then it would have a responsibility to virtually everyone who used a lake in Minnesota in any fashion, she said.

"These public entities would, in turn, be subject to unfettered ­liability for every conceivable harm, small and great, and effectively serve as gratis insurance companies," she wrote.