The brain-eating amoeba found in a west Ascension Parish water system this summer has been eradicated after increased amounts of chlorine were pumped for weeks into water lines outside Donaldsonville, state and parish officials said.

Louisiana Department of Health and Hospitals officials said Friday the results from the new test, which relies on DNA to find the signature of the Naegleria fowleri amoeba, mean the parish can halt the chlorine burn that DHH ordered after the discovery of the amoeba in late July.

Olivia Watkins Hwang, DHH spokeswoman, said an all-clear went out late Thursday after the test results came back negative.

The Ascension Consolidated Utilities District No. 1 serves about 700 people in west Ascension on the outskirts of Donaldsonville.

Under the chlorine burn, the parish had to raise chlorine levels to 1 part per million, or double a new state chlorine standard designed to kill the amoeba, and maintain that higher level for 60 days.

The amoeba was discovered July 28 in the ACUD system, but the 60-day clock for the burn did not start until Aug. 17 once chlorine levels had reached 1 ppm systemwide, DHH officials have said.

The Ascension system is the second of four water systems in Louisiana that have received the all-clear from DHH after the amoeba was found earlier this year.

Hwang said results came back negative for the amoeba in the St. Bernard Parish water system on Oct. 23. Two other systems are still conducting chlorine burns and will not be retested until next month, Hwang said.

Those systems are the Schriever Water System in Terrebonne Parish and the North Monroe Water System that serves the town of Sterlington.

Ken Dawson, chief administrative officer for Ascension Parish government, said the test samples from the ACUD system were taken about a week ago, and parish officials were expecting good news from DHH.

“With a chlorine burn of that length of time, we felt pretty good we had a clean system,” Dawson said Friday. “Now, we’re focused on maintaining the lower chlorine residual at 0.5 ppm.”

While water with the amoeba is safe to drink, DHH officials have said, the water does pose a risk to people if it gets up someone’s nose and has access to a person’s brain.

Since 2011, three deaths have been attributed to the amoeba, prompting DHH to order the state’s water systems to raise their chlorination levels to 0.5 ppm by February 2014. Previously, only trace amounts of chlorine were required.

Parish and DHH officials have cited the system’s miles of lines and few customers as contributing factors to the appearance of the amoeba. The ACUD system also does not have its own water supply but must rely on two providers, another complication in maintaining chlorine levels.

The side of the ACUD system supplied by Assumption Parish had the amoeba. The other half of the system, supplied by St. James Parish, serves Lemannville and has had no discoveries of the amoeba.

Dawson said the parish is continuing to work on chlorine booster stations and to work with Assumption on its chlorination methods.

But he said the parish also is moving forward on the purchase of the Peoples Water Service system inside Donaldsonville. The purchase is expected to help the parish better control chlorine levels, officials have said.

Follow David J. Mitchell on Twitter @NewsieDave.