(Adds girl's condition)
By Suzi Parker
LITTLE ROCK, Ark., July 29 (Reuters) - A popular Arkansas water park voluntarily closed after a 12-year-old girl who swam there was diagnosed with a rare case of parasitic meningitis, authorities said on Monday.
The Arkansas Department of Health and the U.S. Centers for Disease Control and Prevention confirmed the case last week. The owners of Willow Springs Water Park, which has been operating for 85 years, closed the park on Friday.
The disease is caused by a "brain-eating amoeba," according to the CDC website, that is found in warm rivers, lakes and streams, primarily in the southern United States.
The parasite can cause a rare but severe brain infection that is usually fatal. When the parasite enters the body through the nose, the illness can occur, the Arkansas Department of Health said.
Arkansas Health Department spokesman Ed Barham said tests had determined that the amoeba was in the water at the park.
The girl was in critical condition at Arkansas Children's Hospital in Little Rock, the Arkansas Department of Health said on Monday.
This is the sixth case of the disease in Arkansas in 40 years, the health department said, adding that the last case in the state was in 2010. There were 31 cases of the infection in the United States from 2003 to 2012, the CDC said.
"It is exceedingly rare," said Dirk Haselow, a state epidemiologist. "A sporadic case occurs one in 33 million." (Reporting by Suzi Parker; Editing by Greg McCune and Steve Orlofsky)