A six-year-old boy died from a rare brain-eating amoeba that he is thought to have caught while playing in contaminated water from a city's supply.

Officials in Lake Jackson, Texas, have warned residents not to drink the city's tap water or use it for anything other than flushing their toilets in the wake of Josiah McIntyre's death.

The youngster tested positive for the amoeba, known as Naegleria fowleri, after playing at a public splash pad and in a sprinkler at his family's home in the suburb of Houston.

Following his death earlier this month, his family are desperate to know where he contracted the amoeba, with his mum Maria Castillo telling ABC 13: "I'm angry and upset and sad and heartbroken.

Josiah McIntyre (left) was killed by a brain-eating amoeba

"It really means a lot to me because we want to know as a family for peace of mind. I know it doesn't bring him back. The fact that we know how he got it, how he contracted it, gives us peace of mind."

She said Josiah was a huge fan of the Houston Astros baseball team and an "active little boy", adding: “He was a really good big brother. He just loved and cared about a lot of people."

Josiah died in hospital on September 8 after battling a brain infection known as primary amebic meningoencephalitis (PAM), which is caused by the microscopic amoeba Naegleria fowleri.

Mum Maria Castillo says she is "angry,upset, sad and heartbroken"
Josiah is thought to have become infected while playing in contaminated water

The amoeba is found in warm freshwater such as rivers and lakes, and soil.

Infection usually occurs when contaminated water enters through the nose. The amoeba travels to the brain and causes PAM, which is usually fatal, according to the Centers for Disease Control and Prevention (CDC).

It is usually caught when people go swimming in contaminated freshwater, but in very rare cases it can occur in an inadequately chlorinated swimming pool or from heated and contaminated tap water, the CDC said.

After Josiah's death, the city's water supply was tested and the splash pad was closed as a precaution.

Three of 11 samples tested positive for genetic material related to naegleria fowleri, including one from a water hose bib at McIntyre's home, ABC 13 reported.

The other two were from the splash pad - where Josiah played in late August before falling ill - and a fire hydrant nearby, said Lake Jackson City Manager Modesto Mundo.

It was still unclear how Josiah came into contact with the amoeba.