Doctors are urged to be on alert this summer for a very rare but deadly brain disease in children that is contracted by swimming in lakes and rivers.

The warning follows the death of a 12 month-old boy at Townsville Hospital, Australia's latest victim of primary amoebic meningoencephalitis.

PAM is caused by a brain-eating amoeba found in warm fresh water, such as lakes and rivers. Credit:Brendan Esposito

From a nearby west Queensland cattle-farming area, the baby boy was unable to breathe on his own within 18 hours of leaving home with a persistent high fever and lethargy, and died in 2015.

PAM is caused by Naegleria fowleri, a brain-eating amoeba - a type of organism - found in warm fresh water, such as ponds, lakes, rivers, hot springs and poorly maintained municipal water supplies.