An Iranian toddler detained on Nauru had visible signs of tuberculosis for three months before medical tests were ordered and was then forced to wait three weeks for medication to arrive after he tested positive to the deadly bacterial infection.

By the time the medicine arrived, his parents had grown so suspicious about the urgency of the treatment they declined to administer it for another three weeks.

A refugee wanders through the tents at the Nauru detention centre. Credit:Angela Wylie

Sydney paediatrician David Isaacs has risked imprisonment under the federal government's detention gag laws to speak about the case, which he said was symptomatic of a broader indifference to the wellbeing of children on the island by the healthcare contractor International Health and Medical Services.

Children with tuberculosis are not infectious to other people.