The idea of having a parasite is unsettling enough, but the case of a tapeworm that gave its human host cancer takes it to a whole new level.

The New England Journal of Medicine yesterday published a case study about a HIV-positive Colombian man who had tumours that yielded puzzling biopsy results: the cells were definitely cancer-like, but the cells were not human.

Three years of tests finally revealed the man had been infected by a tapeworm that had contracted cancer, which had then spread around the man's body.

The man's weakened immune system made him particularly susceptible to the tapeworm's cancer cells, according to scientists and the US Centres for Disease Control and Prevention (CDC), which helped diagnose the man.

"We were amazed when we found this new type of disease - tapeworms growing inside a person essentially getting cancer that spreads to the person, causing tumours," study lead author Dr Atis Muehlenbachs said.

"We think this type of event is rare. However, this tapeworm is found worldwide and millions of people globally suffer from conditions like HIV that weaken their immune system.

"So there may be more cases that are unrecognised. It's definitely an area that deserves more study."

Unfortunately, the man died just 72 hours after the doctors reached their diagnosis.

The tapeworm in question, Hymenolepis nana, or the dwarf tapeworm, is the most common tapeworm in humans, infecting up to 75 million people at any given time, according to the CDC.

People get the tapeworm by eating food contaminated with mouse droppings or insects or by ingesting faeces from someone else who is infected.

Children are most often affected and most people show no symptoms.

However, in people whose immune systems are weak, including people who have HIV or are taking steroids, the tapeworm can thrive.

 
"I have spoken with people who are locked up in the centre and they say that there is widespread unrest and fires across the facility," she said in a statement.
 
 
Asylum seekers are a hot political issue in Australia. Successive governments have vowed to stop them reaching the mainland, sending those intercepted on unsafe boats to camps on Christmas Island, and more recently Manus island in Papua New Guinea and Nauru in the South Pacific.
 
 
Many detainees on Christmas Island are from neighbouring New Zealand and are awaiting appeals after having been convicted of crimes. Some have lived in Australia for decades and the number of such deportations is a sore spot in the relationship.
 
 
New Zealand Prime Minister John Key urged his citizens not to take part in any rioting, as it may further damage their legal standing.
 
 
"My concerns would be that, like a riot at any corrections facility, there can and may well be consequences as a result of that," Key told reporters.