Doctors suspect some east coast rodent or marsupial populations could be carrying a deadly parasite after the first Australian human case of the potentially lethal tick-borne infection babesiosis was detected at the Canberra Hospital.
A 56-year-old South Coast man died from babesiosis in the hospital last year, a team of doctors and scientists has revealed in the Medical Journal of Australia.
The man, who had several pre-existing medical conditions, was transferred to the Canberra Hospital in November 2010 after suffering serious injuries in a motor vehicle accident.
His condition deteriorated and in April last year parasites were detected in his blood.
It was initially suspected the man had malaria but after babesiosis was diagnosed he was started on medication designed to counter the infection.
He died on April 18.
Canberra Hospital infectious diseases physician Associate Professor Sanjaya Senanayake said it was believed the man had contracted the infection from a tick bite.
It was not known how the tick had acquired the parasite but it had probably come from a rodent.
''About 200 years ago there was the first big rodent migration with the colonial entry in Australia. They may have brought it in,'' Professor Senanayake told The Canberra Times.
This theory was likely because the infection was very similar to a strain found in the northern hemisphere, Professor Senanayake said. ''But having said that, could it be in a rodent and has it jumped from the rodent to a marsupial?
''I ended up learning quite a lot about this disease in terms of what it can do in animals and we've got similar types of bugs here in animals, including marsupials. But not that particular strain.''
Doctors had initially feared the man had contracted the infection from a blood transfusion while in hospital but this was ruled out after the infection was detected in old blood films taken before the car accident.
The disease was deemed to have been contracted in Australia because the man had only travelled overseas once in his life - to New Zealand several years before the accident. Babesiosis was first reported in Croatia in 1957 and cases have been detected in other parts of Europe, the United States, Asia, Africa and South America.
Professor Senanayake said a form of babesiosis sometimes occurred in Australian animals but was not harmful to humans.
''We have babesiosis in cows and dogs here but they are different strains to this one and those strains have never caused human disease anywhere in the world,'' he said.
Babesiosis infected red blood cells and was fatal in 5 to 10 per cent of human cases.
Some people who contracted babesiosis did not suffer any symptoms and others only had minor flu-like symptoms.
If more cases occurred in Australia, it was possible blood donations would have to be routinely screened for the parasite.