An Auckland man has become New Zealand's first reported case of a new and aggressive form of malaria that has jumped the species barrier from monkeys to humans.
Dr Anwar Hoosen, of Travel Clinic North Shore, said yesterday that the 40-year-old man saw his GP in mid-June when he had fever and chills after returning from a trip to Malaysian Borneo.
Malaria was diagnosed, although there was uncertainty over the strain. Drug treatment began and the patient was referred to North Shore Hospital.
"I met him as he was finishing his hospital treatment. Alarm bells rang - I have a special interest in malaria."
The man was recovering, but from his condition Dr Hoosen suspected he had been infected by a more aggressive species of malaria parasite than the one diagnosed.
He checked the patient's blood test results and found he had had a very low platelet count - a marker of the new form of human malaria identified in 2008 and caused by the parasite plasmodium knowlesi.
Malaria is caused by single-cell parasites spread into humans by mosquito bites. P. knowlesi had been thought to infect only monkeys.
But in 2008, researchers described finding it was a significant cause of malaria in humans in Malaysia.
Most of the more than 150 hospital cases in the initial research had been easily treated with medicines, although some developed complications and two died.
Dr Hoosen said the Auckland patient's lab samples were sent to Sydney for DNA analysis, which confirmed that it was P. knowlesi.
Malaria is a major cause of sickness and death in many tropical and subtropical countries, killing nearly a million people a year worldwide.
In New Zealand, only about 50 cases a year are reported - in people who have lived or travelled overseas - of whom half need hospital treatment.
The P. knowlesi species multiplies twice as quickly in human blood - every 24 hours - as the P. falciparum species, which is found most commonly in Africa and causes the deadliest form of malaria.
Auckland City Hospital infectious diseases specialist Dr Mark Thomas said New Zealand was likely to see only rare cases caused by P. knowlesi.
* Discovered in 2008.
* One of five malaria types known to infect humans.
* Previously thought to infect only macaque monkeys in Southeast Asia.
* Potentially fatal.
* Usually treatable with drugs.