7 March 2011
Fifth malaria species has deadly consequences
People travelling in malaria infected countries risk contracting a little-known ‘fifth species’ of malaria
and the consequences could be fatal.
Senior Medical Scientist in the Department of Haematology at Sydney’s Prince of Wales Hospital,
Gillian Rozenberg, said the first case of Plasmodium knowlesi malaria occurring in humans was
identified in 1965. The person was an American man who had been visiting peninsular Malaysia.
Despite the fact that Plasmodium knowlesi is now known to cause 70% of the malaria cases in South
East Asia, many medical professionals are still unaware of its existence.
“This isn’t the kind of parasitic infection you come across every day and you cannot contract it in
countries like Australia or New Zealand. It’s therefore understandable that it has been largely
unnoticed in the medical and wider community in this part of the world,” said Ms Rozenberg.
In 2010, Sydney’s Royal North Shore Hospital treated a 34 year old man after he contracted this ‘fifth
species’ of malaria in the rainforests of Borneo. The treatment he received led to his full recovery.
“Correct diagnosis and timely treatment of this species of malaria is essential for an infected person’s
recovery.
“The clinical symptoms are the same as other forms of malaria, including persistent fever. A scientist
or pathologist doing tests on the person’s blood would see the typical features of anemia with a low
white cell and platelet count.
“Even when malaria is diagnosed, it is vital that the correct species of malarial parasite is identified.
That identification determines the appropriate treatment,” said Ms Rozenberg.
Plasmodium knowlesi has been labeled the ‘fifth species’ of malaria because it is the first malarial
species known to have crossed over from the macaque monkey to humans with the anopheles
mosquito as the carrier. It stands out from the other four species because of its short replication time
in the infected person’s red blood cells.
Under the microscope, the characteristics of the potentially fatal Plasmodium knowlesi parasite are
very similar to more common and less threatening malaria species, plasmodium malariae.
“Because of these similarities, diagnosis needs to be thorough. Anyone travelling in malaria affected
countries should take precautions, especially as some species of malaria are drug resistant.”
Gillian Rozenberg is the author of Microscopic Haematology, a practical guide for the laboratory. She
was also a guest speaker at the Royal College of Pathologists of Australasia conference in Melbourne
over the weekend.
ENDS:
Caption: Malarial infection process of red blood cells
Media enquiries:
Ms Gillian Rozenberg
0419 639 529
or
Martin Powley
S2i Communications
0417 803 890