Researchers in Malaysia have confirmed infections among humans with the Plasmodium knowlesi strain of malaria, which till now was believed to only infect monkeys, in particular the long-tailed and pig-tailed macaques.
According to a study published in `Clinical Infectious Diseases’ journal, that examined the clinical and laboratory features of the strain, researchers Balbir Singh and Janet Cox-Singh of the University Malaysia Sarawak found that the malaria strain was widespread among humans in Malaysia and neighbouring countries.
India is keeping a close watch on the parasite springing up in the country. Though officials from the National Vector Borne Disease Control Programme confirmed to TOI that there was no evidence of local transmission of malaria caused by Plasmodium knowlesi in India, flow of tourists between India and the affected countries like Malaysia and Indonesia could bring the infection here.
“The parasite mainly affected macaques which aren’t found in India. So there is no local transmission. We are, however, staying alert,” an official said.
The latest finding takes the number of species of malaria parasite that infects humans to four which includes Plasmodium falciparum which is the deadliest, Plasmodium malariae which has milder symptoms, Plasmodium Vivax and now Plasmodium knowlesi.
One of the most significant findings of the study is that Plasmodium knowlesi was found to have the ability to reproduce every 24 hours in the blood — meaning infection was potentially deadly. This, according to the researchers, meant early diagnosis and treatment were crucial.
The researchers carried out tests on over 150 patients with malaria infection admitted to hospital in Sarawak between July 2006 and January 2008. They found that knowlesi accounted for more than two-thirds of the infections. Most cases of infection were uncomplicated and easily treated with drugs, including chloroquine and primaquine. However, around one in 10 patients had developed complications, such as breathing difficulties and kidney problems, and two died.
All the knowlesi infected patients had a low blood platelet count, significantly lower than that usually found for other types of malaria. The researchers believe low blood platelet count could be used as a potential way to diagnose infection by knowlesi.
Recently, there were cases of European travellers to Malaysia and an American traveller to the Philippines being admitted to hospital with knowlesi malaria following their return home.
This finding follows an Indian study which had found that a malaria strain considered mild has now been found to be just as potentially fatal. Scientists across the world, including India, were waking up to Plasmodium vivax’s increasing notoriety and said the malaria strain was far from being benign.
Scientists reported that vivax was fast developing resistance to standard treatments making it difficult to treat in countries such as India and Indonesia. Research has also revealed that in a region where multidrug-resistant strains of malaria are common, vivax infection is associated with fatal malaria, particularly in young children.
At present, 50% of malaria cases in India are due to vivax.