New monkey malaria ‘poses human threat’

WASHINGTON - An Indian origin researcher in Malaysia has confirmed the potentially deadly nature of an emerging new form of malaria, mainly found in monkeys, by identifying key laboratory and clinical features of the disease.

Researchers at the University Malaysia Sarawak, led by Professors Balbir Singh and Janet Cox-Singh, showed that Plasmodium knowlesi, a malaria parasite previously thought to mainly infect only monkeys - in particular long-tailed and pig-tailed macaques found in the rainforests of Southeast Asia - was widespread amongst humans in Malaysia.

And after reports in neighbouring Southeast Asian countries, researchers have recognised P. knowlesi as the fifth cause of malaria in humans.

Now, the researchers have for the first time given a detailed prospective study of the clinical and laboratory features of human P. knowlesi infections.

“P. knowlesi malaria can easily be confused with P. malariae since these two parasites look similar by microscopy, but the latter causes a benign form of malaria. In fact, because the P. knowlesi parasites reproduce every twenty four hours in the blood, the disease can be potentially fatal, so early diagnosis and appropriate treatment is essential. Understanding the most common features of the disease will be important in helping make this diagnosis and in planning appropriate clinical management,” said Singh.

The researchers initially recruited over 150 patients admitted to Kapit Hospital in Malaysia, between July 2006 and January 2008 who had tested positive with a blood film slide for Plasmodium species.

Using molecular detection methods, P. knowlesi was found to be by far the most common infection amongst these patients, accounting for over two-thirds of all cases.

As with other types of malaria in humans, P. knowlesi infections resulted in a wide spectrum of disease. Most cases of infection were uncomplicated and easily treated with chloroquine and primaquine- two commonly used anti-malarial drugs.

However, around one in ten patients had developed complications and two died.

Although the researchers saw a case fatality rate of just under 2 percent, which makes P. knowlesi malaria as deadly as P. falciparum malaria, they stressed that an accurate fatality rate is hard to determine given the relatively small number of cases studied so far.

All of the P. knowlesi patients - including those with uncomplicated malaria - had a low blood platelet count, which was even significantly lower than for other malarias.

The researchers believe the low blood platelet count could be used as a potential feature for diagnosis of P. knowlesi infections.

The study has been published in the journal Clinical Infectious Diseases. (ANI)