Monkey malaria widespread in humans and potentially fatal

January 15, 2008

A potentially fatal species of malaria is being commonly misdiagnosed as a more benign form of the disease, thereby putting lives at risk, according to research funded by the Wellcome Trust and the University Malaysia Sarawak.

Researchers in Malaysia studied more than 1,000 samples from malaria patients across the country. Using DNA-based technology they found that more than one in four patients in Sarawak, Malaysian Borneo, were infected with Plasmodium knowlesi, a malaria parasite of macaque monkeys, and that the disease was more widespread in Malaysia than previously thought. Infections were most often misdiagnosed as the normally uncomplicated human malaria caused by P. malariae.

Malaria, which kills more than one million people each year, is caused when Plasmodium parasites are passed into the bloodstream from the salivary glands of mosquitoes. Some types, such as P. falciparum, found most commonly in Africa, are more deadly than others. P. malariae, found in tropical and sub-tropical regions across the globe, is often known as "benign malaria" as its symptoms are usually less serious than other types of malaria.

Until recently, P. knowlesi, was thought to infect only monkeys, in particular long-tailed macaques found in the rainforests of South East Asia. Natural infections of man were thought to be rare until human infections were described in one area in Sarawak, Malaysian Borneo. However, in a study published today in the journal Clinical Infectious Diseases, Professors Janet Cox-Singh and Balbir Singh with colleagues at the University Malaysia Sarawak and three State Departments of Health in Malaysia have shown that knowlesi malaria is widespread in Malaysia.

Under the microscope, the early parasite stages of P. knowlesi look very similar to P. falciparum, the most severe form of human malaria, while the later parasite stages are indistinguishable from the more benign P. malariae. Misdiagnosis as P. falciparum is clinically less important as P. falciparum infections are treated with a degree of urgency and P. knowlesi responds to the same treatment. However, misdiagnosis as the more benign slower growing parasite P. malariae is a problem.

P. knowlesi is unprecedented among the malaria parasites of humans and non-human primates as it reproduces every 24 hours, and one of the features of fatal P. knowlesi infections is the high number of infected red blood cells in these patients. Therefore, even a short delay in accurate diagnosis and treatment could lead to the rapid onset of complications, including liver and kidney failure, and death.

Using DNA detection methods, Professor Cox-Singh and colleagues found malaria infection with P. knowlesi to be widely distributed in Malaysian Borneo and mainland Malaysia, sometimes proving fatal. In addition, single human infections have been reported in Thailand and Myanmar.

"I believe that if we look at malaria infections in South East Asia more carefully, we will find that this potentially fatal type of the disease is more widespread than is currently thought," says Professor Cox-Singh. "Given the evident severity of the illness that it causes, I would recommend that doctors treating patients with a laboratory diagnosis of P. malariae remain alert to the possibility that they may be dealing with the potentially more aggressive P. knowlesi. This would be particularly important in patients who have spent time in the forest fringe areas of South East Asia where the non-human primate host exists."

Source: Wellcome Trust

Explore further: Malaria from monkeys now dominant cause of human malaria hospitalizations in Malaysia

Related Stories

Malaria from monkeys now dominant cause of human malaria hospitalizations in Malaysia

November 3, 2014
The majority of malaria hospitalizations in Malaysia are now caused by a dangerous and potentially deadly monkey-borne parasite once rarely seen in humans, and deforestation is the potential culprit in a growing number of ...

Male farmers at highest risk of contracting 'monkey malaria' in Malaysia

June 9, 2017
Adult male farmers in Malaysia are more than twice as likely to contract Plasmodium knowlesi malaria - an infection usually found only in monkeys - than other people in their communities, according to a new study published ...

Monkeys provide reservoir for human malaria in South-east Asia

April 7, 2011
Monkeys infected with an emerging malaria strain are providing a reservoir for human disease in South-east Asia, according to research published today. The Wellcome Trust-funded study confirms that the species has not yet ...

New findings shed light on complexities of emerging zoonotic malaria

May 28, 2015
Zoonotic malaria has been shown to be caused by two genetically distinct Plasmodium knowlesi parasite subpopulations associated with different monkey host species in Malaysia, according to new research published in PLOS Pathogens. ...

Potential pathway for emergence of zoonotic malaria identified

April 4, 2016
The parasite responsible for a form of malaria now spreading from macaques to humans in South Asia could evolve to infect humans more efficiently, a step towards enhanced transmission between humans, according to a new study ...

Deforestation linked to rise in cases of emerging zoonotic malaria

December 17, 2015
A steep rise in human cases of P. knowlesi malaria in Malaysia is likely to be linked to deforestation and associated environmental changes, according to new research published in Emerging Infectious Diseases. The study, ...

Recommended for you

Gastric acid suppressant lansoprazole may target tuberculosis

November 21, 2017
A cheap and widely used drug, used to treat conditions such as heartburn, gastritis and ulcers, could work against the bacteria that cause tuberculosis (TB), according to new research from UCL and the London School of Hygiene ...

Improving prediction accuracy of Crohn's disease based on repeated fecal sampling

November 21, 2017
Researchers at the University of California San Diego Center for Microbiome Innovation (CMI) have found that sampling the gut microbiome over time can provide insights that are not available with a single time point. The ...

Anti-malaria drug shows promise as Zika virus treatment

November 17, 2017
A new collaborative study led by researchers at Sanford Burnham Prebys Medical Discovery Institute (SBP) and UC San Diego School of Medicine has found that a medication used to prevent and treat malaria may also be effective ...

Decrease in sunshine, increase in Rickets

November 17, 2017
A University of Toronto student and professor have teamed up to discover that Britain's increasing cloudiness during the summer could be an important reason for the mysterious increase in Rickets among British children over ...

Scientists identify biomarkers that indicate likelihood of survival in infected patients

November 17, 2017
Scientists have identified a set of biomarkers that indicate which patients infected with the Ebola virus are most at risk of dying from the disease.

Research team unlocks secrets of Ebola

November 16, 2017
In a comprehensive and complex molecular study of blood samples from Ebola patients in Sierra Leone, published today (Nov. 16, 2017) in Cell Host and Microbe, a scientific team led by the University of Wisconsin-Madison has ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.