A new strain of malaria has been detected that is a mutation of an old and benign strain of malaria whose natural reservoir is the monkey and was not known to infect humans.
Previously known to only cause minor or mild symptoms, the strain has now mutated into a deadly form that can cause the severest symptoms and death. The larger problem too, is that it has acquired the potential to cross the zoonotic barrier and infect humans.
Researchers from the School of Public Health at Harvard have shown that the new strain has adapted to attach itself and invade all types of blood cells, whereas before it attached itself primarily to young red blood cells.
Although the study is not new, and was published a year ago, news of the finding is now making the rounds in the media. And that is because the fear that the strain would jump from animal to human has become all too real in Malaysia. In fact that discovery of the strain in Malaysia brings to light the fact that the strain has already crossed and is already present in humans in much larger numbers than previously believed.
The host reservoir of the disease are macaques, which in Malaysia, as is the case in other countries, are becoming closer to humans because of habitat destruction. Malaysia is now scrambling to understand how the novel strain acts once it has infected humans. The new strain, called Plasmodium knowlesi, is now the focus of vigorous research in that country. A funding effort has created a special task force at Putra Universiti Malaysia entrusted with unraveling the mystery of the new strain.
In the past, knowlesi was known to only infect monkeys, a purely animal strain that had not adapted to humans. What prompted the investigation was the fact in one small corner of Malaysia, a tiny town called Kapit, an unusual number of people were becoming ill with what seemed to be Plasmodium malariae a few years ago. But the patients had severe symptoms, whereas usually this strain was known to give the infected patient only mild symptoms. The other anomaly was that the patients were not children as is usually the case. In fact the rate of infection was 95% adults and 5% children.
Malaria causes tens of thousands of children to die each year in Africa and worldwide. In fact they are the most vulnerable, if the only ones, during an outbreak. The researchers who traveled to Kapit took samples and brought them back to the Putra Universiti lab. What they found troubled them. The strain was malaria, but its DNA tested negative for all known human strains of malaria, but positive for knowlesi.
The research that followed the initial finding is now almost a decade old, but its results are pressing: the strain is fast becoming a main concern. In certain areas of Malaysia, in fact, the new strain was the majority pathogen. Almost 58% of al infections in Kapit were from knowlesi malaria.
Since then, knowlesi has been detected in many other areas of Malaysia. And the strain has not only expanded its range, but also its severity. It had turned, in short, deadly.
One thing that was becoming clear to the researchers was the fact that the parasitic infection was moving from scarcely populated remote rural zones to areas closer to urban areas.
Malaria strains have different degrees of severity. Two strains until recenlty were responsible for the most deaths: P. falciparum and P. vivax. The other leading malaria strain was P. malariae, which was the least dangerous of the three. But the problem is that malariae bears a striking resemblance at first sight to the more dangerous novel strain of knowlesi, and that alone might have allowed it to spread undetected. Only DNA sequencing, in fact, was able to make that distinction. But knowlesi is now at the top of the danger list. Knowlesi is now believed to be the larger threat to humans of all remaining strains.
What makes knowlesi so dangerous is that is replicates much faster than other strains, thereby quickly debilitating its infected host. To put that in simpler numbers, the known strains of malaria are usually able to complete a cycle of infection and replication in 72 hours. Knowlesi can do that in 24 hours. Every time the strain completes the replication process, a new debilitating fever occurs as the body is assaulted anew by the release of the replicated pathogens. Each time there is a release, blood cells burst and release the replicated parasites.
That kind of stress, at such a rapid rate, can completely impair the human body. Organs fails, and lungs struggle to gasp for air.
And that is why knowing knowlesi, and focusing efforts to defeat it, is more important than ever. The Harvard research, for example, showed how knowlesi, which in the host macaque form is usually a slow replicant that prefers young blood cells, was shown to adapt in less than 4 months to use all blood cells, from new to old, to replicate in.
Not all patients experience the same severity of symptoms, but that should not be taken as a reason to delay research and pro-active prevention of the disease.
One of the reasons why South East Asia, and particularly Malaysia, Indonesia and neighboring countries, are most at risk is that in those countries logging and burning of
indigenous forests to make way for palm tree cultivation is done on a massive scale, thereby both displacing the monkeys and bringing humans in closer contact with them.
More dangerous too, is the fact that the pathogen has higher counts in the blood of the infected host makes it more infectious. That is because the parasite's vehicle, the Anopheles latens mosquito can then easily transmit the disease to humans. The mosquito bites both monkeys and humans in parts of Malaysia studied for the disease. Another mosquito, Anopheles hackeri, which was thought to be the bridge, was found to prefer monkeys to feed on, thereby being a lesser threat in transmission. The people who are clearing the forest or hunting in it, are now more than ever in danger of being infected through mosquito bites. The fact that the infected individuals are not clustered in villages or inhabited centers, shows that the cases are individuals who have been infected as they traveled through the forests during deforestation or hunting.
To make matters worse, many malaria strains are acquiring immunity to medical treatments. In some cases, the resistance was caused by simple mutations, in others by poor quality medications, whose active principle was reduced by some manufacturers in an attempt to increase profits.
Source : the Star/4.5.14/ Royal Society of Tropical Medicine and Hygiene-http://scholar.google.com/scholar_url?hl=en&q=http://www.academia.edu/download/29554273/Vythilingam-2006-Natural_transmission.pdf&sa=X&scisig=AAGBfm3aRSCklQPjPa5HA4XKvSWVpvTvYg&oi=scholarr/ 24.5.2006/