This one way of saying that
malaria is a primate disease that has been with us possibly for millions of
years. Recent work suggests that we may
well send the mosquito packing and save us all the aggravation. We now have an apparent successful system
that has been let loose and depending on success will be released worldwide.
There is much to be said for
running down the array of diseases attacking primates and knocking as many of
them out as we can to prevent the real risk of an unhappy crossover. Ebola is believed to have arisen that way as
has AIDs. Of course, even better,
improving living standards will also extinguish the market for bush meat and
further lower those risks.
In the meantime we know that
focusing on the areas with these monkeys will likely drive this malaria strain
into extinction as a human disease at least.
Monkeys Provide Malaria Reservoir for Human Disease in Southeast Asia
ScienceDaily (Apr. 7, 2011) — Monkeys infected with an emerging
malaria strain are providing a reservoir for human disease in Southeast
Asia , according to research published April 7. The Wellcome Trust
funded study confirms that the species has not yet adapted to humans and that
monkeys are the main source of infection.
Malaria is a potentially deadly disease that kills over a million
people each year. The disease is caused by malaria parasites, which are
transmitted by infected mosquitoes and injected into the bloodstream.
There are five species of malaria parasite that are known to cause
disease in humans, of which Plasmodium knowlesi is the most recently
identified. Previously thought to only infect monkeys, researchers have shown
that human P. knowlesiinfections are widely distributed in Southeast Asia
and that it is a significant cause of malaria in Malaysian Borneo .
Until now, it was not clear whether the infection is transmitted from person to
person, or is passed over from infected monkeys.
Researchers led by Professor Balbir Singh at the Malaria Research
Centre, Universiti Malaysia Sarawak, collaborating with Sarawak State Health
Department, St George's University of London and the London School of Hygiene
and Tropical Medicine, examined blood samples from 108 wild macaques from
different locations around the Sarawak division in Malaysian Borneo. Their
results reveal that 78% were infected with the P. knowlesi species of
malaria parasite, and many were infected with one or more of four other species
of monkey malaria parasites that have not yet been found in humans
By comparing the molecular identity of the parasites from monkeys and
those isolated from patients with knowlesi malaria, the team were able to build
a picture of the evolutionary history of the parasite and its preferred host.
Their analysis reveals that transmission of the knowlesi species is more common
amongst wild monkeys, than from monkeys to humans, and that monkeys remain the
dominant host.
"Our findings strongly indicate that P. knowlesi is a
zoonosis in this area, that is to say it is passed by mosquitoes from infected
monkeys to humans, with monkeys acting as a reservoir host," explains
Professor Singh. "However, with deforestation threatening the monkeys'
habitat and increases in the human population, it's easy to see how this
species of malaria could switch to humans as the preferred host. This would
also hamper current efforts aimed at eliminating malaria."
Based on the molecular data, the researchers estimate that the knowlesi
malaria species evolved from its ancestral species between 98 000 and 478 000
years ago. This predates human settlement in the area, meaning that monkeys are
mostly likely to have been the initial host for the parasite when the species
first emerged. This estimate also indicates that the species is as old as, or
older than, the two most common human malaria parasites, P. falciparum and P.
vivax
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