Sneaky Parasite Filmed While Infecting Blood Cells

Robert Roy Britt

Date: 08 August 2006 Time: 06:09 AM ET

Treating malaria and other diseases caused by parasites requires a good understanding of the parasite. A new video of the malaria parasite at work should help researchers develop better treatments.

The malaria parasites, Plasmodium falciparum and its three relatives, have dodged the human immune system for centuries. The disease is transmitted by mosquitoes and kills more than a million people every year.

Scientists know that the parasite first infects the liver and then somehow gets into the bloodstream, where it causes red blood cells to rupture. It is during this stage of the disease that the classic symptoms—high fever and chills—occur.

A paradox

In the liver, the parasite takes the form of a merozoite, one of its lifecycle stages. Studies have shown that liver's immune cells gobble up free-moving merozoites.

"This was a paradox," explained Robert Menard, a researcher at the Howard Hughes Medical Institute. "We could not understand how the rate of infection could be so successful."

By tracking malaria infections in live mice, Menard and his colleagues discovered a sneaky trick. After infecting the liver, the parasite wraps itself in dead liver cells, called merosomes, to cloak and transport itself back into the bloodstream, where it can do further harm. [VIDEO]

About Malaria

Malaria can causefever, chills, and flu-like symptoms. Left untreated, it can kill. Each year 300 million to 500 million cases occur worldwide, and more than one million people die, most of them young children in sub-Saharan Africa.

Malaria was eradicated from the United States in the early 1950s. But it is common in many developing countries, where travelers can get it.

Returning travelers and arriving immigrants could also reintroduce malaria in the United States. The mosquito that transmits malaria, Anopheles, is found throughout much of the United States. If local mosquitoes bite an infected person, those mosquitoes can, in turn, infect local residents.