Malaria is one tricky parasite. Researchers have wondered for a long time how malaria stayed in the female body during pregnancy without being attacked by her immune system. A recent study completed by researchers at Rigshospitalet of Copenhagen University Hospital found the answer. Malaria hides in the female body, almost camouflaged and waits to attack the placenta without alarming the female immune system.
The evolution of the malaria parasite is amazing. The parasite rides through the female body in red blood cells. The immune system does not attack these cells because the kidneys typically clean red blood cells, but malaria is not destroyed that easily. A tiny hook is used to secure the parasite to the wall of the red blood cell. If the immune system destroys the hook, another is right there to replace it. Researchers even found one hook specifically evolved to attach to placental tissue.
About one in 12 people are infected with the malaria parasite. That equals out to more than 500 million infected people. The parasite kills more than one million people a year, some of them pregnant women. The high rate of death from malaria is associated with the evolutionary tactics of the parasite. While inside the red blood cell, the parasite reproduces and attacks more cells. The body cannot find the parasites quickly enough to stop the reproduction and eventually malaria takes over and crucial oxygen and nutrients carried by red blood cells never make it to the final destination.
According to Lars Hviid, one of the research authors, “The first time an African woman conceives her placenta provides a new opportunity for the parasite to hide: a new house, so to speak, and in a way that prevents discovery by the immune system. It takes time for the immune defenses to react to the new threat, and meanwhile, the camouflaged parasite harms the woman and her unborn child.”
The human body does not build up protective forces against malaria quickly, which typically means the first infection could have life-threatening effects to the fetus. Researchers believe the ability of the malaria parasite to hide is one reason the immune system has difficulty repelling the disease.
Source: University of Copenhagen. Professor Lars Hviid. 12 July 2011.