Researchers of the Bernhard Nocht Institute for Tropical Medicine in Hamburg, Germany discovered how malaria parasites in the liver abscond themselves in dead liver cells in their way to the blood stream in order to avoid interfering with the immune system.

The "cleverness" of malaria parasites is similar to that of Greeks in the Trojan Horse myth. Greeks hid themselves in the big hollow wooden Horse in order to enter Troy and destroy the fortress. Malaria parasites hide themselves in dead liver cells to travel from liver to the blood stream without being noticed and detected by our system. This way, malaria sufferers do not become aware of the gravity of their condition and do not know how and when the parasites reach their blood.

"The silent parasites enter the body as a consequence of an individual being bitten by an infected mosquito. On the onset of malaria, the parasites heed towards liver and after this stage they conceal themselves in dead liver cells, avoid immune system, and go to infect the blood stream. In the blood stream, malaria parasites affect red blood cells and cause high fever and chills in infected individuals. Malaria parasite is called Plasmodium falciparum and when reaches the bloodstream, it kills red blood cells, causing the above mentioned symptoms in people, which most often lead to death. The parasite has evolved this complex structure. The best image to describe it is the Trojan horse, because it both transports the parasites and camouflages them," commented one of the scientists involved in the study. The action of the parasite "was a paradox. We could not understand how the rate of infection could be so successful," the researcher added.

The study that led to the discovering of malaria parasite's clever strategy to sneak itself into the blood was conducted on mice. Scientists used parasites labeled with a green fluorescent marker and the blood vessels of the mice were also labeled with a red fluorescent marker. This is how they could watch the parasites traveling safely from liver into the blood.

The findings of the study will further help preventing malaria parasite's spreading into the blood and causing severe health disorders to the infected individuals. This will also considerably cut the mortality rate caused by the Plasmodium falciparum parasite.

After it has been passed on from mosquito saliva into human's blood, the malaria parasite finds its way into the liver. Here, it occupies liver cells and kills them. Dead liver cells detach from their healthy counterparts and, laden with parasites, pass from liver into the blood stream through the extremely thin walls of liver blood vessels. When leaving liver, dead liver cells split into smaller structures which resemble cells, called merosomes.

Each merosome is overloaded with parasites. But merosomes cannot be identified by immune system's white cells because the structures that carry malaria parasites store from the previous liver cell calcium ions. These calcium ions on the surface of the merosomes keep white cells from detecting the abnormal cell-like parasite transporters.
"The parasite did not evolve this complex system for nothing. It is probably very important that the parasite not travel free in the liver. It is now possible to follow in real time and quantitative terms the parasite in its host, and that is something we were only dreaming of a few years ago," concluded the team.