Malaria is a well-known disease; many know that it is transmitted by a mosquito bite or that it causes a high fever, but what numerous probably do not know is what the malaria parasite, Plasmodium chabaudi, does in a weakened immune system. The article linked tells of an experiment done to test just that.
The reasoning behind this experiment was that an organism of any type has to evolve to overcome difficult obstacles, but what if that organism was paired with a nonthreatening environment, say the malaria parasite with a weak immune system? Would the organism lose those evolutionary advantages? The task fell upon evolutionary biologist Andrew Read. He, along with Victoria Barclay, ran a twenty-one week experiment at Penn State. Using immune-weakened mice, Plasmodium chabaudi was injected, and then transferred a week later to a different set of mice with feeble immune systems. Every two weeks, a sample of the malaria parasite was taken and frozen. After the twenty-one weeks, the samples between week ten and week twenty-one were injected into mice with normal, healthy immune systems.
The results not only showed that the parasite was just as effective, but also seemed to have become even more aggressive to the host. Read inferred that because the disease was met with scarce resistance when it attacked, it was allowed to grow, mutate, and mature without any limitations. Fellow evolutionary biologist, Daniel Bolnick, comments that while this study opens a solemn eye on this topic, it does not necessarily mean that humans experience the same thing as mice.