The term “malaria resistance” can be used to refer to two different concepts, both related to malaria. The first is natural resistance to the parasites that cause malaria, observed in some human populations. The second is the development of drug resistance in Plasmodium parasites, the causative agents behind malaria, that makes malaria hard to treat because normally effective medications become useless. Both concepts are of considerable interest to medical researchers and scientists, as well as geneticists.
Malaria resistance in human populations is a very interesting example of how the human genome can be affected by changes in the natural environment. As human populations began engaging in agriculture, changing the landscape to create conditions hospitable to the Anopheles mosquitoes that carry malaria, genetic traits that conferred some resistance to malaria infection began to arise. Selection for these traits began to occur, as people with the traits survived malaria infections, while people without them did not.
Using DNA analysis, researchers have been able to pinpoint the era when malaria resistance began to appear in human populations. It can also be traced to specific regions, showing that resistance evolved specifically in the “malaria belt,” rather than occurring spontaneously. However, malaria resistance came at a cost. The evolutionary traits that conferred resistance could also turn deadly, as seen with conditions like thalassemia anemia and sickle cell anemia. While having these traits limits the activities of Plasmodium in the body and creates malaria resistance, if people inherit the wrong combination of traits, they can experience blood disorders.
In Plasmodium populations, resistance to antimalarial drugs is a global problem. Like other microorganisms, these parasites are highly adaptable, so they can adjust to changes in conditions and take advantage of new ecological niches. When the organisms are exposed to antimalarial drugs, some inevitably have some natural resistance that allows them to survive, and over time, resistant organisms breed with other resistant organisms, creating offspring that have more resistance.
Resistance to antimalarial drugs is a concern among pharmaceutical companies and aid organizations working in regions where malaria is widespread. It is necessary to develop new classes of drugs to treat malaria, with the goal of staying ahead of evolution with drugs that can target organisms that tolerate conventional classes of antimalarials. Part of the problem is that research is extremely expensive and some pharmaceutical companies are reluctant to engage in it because the payoffs for antimalarials tend to be lower than those for medications that can be sold in the developed world.