The apicomplexans are protist parasites that are specialized for living and reproducing within the tissues of animals. They have a unique structure (an apical complex) that is a cluster of microtubules and organelles located in the apex of cells that are in the infectious stage. This structure's function is to facilitate penetration of host cells. The most well-known example of an apicomplexan is Plasmodium , the organism that causes malaria in humans and other animals. Similarly to African Sleeping Sickness and Chagas Disease, malaria is an insect-borne disease spread by mosquitoes.
According to the World Health Organization, there were 247 million new cases of malaria resulting in 619,000 deaths in 2021. Children under 5 years old are the most affected, accounting for 67% of malaria deaths worldwide in 2019. Malaria causes symptoms that typically include fever, fatigue, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. Malaria can strike a person multiple times per year, contributing to a major deficit in productivity, depriving families of income, and plunging many into poverty.
Malaria and poverty are intimately connected. As both a root cause and a consequence of poverty, malaria is most intractable for the poorest countries and communities in the world that face a vicious cycle of poverty and ill health.
The graphic below shows the relationship between malaria and poverty.
Many apicomplexan life cycles are quite complex, and Plasmodium is no exception. As you can see in the image below, there are many stages in the life cycles of this parasite, and each stage infects a different host or tissue within the host. You do not need to know the details of this life cycle, but you should understand the implications of this complexity in the attempt to develop a cure for malaria.
Efforts to control the spread of malaria are focused on several aspects of the disease. Controlling the mosquito populations that spread the disease are one of the efforts. The pesticide DDT (that is now banned in many parts of the world) was used to fight malaria. However, many mosquitoes now show resistance to DDT and other pesticides.
Similarly, different medications have been used to treat people with active malaria infections. However, the Plasmodium organism has developed resistance to most of the medications that have been developed. Currently, malaria is treated with a drug cocktail (a mix of medications effective against malaria) with the hopes that combining drugs in this way will slow the evolution of resistance.
The ultimate goal of malarial research is to develop a vaccine. However, this has proven to be difficult. Currently, there is only a single vaccine in use for preventing malaria in children and while it reduces the rate of severe cases of malaria, the reduction is only 30%. Current vaccine research is focused on other stages of the infection cycle.