What disease is caused by a sporozoan protozoan that infects the liver and blood?

The correct choice identifies malaria, a disease caused by Plasmodium, a genus of sporozoan protozoans that primarily infects red blood cells after being transmitted to humans through the bite of infected Anopheles mosquitoes. Once in the bloodstream, the sporozoites travel to the liver, where they undergo asexual reproduction, proliferating and eventually re-entering the bloodstream to infect more red blood cells.

This process leads to the symptoms commonly associated with malaria, such as fever, chills, and anemia, due to the destruction of red blood cells. Understanding the life cycle of Plasmodium is crucial, as it differentiates malaria from other diseases listed in the options, which have different causative agents and mechanisms of infection. Meningitis, for example, is caused by bacteria or viruses that affect the central nervous system, giardiasis is a gastrointestinal disease caused by a different type of protozoan (Giardia), and cholera is a bacterial infection resulting from the ingestion of contaminated water or food. Each of these diseases has distinct organisms responsible for their pathogenesis, highlighting why malaria is the correct answer in this context.