Which of the following is an example of a disease caused by a protozoan?

Malaria is indeed an example of a disease caused by a protozoan, specifically by the Plasmodium species, which are single-celled eukaryotic organisms. These protozoa are transmitted to humans through the bites of infected female Anopheles mosquitoes. Once in the bloodstream, the Plasmodium parasites enter red blood cells and multiply, leading to the characteristic symptoms of malaria, such as fever, chills, and fatigue.

In contrast, the other diseases listed are caused by different types of pathogens. Strep throat is caused by bacteria, specifically Streptococcus pyogenes. Influenza is caused by viruses of the Orthomyxoviridae family, and tuberculosis is caused by the bacterium Mycobacterium tuberculosis. Understanding the specific type of pathogen responsible for each disease is crucial in microbiology and helps guide effective treatment and prevention strategies.