Diseases Caused by Eukaryotic Pathogens

Steps:

• Define eukaryote as an organism with complex cells containing a nucleus, including protozoa and fungi.
• Identify causative agents: bacteria and viruses are non-eukaryotic (prokaryotic or acellular).
• Examine each option's pathogen type.
• Select the disease with a eukaryotic agent.

Why B is correct:

• Malaria is caused by Plasmodium protozoa, single-celled eukaryotes that infect red blood cells.

Why the others are wrong:

• A: Cholera is caused by Vibrio cholerae, a prokaryotic bacterium.
• C: Measles is caused by a virus, which lacks cellular structure.
• D: Smallpox is caused by the variola virus, which is acellular.

Final answer: B