Classifying Pathogens and Disease Causes

Steps:

• Recall that cholera is a bacterial infection from Vibrio cholerae, not viral.
• Note mosquitoes transmit malaria but are vectors, not pathogens; Plasmodium parasites cause it.
• Remember Mycobacterium bovis affects both cattle and humans, causing bovine TB transmissible to people.
• Identify Plasmodium vivax as a protozoan parasite, classifying it as a protist.

Why D is correct:

• Protists are eukaryotic microorganisms; Plasmodium vivax fits this definition as a single-celled protozoan causing malaria.

Why the others are wrong:

• A: Cholera is caused by the bacterium Vibrio cholerae, not a virus.
• B: Mosquitoes are vectors that transmit the Plasmodium pathogen, not pathogens themselves.
• C: Mycobacterium bovis primarily causes TB in cattle but can infect humans via zoonotic transmission.

Final answer: D