A clinical hematologist examines a blood film from a patient presenting with cyclical fevers and severe anemia. Under high-power magnification, they identify 8 μm8\ \mu\text{m}8 μm to 15 μm15\ \mu\text{m}15 μm unicellular, eukaryotic organisms that contain membrane-bound nuclei but lack cell walls, actively replicating within the patient's erythrocytes (red blood cells).
Which option correctly classifies this pathogen and identifies its primary method of transmission?
Pathogen Class: Protist; Transmission: Vector-borne via the saliva of feeding female Anopheles\textit{Anopheles}Anopheles mosquitoes.
Pathogen Class: Fungus; Transmission: Airborne inhalation of asexual spores.
Pathogen Class: Bacterium; Transmission: Direct contact with contaminated surface water.
Pathogen Class: Virus; Transmission: Sexual transmission or direct blood-to-blood contact.
