Protozoan infections can be transmitted by fecal-oral routes.

• A. Transmitted by vectors
• B. Fecal-oral
• C. Ingested
• D. Direct contact

Answer: (B)

Protozoan infections are commonly transmitted through fecal-oral routes, where ingestion of cysts or spores from contaminated food, water, or hands leads to infection. This route is typical for organisms like Giardia, Entamoeba, and Cryptosporidium, which are shed in feces and contaminate environments people then ingest from.

Why this fits best: the key idea is that exposure comes from fecal contamination that is swallowed, making ingestion the means by which the infection takes hold. The phrase fecal-oral directly links the source (feces) with the route (oral ingestion).

Why the other ideas aren’t as fitting: transmission by vectors involves organisms like mosquitoes or ticks and is not the usual way many protozoa spread. Direct contact can occur in some cases but is not the standard route for most protozoan infections. Simply describing ingestion is too general; the common epidemiological label used for these parasites is fecal-oral because it emphasizes the fecal source and the oral intake.