What is a common characteristic of diseases caused by protozoa?

Diseases caused by protozoa often share the characteristic of being transmitted through contaminated water or food sources. Protozoa, which are single-celled organisms, can enter the human body primarily through ingestion. Inadequate sanitation, poor hygiene practices, and unsafe drinking water are common factors that contribute to the spread of protozoal infections. Examples include Giardia lamblia, which can be contracted from drinking water contaminated with fecal matter, and Entamoeba histolytica, which can be spread through food contaminated during preparation.

The other characteristics listed do not apply universally to protozoal diseases. While some protozoal infections can be mild and self-limiting, many can lead to severe complications if left untreated. Not all protozoal infections require antibiotics for treatment; in fact, some may be treated with specific antiparasitic medications instead. Additionally, while laboratory tests are often necessary for accurate diagnosis, many protozoal infections can exhibit recognizable symptoms that guide preliminary assessment and may not solely rely on lab tests for identification. Thus, the transmission of protozoal diseases through water or food is a defining and common characteristic.