What are the modes of transmission that protozoans can use to cause disease in human?

Protozoans can transmit diseases to humans through various modes, primarily including direct contact, ingestion, and vector-borne transmission. For instance, protozoans like Giardia can be ingested through contaminated water or food, while others, such as Plasmodium, are transmitted via the bites of infected mosquitoes. Additionally, some protozoans can spread through sexual contact or through contact with contaminated surfaces or materials. These transmission routes contribute to the spread of diseases such as malaria, giardiasis, and trichomoniasis.