What type of communicable disease is caused by protozoa?

Protozoa are single-celled eukaryotic organisms that can cause communicable diseases classified as parasitic infections. Well-known examples include malaria (caused by Plasmodium species, transmitted by Anopheles mosquitoes), amoebic dysentery (caused by Entamoeba histolytica), sleeping sickness (caused by Trypanosoma), and giardiasis (caused by Giardia lamblia). Because protozoa live in or on a host organism and derive nutrients at the host's expense, the diseases they cause are categorised as parasitic.

The other categories involve different types of pathogens:

• Viral infections are caused by viruses (e.g. influenza, HIV, measles).
• Bacterial infections are caused by bacteria (e.g. tuberculosis, cholera, typhoid).
• Fungal infections are caused by fungi (e.g. ringworm, athlete's foot, candidiasis).

Exam tip: Protozoa are parasites. Whenever a question links protozoa to a disease category, the answer is parasitic infections.