Protist Diseases and Human Defence Systems

This lesson covers the protist disease malaria (the only protist disease named on the AQA specification) and provides a detailed look at the body's non-specific defence systems. Understanding how the body prevents pathogen entry is essential before studying the specific immune response in the next lesson.

---

What Are Protists?

Protists are eukaryotic organisms — they have cells with a nucleus and membrane-bound organelles. Most protists are free-living and harmless, but some are parasites that cause serious diseases.

Key facts about pathogenic protists:

• They are eukaryotes (unlike bacteria, which are prokaryotes)
• Many pathogenic protists are parasites — they live on or inside a host organism and cause harm
• Some are transmitted by vectors — organisms that carry the pathogen from one host to another without being affected themselves
• The most important protist disease for GCSE Biology is malaria

---

Malaria

Malaria is a life-threatening disease caused by a protist parasite of the genus Plasmodium. It is one of the most significant infectious diseases globally, killing over 600,000 people per year, mostly in sub-Saharan Africa.