🪱 Parasites: The Hitchhikers of the Living World
📝 Last reviewed: August 2026
What parasites are: organisms that live on or inside another organism (the host), taking nutrients at the host's expense. They range from single-celled protozoa to large worms.
The big single-celled ones: Plasmodium causes malaria (spread by mosquitoes, ~600,000 deaths/year, mostly children in Africa); Giardia and amoebas cause diarrhoea; Toxoplasma is caught from cat litter and undercooked meat.
The worms: tapeworms and roundworms live in the gut; hookworms in the small intestine; threadworms are the common "worms" of childhood. Most spread through contaminated food, water, soil or insect bites.
How they are treated: antiparasitic drugs — artemisinin for malaria, albendazole and ivermectin for worms, metronidazole for giardia. Many are cheap and highly effective.
Prevention: safe water, washing hands, cooking meat thoroughly, mosquito nets and repellents in malaria areas, and deworming programmes in endemic regions have saved millions of lives.
Historic note: malaria and hookworm once crippled entire regions; draining swamps, bed nets and mass treatment turned the tide. Parasites remain the quiet burden of tropical health.
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