Biology GCSE: Infested by Toxoplasma gondii

In this short film Dr Michael Mosley describes the infection of household cats with Toxoplasma gondii.

This infection starts with growing cysts in an infected cat. These are excreted and can survive for a long period outside a host. They are eventually accidentally eaten by mice or rats. To complete its life-cycle the parasite must return to a cat.

Michael Mosley interviews a scientist called Joanne Webster who describes her experiment which showed that infected rats have drastically altered behaviours. This includes being attracted to cat urine (not repelled by it).

This makes it easier for the rat to be caught and the parasite to complete its life-cycle.

Amazingly about a quarter of the UK population is infected with this disease.

Evidence suggests that infection may also affect our behaviour.

This short film is from the BBC series, Michael Mosley: Infested! Living with parasites.

Teacher Notes

This short film could provide an interesting introduction to parasitism (and mutualism).

This might lead onto studying the effects of parasites on humans or other organisms, including plants.

Examples could include the suppression of coagulants in malaria-infected mosquitoes and the manipulation of hormones that sacculina causes in host grabs.

The selective disadvantage which infected rats have could also introduce the topic of evolution.

Curriculum Notes

This short film is suitable for teaching biology at KS4/GCSE in England, Wales and Northern Ireland and National 4/5 in Scotland.

More from Michael Mosley: Infested! Living with Parasites:

Infested by hookworm
Infested by leeches
Infested by lice
Infested by tapeworms
Infested with malaria