Toxoplasma

Question 1

Factfile

Answer 1

Caused by Toxoplasma gondii

Zoonotic infection (mainly mammals and birds)

Occurs worldwide

Most infections no/mild symptoms (due to protective host immunity)

Clinical disease in immunocompromised patients or the developing fetus (transplacental transmission). Toxoplasma can lay latent until lowered immune status. Tissue cysts inactive.

No vaccine. Drugs eliminate replicating parasites but not tissue cysts.

Question 2

Life Cycle

Answer 2

Life cycle involves two hosts:
- definitive host: felids (cats)
sexual reproduction and formation of infective oocysts
- intermediate hosts: broad host range (humans, mice, pigs, sheep, poultry, …)
tachyzoites: invade and multiply within host cells; egress and infect new host cells
bradyzoites: intracellular tissue cysts

Infection occurs through:
- ingestion of oocysts from environment (excreted in cat faeces)
- ingestion of tissue cysts by carnivores
-> upon ingestion of oocysts/tissue cysts, T. gondii parasites infect epithelial cells of the intestine and then disseminate in the body.