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Toxoplasmosis is an infection caused by the parasite Toxoplasma gondii. Humans are an accidental host, with cats being the usual vector. Its main importance is as a congenital infection where neurological disease can be severe.


Approximately 40% of adults in the UK have been affected by the age of 50. Toxoplasmosis is much more common in France, where less well cooked meat is consumed more frequently e.g. steak tartare. Hence in France toxoplasma serology is included in routine antenatal screening, whereas it is not currently justified in the UK where only 5 in a million births are affected severely.


Toxoplasma is acquired by ingestion. The toxoplasma oocysts are present in cat faeces, but also in infected meat from other species.

Toxoplasmosis can cause congenital infection if it occurs during pregnancy .


Toxoplasma infection is diagnosed by serology, including IgG, IgM and the Toxoplasma Dye Test, which is the "gold standard" test. IgM is not necessarily diagnostic of recent infection as it can persist in adults.


Eating well-cooked meat. Good hand hygiene for gardeners and cat owners.

No vaccine is currently available.


Most infections caused by Toxoplasma gondii are self-limiting although this has been challenged ever since the classic paper in 2000 "Fatal attraction in rats infected with Toxoplasma gondii"[1] due to the issue of potential associations with human behaviour[2], psychiatric illness[3] and cultural evolution[4].


Treatment is usually not necessary. Exceptions are:

  • Toxoplasma choroidoretinitis
  • In the immunosuppressed
  • Acquired in pregnancy (differential cultural risk so not issue in UK)
  1. Pyrimethamine and sulfadiazine (sulphadiazine) with appropriate specialist advice
  2. Second line:
  3. Spiramycin may reduce the risk of transmission of maternal infection to the fetus or after 1st trimester pyrimethamine and sulfadiazine