2nd August 2023

Toxoplasmosis

Toxoplasmosis, caused by the protozoan Toxoplasma gondii, is transmitted through ingesting oocytes from contamination by cats’ faeces, through vertical transmission, and from an infected donor in organ transplants. Toxoplasmosis infections range in severity and presentation when seen in immunocompetent, immunocompromised and congenital patients.

• Immunocompetent patients are usually asymptomatic but can suffer from a self-limiting syndrome similar to infectious mononucleosis, consisting of fever, malaise and lymphadenopathy. Diagnosed with serology, and treatment is supportive
• In immunosuppressed patients, three forms of the infection are recognised: cerebral toxoplasmosis, pneumonitis and chorioretinitis. Cerebral toxoplasmosis is seen in nearly half of the cerebral lesions associated with HIV. It presents with headache, confusion, reduced GCS and focal neurology. Brain imaging using CT and MRI scans show single or multiple ring enhancing lesions (see image below). Treatment with pyrimethamine and sulfadiazine is required.
• Congenital toxoplasmosis occurs through transplacental transmission from an infected mother to the foetus. Common clinical features include:
  • Neurological abnormalities: chorioretinitis, intracranial calcification, hydrocephalus
  • Lymphoproliferative abnormalities: jaundice, thrombocytopenia, anaemia, hepatosplenomegaly and lymphadenopathy.
  • Retinopathy and microcephaly are less commonly seen.

Multiple ring enhancing lesions on MRI scan

Image Source: Wikimedia Commons (2021). BrainToxoplasmosis MRI 8 22, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:BrainToxoplasmosis_MRI_8_22.png (Accessed: 10 March 2022).