Overview
Toxoplasmosis is a zoonotic protozoal infection caused by Toxoplasma gondii, a parasite found in cats. It causes infection if congenitally acquired and in people with immunocompromise, including acquired immunodeficiency syndrome (AIDS).
Pathophysiology
Toxoplasma gondii infects the body via broken skin, the lungs, or the gastrointestinal tract and releases trophozoites which spread around the body via the blood and lymphatics, including the eyes, brain, and muscles. In immunocompetent people, the infection is asymptomatic and usually leads to lifelong immunity, however, upon becoming immunocompromised, reactivation can occur, leading to toxoplasmosis.
Presentation
Immunocompetent people
In immunocompetent people, the infection is asymptomatic and may cause mild symptoms resembling infectious mononucleosis with fever, malaise, and lymphadenopathy (~10%). In rarer cases, it can cause myocarditis and meningoencephalitis.
Immunocompromised people
In immunocompromised people, symptoms tend to be more severe due to the formation of cerebral lesions:
- Systemic features – headaches, fever, confusion, drowsiness
- Focal neurological symptoms, seizures, and features of elevated intracranial pressure
TORCH syndrome
Toxoplasmosis during pregnancy can cause congenital infection. The risk of transmission is highest in the third trimester. Earlier infection is associated with more severe complications which can include:
- Intrauterine growth restriction and low birth weight
- Hepatosplenomegaly
- Chorioretinitis
- Cerebral intraparenchymal calcifications
- Anaemia
- Hydrocephalus
Investigations
Some investigations include:
- Toxoplasma serology – the investigation of choice
- CT/MRI head – may show single/multiple lesions with ring/nodular enhancement
- Thallium SPECT – negative, helps with differentiating from cerebral lymphoma
Management
Overview
In immunocompetent people without severe infection, no treatment is generally necessary. If a person is immunocompromised or has a severe infection, treatment involves pyrimethamine and sulfadiazine for at least 6 weeks.
