Toxoplasma gondii is an obligate intracellular protozoan that infects the body via the gastrointestinal tract, lung or broken skin. It's oocysts release trophozoites which migrate widely around the body including to the eye, brain and muscle. The usual animal reservoir is the cat, although other animals such as rats carry the disease.
Most infections are asymptomatic. Symptomatic patients usually have a self-limiting infection, often having clinical features resembling infectious mononucleosis (fever, malaise, lymphadenopathy). Other less common manifestations include meningoencephalitis and myocarditis.
Serology is the investigation of choice.
No treatment is usually required unless the patient has a severe infection or is immunosuppressed.
Cerebral toxoplasmosis accounts for around 50% of cerebral lesions in patients with HIV
Cerebral toxoplasmosis: CT scan with contrast showing multiple ring enhancing lesions
Cerebral toxoplasmosis: MRI (T1 C+) demonstrates multiple small peripherally enhancing nodules located predominantly in the basal ganglia as well as the central portions of the cerebellar hemispheres. Only a small amount of surrounding oedema is present.
Immunosuppressed patients may also develop a chorioretinitis secondary to toxoplasmosis.
Congenital toxoplasmosis is due to transplacental spread from the mother. It causes a variety of effects to the unborn child including