Toxoplasmosis

Summary

Toxoplasmosis, caused by Toxoplasma gondii, is usually mild but can cause severe complications in pregnancy and immunocompromised patients. Congenital infection may result in microcephaly, intracranial calcifications, or chorioretinitis. Diagnosis relies on serology and PCR, with treatment using spiramycin in pregnancy and pyrimethamine–sulfadiazine for confirmed cases. Prevention includes avoiding undercooked meat, contaminated soil, and cat feces.

Overview

Toxoplasmosis is an infection caused by Toxoplasma gondii, an obligate intracellular protozoan parasite. Humans acquire infection primarily through ingestion of oocysts from contaminated cat feces, soil, or undercooked meat. While usually asymptomatic in immunocompetent individuals, the infection carries significant risk during pregnancy and in immunocompromised patients.

Epidemiology and Transmission

• Reservoir: Domestic cats (definitive hosts) shed oocysts in feces.

• Routes of transmission:

• Ingestion of oocysts from contaminated soil, water, or vegetables

• Consumption of undercooked or raw infected meat

• Vertical transmission (mother-to-fetus)

• Blood transfusion or organ transplantation (rare)

Clinical Features

• Most pregnant women are asymptomatic.

• Risk to the fetus is highest if infection occurs in early pregnancy, leading to more severe outcomes.

• Congenital toxoplasmosis may present with:

• Microcephaly or hydrocephalus

• Intracranial calcifications

• Chorioretinitis

• Seizures, developmental delay

• Hepatosplenomegaly

• Some infants may be asymptomatic at birth but develop late sequelae, especially ocular disease.

Diagnosis

• Serology (IgM, IgG) is the mainstay for detecting acute or past infection.

• Polymerase chain reaction (PCR): Detects parasite DNA, particularly from amniotic fluid in suspected congenital infection.

• Neuroimaging (CT/MRI): May reveal multiple ring-enhancing lesions in cerebral toxoplasmosis.

• Ultrasound (fetal): Can show ventriculomegaly, intracranial calcifications, or growth restriction.

Management

• Spiramycin: Recommended for maternal infection during pregnancy to reduce vertical transmission (particularly before confirmed fetal involvement).

• Pyrimethamine–sulfadiazine with folinic acid: Used if confirmed fetal infection or maternal infection later in pregnancy.

• Termination of pregnancy may be considered in severe cases with major fetal abnormalities.

Newborns

• Neonates with congenital infection are treated with pyrimethamine–sulfadiazine and folinic acid for prolonged courses to reduce long-term complications.

Prevention

• Avoid consumption of raw or undercooked meat.

• Wash fruits and vegetables thoroughly.

• Practice strict hand hygiene after handling raw meat or soil.

• Pregnant women and immunocompromised individuals should avoid cleaning cat litter or should use protective gloves and proper hygiene measures.

• Freeze meat before cooking to reduce infectivity.