Toxoplasmosis
Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management
Definition
Toxoplasmosis is an infection caused by the protozoan parasite Toxoplasma gondii, which can lead to systemic or neurological complications, particularly in immunocompromised individuals and during pregnancy.
Aetiology
- Caused by ingestion of Toxoplasma gondii oocysts from contaminated soil, water, or food.
- Vertical transmission from mother to fetus (congenital toxoplasmosis).
- Reactivation of latent infection in immunocompromised individuals.
Pathophysiology
- Oocysts transform into tachyzoites, which disseminate and form tissue cysts.
- Latent infection occurs in neural and muscle tissues, which can reactivate under immunosuppression.
- Congenital infection can lead to neurological damage and chorioretinitis.
Risk Factors
- Consumption of undercooked or raw meat.
- Exposure to cat faeces (handling litter boxes).
- Immunosuppression (HIV, organ transplant recipients).
- Pregnancy (risk of congenital toxoplasmosis).
Signs and Symptoms
- Acute infection: fever, lymphadenopathy, myalgia, fatigue.
- Ocular toxoplasmosis: blurred vision, photophobia, chorioretinitis.
- Congenital toxoplasmosis: hydrocephalus, intracranial calcifications, chorioretinitis.
- CNS toxoplasmosis (in immunocompromised patients): headache, seizures, focal neurological deficits.
Investigations
- Serology: IgM and IgG antibodies to detect acute or past infection.
- Polymerase chain reaction (PCR): detects T. gondii DNA in blood or cerebrospinal fluid.
- Ophthalmic examination: to assess for chorioretinitis.
- Brain MRI: ring-enhancing lesions in CNS toxoplasmosis.
Management
1. Supportive Care:
- Most immunocompetent individuals require no treatment.
- Analgesia and antipyretics for symptom relief.
2. Combination Therapy:
- Symptomatic or severe infection: pyrimethamine + sulfadiazine + folic acid.
3. Prevention:
- Cook meat thoroughly to kill parasites.
- Hand hygiene after handling raw meat or soil.
- Avoid cat litter handling during pregnancy.
4. Referral:
- Infectious diseases: for immunocompromised patients or CNS toxoplasmosis.
- Ophthalmology: if ocular toxoplasmosis is present.
- Obstetrics: for congenital toxoplasmosis risk assessment.