Toxoplasmosis Flashcards
What is the causative agent of toxoplasmosis?
Toxoplasma gondii, an intracellular parasitic protozoan.
Where in the world is toxoplasmosis most endemic?
South America.
What are the three main modes of transmission of Toxoplasma gondii?
Consumption of raw or undercooked meat with tissue cysts, ingestion of contaminated water or vegetables with oocysts from infected cat feces, and vertical transmission from mother to fetus.
What population groups are at highest risk for severe toxoplasmosis?
Pregnant women (risk of congenital toxoplasmosis) and immunocompromised patients, particularly those with HIV/AIDS.
What are the symptoms of toxoplasmosis in immunocompetent individuals?
Usually asymptomatic, but may present with a mononucleosis-like illness including fever, lymphadenopathy, and fatigue.
What is the classic triad of congenital toxoplasmosis?
- Chorioretinitis
- Hydrocephalus (can be microcephalic due to cortical atrophy)
- Diffuse intracranial calcifications
Although toxoplasmosis infection is typically asymptomatic in an immunocompetent adult, it can cause severe consequences in the fetus or newborn. After maternal ingestion, tachyzoites transmitted through the placenta invade developing fetal cells, most commonly in the muscle and brain. Classic congenital manifestations include eye abnormalities (eg, chorioretinitis), neurologic findings (eg, intracranial calcifications, hydrocephalus), and hearing impairment. When infection is suspected prenatally, diagnosis is made via maternal serology or amniocentesis. When the infection is suspected in a newborn, diagnosis is with neonatal serology. Treatment is with antiparasitic therapy (ie, pyrimethamine and sulfadiazine) and supplemental folate for a year.
What additional symptoms may be present in congenital toxoplasmosis?
- Microcephaly due to brain atrophy
- Macrocephaly due to hydrocephalus
- Seizures
- Jaundice
- Hepatosplenomegaly
- Rash (blueberry muffin rash)
- Growth restriction
- Potential deafness
How is toxoplasmosis diagnosed?
- Serology (IgM for active infection, IgG for past exposure)
- PCR
- Tissue biopsy (especially in HIV patients with encephalitis)
- Brain biopsy may be utilized to distinguish between cerebral toxoplasmosis and CNS lymphoma
What imaging findings are associated with toxoplasmosis in HIV/AIDS patients?
Multiple ring-enhancing lesions on brain MRI, typically in the basal ganglia.
What is the first-line treatment for toxoplasmosis?
- Pyrimethamine
- Sulfadiazine
- Folinic acid (leucovorin).
What alternative treatment can be used for toxoplasmosis?
Trimethoprim-sulfamethoxazole (TMP-SMX).
What is the prophylaxis for toxoplasmosis in HIV patients?
TMP-SMX (Bactrim) for CD4 count <100 cells/mm³ if IgG positive for Toxoplasma gondii.
How does toxoplasmosis spread in the body after ingestion?
Oocysts invade the intestines, disseminate hematogenously, and form tissue cysts in organs including the brain, eyes, and muscles.
What is the role of cats in toxoplasmosis transmission?
Cats are the definitive host and shed infectious oocysts in their feces, which can contaminate soil, water, and food sources.
How does toxoplasmosis affect the eye?
Causes chorioretinitis, which can lead to vision loss, especially in congenital or reactivated infections.
What are the risk factors for toxoplasmosis reactivation?
Severe immunosuppression, such as in HIV/AIDS patients with CD4 counts <100, organ transplant recipients, and patients on immunosuppressive therapy.
Why is folinic acid (leucovorin) given with pyrimethamine?
To prevent bone marrow suppression due to pyrimethamine-induced folate deficiency.
How is congenital toxoplasmosis diagnosed?
Toxoplasma serology (IgM, IgG), PCR of amniotic fluid, or postnatal testing with IgM in neonates.
What is the recommended treatment for congenital toxoplasmosis?
Pyrimethamine, sulfadiazine, and folinic acid (leucovorin).
How long is congenital toxoplasmosis treatment given?
Usually for one year to prevent complications and recurrence.
What are preventive measures for toxoplasmosis?
Avoiding raw or undercooked meat, washing produce thoroughly, wearing gloves when handling soil or cat litter, and ensuring pregnant women avoid exposure to cat feces.
