Toxoplasmosis: Disease Overview, Diagnosis, and Treatment
Toxoplasmosis is a parasitic disease caused by the obligate intracellular protozoan Toxoplasma gondii. This widespread infection affects nearly one-third of the global population. While most immunocompetent individuals remain asymptomatic or experience only mild flu-like symptoms, toxoplasmosis can cause severe disease in immunocompromised patients and during pregnancy.
Who Is at Risk for Severe Toxoplasmosis?
Individuals with weakened immune systems, including those with HIV/AIDS, those undergoing chemotherapy, or organ transplant recipients, are at high risk for acute toxoplasmosis or reactivation of latent Toxoplasma infection. In pregnant women, primary infection with Toxoplasma gondii can result in vertical transmission, infecting the fetus and causing congenital toxoplasmosis. The severity of congenital disease depends on the timing of maternal infection and possibly the genotype of the infecting strain.
Ocular Toxoplasmosis
Toxoplasma gondii is also a major cause of ocular disease, particularly in South America, where it is one of the leading causes of blindness. Some Toxoplasma strains are associated with retinal disease in immunocompetent individuals. Our lab studies how strain-specific variation contributes to the pathogenesis of toxoplasmosis, with the goal of identifying mechanisms that explain these clinical outcomes.
Diagnosis of Toxoplasmosis
Toxoplasmosis diagnosis typically involves serological testing for antibodies against Toxoplasma gondii. Elevated IgM titers suggest acute infection, whereas high IgG in the absence of IgM indicates past exposure or latent infection. Because IgM antibodies can persist for months, IgG avidity testing is often used to determine the timing of infection; higher avidity is associated with chronic stages. For more information, visit the Toxoplasma Serology Laboratory.
Treatment of Toxoplasmosis
Treatment for toxoplasmosis targets only the acute phase of infection. The standard regimen includes pyrimethamine, sulfadiazine, and folinic acid. These therapies are not effective against the latent chronic stage of the parasite, during which Toxoplasma persists in tissue cysts. There is a clear need for new therapeutic approaches that eliminate latent infection and prevent reactivation in susceptible individuals.