Clinical Features:
Acquired infection with Toxoplasma in immunocompetent persons is generally an asymptomatic infection.  However, 10% to 20% of patients with acute infection may develop cervical lymphadenopathy and/or a flu-like illness.  The clinical course is usually benign and self-limited; symptoms usually resolve within a few weeks to months.  In rare cases ocular infection with visual loss can occur.  Immunodeficient patients often have central nervous system (CNS) disease but may have retinochoroiditis, pneumonitis, or other systemic disease.  In patients with AIDS, toxoplasmic encephalitis is the most common cause of intracerebral mass lesions and is thought to be caused by reactivation of chronic infection.  Toxoplasmosis in patients being treated with immunosuppressive drugs may be due to either newly acquired or reactivated latent infection.
Congenital toxoplasmosis results from an acute primary infection acquired by the mother during pregnancy.  The incidence and severity of congenital toxoplasmosis vary with the trimester during which infection was acquired.  Because treatment of the mother may reduce the incidence of congenital infection and reduce sequelae in the infant, prompt and accurate diagnosis is important.  Many infants with subclinical infection at birth will subsequently develop signs or symptoms of congenital toxoplasmosis.  Ocular Toxoplasma infection, an important cause of retinochoroiditis in the United States, can be the result of congenital infection, or infection after birth.  In congenital infection, patients are often asymptomatic until the second or third decade of life, when lesions develop in the eye.

Laboratory Diagnosis:
The diagnosis of toxoplasmosis may be documented by:

• Observation of parasites in patient specimens, such as bronchoalveolar lavage material from immunocompromised patients, or lymph node biopsy.
• Isolation of parasites from blood or other body fluids, by intraperitoneal inoculation into mice or tissue culture.  The mice should be tested for the presence of Toxoplasma organisms in the peritoneal fluid 6 to 10 days post inoculation; if no organisms are found, serology can be performed on the animals 4 to 6 weeks post inoculation.
• Detection of parasite genetic material by PCR, especially in detecting congenital infections in utero.
• Serologic testing is the routine method of diagnosis.

Diagnostic findings

• Microscopy
• Antibody detection

Treatment:
Treatment is not needed for a healthy person who is not pregnant.  Symptoms will usually go away within a few weeks.  Treatment may be recommended for pregnant women, persons who have weakened immune systems, or persons with ocular disease or severe illness.  For additional information, see the recommendations in The Medical Letter (Drugs for Parasitic Infections).