Clinical Overview of Toxoplasmosis

Key points

  • There are several tests available to detect Toxoplasma.
  • Drugs are available for patients who require treatment.


Diagnosis of toxoplasmosis is usually made by detection of Toxoplasma-specific IgG, IgM, IgA, or IgE antibodies. There are several tests available that detect these immunoglobulin antibodies within several weeks of infection:

  • Dye test (DT)
  • Indirect fluorescent antibody test (IFA)
  • Enzyme immunoassays (ELISA, immunoblots)
  • Agglutination test
  • Avidity test

If acute infection is suspected, the patient's serum should be tested for IgG and IgM Toxoplasma-specific antibodies. Some serological tests are available at commercial laboratories. However, due to the inherent difficulty in diagnosing acute toxoplasmosis, physicians are advised to seek confirmatory testing through the reference laboratory at Palo Alto Medical Foundation / Jack S. Remington Laboratory for Specialty Diagnostics.

Serologic tests are sometimes unreliable in immunosuppressed patients. Because of the persistence of Toxoplasma cysts and antibody in asymptomatic chronic latent infections, immunosuppressed persons with both positive PCR and serologic results should have their diagnostic testing results interpreted in relation to clinical features of an active infection. A negative PCR does not rule out active infection. PCR can also be performed on amniotic fluid, which can be helpful in determining fetal infection following acute acquired infection of the mother.

Diagnosis can be made by direct observation of the parasite in stained tissue sections, cerebrospinal fluid (CSF), or other biopsy material. These techniques are used less frequently because of the difficulty of obtaining these specimens. Parasites can also be isolated from blood or other body fluids (e.g., CSF) but this process can be difficult and requires considerable time.

Eye disease is diagnosed primarily by ocular examination, including appearance of the lesions in the eye, symptoms, course of disease, and often serologic testing.