Resources for Health Professionals

On This Page

Diagnosis

 

 

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 Toxoplasma Serology Laboratory.

For more information: http://www.pamf.org/serology/external icon

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 (for example, CSF) but this process can be difficult and requires considerable time.

Eye disease is diagnosed primarily by ocular examination.

Treatment

Currently recommended treatment drugs for toxoplasmosis target the tachyzoite stage of the parasite and do not eradicate encysted parasites in the tissues. Pyrimethamine, considered the most effective drug against toxoplasmosis, is a standard component of therapy. Pyrimethamine is a folic acid antagonist and can cause dose-related suppression of the bone marrow, which is mitigated by concurrent administration of folinic acid (leucovorin). Leucovorin protects the bone marrow from the toxic effects of pyrimethamine. A second drug, such as sulfadiazine or clindamycin (if the patient has a hypersensitivity reaction to sulfa drugs), should also be included. The fixed combination of trimethoprim with sulfamethoxazole has been used as an alternative, as well as other drugs such as atovaquone and pyrimethamine plus azithromycin, which have not been extensively studied (see: Montoya JG, Boothroyd JC, Kovacs JA. Toxoplasma gondii in Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases, 8th, Edition, 2017  Mandell GL, Bennett JE, Dolin R, Eds. Churchill Livingstone Elsevier, Philadelphia, PA.)

Treatment of immunocompetent adults with lymphadenopathic toxoplasmosis is rarely indicated; this form of the disease is usually self-limited. If visceral disease is clinically evident or symptoms are severe or persistent, treatment may be indicated for 2 to 4 weeks.

Treatment for ocular diseases should be based on a complete ophthalmologic evaluation. The decision to treat ocular disease is dependent on numerous parameters including acuteness of the lesion, degree if inflammation, visual acuity, and lesion size, location, and persistence. Healed lesions should not be treated. The “classic therapy” for ocular toxoplasmosis consists of the following:

  • Adults: pyrimethamine 100 mg for 1 day as a loading dose, then 25 to 50 mg per day, plus sulfadiazine 2 to 4 grams daily for 2 days, followed by 500mg to 1 gram dose four times per day, plus folinic acid (leucovorin) 5-25 mg with each dose of pyrimethamine;
  • Pediatric dose: pyrimethamine 2 mg/kg first day then 1 mg/kg each day, plus sulfadiazine 50 mg/kg two times per day, plus folinic acid (leucovorin) 7.5 mg per day)
  • Therapy should be given for 4 to 6 weeks, followed by reevaluation of the patient’s condition. (See: de-la-Torre A, Stanford M, Curi A, Jaffe GJ, Gomez-Marin JE.  Therapy for ocular toxoplasmosis. Ocul Immunol Inflamm. 2011;19:314-20.) Corticosteroids are sometimes prescribed in addition to antiparasitic agents.

Management of maternal and fetal infection varies depending on the treatment center. In general, spiramycin is recommended for women whose infections were acquired and diagnosed before 18 weeks gestation and infection of the fetus is not documented or suspected. Spiramycin acts to reduce transmission to the fetus and is most effective if initiated within 8 weeks of seroconversion. Spiramycin can be obtained from the U.S. Food and Drug Administration, telephone 301-796-1400. Pyrimethamine, sulfadiazine and leucovorin are recommended for infections acquired at or after 18 weeks gestation or infection in the fetus is documented or suspected. PCR is often performed on the amniotic fluid at 18 gestation weeks to determine if the infant is infected.

For additional information regarding management of toxoplasmosis in pregnant women, see Montoya JG, Remington JS. Management of Toxoplasma gondii infection in pregnancy. Clin Infect Dis 2008 ;47:554-566 and Maldonado YA, Read JS, AAP Committee on Infectious Diseases. Diagnosis, treatment, and prevention of congenital toxoplasmosis in the United States. Pediatrics. 2017;139(2):e20163860.

Congenitally infected newborns are generally treated with pyrimethamine, a sulfonamide, and leucovorin for 12 months. Recommendations from the National Reference Laboratory for Toxoplasmosis (PAMF-TSL) and the Toxoplasmosis Center at the University of Chicago for treatment of congenitally infected infants are:

  • Pyrimethamine: 2 mg/kg per day orally, divided twice per day for the first 2 days; then from day 3 to 2 months (or 6 months if symptomatic) 1 mg/kg per day, orally, every day; then 1 mg/kg per day, orally, 3 times per week
  • Sulfadiazine: 100 mg/kg per day, orally, divided twice per day
  • Folinic acid (leucovorin): 10 mg, 3 times per week
  • See Maldonado YA, Read JS, AAP Committee on Infectious Diseases. Diagnosis, treatment, and prevention of congenital toxoplasmosis in the United States. Pediatrics. 2017;139(2):e20163860.

Toxoplasmosis in immunodeficient patients is often fatal if not treated. Treatment is recommended for at least 4 to 6 weeks beyond resolution of all clinical signs and symptoms, but may be required for 6 months or longer. Relapses are known to occur in AIDS patients and maintenance therapy is recommended until a significant immunologic improvement is achieved in response to antiretroviral therapy. Pyrimethamine, folinic acid (leucovorin), and sulfadiazine are standards of therapy for immunodeficient patients. For additional information, see Guidelines for the Prevention and Treatment of Opportunistic Infections in HIV-Infected Adults and Adolescentsexternal icon and Guidelines for the Prevention and Treatment of Opportunistic Infections Among HIV-Exposed and HIV-Infected Childrenexternal icon.

Related Links

This information is provided as an informational resource for licensed health care providers as guidance only. It is not intended as a substitute for professional judgment.

Pyrimethamine

Sulfadiazine

Clindamycin

Trimethoprim–sulfamethoxazole

Page last reviewed: May 26, 2020